Method for determining the release of formaldehyde and other harmful volatile chemicals in climatic chambers. Methods for determining formaldehyde in air Method for determining formaldehyde
Formaldehyde determination method
a common part
The technique is intended to determine the concentration of formaldehyde in the atmospheric air of settlements in the range of 0.01 - 0.3 mg / m 3 with a sample volume of 20 dm 3. Used to measure single concentrations.
The method is based on the capture of formaldehyde from the air with a solution of sulfuric acid and its photometric determination on the colored compound formed as a result of interaction in an acidic medium of formaldehyde with phenylhydrazine hydrochloride and chloramine B.
Preparation of solutions
1 Distilled water. When measuring the concentration of formaldehyde in the ambient air, freshly prepared distilled water is used.
2 Iodine, solution 0.05 mol / dm 3 (0.1 N). Prepared from a standard titer.
3 Starch, 0.5% solution. 0.25 g of starch is mixed with 10 cm 3 of water until a uniform suspension is obtained. A suspension of starch is added to 40 cm 3 of water heated to 60 - 70 ° C with continuous stirring, boiled for 1 min and cooled.
4 Sulfuric acid, 20% solution. To 80 cm 3 of distilled water, carefully add 11 cm 3 of concentrated sulfuric acid.
5 Hydrochloric acid, 10% solution. To 78.1 cm 3 of distilled water, 21.9 cm 3 of concentrated hydrochloric acid are carefully added.
6 Sodium hydroxide, 20% solution. 20 g of sodium hydroxide is dissolved in distilled water. The volume is adjusted to 100 cm 3.
7 Sodium thiosulfate, solution 0.1 mol / dm 3 (0.1 N). Prepared from a standard titer.
8 Phenylhydrazine hydrochloric acid, 5% solution. 5 g of phenylhydrazine hydrochloric acid is dissolved in distilled water. The volume is adjusted to 100 cm 3. The solution is prepared on the day of analysis. If turbidity is present, filter through a "blue ribbon" filter.
9 A mixture of ethanol with phenylhydrazine. To 10 cm 3 of ethanol is added 2 cm 3 of a 5% phenylhydrazine solution and stirred.
10 Chloramine B, 0.5% solution. 0.25 g of chloramine B is dissolved in distilled water. The volume is adjusted to 50 cm 3. The solution is prepared on the day of analysis.
11 Stock solution of formaldehyde (c = 10 μg / cm 3). Prepare approximately 1% formaldehyde solution, for which 2.5 cm 3 formalin is dissolved in water in a volumetric flask with a capacity of 100 cm 3 and then accurately determine its concentration by iodometric titration. Having determined the concentration of formaldehyde in the solution, a solution containing 10 μg / cm 3 of the substance is prepared by appropriate dilution.
12 Working solution of formaldehyde (c = 1 μg / cm 3). 10 cm 3 of the original solution (see listing 11) is diluted in a volumetric flask to 100 cm 3 with water. The solution is prepared before use.
13 Absorption solution - sulfuric acid, solution 0.005 mol / dm 3. Prepared by adding 0.27 cm 3 of concentrated sulfuric acid to 1000 cm 3 of distilled water.
Table 6 - Solutions for establishing the calibration characteristic when determining the concentration of formaldehyde
Establishment of the calibration characteristic
The calibration characteristic, which expresses the dependence of the optical density of the solution on the concentration of formaldehyde, is set in five series of calibration solutions. Each batch of six solutions is prepared from a freshly prepared formaldehyde solution.
Solutions for establishing the calibration characteristics are prepared in volumetric flasks with a capacity of 100 cm 3. For this, a working solution of formaldehyde is poured into each flask in accordance with the table. 6, bring the volume up to the mark with the absorbent solution and mix thoroughly.
To establish the calibration characteristic, 5 cm 3 of each solution is taken into test tubes for calibration, 1.2 cm 3 of a freshly prepared mixture of ethanol and phenylhydrazine are added, and mixed. After 15 minutes, add 1 cm 3 of a 0.5% solution of chloramine B and mix again. After 10 minutes, add 2 cm 3 of a 20% sulfuric acid solution to each sample, mix. After 10 min, the optical density is measured at 520 nm with respect to water in cuvettes with a distance between the working edges of 20 mm. Simultaneously, the optical density of the zero solution is measured: 5 cm 3 of the absorption solution, to which the same reagents have been added. The actual values of the optical density are found from the difference between the optical densities of the calibration solutions and the zero solution.
Sample selection
To determine the one-time concentration of formaldehyde, the test air is aspirated through a Richter absorber filled with 6 cm 3 of an absorbing solution at a flow rate of 1 dm 3 / min for 20 minutes. The sample is analyzed on the day of collection.
Taking measurements
Transfer 5 cm 3 of a sample solution into a test tube, add 1.2 cm 3 of a freshly prepared mixture of ethanol with phenylhydrazine, mix. After 15 minutes, add 1 cm 3 of a 0.5% solution of chloramine and mix. After 10 minutes, add 2 cm 3 of a 20% sulfuric acid solution to the sample and mix again. After 10 min, the optical density is measured at 520 nm with respect to water in cuvettes with a distance between the working edges of 20 mm. Three zero samples are analyzed in a similar way, each of which is 5 cm 3 of the absorption solution. The time from adding the last reagent to measuring the absorbance of all samples should be the same. The average value of the optical density of the blank sample should not exceed 0.04.
The mass of formaldehyde in the sample is determined using the established calibration characteristic by the difference between the optical densities of the sample solutions and the average optical density of zero samples.
The calculation of the measurement result is carried out according to the formula:
where: с - mass concentration (mg / m3) of suspended particles in air
V a - the volume of the solution taken for analysis, cm 3
V p is the total volume of the sample solution, cm 3
V about - the volume of the air sample, reduced to standard value, dm 3.
atmospheric pollution ammonia phenol
State system of sanitary and epidemiological
rationing Russian Federation
4.1. CONTROL METHODS. CHEMICAL FACTORS
Methodical instructions
to determine the concentration of chemical
substances in the water of the centralized
household and drinking water supply
Collection of guidelines
Ministry of Health of Russia
Moscow 1997
1. Prepared by a creative team of specialists consisting of: A.G. Malysheva; (leader), Zinovieva N.P., Suvorova Y.B., Rastyannikov E.G., Toporova I.N., Evstigneeva M.A., with the participation of A.I. Kucherenko. (State Committee for Sanitary and Epidemiological Supervision of Russia).
2. Approved and put into effect by the First Deputy Chairman of the State Committee for Sanitary and Epidemiological Surveillance of Russia - Deputy Chief State Sanitary Doctor of the Russian Federation S.V. Semenov October 31, 1996
Application area
Guidelines for the determination of concentrations chemical substances in water are intended for use by bodies of state sanitary and epidemiological supervision in the implementation of state control over compliance with water quality requirements for centralized drinking water supply, water management organizations, production laboratories of enterprises that monitor the state of water bodies, as well as research institutes working in the field of hygiene water bodies.
The methodological instructions included in the collection have been developed in accordance with the requirements of GOST 8.010-90 "Methods for performing measurements", GOST 17.0.0.02-79 "Nature protection. Metrological support for monitoring pollution of the atmosphere, surface waters and soil. Basic Provisions ". The collection contains methods for measuring the concentrations of 40 chemicals.
The methods were carried out using modern physical and chemical methods for studying gas chromatography with various types of detection, metrologically certified and make it possible to control the content of chemical substances at and below their maximum permissible concentrations in water established in SanPiN 2.1.4.559-96 " Drinking water... Hygienic requirements for water quality of centralized drinking water supply systems. Quality control ", and for substances not included in the list of the new document - in the current" Sanitary rules and norms for the protection of surface waters from pollution ".
The guidelines were approved and adopted at a joint meeting of the group of the Chief Expert of the Commission on Sanitary and Hygienic Standardization "Laboratory and Instrumental Business and Metrological Support" of the State Committee for Sanitary and Epidemiological Supervision of Russia and the Bureau of the Section on Physical and Chemical Methods of Environmental Research of the Problem Commission " Scientific basis human ecology and environmental hygiene ”.
4.1. CONTROL METHODS. CHEMICAL FACTORS
Methodical instructions
by reaction chromatographic determination
formaldehyde in water
These guidelines establish a method for quantitative reaction-chromatographic analysis of centralized drinking water supply to determine the formaldehyde content in it in the concentration range 0.02 - 10.0 mg / m3.
CH2O mol. weight 30.03
Formaldehyde is a colorless gas with a pungent, irritating odor. Melting point - 92 ° С, boiling point - 19 ° С. Let's well dissolve in water, ethanol and ether. Easy to polymerize.
Formaldehyde is generally toxic, irritating to the mucous membranes of the upper respiratory tract, eyes and skin. The maximum permissible concentration in the water of water bodies of domestic and drinking and cultural and domestic water supply is 0.05 mg / dm3, belongs to the 2nd hazard class.
1. Measurement error
The technique provides measurements with an error not exceeding ± 22%, with a confidence level of 0.95.
2. Measurement method
Formaldehyde concentration measurements are performed by reaction gas chromatography. The method is based on the reaction of formaldehyde with 2,4-dinitrophenylhydrazine in an acidic medium with the formation of 2,4-dinitrophenylhydrazone formaldehyde, followed by gas chromatographic analysis of the derivative on a chromatograph with a flame ionization detector.
The lower limit of measurement in the analyzed sample volume is 0.02 μg.
The determination does not interfere with hydrocarbons, alcohols, aldehydes, acids, phenols and other organic compounds.
3. Measuring instruments, auxiliary devices, materials, reagents
When performing measurements, the following measuring instruments, auxiliary devices, materials and reagents are used.
3 .1 . Funds measurements
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Gas chromatograph with flame ionization detector |
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Aneroid barometer M-67 |
TU 2504-1797-75 |
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Analytical balance VLA-200 |
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Measuring ruler |
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Measuring magnifier |
GOST 8309-75 |
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Mass measures |
GOST 7328-82E |
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Microsyringe type MSh-10M |
GOST 8043-75 |
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Laboratory glassware |
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Stopwatch SDS pr-1-2-000 |
GOST 5072-79 |
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Laboratory scale thermometer TL-2, measurement range 0 - 100 ° С, graduation 1 ° С |
3 .2 . Subsidiary devices
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Chromatography column made of stainless steel, 3 m long and 3 mm inner diameter |
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Bath water |
TU 64-1-2850-76 |
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Rotary vacuum evaporator |
MRTU 25-11-67-77 |
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Vacuum water jet pump |
GOST 10696-75 |
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Distiller |
TU 61-1-721-79 |
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Hydrogen reducer |
TU 26-05-463-76 |
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Oxygen reducer |
TU 26-05-235-70 |
3 .3 . Materials (edit)
3 .4 . Reagents
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Acetone, analytical grade |
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Distilled water |
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Hexane, chemically pure |
TU 6-09-4521-77 |
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2,4-dinitrophenylhydrazine, ch. |
TU 6-09-2394-77 |
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Iodine, analytical grade |
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Hydrochloric acid, chemically pure, pl. 1.19 g / cm3 |
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Soluble starch (amylodextrin), analytical grade |
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Sodium hydroxide, chemically pure |
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Sodium thiosulfate, analytical grade |
TU 6-09-2540-72 |
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Silicone SE-30, 5% on chromaton N-AW-DMCS with grain size 0.1 - 0.125 mm (Chemapol, Czech Republic) |
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Toluene, analytical grade |
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Formalin, 40% formaldehyde solution in water |
4. Safety requirements
4.1. When working with reagents, the safety requirements established for working with toxic, caustic and flammable substances in accordance with GOST 12.1.005-88 are observed.
4.2. When performing measurements using a gas chromatograph, the electrical safety rules are observed in accordance with GOST 12.1.019-79 and the instructions for using the device.
5. Requirements for the qualifications of operators
Only persons with qualifications of at least a chemical engineer with experience of working with a gas chromatograph are allowed to perform measurements.
6. Measurement conditions
When performing measurements, the following conditions are met.
6.1. The processes of preparation of solutions and preparation of samples for analysis are carried out under normal conditions in accordance with GOST 15150-69 at an air temperature of (20 ± 10) ° C, atmospheric pressure of 630 - 800 mm Hg. and air humidity no more than 80%.
6.2. Performing measurements on a gas chromatograph is carried out under the conditions recommended by the technical documentation for the device.
7. Preparing to take measurements
Before performing measurements, the following work is carried out: preparation of solutions, preparation of a chromatographic column, establishment of a calibration characteristic, selection and preparation of samples.
7 .1 . Preparation solutions
10% hydrochloric acid solution. 24.1 cm3 of acid (pl. 1.19 g / cm3) is placed in a volumetric flask with a capacity of 100 cm3, brought to the mark with distilled water and mixed thoroughly. The shelf life of the solution is 2 weeks.
2 M hydrochloric acid solution. 73 cm3 of acid (pl. 1.19 g / cm3) is placed in a volumetric flask with a capacity of 1000 cm3, brought to the mark with distilled water and mixed thoroughly. The shelf life of the solution is 2 weeks.
20% sodium hydroxide solution. Add 20 g of the reagent to a 100 cm3 volumetric flask, bring to the mark with distilled water and mix thoroughly. The shelf life of the solution is 30 days.
0.1 M iodine solution is prepared from the fixanal according to the attached instructions.
0.1 M sodium thiosulfate solution is prepared from the fixed channel.
0.5% starch 0.5 g of starch is placed in a volumetric flask with a capacity of 100 cm3, brought to the mark with water and mixed thoroughly. Prepare on the day of analysis.
The initial 1% formaldehyde solution for calibration is prepared from formalin. Place 26 cm3 of formalin in a volumetric flask with a capacity of 1000 cm3, bring to the mark with distilled water and mix thoroughly. The exact content of formaldehyde in the calibration solution is determined by the iodometric method. To 1.0 cm3 of 1% aqueous formaldehyde solution, add 10 cm3 of distilled water, 10 cm3 of 0.1 M iodine solution and dropwise 20% sodium hydroxide solution until a stable light yellow color is obtained. The flask is closed with a stopper and left for 10 minutes, after which 5 cm3 of a 10% hydrochloric acid solution is acidified, and after 10 minutes, adding a few drops of a 0.5% starch solution, the mixture is titrated with a 0.1 M sodium thiosulfate solution (working sample ).
The concentration of formaldehyde in the original solution is calculated by the formula:
С = (а - в) ∙ К, where
a - volume (cm3) of 0.1 M sodium thiosulfate solution used for titration of the control experiment;
c - volume (cm3) of 0.1 M sodium thiosulfate solution used for sample titration;
K - coefficient equal to 1.5 mg / cm3;
The shelf life of formaldehyde solution is 14 days in a dark glass bottle.
Working solution No. 1 of formaldehyde ( with= 10 mg / dm3) in distilled water is prepared from the original solution. The shelf life is no more than 7 days.
Working solution No. 2 of formaldehyde ( with= 0.1 mg / dm3). 1.0 cm3 of working solution No. 1 of formaldehyde ( with= 10 mg / dm3) is placed in a volumetric flask with a capacity of 100 cm3, brought to the mark with distilled water and mixed thoroughly. The solution is prepared on the day of analysis.
0.02% solution of 2,4-dinitrophenylhydrazine in 2 M hydrochloric acid. 50 mg of the reagent is introduced into a volumetric flask with a capacity of 250 cm3, brought to the mark with 2 M acid and mixed thoroughly. The shelf life of the solution is 30 days.
7 .2 . Training chromatographic columns
Before filling with the packing, the chromatographic column is washed with distilled water, acetone, hexane and dried in a stream of inert gas. The chromatographic column is filled with a nozzle using a vacuum water-jet pump. The ends of the column are covered with glass fiber and, without being connected to the detector, conditioned in a flow of carrier gas (nitrogen) at a flow rate of 40 cm3 / min at a temperature of 200 ° C for 12 hours. After cooling, the column is connected to the detector, the zero line is recorded in the operating mode. If there is no zero line drift, the dispenser is ready for operation.
The volume of the working solution of formaldehyde No. 1 ( with= 10 mg / dm3), cm3
The volume of the working solution of formaldehyde No. 2 ( with= 0.1 mg / dm3), cm3
The solutions are brought to a volume of 1.0 cm3 with distilled water (except for solution No. 6), then poured into a cone-shaped test tube with a capacity of 10 cm3 and, after stratification of the liquid, the lower aqueous layer is taken with a pipette and discarded. The upper toluene layer containing 2,4-dinitro-phenyltidrazone formaldehyde is evaporated to dryness on a rotary evaporator (in a stream of nitrogen) in a water bath to 35-40 ° C. Toluene 50 mm3 is added to the yellow-red precipitate with a microsyringe and the solution is stirred until the precipitate is completely dissolved. 2 mm3 of the resulting solution is introduced into the evaporator of the chromatograph for analysis under the following conditions:
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Column oven temperature |
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Evaporator temperature |
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Detector temperature |
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Carrier gas consumption (nitrogen) |
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Hydrogen consumption |
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Air consumption |
250 cm3 / min |
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Amplifier current scale |
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Chart tape speed |
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Retention time of 2,4-dinitrophenylhydrazone formaldehyde |
2 min 5 sec |
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Toluene retention time |
35 sec 7.3). 9. Calculation of measurement resultsThe concentration of formaldehyde in water (mg / dm3) is calculated by the formula: m- the mass of formaldehyde in the sample, found by the calibration characteristic, μg; V- volume of water sample taken for analysis, cm3. Methodological guidelines were developed by A.G. Malysheva (A.N.Sysin Research Institute of Human Ecology and Environmental Hygiene, Russian Academy of Medical Sciences), A.A. Bezzubov, Yu.S. Drugov (Analytical Center of the Geological Institute of the Russian Academy of Sciences). |
Group K29
INTERSTATE STANDARD
FURNITURE, WOOD AND POLYMER MATERIALS
Method for determining the release of formaldehyde and other harmful volatiles
chemicals in climatic chambers
Furniture, timber and polymers.
Method for determination of formaldehyde and other volatile chemicals in
the air of climatic chambers
OKS 79.97.140
Date of introduction
Foreword
1 DEVELOPED by the All-Russian Design Technological Institute of Furniture (VPKTIM), the All-Russian Research Institute of the Woodworking Industry (VNIIDrev) and the Scientific and Practical Center for Hygienic Expertise of the State Committee for Sanitary and Epidemiological Supervision of Russia
INTRODUCED by the Technical Secretariat of the Interstate Council for Standardization, Metrology and Certification
2 ACCEPTED by the Interstate Council for Standardization, Metrology and Certification
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State name |
Name of the national standardization body |
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Republic of Belarus |
Belstandard |
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The Republic of Moldova |
Moldovastandart |
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The Republic of Kazakhstan |
Gosstandart of the Republic of Kazakhstan |
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State Standard of Ukraine |
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the Russian Federation |
Gosstandart of Russia |
3 By the Resolution of the Committee of the Russian Federation for Standardization, Metrology and Certification of 23.08.95 N 448, the interstate GOST standard was put into effect directly as a state standard of the Russian Federation from July 1, 1996
4 INTRODUCED FOR THE FIRST TIME
1 AREA OF USE
This standard establishes a method for determining in climatic chambers the release of formaldehyde and other harmful volatile substances into the air from furniture products, chipboard and fiberboard, plywood, parts and blanks from them, parquet products, as well as polymeric, structural , facing, finishing and adhesive materials.
GOST 8.207-76 GSI. Direct measurements with multiple observations. Methods for processing observation results. Basic Provisions
GOST 1770-74 Laboratory glassware. Cylinders, beakers, flasks, test tubes. Technical conditions
GOST 3117-78 Acetic ammonium. Technical conditions
GOST 3118-77 Hydrochloric acid. Technical conditions
GOST Soluble starch. Technical conditions
GOST Acetylacetone. Technical conditions
GOST Furniture. General specifications
GOST Chairs for auditoriums. General specifications
GOST Furniture for sitting and lying. General specifications
GOST Furniture for educational institutions... Technical conditions
3 TEST TOOLS AND ACCESSORIES
3.1 Climatic chambers with a working space from 0.12 to 50 m
3.1.1 The design of the chamber should ensure tightness, automatic regulation of temperature and humidity. For lining the inner surfaces of the chamber, materials with low sorption capacity (stainless metal, glass) must be used.
3.1.2 The ventilation system should ensure uniform air circulation throughout the entire working volume of the chamber with installed samples.
3.1.3 The following parameters should be maintained in the working volume of the chamber during the tests:
air temperature - (23 ± 2) ° С;
relative air humidity - (45 ± 5)%;
air exchange per hour - 1 ± 0.1.
Testing of parquet products is carried out with air exchange (0.5 ± 0.05) per hour.
3.2 Aspiration device with a flow meter for determining the speed or volume of air.
3.3 Absorption devices such as Polezhaev, Richter, with porous plates.
3.4 Chromatographs, spectrophotometers, electrophoto colorimeters, ensuring the determination of the content of a volatile chemical in the sampled air (selected depending on the type of analyte).
3.5 Laboratory balance with a maximum weighing limit of 500 g with a weighing error of ± 0.02 g.
3.6 Analytical balance with a maximum weighing limit of 200 g with a weighing error of ± 0.0005 g.
3.7 Aneroid barometer.
3.8 Stopwatch with 0.2 second divisions.
3.9 Psychrometer or other device for monitoring air temperature and humidity.
3.10 Universal measuring instruments for measuring the dimensions of samples with an accuracy of ± 1 mm.
3.11 Measuring instruments, auxiliaries, materials, chemical reagents, laboratory glassware - in accordance with the methods for determining harmful volatile chemicals approved by the sanitary and epidemiological supervision authorities.
4 COLLECTION AND PREPARATION OF SAMPLES
4.1 To test furniture products, samples are taken in an amount that creates a given saturation of the chamber volume:
For cabinet furniture, tables, beds - 1 m of the sample surface area per 1 m of the volume of the climatic chamber;
For furniture items for sitting and lying - 0.3 m of the sample surface area per 1 m of the volume of the climatic chamber.
The surface area of the samples is calculated with an error of ± 3%. It includes the total area from 2 sides of all furniture parts (surfaces of the rear walls, the bottom of drawers, shelves, surfaces behind mirrors, plugs in furniture for sitting and lying, etc.).
Tests in a climatic chamber, as a rule, are subjected to furniture items selected for physical and mechanical tests in accordance with the requirements of GOST 16371, GOST 19917, GOST 22046, GOST 16854.
4.2 To test parts and blanks, parquet products, as well as structural, facing, finishing and adhesive materials, at least 3 samples are taken, made in accordance with the technical documentation.
4.2.1 Paints and varnishes are applied to the surface of glass, tin or wood according to the consumption rates used in the production of materials, parts and products.
4.2.2. Adhesive materials are applied to the surface of glass, tin or wood according to the consumption rates used in production, and a sample of the material for which the adhesive is intended is glued.
4.2.3 Samples of wood-based panels and plywood are taken from the zone of the panel, spaced from its edges at a distance of at least 300 mm.
4.2.4 Samples of polymer and facing materials are presented with dimensions that create a given saturation.
4.2.5 The area of the sample (in layers on both sides) intended for testing in chambers with a volume of 0.12 to 1 m inclusive is calculated with an error of ± 3%, based on the saturation of 1 m of the sample surface area per 1 m of the chamber volume.
The area of samples of parquet products is determined only from the front side. The saturation for parquet products is taken equal to 0.4 m of the sample surface area per 1 m of the chamber volume. The dimensions of the samples in length and width are determined based on the internal dimensions of the climatic chambers.
4.2.6 If the assessment of the release of harmful volatile chemicals through the layers is carried out, then the edges of the samples should have a sealed protective coating (edging plastic, aluminum foil glued with silicate glue, etc.).
The edges of samples of parquet products do not protect.
4.2.7 Transportation and storage of samples - in accordance with the regulatory documents for the tested products, materials.
4.3 Testing of samples made with adhesives or adhesive joints is carried out no earlier than 7 days after their manufacture, unless otherwise specified in the regulatory documents.
Before testing, furniture products made of wood and wood materials are kept for at least 3 days in a room with a relative humidity of 45 to 70% and a temperature of 15 to 30 ° C.
4.4 Samples submitted for testing must be accompanied by a passport containing their characteristics (Appendix A).
5 TESTING
5.1 Test preparation
5.1.1 Testing of chipboard, fibreboard, plywood, parts and blanks from them, parts of parquet products, construction, facing, finishing, polymer and adhesive materials is carried out in climatic chambers with a volume of 0.12 to 1 m inclusive.
Testing of furniture items is carried out in chambers with a volume of more than 1 m , allowing you to place these products in accordance with the specified conditions.
5.1.2 The samples are placed in the chamber on a stand or in another way that provides free air circulation, while the contact area should not exceed 0.5% of the sample surface area.
5.1.3 Samples of parquet products are placed on the floor of the chamber, the front surface of the samples should be turned up. Another way of installing the samples is allowed, while their non-working surface must be protected by a gas-tight material (foil, etc.).
5.1.4 Furniture items are placed in the chamber, evenly distributing them over the floor area. Products should be located at a distance of at least 0.1 m from each other and from the walls of the chamber. Doors of products must be open at an angle of at least 30 °, drawers extended by at least a third of their length.
5.1.5 In chambers with a volume of more than 1 m (Figure 1), fix the air sampling tubes and connect them to the appropriate outlets of the chamber.
In chambers with a volume of up to 1 m inclusive, air sampling can be carried out through one outlet.
5.1.6 After placing the samples, close the chamber doors hermetically. The air conditioning and ventilation system is switched on, and after reaching the preset parameters, the automatic mode of operation of the chamber is set.
The control of the operating parameters of the air is carried out by the instruments included in the design of the chamber, and by the control device, which operates autonomously.
5.2 Carrying out tests in chambers with a volume of up to 1 m inclusive
5.2.1 Throughout the test, air samples are taken from the working volume of the chamber at a predetermined frequency.
The first air sampling is carried out 24 hours after the stabilization of the air parameters in the chamber in accordance with the requirements of 3.1.3. The second, third and subsequent sampling is carried out every 24 hours within 5 days from the beginning of the test.
5.2.2 In such a case, when, based on the results of three successive sampling, it is established that the concentration of volatile substances in the chamber is constant (i.e., the standard deviation of the measurement results is not more than 15%), the test is stopped before the expiration of 5 days.
5.2.3 Simultaneously with sampling from the climatic chamber, the air supplied to the chamber is taken.
5.2.4 Air sampling is carried out using an aspiration device (3.2) and absorption devices (3.3), selected depending on the type of controlled substances and the method for determining their concentration.
5.2.5 Air samples are analyzed on the day of sampling in accordance with the methods for measuring the concentration of harmful volatile chemicals approved by the sanitary and epidemiological surveillance authorities. To determine the concentration of harmful volatile chemicals, photoelectric colorimeters, spectrophotometers or chromatographs of any type are used, which provide the necessary resolution and measurement error (3.4 and 3.5).
5.2.6 The procedure for determining formaldehyde with an acetylacetone reagent (colorimetric method) is given in Appendix B. To determine the concentration of formaldehyde, use a spectrophotometer or photoelectrocolorimeter.
5.2.7 The measurement results are recorded in the work log.
5.3 Testing of furniture items in chambers with a volume of more than 1 m
5.3.1 The first air sampling from the chamber and control air sampling at the entrance to the chamber shall be carried out 72 hours after the establishment of the operating mode of the air in the chamber.
5.3.2 Subsequent air sampling is carried out every 24 hours.
5.3.3 In the event that, based on the results of three successive samplings, it is established that the concentration of monitored volatile substances is constant (the standard deviation of the measurement results does not exceed 15%), the test is stopped.
After 21 days, the test is stopped regardless of the concentration of the monitored volatile substances.
5.3.4 Air sampling is carried out at six points shown in Figure 1, located at two levels of the chamber height.
I - air sampling levels (750; 1500 mm); // - tubes for sampling
air from the chamber; 1 ; 2; 3; 4; 5; 6 - air sampling points
Picture 1
At each level, three points are determined, evenly distributed along the length and width of the chamber.
It is allowed to take air samples from a smaller number of points, but not less than two located on different levels heights.
5.3.5 Air sampling and analysis is carried out in accordance with 5.2.3-5.2.7.
6 PROCESSING OF TEST RESULTS
6.1 The concentration of volatile chemicals in the air of the climatic chamber in milligrams per cubic meter is calculated in accordance with the measurement procedures for controlled substances (5.2.5).
6.2 The absolute value of the concentration of the volatile chemical released by the test sample into the air of the climatic chamber is calculated by the formula
where is the concentration of volatile matter in the air of the climatic chamber, mg / m;
Concentration of volatile matter in the air entering the chamber, mg / m.
6.3 The concentration value of a volatile chemical released into the air of a climatic chamber with a volume of up to 1 m inclusive is found as the arithmetic mean of the test results of at least three samples according to the formula
where is the number of repetitions of the observation.
6.4 The standard deviation of the measurement results,%, is determined by the formula
. (3)
6.5 Concentration of volatile chemical for each measurement carried out in accordance with 5.3.1, 5.3.2 and 5.3.4 in chambers with a volume of more than 1 m3 , is determined as the arithmetic mean of the measurement results at different points of the camera according to the formula (2).
6.6 The final value of the concentration of a harmful volatile chemical in climatic chambers with a volume of more than 1 m3 when testing furniture products is calculated as the arithmetic mean () measurement results for the last three air sampling, calculated by formulas (1) and (2). The standard deviation is determined by the formula (3).
In the case when the concentration of a substance is constant (5.3.3) in three successive measurements, the arithmetic mean value is taken as a characteristic of the controlled parameter.
In the case when the concentration of a substance is not constant (decreases or increases), the concentration value obtained at the last selection and calculated by formula (1) is taken as the characteristic.
6.7 Evaluation of the test results is carried out by comparing them with the maximum permissible concentrations of harmful substances in the atmospheric air, approved in the prescribed manner by the bodies of the State Sanitary and Epidemiological Surveillance.
6.8 The samples are considered to have passed the test if the results obtained are less than or equal to the standards established in the regulatory documents for the product.
6.9 The test results are documented in a protocol (Appendix B).
Form of the passport of the sample submitted for testing
THE PASSPORT
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name of the sample, product, set of furniture, project, designation, |
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index (if available) |
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Manufacturer's (customer's) name | |
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Sample production date | |
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Name of product regulatory documents | |
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for products and materials |
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Characteristics of samples:
The sample was made using the following materials:
1 Plate
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Material name |
Designation (brand) according to ND |
formaldehyde emissions by punch |
Sample size, |
Note* |
Wood-shaving
Fiberboard
* If necessary, indicate the type of binder and other characteristic features of the sample.
2 Facing materials, flooring and other polymeric materials
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Material name |
Designation of normative documents |
Basic chemical composition (if necessary) |
Sample size, |
Intelligence about permission to use |
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Material name |
Designation of normative documents |
Sample size, |
Intelligence about permission material to use |
Note - Depending on the type and purpose of the test, other information is given in agreement with the testing laboratory.
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Signatures of the customer's manager and the person in charge for communication with the testing laboratory (center), decryption of signatures, date |
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APPENDIX B
(required)
PROCEDURE FOR DETERMINING FORMALDEHYDE
WITH ACETYL ACETONE REAGENT
B.1 SCOPE
This method is designed to determine the concentration of formaldehyde in the air of residential premises and climatic chambers.
B.2 ESSENCE AND CHARACTERISTIC OF THE METHOD
The method is based on the reaction of interaction of formaldehyde with an acetylacetone reagent in an ammonium acetate medium with the formation of a yellow colored product.
The lower limit of detection for formaldehyde is 0.001 mg in 10 cm3 of the analyzed solution.
The error of determination is ± 10%.
The range of measured concentrations of formaldehyde in atmospheric air, indoor air and climatic chambers is from 0.008 to 1.3 mg / m with air sampling not less than 120 dm3.
Methyl and ethyl alcohols, ethylene glycol, hydrogen sulfide, and ammonia do not interfere with the determination of formaldehyde.
B. C MEASURING DEVICES AND ACCESSORIES
B.3.1 Aspiration device providing an air flow rate of 2 dm3 / min.
B.3.2 Spectrophotometer or photoelectric colorimeter with a light filter with a maximum light absorption at a wavelength of 412 nm and a cuvette with a working layer width of 10 mm.
B.3.3 Volumetric flasks 50, 250 and 1000 cm in accordance with GOST 1770.
B.3.4 Conical flasks 100 cm in accordance with GOST 1770.
B.3.5 Absorption devices such as Polezhaev, Richter.
B.4 REAGENTS AND SOLUTIONS
B.4.1 Acetylacetone, analytical grade according to GOST 10259.
B.4.2 Acetic acid, glacial x. h
B.4.3 Ammonium acetate, analytical grade according to GOST 3117.
B.4.4 Formalin, 40% formaldehyde solution.
B.4.5 Sodium hydroxide, analytical grade 30% solution.
B.4.6 Hydrochloric acid, conc. p.a. according to GOST 3118, diluted 1: 5.
B.4.7 Sodium sulfate NSO · fixanal, 0.1N solution.
B.4.8 Iodine, fixed 0.1 N solution.
B. 4.9 Soluble starch according to GOST 10163, 1% solution.
B.4.10 Acetylacetone reagent: Dissolve 200 g of ammonium acetate in 800 ml of water in a 1 L volumetric flask. To the solution are added 3 cm3 of acetylacetone, 5 cm3 of acetic acid, and the solution in the flask is brought up to the mark with water (absorption solution).
B.4.11 Stock solution for calibration: 5 ml of formalin is introduced into a 250 ml volumetric flask and brought to the mark with water. Then determine the content of formaldehyde in this solution. To do this, 5 cm of solution is placed in a 250 cm conical flask with a ground stopper, 20 cm of 0.1 N iodine solution is poured in and a 30% sodium hydroxide solution is added dropwise until a stable pale yellow color appears. The flask is left for 10 minutes, then a solution of 2.5 ml of hydrochloric acid (diluted 1: 5) is carefully acidified, left for 10 minutes in the dark, and the excess of iodine is titrated with 0.1 N sodium thiosulfate solution. When the solution turns light yellow, add a few drops of starch. Pre-set the amount of thiosulfate consumed for the titration of 20 cm of 0.1 N iodine solution. From the difference between the amount consumed for the control titration and the excess of iodine that did not react with formaldehyde, the amount of iodine that went into the oxidation of formaldehyde is determined. 1 cm of 0.1 N iodine solution corresponds to 1.5 mg of formaldehyde. Having established the formaldehyde content in 1 cm of the solution, the initial and working solutions of formaldehyde are prepared by appropriate dilution with water with a content of 0.1 mg / cm and 0.01 mg / cm, respectively. The content of formaldehyde in solutions is determined titrometrically.
B.5 SAMPLING
B.5.1 When testing polymeric materials and products in climatic chambers, sample preparation and sampling procedure are carried out in accordance with Sections 4 and 5 of this standard.
B.5.2 To determine the maximum one-time concentration of formaldehyde in the air of a climatic chamber or an enclosed space, air is aspirated at a rate of 2 dm3 / min in a volume of 60-120 dm3 through two series-connected absorption devices such as Polezhaev, Richter, filled with 7 cm of absorbing solution and 3 cm distilled water. The sampling process produces a non-volatile formaldehyde derivative.
B.5.3 At the same time, a control sample of the air supplied to the climatic chamber is taken.
Sampling is carried out in accordance with 5.2.
B.6 STROKE OF ANALYSIS
B.6.1 The taken samples are placed in a water bath heated to 40 ° С and kept for 30 min.
B.6.2 After cooling the samples, measure the optical density of the colored solutions using a spectrophotometer or photoelectrocolorimeter at a wavelength of 412 nm in cuvettes with a working layer width of 10 mm. Evaluation of the quantitative content of formaldehyde in the sample is carried out according to the calibration characteristic.
B.7 ESTABLISHMENT OF THE GRADING CHARACTERISTICS
B.7.1 Add a working solution of formaldehyde (B.4.11) into a 10 cm measuring tube with a 2 cm pipette, add water with a 5 cm pipette, bring the absorbent solution to the mark and prepare solutions for calibration in accordance with Table B.1 (when determining low concentrations of formaldehyde) and Table B.2 (when determining high concentrations of formaldehyde).
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Solutions, cm | ||||||||
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Working solution of formaldehyde with a content of 0.01 mg / cm | ||||||||
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Acetylacetone reagent |
7 cm in each tube |
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Note - When preparing solutions 1 and 2, use a capillary pipette or an automatic microdispenser.
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Solutions, cm |
Calibration solution numbers |
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Stock solution of formaldehyde with a content of 0.1 mg / cm | ||||||||
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Acetylacetone reagent |
7 cm in each tube |
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B.7.2 The solutions for calibration are heated in a water bath for 30 min at T - 40 ° C, cooled and the optical density is measured in them (wavelength is 412 nm, the width of the working layer of the cuvette is 10 mm). - atmospheric pressure, mbar;
- air sample volume, m;
Optical density of the analyzed sample, calculated as the difference between the sum of the optical densities of the analyzed solutions in 2 absorbers and zero (blank) solution;
0.00371 - normalization factor.
Test report form
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name of the accredited testing laboratory (center) |
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number and date of the accreditation certificate in the GOST R certification system |
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mailing address and telephone number of the testing laboratory (center) |
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APPROVED Head of the testing laboratory (center) | |||||||||||||||||
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full name | |||||||||||||||||
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PROTOCOL N |
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test type |
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name and designation of the tested samples |
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1 Manufacturer | |||||||||||||||||
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name and address |
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2 Date of manufacture and sampling | |||||||||||||||||
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3 Basis for the test | |||||||||||||||||
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number and date of letter |
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(contract) of the customer |
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4 Designation of regulatory documents for products | |||||||||||||||||
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5 Defined indicators | |||||||||||||||||
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list of identified |
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monitored indicators |
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6 List (designation) of regulatory documents |
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on test methods | |||||||||||||||||
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7 List of approved test equipment | |||||||||||||||||
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designation, number and date of the certificate (certificate, stamps) |
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8 Sample characteristics | |||||||||||||||||
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9 Test conditions | |||||||||||||||||
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temperature and relative |
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air humidity in the chamber, saturation, air exchange |
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10 Test results | |||||||||||||||||
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text or tables |
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with indication of standard values |
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11 Conclusion | |||||||||||||||||
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Performers' signatures |
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position |
full name |
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The text of the document is verified by:
official publication
Moscow: IPK Standards Publishing House, 1995
Foreword
The goals and principles of standardization in the Russian Federation are established by the Federal Law of December 27, 2002 No. 184-FZ "On technical regulation", and the rules for the application of national standards of the Russian Federation - GOST R 1.0 - 2004 "Standardization in the Russian Federation. Basic Provisions "Information about the standard 1. PREPARED by the Open Joint-Stock Company" Scientific Research Center for Control and Diagnostics of Technical Systems "(JSC" NIC KD ") on the basis of its own authentic translation of the standard specified in paragraph 4 2. SUBMITTED by the Technical Committee for Standardization TC 457 "Air quality" 3. APPROVED AND PUT INTO EFFECT by the Order of the Federal Agency for Technical Regulation and Metrology dated December 27, 2007 No. 590-st 4. This standard is identical to the international standard ISO 16000-3: 2001 "Air in enclosed spaces. Part 3. Determination of the content of formaldehyde and other carbonyl compounds. Active sampling method "(ISO 16000-3: 2001" Indoorair - Part 3: Determination of formaldehyde and other carbonyl compounds - Active sampling method "). When applying this standard, it is recommended to use, instead of the reference international standards, the corresponding national standards, information about which is given in Appendix C 5. INTRODUCED FOR THE FIRST TIME Information on changes to this standard is published in the annually published information index "National Standards", and the text of changes and amendments - in the monthly published information indexes "National Standards". In case of revision (replacement) or cancellation of this standard, the corresponding notice will be published in the monthly published information index "National standards". Relevant information, notice and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet
| 1. Scope 2. Normative references 3. Essence of the method 4. Restrictions and interfering substances 4.1. General provisions 4.2. Interfering effect of ozone 5. Safety requirements 6. Apparatus 7. Reagents 8. Preparation of reagents and cartridges 8.1. Purification of 2,4-dinitrophenylhydrazine 8.2. Preparation of DNPH-derivative of formaldehyde 8.3. Preparation of stock solutions of DNPH-formaldehyde derivative 8.4. Preparation of cartridges coated with silica gel DNFG 9. Procedure 9.1. Sampling 9.2. Blank samples 9.3. Analysis of samples 10. Calculation of measurement results 11. Efficiency criteria and quality control of measurement results 11.1. General provisions 11.2. Standard operating procedures 11.3. HPLC System Efficiency 11.4. Sample loss 12. Precision and uncertainty Appendix A (informative) Precision and uncertainty Appendix B (informative) Melting points of DNPH derivatives of carbonyl compounds Appendix C (informative) Information on the compliance of national standards of the Russian Federation with reference international standards Bibliography |
Introduction
This International Standard applies to the analysis of indoor air during sampling in accordance with ISO 16000-2. The standard is used to determine the content of formaldehyde and other carbonyl compounds. The standard was tested against 14 aldehydes and ketones. Formaldehyde is the simplest carbonyl compound, made up of one carbon, one oxygen, and two hydrogen atoms. In its pure form in a monomolecular state, it is a colorless, with a pungent odor, reactive gas. Formaldehyde is used in the production of urea-formaldehyde polymers, adhesives and insulation foams. The main source of formaldehyde in indoor air is its release from chipboards and insulation materials used in construction. Sampling for formaldehyde determination is carried out by pumping air through a reactive medium, which results in the formation of a derivative with a lower vapor pressure, which is more efficiently retained in the sampling device and can be analyzed more easily. This standard establishes a method for the determination of formaldehyde and other carbonyl compounds, which is based on the reaction of these compounds with 2,4-dinitrophenyl-hydrazine applied to a sorbent to convert them into the corresponding hydrazones, which can be recovered, and their content is measured with a high sensitivity, precision and accuracy. The method described in this International Standard is also used to determine other carbonyl compounds released into the air by solvents, binders, cosmetics and other sources. The sampling methodology given in this standard is based on the TO-11 A method [1]. When applying the methodology specified in this standard, it should be borne in mind that formaldehyde and some other carbonyl compounds are highly toxic substances [2].
NATIONAL STANDARD OF THE RUSSIAN FEDERATION
Date of introduction - 2008-10-01
1 area of use
This International Standard specifies a method for the determination of formaldehyde (HCHO) and other carbonyl compounds 1) (aldehydes and ketones) in air. The method used for the determination of formaldehyde, after appropriate modification, is used for the detection and quantitative determination of other carbonyl compounds (at least 13 compounds). The method is used to determine formaldehyde and other carbonyl compounds in the range of mass concentration values from approximately 1 μg / m 3 to 1 mg / m 3. Using the method specified in the standard, a time-averaged sample is obtained. The method can be used both for long-term (from 1 to 24 hours) and short-term (from 5 to 60 minutes) air sampling to determine the formaldehyde content in it. This International Standard specifies the sampling and analysis of air samples to determine the content of formaldehyde and other carbonyl compounds in it by capturing them from the air using cartridges coated with 2,4-dinitrophenylhydrazine (DNPH) and subsequent analysis by the method of high efficiency liquid chromatography(HPLC) with ultraviolet (UV) detector [1], [3]. The method described in the standard is specially designed for sampling and analysis of samples for determining the content of formaldehyde in air using a cartridge filled with an adsorbent, followed by HPLC. The method is also applicable for determining the content of other aldehydes and ketones in the air. 1) In this standard, common names of compounds are given instead of names according to the PAC ID nomenclature given in parentheses: formaldehyde (methanal); acetaldehyde (ethanal); acetone (propane-2-one); butyraldehyde (butanal); crotonaldehyde (2-butenal); isovaleric aldehyde (3-methylbutanal); propionic aldehyde (propanal); m - toluyl aldehyde (3-methylbenzaldehyde); o - toluyl aldehyde (2-methylbenzaldehyde); p - toluyl aldehyde (4-methylbenzaldehyde); valeraldehyde pentanal - The method described in this part of ISO 10993 is used to determine the following carbonyl compounds:2. Normative references
This standard uses normative references to the following standards: ISO 9001: 2000 Quality management systems. ISO 16000-1 requirements, Air in confined spaces. Part 1. Sampling. General provisions ISO 16000-2, Air in confined spaces. Part 2. Methodology for sampling formaldehyde ISO 16000-4 Indoor air. Part 4. Determination of formaldehyde. Diffusion sampling method ISO 17025: 2005 General requirements to the competence of testing and calibration laboratories3. The essence of the method
This standard specifies a method for pumping air through a cartridge containing silica gel coated with DNPH. The method is based on the specific reaction of the carbonyl group of the analyzed compound with DNPH in the presence of an acid with the formation of stable derivatives (Figure 1). The starting aldehydes and ketones are determined by their DNPH-derivatives by HPLC using a UV detector or a diode array detector. Other carbonyl compounds can be determined by the indicated detection methods according to 9.3.5. This International Standard provides guidance for preparing sampling cartridges based on commercially available chromatography cartridges containing silica gel by adding acidified DNPH to each cartridge. It is recommended to use commercially available cartridges containing silica gel coated with DNPH, since they are more uniform and have a low level of blank readings. However, commercially available cartridges must be checked for compliance with this standard before use. Another advantage of commercially available cartridges is that they contain silica gel with a larger particle size, which results in less air pressure drop in the cartridge. These low pressure drop cartridges can be useful for sampling breathing air using battery powered pumps.
R is an alkyl or aromatic group for ketones, or H for aldehydes; R "is an alkyl or aromatic group for ketones.
Figure 1 - Scheme of the reaction of carbonyl compounds with DNPH
4. Restrictions and interfering substances
4.1. General Provisions
The requirements of this standard have been confirmed by taking air samples for a flow rate not exceeding 1.5 l / min. This flow limitation is due to the high pressure drop (over 8 kPa at 1.0 L / min) through a user-prepared silica cartridge with a particle size of 55 to 105 µm. These cartridges are not compatible with battery powered pumps used for sampling breathing air (eg for industrial hygiene purposes). For the selection and analysis of air samples to determine the formaldehyde content in it, a specific sampling method for a solid sorbent is used. Difficulties may arise in the implementation of the method due to the presence of some isomers of aldehydes or ketones, which cannot be separated by HPLC in the analysis of other aldehydes and ketones. Interfering substances are also organic compounds that have the same retention time and significant absorption at 360 nm as DNPH, a formaldehyde derivative. The influence of interfering substances can be eliminated by changing the separation conditions (for example, using other HPLC columns or changing the composition of the mobile phase). There is often a problem of formaldehyde contamination of DNPH. In such cases, DNPH is purified by repeated recrystallization from acetonitrile, which is pure in the UV region of the spectrum. The recrystallization is carried out at a temperature of 40 ° C to 60 ° C by slowly evaporating the solvent to obtain crystals of the maximum size. The content of impurities of carbonyl compounds in DNPH is preliminarily determined by HPLC, and it should be no more than 0.15 μg per cartridge. DNPG-coated sampling cartridges should not be exposed to direct sunlight to avoid the appearance of spurious peaks [4]. This technique is not used to accurately quantify acrolein in air. Inaccurate results of quantitative determination of acrolein may be due to the appearance of several peaks of its derivatives and the instability of the peak ratios [5]. NO 2 reacts with DNPH. The high content of MO 2 (for example, when using gas stoves) can lead to problems, since the retention time of its DNPH - derivative may coincide with the retention time of DNPH - formaldehyde derivative, depending on the HPLC column and analysis parameters [6], [7] , [ eight].4.2. Interfering effects of ozone
Special precautions should be taken if high levels of ozone in the air are expected in the sampling area (eg from office copiers). The presence of ozone leads to an underestimation of the result of determining the content of analytes, since in the cartridge it reacts with both DNPH and its derivatives (hydrazones) [9]. The degree of interfering effect depends on changes in ozone and carbonyl compounds over time, as well as on the duration of sampling. A significant underestimation of the determination result (negative interfering effect of ozone) was observed even at the values of the mass concentration of formaldehyde and ozone corresponding to clean atmospheric air (2 and 80 μg / m 3, respectively) [10]. During the analysis, the presence of ozone in the sample can be judged by the appearance of new compounds, the retention time of which is shorter than the retention time of formaldehyde hydrazone. Figure 2 shows chromatograms of formaldehyde-enriched air with and without ozone. The simplest solution to reduce the interfering effect of ozone is to remove it before the bleed air reaches the cartridge. This can be achieved with an ozone trap or ozone scrubber upstream of the cartridge. Use commercially available ozone traps and scrubbers. Also, the ozone trap can be made from a copper tube 1 m long, 0.64 cm in outer diameter and 0.46 cm in inner diameter, which is filled with a saturated aqueous solution of potassium iodide, left for several minutes (for example, 5 minutes), then the solution is drained and the tube dried in a stream of clean air or nitrogen for about 1 hour. The throughput of such an ozone removal device is about 200 μg / m 3 per hour. The analyzed aldehydes (formaldehyde, acetaldehyde, propionic aldehyde, benzaldehyde, and n - toluyl aldehyde), introduced into the sampled air flow in a dynamic mode, passed through the ozone trap practically without losses [11]. Serially produced ozone scrubbers, which are a cartridge filled with granular potassium iodide weighing from 300 to 500 mg, are also effective for ozone removal [12].
X - unknown connection; 0 - DNFG; 1 - formaldehyde; 2 - acetaldehyde; a - with ozone; b - without ozone
Figure 2 - Examples of chromatograms for formaldehyde in an air stream with and without ozone
5. Safety requirements
5.1. This International Standard does not specify all the safety requirements that must be met in its application. The user of the standard should develop appropriate safety and health measures, taking into account the requirements of legal acts. 5.2. DNPH is explosive when dry and should be handled with extreme care. It is also toxic, mutagenic in some experiments, and irritant to the eyes and skin. 5.3. Perchloric acid with a mass fraction of less than 68% is stable and does not oxidize at room temperature. However, it readily dehydrates at temperatures above 160 ° C, which can lead to an explosion if it comes into contact with alcohols, wood, cellulose and other oxidizable materials. It should be stored in a cool, dry place and only used with extreme care in a fume hood.6. Apparatus
In addition to the usual laboratory equipment, the following equipment is used. 6.1. Sampling 6.1.1. Sample cartridge, filled with silica gel, coated with DNPH, prepared in accordance with Section 8 or commercially available. The cartridge must contain at least 350 mg of silica gel, and the mass fraction of DNPH applied to it must be at least 0.29%. The ratio of the diameter of the silica gel layer to its thickness should be no more than 1: 1. The permissible load of the cartridge for the determination of formaldehyde must be at least 75 μg, and the collection efficiency must be at least 95% at an air flow rate of 1.5 l / min. Low blank and high performance sampling cartridges are available commercially. NOTE At an air flow rate of 1.5 l / min, the pressure drop across the user prepared cartridge has been observed to be approximately 19 kPa. Some commercially available pre-coated DNPH cartridges have a lower pressure drop, allowing battery-powered pumps to be used for sampling in the breathing zone. 6.1.2. Air sampling pump providing accurate and precise flow rates in the 1.0-1.5 L / min range. 6.1.3. A flow regulator, flow meter, flow regulator or similar device for measuring and regulating the air flow through a sampling cartridge in the range of 0.50 - 1.20 l / min. 6.1.4. A flow calibrator, such as a rotameter, a soap bubble meter, or a liquid-sealed drum gas meter. 6.2. Sample preparation 6.2.1. Cartridge containers, borosilicate glass tubes (20 to 125 mm long) with PP screw caps, or other containers suitable for transporting loaded cartridges. 6.2.2. Polyethylene gloves for carrying silica gel cartridges. 6.2.3. Shipping containers, metal boxes (4 L capacity) with a sealed lid, or other suitable containers with bubble wrap or other suitable filler to retain and cushion the impact of sealed cartridge containers. NOTE To store sample cartridges, use a thermally sealed plastic bag with foil interlayers supplied with commercially available cartridges coated with DNPH. 6.2.4. Device for applying DNPG to cartridges The syringe rack is an aluminum plate (dimensions 0.16 × 36 × 53 cm) with four adjustable legs. Plate with round holes (5 × 9 holes) slightly larger than the diameter of 10 ml syringes, symmetrically positioned from the center of the plate, allows cleaning, DNPH application and / or sample elution for 45 cartridges (see Figure 3) ...
a - a device for applying DNFG; b - device for drying cartridges; 1_ glass syringe with a capacity of 10 ml; 2 - rack for syringes; 3 - cartridges; 4 - drain glass; 5 - stream N 2; 6 - fitting for syringes; 7 - waste cup
Figure 3 - Devices for applying DNPH and drying cartridges for sampling
6.2.5. Cartridge dryer with gas inlets and multiple fittings for standard syringes (see Figure 3). Note - The equipment specified in 6.2.4 and 6.2.5 is required only if the user independently manufactures cartridges with applied DNFG 6.3. Sample analysis 6.3.1. The HPLC system consists of a mobile phase vessel, a high pressure pump, an injection valve (automatic dispenser with a loop volume of 25 μL or other suitable loop volume), a C-18 reversed phase column (e.g. 25 cm long, 4.6 mm, filler particle size 5 μm), a UV detector or a diode array detector operating at a wavelength of 360 nm, a data processing system or an electric recording instrument. DNPH-formaldehyde derivative is determined by reverse phase HPLC in isocratic eluent mode based on the readings of a UV absorbance detector operating at 360 nm. The blank cartridges are stripped and analyzed in the same way. Formaldehyde and other carbonyl compounds in the sample are identified and quantified by comparing their retention times and the height or area of the peaks obtained by analyzing the sample and analyzing the calibration solutions. NOTE Most commercially available HPLC analytical systems are suitable for this purpose. 6.3.2 Syringes and pipettes 6.3.2.1. HPLC injection syringes with a capacity of at least four times the loop volume (see 6.3.1). 6.3.2.2. Syringes with a capacity of 10 ml used for applying DNPG to cartridges (it is allowed to use syringes made of polypropylene). 6.3.2.3. Fittings and plugs used to connect the cartridges to the sampling system and to close the prepared cartridges. 6.3.2.4. Automatic pipette dispenser, operating on the principle of positive displacement, multiple dispensing with a variable volume in the range from 0 - 10 ml (hereinafter - pipette dispenser).
7. Reagents
7.1. DNPH, recrystallized at least twice from UV-pure acetonitrile before use. 7.2. Acetonitrile, UV-clear (each portion of the solvent must be checked before use). 7.3. Perchloric acid, solution with a mass fraction of 60%, ρ = 1.51 kg / l. 7.4. Hydrochloric acid, solution with a mass fraction of 36.5% to 38%, ρ = 1.19 kg / l. 7.5. Formaldehyde (formalin), solution with a mass fraction of 37%. 7.6. Aldehydes and ketones, high purity, used to prepare calibration samples of DNPH derivatives (optional). 7.7. Ethanol or methanol for chromatography. 7.8. High purity nitrogen. 7.9. Granular charcoal (superior quality). 7.10. High purity helium (superior quality).8. Preparation of reagents and cartridges
8.1. Purification of 2,4-dinitrophenylhydrazine
The problem of formaldehyde contamination of DNPH is often encountered. Purification of DNPH is carried out by repeated recrystallization from acetonitrile, which is pure in the UV region of the spectrum. Recrystallization is carried out at a temperature of 40 ° C to 60 ° C by slowly evaporating the solvent to obtain crystals of maximum size. The content of impurities of carbonyl compounds in DNPH, which is determined before analysis by HPLC, should not exceed 0.15 μg per cartridge and per individual compound. A supersaturated DNPH solution is prepared by boiling a solution containing an excess of DNPH in 200 ml of acetonitrile for about 1 hour. The supernatant is then separated and poured into a beaker with a lid on a hot plate and gradually cooled to 40 ° C-60 ° C. ... Maintain the solution at this temperature (40 ° C) until 95% of the solvent volume has evaporated. The solution is filtered, and the remaining crystals are washed twice with acetonitrile with a volume of three times the apparent volume of the crystals. The crystals are transferred to another clean beaker, 200 ml of acetonitrile are added, heated to boiling, and the crystals are allowed to grow again upon cooling to 40 ° C-60 ° C until 95% of the solvent has evaporated. The crystal washing process is repeated. An aliquot of the solution is taken and diluted in tenfold volume with acetonitrile, then acidified with 1 ml of perchloric acid (3.8 mol / L) per 100 ml of DNPH solution and analyzed by HPLC in accordance with 9.3.4. Warning - DNPH cleaning must be carried out with the ventilation switched on with the obligatory use of explosion protection means (screen). NOTE Acid is required to catalyze the reaction of carbonyl compounds with DNPH. For these purposes, the strongest inorganic acids are used, such as perchloric, sulfuric, phosphoric or hydrochloric. In rare cases, the use of hydrochloric and sulfuric acids can lead to adverse effects. The level of content of impurities of hydrazone formaldehyde in recrystallized DNPH is considered acceptable if the mass concentration is less than 0.025 μg / ml or the mass fraction of impurities in DNPH is less than 0.02%. If the level of impurity content is unacceptable for the specific sampling conditions, then recrystallization is repeated. The purified crystals are transferred into a glass flask, 200 ml of acetonitrile is added, closed with a stopper, shaken slightly and allowed to settle for 12 hours. Analyze the supernatant liquid on a chromatograph by HPLC according to 9. 3.4. If the level of impurities is unacceptable, then remove the entire supernatant solution with a pipette, then add 25 ml of acetonitrile to the remaining purified crystals. Repeat the washing of the crystals with acetonitrile in 20 ml portions; after each addition of a portion of acetonitrile, the resulting supernatant is analyzed by HPLC until an acceptable level of impurities in the supernatant is confirmed. If the level of impurities is acceptable, add 25 ml of acetonitrile, close the flask with a stopper, shake and set aside for later use. The resulting saturated solution over purified crystals is the main starting DNPH solution. Maintain the minimum volume of saturated solution required for daily use, which minimizes the loss of purified reagent when it is necessary to rewash the crystals to reduce the level of impurities in the case of more stringent requirements for the degree of purity. The volume of the main initial saturated solution of DNPH required for the analysis is taken with a clean pipette. Do not pour the stock solution directly from the flask.8.2. Preparation of DNPH-Formaldehyde Derivative
Sufficient hydrochloric acid (2 mol / L) was added to a portion of the recrystallized DNPH to obtain an almost saturated solution. Formaldehyde (formalin) is added to this solution in a molar excess with respect to DNPH. Filter the precipitate of DNPH-derivative of formaldehyde, wash it with hydrochloric acid (2 mol / l) and water and leave in air until dry. Check the purity of the DNPH-derivative of formaldehyde by determining its melting point (165 ° C to 166 ° C) or HPLC analysis. If the level of impurities is unacceptable, the derivative is recrystallized from ethanol. Repeat the check of the degree of purity and recrystallization until an acceptable level of purity is reached (for example, mass fraction of the main component 99%). DNPH-derivative of formaldehyde is stored refrigerated (at a temperature of 4 ° C), protected from light. It should be stable for at least 6 months. Storage under nitrogen or argon will prolong the shelf life of the DNPH derivative. The melting points of DNPH derivatives of some carbonyl compounds are given in Appendix B. DNPH derivatives of formaldehyde and other carbonyl compounds used as standard samples are commercially available both as pure crystals and as individual or mixed stock solutions in acetonitrile.8.3. Preparation of stock solutions of DNPH-formaldehyde derivative
A stock solution of DNPH-derivative of formaldehyde is prepared by dissolving a precisely known amount of the derivative in acetonitrile. A working calibration solution is prepared from the initial solution. The content of DNPH-derivative of formaldehyde in calibration solutions should correspond to the expected range of values of its mass concentration in real samples. Stock solutions with a mass concentration of about 100 mg / L can be prepared by dissolving 10 mg of the solid derivative in 100 ml of acetonitrile. These solutions are used to prepare calibration solutions containing the corresponding derivatives in the range of mass concentration values from 0.5 to 20 μg / ml. Store all standard solutions protected from light in hermetically sealed vials in a refrigerator. Before use, the solutions are kept at room temperature until thermal equilibrium is reached. After four weeks, the solutions should be replaced with fresh ones.8.4. Preparation of cartridges coated with silica gel DNFG
8.4.1. General The procedure is carried out in a laboratory with a very low aldehyde content in the air. All glass and plastic laboratory glassware is thoroughly cleaned and rinsed in deionized water and aldehyde-free acetonitrile. Contact of reagents with air in the laboratory should be minimal. Wear polyethylene gloves when handling cartridges. 8.4.2. Solution for applying DNPH Using a pipette, add 30 ml of a saturated stock solution of DNPH into a volumetric flask with a capacity of 1000 ml, add 500 ml of acetonitrile and acidify with 1.0 ml of concentrated hydrochloric acid. The air above the acidified solution is filtered through a silica gel cartridge coated with DNPH to minimize contamination from laboratory air into the solution. The flask is shaken, then the solution is brought to the mark with acetonitrile. The flask is closed, inverted, shaken several times until the solution becomes homogeneous. Transfer the acidified solution to a pipette dispenser with a scale of 0 to 10 ml. From the dispenser, 10 to 20 ml of the solution is slowly poured into the drain glass. Inject an aliquot of the solution into a vial and check the level of impurities in the acidified solution by HPLC in accordance with 9.3.4. The mass concentration of formaldehyde in the solution should be no more than 0.025 μg / ml. 8.4.3. Application of DNPG to silica gel in a cartridge The cartridge is taken out of the package, the short end of the cartridge is connected to a 10 ml syringe, which is placed in the device for applying DNPG as shown in Figure 3a). Using a pipette dispenser, 10 ml of acetonitrile is injected into each syringe. The liquid should drain off by gravity. Air bubbles formed between the syringe and the silica gel cartridge are removed from the syringe using acetonitrile. Adjust the pipette dispenser containing the acidified solution for applying DNPH to inject 7 ml into each cartridge. As soon as the flow of acetonitrile at the outlet of the cartridge stops, add 7 ml of solution for applying DNPH to each syringe. The solution for applying DNPH flows through the cartridge by gravity until flow stops at the other end of the cartridge. Excess liquid at the outlet of each cartridge is removed with filter paper. Assemble the cartridge dryer (see Figure 3 b). At each outlet, a pre-prepared cartridge with applied DNPH is installed (for example, a scrubber or a "protective" cartridge). These "guard" cartridges are designed to remove traces of formaldehyde that may be present in the nitrogen feed. They are prepared by drying several re-soaked cartridges according to the instructions below and used to keep the remaining cartridges clean. Install the cartridge adapter (widened on a cone at both ends, with an outer diameter of 0.64 to 2.5 cm, made of a fluorocarbon tube, with an inner diameter slightly less than the outer diameter of the cartridge inlet) on the long end of the "protective" cartridge. Disconnect the cartridges from the syringes and connect the short ends of the cartridges to the free ends of the adapters already attached to the "protective" cartridges. Nitrogen is passed through each cartridge at a flow rate of 300-400 ml / min. Wash the outer surfaces and outlet ends of the cartridges with acetonitrile using a Pasteur pipette. After 15 minutes, the nitrogen supply is stopped, the residual acetonitrile is removed from the outer surfaces of the cartridges, and the dried cartridges are disconnected. Both ends of the loaded cartridges are sealed with standard polypropylene syringe plugs and the sealed cartridges are placed in borosilicate glass tubing with polypropylene screw caps. Each individual glass container for storing the cartridge is labeled with the batch and batch number and stored the entire batch in the refrigerator until use. It was found that the contents of the loaded cartridges remain stable for at least 6 months. when stored at 4 ° C in a dark place.9. Methodology
9.1. Sample selection
Assemble the sampling system and verify that the pump provides a constant flow throughout the sampling period. Loaded cartridges can retain their sampling performance if the ambient temperature is above 10 ° C. Install an ozone scrubber or trap if necessary (see 4.2). Before starting sampling, check the tightness of the system. Close the inlet (short) end of the cartridge so that there is no air flow at the outlet of the pump. In this case, the flow meter should not record the air flow through the sampling system. During unattended or extended sampling periods, it is recommended to use a flow regulator or pump with flow compensation to maintain a constant air flow when sampling the breathing zone. Adjust the flow regulator so that the flow rate is at least 20% below the specified maximum cartridge air flow rate. NOTE The silica gel in the cartridge is held between two fine-pore filters. Air flow during sampling may vary due to aerosol deposition on the front filter. The variation in flow can be significant when sampling air with a high particulate content. Install the sampling system (including the blank cartridge) and check the air flow close to expected. Typically, the air flow is set in the range of 0.5 - 1.2 l / min. The total number of moles of carbonyl compounds in the sampled air volume should not exceed the amount of DNPH in the cartridge (2 mg or 0.01 mol; from 1 to 2 mg when using commercially available pre-loaded cartridges). Typically, an approximate estimate of the mass of analyte in a sample should be less than 75% of the mass of DNPH loaded into the cartridge [100 to 200 µg in the case of HCHO, including interfering substances (see section 4)]. Calibration is carried out using a soap-foam bubble flow meter or a drum gas meter with a liquid seal connected to the flow outlet, provided that the system is tight. Note - The calibration method, which does not require tightness of the system after the pump, is given in [13]. To determine the sample volume, record and record the flow rate at the beginning and at the end of the sampling period. If the sampling period is more than 2 hours, then the flow rate is measured several times during sampling. To monitor the flow rate without interfering with the sampling process, a rotameter is installed in the system. It is also permissible to use a sampling pump with direct measurement and continuous flow rate recording. Before sampling begins, the loaded cartridge is removed from a sealed metal or other suitable container for transportation. Before connecting to a flow rate stimulator (aspirator, pump), the cartridge is kept at room temperature until thermal equilibrium is reached, without removing it from the glass container. Commercially available pre-loaded cartridges are subjected to the same procedure. Wearing plastic gloves, remove the cartridge plug and connect it to the flow rate booster using an adapter. Connect the cartridge so that its short end is the sample inlet end. The connection of commercially available pre-coated DNPH cartridges is carried out in accordance with the manufacturer's instructions. Some commercially available cartridges are sealed glass tubes. In this case, it is necessary to break off the ends of the tube with the preliminary use of a glass cutter. Connect the end of the cartridge with less sorbent to the sampling line so that more sorbent is at the air sample inlet. Take care when handling broken tube ends. Turn on the pump and set the required flow rate. Typically, the flow through one cartridge is 1.0 l / min, and in the case of two cartridges connected in series, 0.8 l / min. Sampling is carried out for a specified period of time, while the values of the sampling parameters are periodically recorded. If the ambient temperature is below 10 ° C during sampling, ensure that the sampling cartridge is at a higher temperature. When sampling was carried out in different weather conditions - in cold, humid and dry winter months, in hot and humid summer months - no significant influence relative humidity on the sampling results. At the end of sampling, turn off the pump. Check the air flow immediately before turning it off. If the air flow values at the beginning and end of the sampling period differ by more than 15%, then the sample is marked as doubtful. Immediately after sampling, the cartridge is disconnected from the sampling system (wearing polyethylene gloves), capped and placed back in the labeled container. The container is sealed with fluoroplastic tape and placed in a metal container containing a layer of granular charcoal with a thickness of 2 to 5 cm, or in another suitable container with an absorbent. If necessary, use a heat-sealed plastic bag with foil interlayers to store the sample cartridge. Store the sample cartridge in the refrigerator until analysis. The storage time of the cartridge in the refrigerator should not exceed 30 days. If a sample needs to be transported to an analytical laboratory for analysis, the storage time of the sample cartridge without a refrigerator should be minimized and should not exceed two days. Average sampling rate q A, ml / min, is calculated by the formulaq A = / n, (1)
Where q 1, q 2, ... q n - flow rates at the beginning, intermediate points and end of sampling; n is the number of averaging points. The total volume of air V m, l, sampled at a known temperature and pressure during the sampling process, is calculated by the formula
V m = (T 2 - T 1) q A / 1000, (2)
Where T 2 - time of the end of sampling; T 1 is the start time of sampling; T 2 - T 1 - sampling duration, min; q A - average flow rate, ml / min.
9.2. Blank samples
For each batch of samples, it is necessary to analyze at least one blank sample obtained under sampling conditions. If a batch includes 10 - 20 samples, then the number of blank samples should be at least 10% of the total number of samples. To determine the number of blanks required, the total number of samples within a batch or time interval should be recorded. At the sampling site, the blank sample cartridges are handled in the same way as the actual sample cartridges, except for the sampling process itself. The collection of blank samples shall comply with the requirements given in 9.1. It is also advisable to analyze the blank cartridges left in the laboratory to distinguish between contamination that may be introduced at the sampling site and in the laboratory.9.3. Sample analysis
9.3.1. Sample preparation The samples are transported to the laboratory in a suitable container containing a 2 to 5 cm thick layer of granular charcoal and stored in a refrigerator until analysis. Samples can also be stored in individual containers. The time interval between sampling and analysis of samples should be no more than 30 days. 9.3.2. Desorption of Samples The short end (inlet) sample cartridge is connected to a clean syringe. To prevent insoluble particles from entering the eluate, the direction of the liquid flow during desorption must match the direction of the air flow during sampling. If the eluate is filtered prior to HPLC analysis, then reverse desorption can be performed. For each batch of samples, the filtered clean extract is analyzed to confirm that the filter is free of contamination. The syringe with the cartridge attached is placed on the syringe rack. Desorption of DNPH-derivatives of carbonyl compounds and unreacted DNPH is carried out, allowing 5 ml of acetonitrile to drain from the syringe by gravity through the cartridge into a graduated test tube or volumetric flask with a capacity of 5 ml. Depending on the cartridge used for sampling, other volumes of acetonitrile can be injected. Note - The free volume of the dry silica cartridge is slightly over 1 ml. The flow of eluate may stop before all of the acetonitrile has flowed from the syringe into the cartridge due to the presence of air bubbles between the cartridge filter and the syringe. In this case, air bubbles are removed by injecting acetonitrile into the syringe using a long Pasteur pipette. The solution is adjusted to 5 ml with acetonitrile. The flask is labeled in the same way as the sample. An aliquot is pipetted into a fluorocarbon membrane vial. An aliquot is analyzed for the content of DNPH-derivatives of carbonyl compounds by HPLC. As a backup, a second aliquot can be taken and stored in the refrigerator until analysis is complete and valid results are obtained from the first aliquot. If necessary, a second aliquot is used for a confirmatory analysis. When using glass sealed tubes for sampling containing two layers of sorbent coated with DNPH, break off the end of the tube located closer to the second layer of sorbent (outlet end). Carefully remove the spring and glass wool plug retaining the sorbent layer. Pour the sorbent into a clean 4 ml glass vial with a fluorocarbon membrane or lid. The vial is marked as a reserve portion of the sample. Carefully remove the second glass wool stopper and pour the remaining sorbent into another 4 ml vial. The vial is labeled as the bulk of the sample. Add 3 ml of acetonitrile to each vial with a pipette, close the vials and leave for 30 minutes, during which time the vials are shaken periodically. 9.3.3. HPLC calibration Calibration solutions are prepared by dissolving DNPH-formaldehyde derivative (8.3) in acetonitrile. Prepare individual stock solutions with a mass concentration of 100 mg / l by dissolving 10 mg of the solid derivative in 100 ml of the mobile phase. The analysis of each calibration solution is carried out twice (at least five different values of mass concentration) and a table is made of the dependence of the values of the output signals corresponding to the area of chromatographic peaks on the introduced mass of the corresponding substance (or, which is more convenient, on the introduced mass of DNPH-derivative of formaldehyde at fixed loop volume (see Figures 4 and 5)). In the process of calibration, the operations are carried out corresponding to the operations carried out during the analysis of the sample and established in 9.3.4. To avoid the memory effect of the chromatograph, the analysis begins with the solution with the lowest mass concentration. When using a UV detector or a detector based on a diode matrix, a linear dependence of the output signal should be obtained with the introduction of solutions with a mass concentration in the range of 0.05 - 20 μg / ml with an injected volume of 25 μl. The results obtained are used to construct a calibration graph (see Figure 6). The calibration characteristic (the dependence of the output signal corresponding to the peak area on the value of the mass concentration) obtained by the least squares method is considered linear if the correlation coefficient is not less than 0.999. The retention times for each analyte should not differ from each other by more than 2%. After establishing a linear calibration characteristic, its stability is checked daily using a calibration solution with a mass concentration value close to the expected value of each component, but not less than 10 times higher than the detection limit. The relative change in the output signal determined during daily verification should not exceed 10% for analytes with a mass concentration of at least 1 μg / ml and 20% for analytes with a mass concentration of approximately 0.5 μg / ml. If a larger change is observed, it is necessary to recalibrate or build a new calibration graph based on freshly prepared calibration solutions.
Chromatography conditions: column: C-18 with reverse phase; mobile phase: with a volume ratio of 60% acetonitrile / 40% water; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1 ml / min; retention time: for DNPH-derivative of formaldehyde approximately 7 min; volume of injected sample: 25 μl.
Figure 4 - An example of a chromatogram of DNPH - formaldehyde derivative
Chromatography conditions: column: C-18 with reverse phase; mobile phase: with a volume ratio of 60% acetonitrile / 40% water; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1 ml / min; retention time: for DNPH-derivative of formaldehyde approximately 7 min; volume of injected sample: 25 μl.
Figure 5 - Examples of chromatograms of DNPH-derivative of formaldehyde at its various mass concentrations
Chromatographic conditions: correlation coefficient: 0.9999; column: C-18 reverse phase; mobile phase: with a volume ratio of 60% acetonitrile / 40% water; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1 ml / min; retention time: for DNPH-derivative of formaldehyde approximately 7 min; volume of injected sample: 25 μl;
Figure 6 - Example of a calibration curve for formaldehyde
9.3.4. Formaldehyde analysis by HPLC. Assemble and calibrate the HPLC system in accordance with 9.3.3, with the following typical for the system: column: C-18, internal diameter 4.6 mm, length 25 cm, or equivalent; it is not necessary to control the column temperature; mobile phase: 60% acetonitrile / 40% water (v / v), isocratic; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1.0 ml / min; retention time: for DNPH-derivative of formaldehyde 7 min - using one C-18 column, 3 min - using two C-18 columns; volume of injected sample: 25 μl. The baseline of the detector is checked prior to each analysis to ensure stable conditions. Prepare the mobile phase for HPLC by mixing 600 ml of acetonitrile and 400 ml of water, or set the appropriate parameters for the gradient elution. The resulting mixture is filtered through a polyester membrane filter with a pore size of 0.22 μm in a vacuum filtration device made of glass or fluoroplastic only. Degas the filtered mobile phase by flushing with helium for 10 to 15 min (100 ml / min) or by heating to 60 ° C for 5 to 10 min in a laboratory conical flask covered with a watch glass. To prevent the formation of gas bubbles in the detector cell, a permanent resistance limiter (350 kPa) or a short (15 - 30 cm) fluoroplastic tube with an inner diameter of 0.25 mm is installed after it. The mobile phase is poured into a solvent container and the flow rate is adjusted to 1.0 ml / min. Before the first analysis, the pump must run for 20 - 30 minutes. The detector is turned on at least 30 minutes before the start of the first analysis. The output of the detector is recorded using an electrical metering recorder or similar output device. For systems with manual injection of samples, draw at least 100 μL of the sample into a clean injection syringe for injection into the chromatograph. The loop of the metering valve is filled with the mobile phase (the metering valve must be set to the "loading" position), adding excess sample with a syringe. To start chromatography, the dosing valve is moved to the "sample injection" position. Simultaneously with the input, the data processing system is activated, the input point is turned on and marked on the chart tape of the electric measuring recorder. After about 1 min, move the dosing valve from the “sample inlet” position to the “loading” position, rinse or flush the syringe and the dosing loop with an acetonitrile-water mixture to prepare for the analysis of the next sample. It is not allowed to inject the solvent into the loop of the dosing valve when the valve is in the “sample inlet” position. After elution of DNPH-derivative of formaldehyde (see Figure 4), stop data logging and calculate the mass concentration of the components in accordance with section 10. The system can be used for further analysis of samples after a stable baseline position has been reached. NOTE - After several analyzes, column contamination (as evidenced, for example, by an increase in pressure with each subsequent injection at a given flow rate and solvent composition) can be eliminated by flushing it with 100% acetonitrile of several times the column volume. Similar protection can be achieved using forecolumns. If the value of the mass concentration of the analyte goes beyond the linear section of the calibration characteristic of the system, the sample is diluted with the mobile phase or a smaller sample volume is introduced into the chromatograph. If the retention times obtained from previous injections are not reproducible (maximum tolerance ± 10%), then the acetonitrile-water ratio can be increased or decreased to obtain an appropriate retention time. If the retention time is too long, the ratio is increased; if too little, the ratio is reduced. If it is necessary to change the solvent, recalibrate before injecting the sample (see 9.3.3). NOTE The given chromatographic conditions should be optimized for the determination of formaldehyde. The analyst is recommended to conduct studies with the available HPLC system to optimize the chromatographic conditions for solving a specific analytical problem. HPLC systems with automatic sample injection and data collection can also be used. The resulting chromatogram is examined for the interfering effect of ozone in accordance with 4.2 and Figure 2. 9.3.5 HPLC analysis of other aldehydes and ketones 9.3.5.1. General Provisions Optimization of chromatographic conditions through the use of two C-18 columns connected in series and a gradient mode of eluent supply allows the analysis of other aldehydes and ketones taken from the air. In particular, the chromatographic conditions are optimized for the separation of acetone, propionaldehyde and some other aldehydes with a higher molecular weight with an analysis duration of approximately 1 hour.The composition of the mobile phase is periodically changed according to a linear gradient program to obtain the maximum separation of C3, C4 and benzaldehyde in the corresponding region of the chromatogram. ... For this purpose, the following gradient program has been developed: at the moment of sample injection, the volume ratio of solutions is changed from 60% acetonitrile / 40% water to 75% acetonitrile / 25% water within 36 minutes; up to 100% acetonitrile - within 20 minutes; 100% acetonitrile - within 5 minutes; change the direction of linear gradient programming from 100% acetonitrile to 60% acetonitrile / 40% water for 1 min; maintain a volume ratio of 60% acetonitrile / 40% water for 15 minutes. 9.3.5.2. Analysis of samples for other carbonyl compounds Assemble and calibrate the HPLC system in accordance with 9.3.3. Typical systems would be: column: two C-18 columns connected in series; mobile phase: acetonitrile / water; linear gradient mode; detector: UV detector operating at a wavelength of 360 nm; flow rate: 1.0 ml / min; gradient program: according to 9.3.4. The chromatographic conditions above were optimized for gradient HPLC systems with UV or diode array detectors, an autosampler with a dosing loop volume of 25 μL, two C-18 columns (4.6 × 250 mm) and an electric metering recorder or electronic integrator. The analyst is recommended to conduct studies on the available HPLC system in order to optimize the chromatographic conditions for solving a specific analytical problem. Optimization is necessary at least for the separation of acrolein, acetone and propionaldehyde. NOTE Column manufacturers generally provide guidance on optimal separation conditions for DNPH derivatives for reversed phase columns. These guidelines can eliminate the need for two columns without compromising carbonyl separation. Carbonyl compounds in a sample are determined qualitatively and quantitatively by comparing their retention times and peak areas with those for comparison samples of DNPH derivatives. Formaldehyde, acetaldehyde, acetone, propionic aldehyde, cretonaldehyde, benzaldehyde and o-, m-, p-toluyl aldehydes are determined with a high degree of reliability. Determination of butyraldehyde is less reliable due to its co-elution with isobutyraldehyde and methyl ethyl ketone under the chromatographic conditions specified above. A typical chromatogram obtained with a gradient elution HPLC system is shown in Figure 7. The mass concentration of the individual carbonyl compounds is determined according to 9.3.4.
|
Peak identification |
Compound |
Mass concentration, μg / ml |
Formaldehyde | Acetaldehyde | Acrolein | Acetone | Propionaldehyde | Crotonic aldehyde | Butyraldehyde | Benzaldehyde | Izovaleraldehyde | Valeraldehyde | o - Toluyl aldehyde | m - Toluyl aldehyde | l - Toluyl aldehyde | Hexanal | 2, 5- D and methyl benzaldehyde |
Figure 7 - An example of chromatographic separation of DNPH - derivatives of 15 carbonyl compounds
10. Calculation of measurement results
The total mass of the analyte (DNPH-derivative) for each sample is calculated by the formulam d = m s - m b, (3)
Where m d - corrected mass of DNPG - derivative extracted from the cartridge, μg; m s - uncorrected mass of the sample cartridge, μg:
m s = A s ( c std / A std) V s d s; (4)
m b is the mass of the analyte in the cartridge with a blank sample, μg:m b = A b ( c std / A std) V b d b; (five)
A s — peak area of the analyte eluted from the sample cartridge, arbitrary units; BUT b is the peak area of the analyte eluted from the cartridge with a blank sample, arbitrary units; A std is the area of the analyte peak in the calibration solution for daily calibration, conventional units; c std is the mass concentration of the analyte in the calibration solution for daily calibration, m kg / ml; V s is the total volume of the eluate obtained for the cartridge with the sample, ml; V b - the total volume of the eluate obtained for the cartridge with a blank sample, ml; d s is the dilution factor of the sample eluate: 1 if the sample was not diluted again; V d / V a, if the sample was diluted so that the output signal was in the linearity region of the detector, where V d - volume after dilution, ml; V a - aliquot used for dilution, ml; d b is the blank dilution factor equal to 1.0. The mass concentration of the carbonyl compound with A, ng / L, in the sample is calculated by the formulac A = m d ( M c / M der) 1000 / V m, (6)
Where M with - the molecular weight of the carbonyl compound (for formaldehyde is 30); M der is the molecular weight of DNPH-derivative (for formaldehyde it is 210); V m is the total volume of the indoor air sample taken according to 9.1, l. NOTE It is not recommended to use parts per million and parts per million. However, for the convenience of some users, the volume ratio of the carbonyl compound ca in parts per million (ppb) is calculated by the formula
c A = c As ∙ 24.4 / M c, (7)
The total volume of the air sample V s, l, reduced to a temperature of 25 ° C and a pressure of 101.3 kPa, is calculated by the formulaV s = (( V m ρ A) / 101.3) (298 / (273 + T A)), (8)
Where ρ A - average atmospheric pressure inside a closed room, kPa; T A is the average ambient temperature in a closed room, ° C. If it is necessary to express the analyte content in parts per million (ppm) at standard ambient conditions (temperature 25 ° C and pressure 101.3 kPa) for comparison with reference samples, the composition of which is set in the same values, the sampled volume should not be reduced to standard conditions.
11. Performance criteria and quality control of measurement results
11.1. General Provisions
This clause specifies the measures necessary to ensure quality control of the measurement results and provides guidance on meeting the performance criteria to be met. The user of the standard must comply with the requirements of ISO 9001, ISO 17025.11.2. Standard operating procedures
The user of the standard should develop standard operating procedures for the following activities in the laboratory: assembly, calibration and application of the sampling system, indicating the manufacturer and model of the equipment used; preparation, cleaning, storage and processing of reagents used in sampling, and the samples themselves; assembly, calibration and application of the HPLC system, indicating the brand and model of the equipment used; a method for registering and processing data with an indication of the computer hardware and software used. The description of standard operating procedures should include step-by-step instructions and be accessible and understandable to laboratory personnel. Standard operating procedures shall be consistent with the requirements of this standard.11.3. HPLC system efficiency
The efficiency of the HPLC system is determined by the efficiency of the column η (number of theoretical plates), which is calculated by the formulaη = 5.54 ( t r / w 1/2) 2, (9)
Where t r — retention time of the analyte, s; w 1/2 is the width of the peak, one component at half maximum, s. The column efficiency should be at least 5000 theoretical plates. The relative standard deviation of the output signal with repeated daily injections of samples into the HPLC system should not be more than ± 10% for calibration solutions with a mass concentration of the analyte of at least 1 μg / ml. With a mass concentration of some carbonyl compounds of no more than 0.5 μg / ml, the precision of repeated analyzes can increase up to 20%. The precision of the retention time should be within ± 7% on any day of analysis.
11.4. Loss of sample
Sample loss occurs when the permissible sorbent load is exceeded or if the volumetric flow exceeds the maximum permissible for the used sampling system. Sample loss can be prevented by installing two sampling cartridges connected in series and then analyzing the contents of each, or by installing a two-piece sorbent cartridge and then analyzing both sections. If the amount of analyte in the backup section is more than 15% of the amount of analyte in the main section, an assumption of "slip" is made and the accuracy of the results obtained is questioned.12. Precision and Uncertainty
As in the analysis of other compounds, the precision and uncertainty of the result of determining the formaldehyde content in indoor air are influenced by two factors: the reproducibility of the analytical procedure and the time variation in the analyte content in the air. The latter factor is believed to have a much greater impact than the former, although it is difficult to quantify the impact of changes in source intensity and ventilation conditions. General information on uncertainty values related to the analytical procedure is given in Appendix A.Appendix A
(reference)
Precision and Uncertainty
An evaluation was carried out on a methodology similar to the method of analysis given in this International Standard. The precision related to the analytical procedure shall be within ± 10% with an analyte mass concentration of at least 1 μg / ml. At a mass concentration of no more than 0.5 μg / ml, the precision in repeated analyzes of some carbonyl compounds can increase up to 25%. Circular tests [14] - [16] evaluated the method using silica gel cartridges (particle size 55 to 105 µm) coated with DNPH, similar to the method specified in this International Standard. The results of the assessment, given below, can be used to evaluate the effectiveness of using this method for analyzing the air in enclosed spaces. Two different laboratories used cartridges to conduct more than 1,500 measurements of formaldehyde and other carbonyl compounds in ambient air as part of a research program in 14 cities in the United States [15], [16]. The precision of 45 repeated injections of the DNPH calibration solution, a formaldehyde derivative, into the HPLC system within 2 months, expressed as a relative standard deviation, was 0.85%. Based on the results of three-fold analysis of each of 12 identical samples from cartridges with applied DNPH, formaldehyde content values were obtained, which agree within a relative standard deviation of 10.9%. 16 laboratories from the USA, Canada and Europe took part in the circular tests. These tests analyzed 250 cartridges with blank samples, three sets of 30 cartridges with three values of the content of injected DNPH-derivatives and 13 series of cartridges exposed in an environment with vehicle exhaust gases [14] - [16]. The cartridges meeting the requirements of 4.2 were prepared by the same laboratory. All samples were randomly distributed among the laboratories participating in the round robin. The results of the circular tests are summarized and shown in Table A.1. NOTE The round robin test did not use a standardized HPLC method. The test participants used the same HPLC-based techniques that they use in practice in their laboratories. Absolute value the difference, expressed as a percentage, between the results of two series of measurements (sampling from the same place), carried out under the US research program in 1988, was 11.8% for formaldehyde (n = 405), acetaldehyde - 14.5 % (n = 386) and acetone - 16.7% (n = 346) [15], [16]. As a result of the analysis of two samples taken practically at one point within the framework of this program for formaldehyde content by another laboratory, the relative standard deviation was 0.07, the correlation coefficient was 0.98, and the uncertainty was minus 0.05 for formaldehyde [15]. The corresponding values for acetaldehyde were 0.12; 0.95 and minus 0.50, and for acetone - 0.15; 0.95 and minus 0.54 [16]. Analysis of the cartridges after the introduction of DNPH into them, carried out by one laboratory during the year, showed that the average uncertainty was 6.2% for formaldehyde (n = 14) and 13.8% for acetaldehyde (n = 13). An analysis of 30 cartridges after the introduction of DNPH into them, carried out by one laboratory under this program, showed that the average uncertainty was 1.0% (in the range from minus 49% to plus 28%) for formaldehyde and 5.1% (in the range from minus 38% to minus 39%) for acetaldehyde. Table A.1 - Results of circular tests |
Sample type |
Formaldehyde |
Acetaldehyde |
Propionaldehyde |
Benzaldehyde |
Blank cartridges: | aldehyde, μg | rsd,% | n | Sample cartridge 3): | recovery,% (rsd,%) | short | average | high | n | Samples in environment with car exhaust gases: | aldehyde, mg | rsd,% | n | a) Low, medium and high levels of aldehyde introduced into the cartridge were approximately 0.5; 5 and 10 μg, respectively. Note - 16 laboratories took part in the research. The values were obtained from the data set after the outliers were removed from the data set. Table designations: rsd - relative standard deviation; n is the number of measurements. |
Appendix B
(reference)
Melting points of DNPH derivatives of carbonyl compounds
Table B.1 - Melting points of DNPH derivatives of carbonyl compounds |
Name of the carbonyl compound |
Melting point of DNPH - derivative [17], ° С |
Acetaldehyde | 152 to 153 (168.5 [18], 168 [19]) | Acetone | 125 to 127 (128 [18], 128 [19]) | Benzaldehyde | 240 to 242 (235 [19]) | Butyraldehyde | 119 to 120 (122 [19]) | Cretonaldehyde | 191 to 192 (190 [19]) | 2,5-dimethylbenzaldehyde | 216.5 to 219.5 | Formaldehyde | 166 (167 [ 18], 166 [ 19]) | Hexanaldehyde | 106 to 107 | Izovaleraldehyde | 121.5 to 123.5 | Propionaldehyde | 144 to 145 (155 [19]) | o - Toluyl aldehyde | 193 to 194 (193 to 194 [19]) | m - Toluyl aldehyde | 212 (212 [ 19]) | n - Toluyl aldehyde | 234 to 236 (234 [19]) | Valeraldehyde | 108 to 108.5 (98 [19]) |
Appendix C
(reference)
Information on the compliance of national standards of the Russian Federation with reference international standards
Table C.1 |
Designation of the referenced International Standard |
Designation and title of the relevant national standard |
ISO 9001: 2000 | GOST R ISO 9001-2001 Quality management systems. Requirements | ISO 16000-1: 2004 | GOST R ISO 16000-1-2007 Air in enclosed spaces. Part 1. Sampling. General Provisions | ISO 16000-2: 2004 | GOST R ISO 16000-2-2007 Indoor air. Part 2. Sampling for formaldehyde content. Basic Provisions | ISO 16000-4: 2004 | GOST R ISO: 16000-4-2007 Air in enclosed spaces. Part 4. Determination of formaldehyde. Diffusion sampling method | ISO / IEC 17025: 2005 | GOST R ISO / IEC 17025-2006 General requirements for the competence of testing and calibration laboratories | * There is no corresponding national standard. Prior to its approval, it is recommended to use the Russian translation of this International Standard. The translation of this international standard is in the Federal Information Fund of Technical Regulations and Standards. |
Bibliography
| Method TO-11A, EPA-625 / R-96-010b, Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air, U.S. Environmental Protection Agency, Cincinnati, OH, 1996 | Air Quality Guidelines for Europe. Copenhagen: WHO Regional Office for Europe. WHO Regional Publications. European series No. 23/1987 | Revised values see webpages: | www.who.int.peh, www.who.dk/envhlth/pdf/airqual.pdf | Tejada, S. B., Evaluation pf silica gel cartridges coated in situ with acidified 2,4-dinitrophenylhydrazine for sampling aldehydes and ketones in air, Int. J. Environ. Anal. Chem., 26, 1986, pp. 167 - 185 | Grosjean, D., Ambient levels of formaldehyde, acetaldehyde, and formic acid in southern California: Results of a one-year baseline study, Environ. Sci. Technol., 25, 1991, pp. 710 - 715 | J.-O. Levin and R. Lindahl, Aldehyde measuring methods using DNPH-coated filters - Summary and conclusions, Proc. Workshop "Sampling Project", 27 - 28 June, 1996, Mol, Belgium | VDI 3862 Part 2 | Gaseous Emission Measurement - Measurement of Aliphatic and Aromatic Aldehydes and Ketones - DNPH Method - Impinger Method | VDI 3862 Part 3 | Gaseous Emission Measurement - Measurement of Aliphatic and Aromatic Aldehydes and Ketones - DNPH Method - Cartridges Method | A. Sirju and P.B. Shepson, Laboratory and field investigation of the DNPH cartridge technique for the measurement of atmospheric carbonyl compounds, Environ. Sci. Technol., 29, 1995, pp. 384 - 392 | Arnts, R.R., and Tejada, S. B., 2,4-Dinitrophenylhydrazine-coated silica gel cartridge method for determination of formaldehyde in air: Identification of an ozone interference, Environ. Sci. Technol., 23, 1989, pp. 1428 - 1430 | Sirju, A., and Shepson, P.B. Laboratory and field evaluation of the DNPH cartridge technique for the measurement of atmospheric carbonyl compounds, Environ. Sci. Technol., 29, 1995, pp. 384 - 392 | R.G. Merrill, Jr., D-P. Dayton, P.L. O "Hara, and RF Jongleux, Effects of ozone removal on the measurement of carbonyl compounds in ambient air: Field experience using Method TO-11, in Measurement of Toxic and Related Air Pollutants, Vol. 1, Air & Waste Management Association Publication VIP -21, Pittsburgh, PA, USA, 1991, pp. 51-60 | T.E. Kleindienst, E.W. Corse, F.T. Blanchard, and W.A. Lonneman, Evaluation of the performance of DNPH-coated silica gel and C1 8 cartridges in the measurement of formaldehyde in the presence and absence of ozone, Environ. Sci. Technol., 32, 1998, pp. 124 - 130 | EN 1232: 1997 | Workplace atmospheres - Pumps for personal sampling of chemical agents - Requirements and test methods | ASTM D51 97-97 Standard Test Method for Determination of Formaldehyde and Other Carbonyl Compounds in Air (Active Sampler Methodology), Annual Book of ASTM Standards, 11.03, American Society for Testing and Materials, West Conshohoken, PA, U.S.A. , pp. 472 - 482 | USEPA, 1 989 Urban airtoxics monitoring program: Formaldehyde results, Report No. 450 / 4-91 / 006. U.S. Environmental Protection Agency, Research Triangle Park, NC, U.S.A., January 1991 | USEPA, 1990 Urban Air Toxics Monitoring Program: Carbonyl Results, Report No. 450 / 4-91 / 025, U.S. Environmental Protection Agency, Research Triangle Park, NC, U.S.A., July 1991 | Certificate of Analysis, Radian International, Austin, TX, U.S.A | Handbook of Chemistry and Physics, CRC, 18901 Cranwood Parkway, Cleveland, OH, U.S.A | Organikum, Organisch-chemisches Grundpraktikum, Wiley-VCH, Weinheim, Germany |
Methodical instructions.
Formalin - an aqueous solution of formaldehyde (35-40%). It is a colorless transparent liquid with a characteristic odor; when stored in a refrigerated state, formalin becomes cloudy with the formation of a precipitate. For disinfection, a solution is prepared with a certain formaldehyde content in formalin.
Before disinfection, it is necessary to check the percentage of formaldehyde in the solution. Usually formaldehyde solution is prepared from formalin containing 35-40% formaldehyde. For example, to prepare a 4% formaldehyde solution from the available 40% formalin, you must first make the following proportion:
100: 40 = x: 4, whence x = 100 ∙ 4/40 = 10
The found value means that to obtain a 4% formaldehyde solution, you need to take 10 ml of the available 40% formalin and 90 ml of water.
Each batch of formalin must have a passport, which indicates the name of the drug, the name of the plant, weight and percentage of formaldehyde.
Formalin is used to disinfect livestock facilities. It can be used in aqueous solutions, in a gaseous state (vapor-formalin chambers, aerosols) both in pure form and in a mixture with other chemicals. The bactericidal action is based on the ability of formaldehyde to denature microbial proteins.
Exercise 1.Determination of the percentage of formaldehyde in formalin (titration method)
Dishes and reagents: conical flask 500 ml, burettes, normal sodium hydroxide solution, decinormal solution of iodine, decinormal solution of sodium thiosulfate, hydrochloric acid - 1 N. solution, 1% starch solution.
Definition progress: 30 ml of normal sodium hydroxide solution, 50 ml of formalin diluted 20 times are poured into a conical flask (95 ml of distilled water is added to 5 ml of formalin) and 100 ml of 0.1 N. iodine, which is poured from the burette in small portions, carefully in a circular motion flasks mixing the poured portion of iodine with the liquid in the flask. Then the flask is closed with a stopper and placed in a dark place for 30 minutes, after which 40 ml of 1 N HCI is added. hydrochloric acid solution. In this case, the almost colorless liquid (mixture) becomes brown. It is titrated with a decinormal thiosulfate solution. When the mixture becomes slightly yellow, 1 ml of a 1% starch solution (indicator) is poured into the flask. The liquid turns blue and then becomes discolored as the titration continues. The percentage of formaldehyde in formalin is determined by the formula:
x = (100 - y) ∙ 0.0015 ∙ 20 ∙ 20,
100 - the amount of iodine solution, ml;
y is the amount of thiosulfate used for titration, ml;
0.0015 - gram formaldehyde equivalent;
20 - formalin dilution;
20 is a multiplier for converting to percent.
Task 2. Determination of formaldehyde in formalin by density
Dishes and reagents: glass cylinder of 0.5 or 1 liter, densimeter with divisions 1.08-1.16, test formalin (should have a temperature of 18 ... 20 0 С).
Definition progress: formalin is poured into a glass cylinder up to ⅔ of its height and its density is determined with a densimeter. The percentage of formaldehyde is calculated by the formula:
x = 1000 (D - 1) / 2.5,
D is the density of formalin;
1 - water density;
1000 - a multiplier for converting fractional numbers to an integer;
2.5 is a constant.
Dry formalin(paraform) contains 95-96% formaldehyde. It is a white powder. To obtain a solution of 1% concentration, take 1 part of dry formalin and 99 parts of water (for a 3% concentration, respectively, 3 parts of powder and 97 parts of water, etc.). The water must be heated up to 50 ... 60 0 С.
Solutions of dry formalin are used for disinfection in the same manner and at the same concentrations as formaldehyde solutions.
Parasod and Fospar are white powders, readily soluble in hot water (50 ... 60 0 С), stable during storage. They are prepared on the basis of paraform, sodium carbonate and trisodium phosphate and contain 50% paraform. They have high bactericidal and virucidal properties. For wet disinfection, 3-4% solutions of parasod and fospar are used.
To obtain solutions of this concentration, take respectively 3 or 4 kg of one of the preparations, gradually add 50 liters of hot water (50 ... 60 0 С), stirring until complete dissolution, then add cold water to obtain 100 liters of disinfectant.
With the aerosol method, parasod and fospar are used in the form of 40% solutions at the rate of 30 ml per 1 m 3 of the room. To prepare 40% solutions, take 40 kg of one of the preparations per 100 liters of water.
