Photometric determination of manganese
INTERSTATE COUNCIL FOR STANDARDIZATION. METROLOGY AND CERTIFICATIONS
INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION
INTERSTATE
STANDARD
DRINKING WATER
Determination of manganese content by photometric methods
(ISO 6333: 1986, NEO)
Official edition
Stagesartyforms
Foreword
The goals, basic principles and procedure for carrying out work on interstate standardization are established by GOST 1.0-92 and the Interstate Standardization System. Basic provisions) "and GOST 1.2-2009" Interstate standardization system. Interstate standards, rules and recommendations for interstate standardization. Rules for development, acceptance, application, updating and cancellation "
Information about the standard
1 PREPARED by Limited Liability Company "Protector" together with Limited Liability Company "Lumex Marketing"
2 INTRODUCED by the Federal Agency for Technical Regulation and Metrology. Technical Committee for Standardization TC 343 "Water Quality"
3 ACCEPTED by the Interstate Council for Standardization, Metrology and Certification (minutes of October 20, 2014 No. 71 -P)
4 This International Standard has been drafted with the main regulations international standard ISO 6333: 1986 Water quality - Determination of manganese - Fonmaldoxime spectrometric method. in part of section 7
Compliance Degree - Non-Equivalent (NEO)
5 REPLACE GOST 4974-72
6 By order of the Federal Agency for Technical Regulation and Metrology dated November 11, 2014 No. 1539-st, the interstate standard GOST 4974-2014 was put into effect as a national standard Russian Federation from January 1, 2016
Information about changes to this standard is published in the annual information index "National Standards", and the text of changes and amendments is published in the monthly information index "National Standards". In case of revision (replacement) or cancellation of this standard, a corresponding notice will be published in the monthly information index "National Standards". Relevant information. notice and texts are also posted on the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet
© Standartinform. 2015
In the Russian Federation, this standard cannot be reproduced in whole or in part. replicated and distributed as an official publication without the permission of the Federal Agency for Technical Regulation and Metrology
1 area of use............................................... .................................................. ....................................one
3 Sampling ............................................... .................................................. ..................................
4 Requirements for the conditions of measurements ............................................ ..........................
5 Measuring instruments, auxiliary equipment, reagents, materials ....................
6 Determination of manganese content using oxidation to permanganate ions
INTERSTATE STANDARD
DRINKING WATER
Determination of manganese content by photometric methods Drinking water. Determination ot manganese content by photometric methods
Date of introduction - 2016-01-01
1 area of use
This standard applies to drinking water, including packaged in containers, and water from underground and surface sources of drinking water supply and establishes photometric methods for determining the content of manganese in the range of mass concentrations from 0.01 to 5.00 mg / dm 3 using:
* oxidation of manganese compounds to permanganate ions after elimination of the interfering effect of chloride ions (method A):
Formation of a colored compound with formaldoxime (method B).
If the mass concentration of manganese exceeds 5 mg / dm 3. then the analyzed sample is diluted with distilled water, but not more than 100 times.
The methods provide comparable results.
This standard uses normative references to the following interstate standards:
GOST OIML R 76-1-2011 State system for ensuring the uniformity of measurements. Scales of non-automatic operation. Part 1. Metrological and technical requirements. Testing
GOST 17.1.5.05-65 Nature Protection. Hydrosphere. General requirements to sampling surface and sea waters... ice and precipitation
GOST 195-77 Reagents. Sodium sulfate. Specifications GOST 1277-75 Reagents. Silver nitrate. Specifications GOST 1625-89 Technical formalin. Technical conditions
GOST 1776-74 (ISO 1042-63, ISO 4788-60) Laboratory glassware. Cylinders. beakers, flasks, test tubes. General specifications
GOST 3760-79 Reagents. Ammonia water. Specifications GOST 4146-74 Reagents. Potassium perhydrate. Specifications GOST 4204 - 77 Reagents. Sulfuric acid. Technical conditions
GOST 4208-72 Reagents. Salt of ferrous oxide and ammonium double sulfate (Mohr's salt). Technical conditions
GOST 4328-77 Reagents. Sodium hydroxide. Specifications GOST 4461-77 Reagents. Nitric acid. Specifications GOST 4523 -77 Reagents. Magnesium sulfate 7-water. Specifications GOST 4919.1-77 Reagents and especially pure substances... Methods for preparing indicator solutions
GOST 5456-79 Reagents. Hydroxylamine hydrochloride. Technical conditions
Official edition
GOST ISO 5725-6-2003 Accuracy (correctness and precision) of measurement methods and results. Part 6. Using precision values in practice
GOST 6552-80 Reagents. Orthophosphorium acid. Specifications GOST 6709-72 Distilled water. Technical conditions
GOST 9147 * 80 Porcelain laboratory glassware and equipment. Specifications GOST 10652-73 Reagents. Disodium salt ethylenediamine-MXN ".M'-tetraacetic acid 2-aqueous (Trilon B). Specifications
GOST 10733 * 98 Mechanical wrist and pocket watches. General specifications GOST 10929 * 76 Reagents. Hydrogen peroxide. Technical conditions
GOST 14919-83 Household electric stoves, hotplates and electric ovens. General specifications
GOST ISO IEC 17025-2009 General requirements for the competence of testing and calibration laboratories
GOST 19908 * 90 Crucibles, bowls, glasses, flasks, funnels, test tubes and tips made of transparent quartz glass. General specifications
GOST 20478-75 Reagents. Ammonium persulphate. Technical conditions
GOST 23350 * 98 Wrist watches and electronic pocket watches. General specifications
GOST 24147-80 High purity water ammonia. Technical conditions
GOST 25336-82 Laboratory glassware and equipment. Types, main parameters and dimensions
GOST 26272 * 98 Electronic * mechanical quartz wrist and pocket watches. General specifications
GOST 29227-91 (ISO 835-1-61) Laboratory glassware. Graduated pipettes. Part 1. General requirements
GOST 31861-2012 Water. General requirements for sampling GOST 31862-2012 Drinking water. Sample selection"
Note - When using this standard, it is advisable to check the validity of the reference standards in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrolopes on the Internet or according to the annual information index "National Standards", which was published as of January 1 of the current pod. and on the issues of the monthly information index "National Standards" for the current year. If the reference "1st standard is replaced (changed), then when using this standard, one should be guided by the replacing (modified) standard. If the reference standard is canceled without replacement, then the provision in which the reference to it is given applies to the extent not affecting this reference.
3 Sampling
3.1 Water samples are taken in accordance with GOST 31861. GOST 31862 and GOST 17.1.5.05 with a volume of at least 1000 cm 3 in containers made of glass or polymer material.
3.2 If the determination of manganese by method A is supposed to be carried out not earlier than 12 hours after sampling, then the selected sample is preserved by adding concentrated nitric acid at the rate of 5 cm 3 of acid per 1000 cm 3 of the sample. If the pH of the preserved sample is higher than 2., add nitric acid until the pH reaches less than 2 (control using universal indicator paper).
3.3 When using method B, the sample is preserved by adding 10 cm 3 of a sulfuric acid solution according to 7.3.6. If the pH of the preserved sample is higher than 2, then add a solution of sulfuric acid until the pH reaches less than 2 (control by universal indicator paper).
3.4 The shelf life of a sample preserved according to 3.2 or 3.3 is no more than 1 month. at a temperature from 2 ° C to 8 ° C.
4 Requirements for measurement conditions
4.1 When preparing for measurements and during their conduct, it is necessary to comply with the conditions established in the operating manuals or in the passports of measuring instruments and auxiliary equipment.
The Russian Federation has GOST R 56237 * 2014 (ISO 5667-6: 2006)
4.2 Measurements of volumes of water and solutions are carried out at a temperature environment from 15 s C to 25 ° C.
4.3 All solutions, unless otherwise specified, should be stored at an ambient temperature of 15 ° C to 25 ° C in closed containers.
4.4 Laboratories conducting tests must comply with the requirements of GOST ISO / IEC 17025.
5 Measuring instruments, auxiliary equipment, reagents, materials
Photometer, spectrophotometer, photoelectrocolorimeter, photometric analyzer (hereinafter referred to as the device), allowing to measure the optical density of a solution in the wavelength range from 400 to 700 nm with an admissible absolute measurement error of the spectral transmittance of no more than ± 2% in optical cells with a thickness of the light-absorbing layer from 1 to 10 cm.
Interstate standard sample of the composition of aqueous solutions of manganese (II) ions with a mass concentration of 1 g / dm 3 with a permissible relative error of the certified value of no more than ± 2% at a confidence level of P = 0.95.
Scales of non-automatic operation in accordance with GOST OIML R 76-1 with limits of permissible absolute error no more than ± 0.001 g.
Volumetric flasks 2-50-2,2-100-2, 2-200-2.2-1000-2 in accordance with GOST 1770.
Measuring cylinders 2-10-2, 2-25-2, 2-50-2.2-100-2. 2-200-2.2-500-2, 2-1000-2 in accordance with GOST 1770.
Pipettes, graduated 1-1 -2-1, 1-1 -2-2. 1-1 -2-5. 1-1-2-10 or other types and designs in accordance with GOST 29227.
Household electric stove in accordance with GOST 14919.
Water bath of any type.
Mechanical or electronic stopwatch or mechanical clock according to GOST 10733, or electronic clock according to GOST 23350. or electronic-mechanical quartz clock according to GOST 26272 of any brand or timer.
A centrifuge of any type, suitable for centrifuging liquid volumes up to 100 cm3 and providing a rotation speed of at least 85 s "(5000 obUminugu)
Household refrigerator of any type, providing temperature from 2 ° С to 8 ° С.
Conical heat-resistant flasks with a capacity of 50.100, 250.500.1000.1500 cm 3 in accordance with GOST 25336.
Chemical glasses with a capacity of 1000 cm 3 in accordance with GOST 25336.
Evaporation bowls are porcelain GOST 9147 or quartz bowls in accordance with GOST 19908.
Glass sticks
Ash-free filters and red tape "
Ammonium persulphate (persulfate) in accordance with GOST 20478. analytical grade.
Magnesium sulfate 7-aodic according to GOST 4523. x. h. or h. d. a.
Sodium hydroxide (sodium hydroxide) in accordance with GOST 4328. х. h. or h. d. a.
Orthophosphoric acid in accordance with GOST 6552. х. h. or h. d. a.
Nitric acid in accordance with GOST 4461. х. h. or h. d. a.
Sulfuric acid in accordance with GOST 4204, analytical grade.
Silver nitrate according to GOST 1277, analytical grade
Mercury sulfate oxide. p.a., mass fraction of the main substance not less than 98%
Distilled water in accordance with GOST 6709.
Potassium persulfate (persulfate) according to GOST 4146 or sodium persulfate (persulfate), analytical grade
Sodium sulfate (sodium sulfate) in accordance with GOST 195. anhydrous, analytical grade.
Sodium sulfite in accordance with GOST 195. anhydrous, analytical grade.
Hydrogen peroxide in accordance with GOST 10929. x. h. or h. d. a.
Disodium ethylenediamium salt-MMNo.No "Tetraacetic acid 2-aqueous (Trilon B) according to GOST 10652.
Note - It is allowed to use tetrahydrate (C.oHuNiNa ^^ H.-O) or dihydrate (CioHwl4 / Na «Oo * 2H-0) of tetra sodium salt of ethylenediaminetraacetic acid.
Hydroxylamine hydrochloride according to GOST 5456.
Formaldehyde (НСНО), water solution(formalin) in accordance with GOST 1625.
Ammonia water in accordance with GOST 3760. chemically pure. or according to GOST 24147, special ch.
Salt of ferrous oxide and ammonium double sulfate (Mohr's salt) in accordance with GOST 4208.
Phenolphthalein (indicator), alcohol solution with a mass fraction of 0.1% according to GOST 4919.1.
Universal indicator paper.
Note - It is allowed to use other measuring instruments, apparatus, auxiliary devices and materials with metrological and technical characteristics not worse than those specified in this standard, as well as chemical reagents of higher qualification.
6 Determination of manganese content using oxidation to permanganate ions (method A)
6.1 The essence of the method
The essence of the method lies in the catalytic oxidation of manganese compounds with potassium persulfate or sodium persulfate to permanganate ions, followed by measuring the optical density of the solution and calculating the mass concentration of manganese in the water sample. When using an instrument equipped with a monochromator, set the operating wavelength to 525 nm. when using filter devices, select a filter that has an absorption maximum in the region of (530 ± 20) nm.
Depending on the method for eliminating the interfering effect of chloride ions, the following method options are established:
1 using magnesium hydroxide coprecipitation:
2 with evaporation with sulfuric acid:
3 using complexation with mercury (II).
6.2 Interfering influences
Interfering influences are eliminated during sample preparation. Elimination of interfering influences in variant 3 is effective if the content of chloride ions in an aliquot of a sample taken for analysis does not exceed 0.1 g.
6.3 Determination of manganese content with elimination of the interfering effect of chloride ions
coprecipitation with magnesium hydroxide (option 1)
6.3.1 Preparing for measurements
6.3.1.1 Preparation of a stock solution of manganese with a mass concentration of 10 mg / dm e
In a volumetric flask with a capacity of 100 cm 3, pipette 1 cm 3 of a standard sample of the composition of a solution of manganese (II) ions with a mass concentration of 1 g / dm 3, dilute with distilled water to about half the volume of the flask, add 0.5 cm3 of concentrated nitric acid and bring to the mark with distilled water.
6.3.1.2 Preparation of a 10% solution of magnesium sulfate
In a conical flask (or glass) with a capacity of 100 cm 3, add 10 g of 7-aqueous magnesium sulfate and dissolve in 90 cm 3 of distilled water.
The shelf life of the solution is not more than 6 months.
6.3.1.3 Preparation of a 20% volume fraction of phosphoric acid solution
800 cm 3 of distilled water is placed in a glass with a capacity of 1000 cm 3 and 200 cm 3 of e orthophosphoric acid is added carefully with stirring and, if necessary, with external cooling.
6.3.1.4 Preparation of 4% sodium hydroxide solution
In a conical flask with a capacity of 100 cm 3 place 96 cm 3 of distilled water and add 4 g of sodium hydroxide. After dissolving sodium hydroxide, the solution is transferred to a vessel made of polymeric material.
The shelf life of the solution is no more than 2 months.
6.3.1.5 Preparation of 1% silver nitrate solution
1 g of silver nitrate is introduced into a volumetric flask with a capacity of 100 cm 3, dissolved in distilled water and then brought to the mark with distilled water.
6.3.1.6 Preparation of calibration solutions
In conical heat-resistant flasks with a capacity of 50 or 100 ml oe add 0.00: 0.25 with a pipette; 0.50; 1.00; 2.00; 3.00: 4.00; 5.00 cm 3 stock solution of manganese (6.3.1.1). Add to each flask 10 ml of phosphoric acid solution 20% by volume (see 6.3.1.3). 10 cm 3 of silver nitrate solution (see 6.3.1.5) and 0.3 g of potassium persulfate or sodium persulfate. The contents of the flasks are diluted with distilled water to about 40 cm 3, brought to a boil on a hotplate and boiled for 3 minutes.
The solutions are cooled in a current cold water, transferred into volumetric flasks with a capacity of 50 ml. bring to the mark with distilled water and mix. The mass concentration of manganese in the prepared calibration solutions is equal to 0.00, respectively; 0.05; 0.10; 0.20; 0.40; 0.60; 0.80; 1.00 mg / dm 3.
The manganese-free calibration solution is a blank for calibration.
6.3.1.7 Preparing the device
6.3.1.8 G instrument radiometer
Measure the absorbance of all calibration solutions and the calibration blank (6.3.1.6) three times at the wavelength specified in 6.1. in an optical cell with a thickness of the light-absorbing layer from 2 to 4 cm. using distilled water as a reference solution.
For each calibration solution, the arithmetic mean value is calculated from the obtained optical density values.
The calibration characteristic is set in the form of the dependence of the arithmetic mean values of the optical density of the calibration solutions minus the arithmetic mean of the optical density of the blank sample from the mass concentration of manganese in the corresponding solution. Wherein:
If the device is equipped with a computer (microprocessor) system for collecting and processing information. then the calibration characteristic is set in accordance with the manual (instruction) for the operation of the device:
If the device does not provide for automated calibration, then the obtained calibration characteristics are processed by the method linear regression using the software designed for this purpose. In the absence of such a possibility, the slope of the calibration characteristic b is calculated. (optical density units) dm 3 mg ". according to the formula
1 (C,) 2
where C is the mass concentration of manganese in the w calibration solution, mg / dm 3;
A is the arithmetic mean of the optical density of the / th calibration solution minus the optical density of the blank sample for calibration, optical density units:
I is the number of calibration solutions.
Note - The software for some devices allows you to calculate the calibration coefficient K, equal to 1 / b.
6.3.1.9 Verification of the acceptability of the calibration characteristic
The verification of the acceptability of the calibration characteristic using a computer (microprocessor) system for collecting and processing information is carried out in accordance with the manual (instruction) for the operation of the device.
If the device does not have software providing for automated calibration, then for each calibration solution, calculate the value of the slope of the calibration characteristic L * (optical density units) dm 3 mg ". According to the formula
where A and C, - see 6.3.1.8.
The calibration characteristic is recognized as acceptable when the conditions are met at each calibration point
! ^ - 4s0.10. (3)
where 6 is the value of the slope of the calibration characteristic, calculated by the formula (1). (optical density units) dm 3 * mg ".
If this condition is not met, then the establishment of the calibration characteristic is repeated.
6.3.1.10 Control of the stability of the calibration characteristic
The stability of the calibration characteristic is monitored at least once a quarter, as well as when replacing reagents, after repair or a long downtime of the device. For control, use one or two newly prepared calibration solutions according to 6.3.1.6 (hereinafter referred to as control solutions).
Measure the absorbance of the control solutions in the same way as in 6.3.1.8 and. using the calibration characteristic, on the obtained values of the optical density, the value of the mass concentration of manganese in the control solutions is calculated.
The calibration characteristic is considered stable when the condition
I 0 - "- ~ C" I $ 0.12. (4)
where C meas is the mass concentration of manganese in the calibration solution obtained with the control
measurement. mg / dm 3;
C i is the actual value of the mass concentration of manganese in the calibration solution. mg / dm 3.
If condition (4) is not met for only one control solution, then this control solution is prepared again and repeated measurements are made. The results of the repeated control are considered final. In this case, if the condition of stability of the calibration characteristic is not met. then the instrument is calibrated again.
6.3.1.11 Preparing water samples for analysis
6.3.1.11.1 If the water sample has been preserved (3.2), then determine the volume of 4% sodium hydroxide solution required to neutralize the acid.
To do this, take an aliquot of water with a volume of Vi = 100 cm 3, add 3 to 5 drops of a 1% alcohol solution of phenolphthalein and pour in a 4% sodium hydroxide solution (6.3.1.4) from a graduated pipette until a pink color appears for 30 s. coloring. Record the volume of the sodium hydroxide solution consumed and, if necessary, recalculate it by the volume of the aliquot of the sample taken for the determination according to 6.3.1.11.2. Discard the aliquot used to find the volume of the sodium hydroxide solution.
6.3.1.11.2 If the water sample was not preserved during sampling, add 2 ml of a 4% sodium hydroxide solution (6.3.1.4) to a 100 ml aliquot of the sample. stir, add 2 cm 3 of a 10% solution of magnesium sulfate (6.3.1.2). mix again and leave until sediment of magnesium hydroxide, with which manganese is coprecipitated, to the bottom of the glass. 8 depending on the expected value of the mass concentration of manganese, the volume of the aliquot can be increased to 500 cm 3. In this case, the volume of the added solutions of sodium hydroxide and magnesium sulfate is changed proportionally.
If the water sample was preserved during sampling, then the volume of sodium hydroxide solution determined in accordance with 6.3.1.11.1 is added to the sample aliquot and then all the operations provided for the unconserved sample are carried out, starting with the addition of magnesium sulfate solution.
6.3.1.11.3 After settling most the solution over the precipitate is decanted, and the residue is filtered through an obesopenny filter "red penta". The filter cake is washed two to three times with distilled water and dissolved in 10 cm 3 of orthophosphoric acid solution (6.3.t.3), collecting the filtrate in a volumetric flask with a capacity of V? = 50 cm 3.
Wash the filter with distilled water two to three times like this. so that the total volume of the filtrate and wash water in the flask is approximately 35 cm 3. Then add 10 cm 3 of 1% silver nitrate solution (6.3.1.5) and mix. In this case, there should be no clouding of the solution due to the formation of silver chloride. About 0.3 g of ammonium persulfate or potassium persulfate is added to the solution, brought to a boil on a hotplate and kept in a boiling water bath for 10 minutes.
After cooling, the solution is brought to the mark with distilled water and the optical density is measured according to 6.3.2.
6.3.1.11.4 If, after adding the silver nitrate solution (6.3.1.5), a white precipitate or cloudiness forms, shake the flask containing the solution until then. until the precipitate gathers into lumps and the solution clears. Then the solution is centrifuged or filtered through a dry "red tape" filter into another volumetric flask with a capacity of 50 ml of e. the precipitate is washed 2-3 times with a small amount of distilled water and discarded. 0.3 g of ammonium persulfate or potassium persulfate (Section 5) is added to the filtrate with wash water. bring to a boil on a hotplate and incubate in a boiling water bath for 10 minutes. After cooling, the solution is brought to the mark with distilled water and the optical density is measured according to 6.3.2.
6.3.1.11.5 Prepare a blank sample in the same way, replacing the sample of the analyzed water with distilled water. If the water sample has been preserved (see 3.2). then, before analyzing a blank sample, nitric acid is added to it in the same volume as when the water sample was preserved.
6.3.2 Carrying out measurements
Measure the optical density of the sample and the blank sample prepared in accordance with 6.3.1.11 with respect to distilled water at least three times under the same conditions in which the calibration solutions were measured (see 6.3.1.8).
Calculate the arithmetic mean of the values obtained.
If the value of the optical density of the prepared sample is outside the upper limit of the range of the calibration characteristic, then the analysis of the sample is repeated by taking a smaller aliquot, or the water sample is diluted with distilled water before the start of the analysis and all operations are carried out with the diluted sample according to 6.3.1.11.1 6.3.1.11.4 ...
Dilution factor (calculated by the formula
where V t is the volume of the volumetric flask used to dilute the sample, cm 3:
V A is the volume of the sample aliquot taken for dilution, cm 3.
6.3.3 Processing of measurement results
6.3.3.1 If there is a computer (microprocessor) system for collecting and processing information, the procedure for processing the results is determined by the manual (instruction) for the operation of the device.
6.3.3.2 In the absence of a computer (microprocessor) system for collecting and processing information, the mass concentration of manganese in the water sample X, mg / dm 3. calculated by the formula
where A is the optical density of the prepared water sample (6.3.2). optical density units;
A a is the optical density of a blank water sample (6.3.2). optical density units:
V 2 is the volume of the sample prepared according to 6.3.1.11.3, cm 3:
/ is the dilution factor (formula (5)].
b is the slope of the calibration characteristic [formula (1)]. (optical density units) dm 3 mg
Vt is the volume of the sample aliquot (original or diluted according to 6.3.2). taken to carry out the definition no 6.3.1.11.1 or 6.3.1.11.2. cm 3:
6.3.3.3 The arithmetic mean of the results of two measurements X and Xr is taken as the result of measurements of the mass concentration of manganese. obtained under repeatability conditions, when the condition
200 | X 1 -X 2 | £ g (X 1 - "- X 2), (7)
where r is the value of the repeatability limit according to table 1.
If condition (7) is not met, methods of checking the acceptability of measurement results are used. obtained under repeatability conditions, and establishing the final measurement result in accordance with GOST ISO 5725-6, subsection 5.2.
Note - When obtaining measurement results in two laboratories, the arithmetic mean value of the measurement results obtained in two laboratories X \ p and X? L is taken as the measurement result when the condition
where R is the value of the reproducibility limit by tabts | e 1.
If condition (8) is not met, each laboratory must follow the procedures in accordance with ISO 5725-6 clauses 5.2.2 to verify acceptability under reproducibility conditions. 5.3.2.2.
6.3.4 Metrological characteristics
The method provides for obtaining measurement results with metrological characteristics not exceeding the values given in Table 1. with a confidence level of P = 0.95.
Table 1
|
Repeatability length |
Reproducibility limit |
Accuracy index |
|
|
(relative value |
(otiositep value |
(boundaries * relative |
|
|
acceptable discrepancy |
acceptable discrepancy |
error at |
|
|
Measurement range of mass |
between the two result- |
probabilities |
|
|
under the same conditions, repeating |
conditions reproducibly | ||
|
capacity at P "0.95) | |||
|
P - 0.95) 1 b. % |
|||
|
0.01 to 0.05 incl. | |||
|
Behold. 0.05 to 5.00 incl. | |||
|
* The established numerical values of the gram of the relative error correspond to the numerical |
|||
|
expanded uncertainty values (in relative units) 1) c. h with a coverage ratio k = 2. |
|||
If the water sample was diluted according to 6.3.2. then use the values of the metrological characteristics according to table 1 for the diluted sample.
6.3.5 Quality control of measurement results
Quality control of measurement results in the laboratory provides for monitoring the stability of measurement results taking into account the requirements of GOST ISO 5725-6 or recommendations (1).
6.3.6 Registration of measurement results
The measurement results are recorded in a test report, which is drawn up in accordance with the requirements of GOST ISO / IEC 17025. In this case, the test report must contain a reference to this standard indicating the measurement method.
Results of measurements of the mass concentration of manganese. mg / dm e. represent in the form
X ± 0.01-5-X at P = 0.95 or X ± 0.01 U cmH X at k = 2. (9)
where b - confidence limits of the relative measurement error of the mass concentration of manganese according to table 1,%;
Tsm "- relative expanded uncertainty. %, with a coverage factor of k = 2 according to table 1.
The numerical value of the measurement result must end with a digit of the same digit as the absolute value of the measurement accuracy, expressed in milligrams per cubic decimeter. The absolute value of the measurement accuracy indicator is represented by two significant digits, if the first digit does not exceed three. In other 8 cases, one significant digit is left.
6.4 Determination of manganese content with elimination of the interfering effect of chloride * ions
by evaporation with sulfuric acid (option 2)
6.4.1 Preparation for measurements - according to 6.3.1 with the following clarifications below.
6.4.1.1 Preparation of a solution of silver nitrate with a molar concentration of 0.1 mol / dm 3
In a conical flask with a capacity of 1500 cm 3 dissolve 17 g of silver nitrate in 1000 cm 3 of distilled water.
The shelf life of the solution in a dark glass container is no more than 1 month.
Note - It is allowed to prepare a smaller volume of solution, based on the need.
6.4.1.2 Preparation of a solution of sulfuric acid with a volume fraction of 33.3%
In a heat-resistant glass with a capacity of 1000 cm 3 is placed 500 cm 3 of distilled water and carefully, with stirring and external cooling, poured 250 cm 3 of concentrated sulfuric acid.
The shelf life of the solution is not limited.
6 4.1.3 Preparing water samples for analysis
In a porcelain bowl, add an aliquot of the water sample, measured with a cylinder, carefully add 5 cm 3 of the sulfuric acid solution (6.4.1.2) and evaporate first in a water bath and then on an electric stove to completely remove the acid.
Note - The recommended volume of a sample aliquot is 100 cm 3 with the expected value of the mass concentration of manganese in the sample from 0.05 to 1 mg / dm 3. At a higher content of manganese (from 0.01 to 0.05 mg / dm 3), the volume of liquid should be increased to 250 500 cm 3, and at a higher content (over 1 mg / dm 3), it should be reduced to 20 or 25 cm 3.
The dry residue is moistened with a small amount of distilled water, 5 cm 3 of concentrated nitric acid are added (Section 5). 10 cm 3 of hot distilled water and heated until the precipitate dissolves. The solution is transferred into a heat-resistant conical flask with a capacity of 50 cm 3, add 3 cm 3 of a solution of silver nitrate with a molar concentration of 0.1 mol / dm 3 (see 6.4.1.1), add 0.2 g of ammonium persulfate (section 5). heat to a boil and boil on a hotplate for 3 minutes.
The flask is cooled under a stream of cold water, its contents are quantitatively transferred into a volumetric flask with a capacity of 50 cm 3 and its volume is brought up to the mark with distilled water, then measurements are carried out according to 6.4.2.
6.4.1.4 Prepare a blank sample according to 6.3.1.11.5.
6.4.2 Carrying out measurements - according to 6.3.2 using the calibration characteristic according to 6.3.1.8. Distilled water is used as a reference solution.
6.4.3 Processing of measurement results - according to 6.3.3.
6.4.4 Metrological characteristics - according to 6.3.4.
6.4.5 Quality control of measurement results - according to 6.3.5.
6.4.6 Registration of measurement results - according to 6.3.6.
6.5 Determination of manganese content with elimination of the interfering effect of chloride ions
adding mercury sulfate (option 3)
6.5.1 Preparation for measurements - according to 6.3.1 with the following clarifications below.
6.5.1.1 Preparing mixed reagent
In a heat-resistant conical flask with a capacity of 1000 cm 3 add 200 cm 3 of distilled water. 40 (Concentrated nitric acid and 75 g of oxide mercury sulfate, then add 200 cm 3 of orthophosphoric acid (section 5) and (35 ± 1) g of silver nitrate (section 5). After cooling, the contents of the flask are transferred into a volumetric flask with a capacity of 1000 cm 3 and bring to the mark with distilled water.
The shelf life of the mixed reagent is no more than 6 months.
Note - It is allowed to prepare a smaller volume of the mixed reagent, depending on the need.
6.5.1.2 Preparing calibration solutions
In heat-resistant conical flasks with a capacity of 100 cm 3 pipettes add 0.00: 0.50: 1.00; 2.00: 4.00; 6.0; 8.0 and Yu.O cm 3 stock solution of manganese (6.3.1.1).
The contents of the flasks are diluted with distilled water to a volume of 80 - 90 cm 3 and 5 cm 3 of the mixed reagent (6.5.1.1), 1.0 g of ammonium persulfate (section 5) are added to each flask. bring the solution to a boil and boil on an electric stove for 3 minutes.
The flasks are quickly cooled under a stream of cold water, their contents are transferred into volumetric flasks with a capacity of 100 cm 3, brought to the mark with distilled water and mixed.
A manganese-free calibration solution (with a mass concentration of manganese equal to zero) is a blank for calibration. The mass concentration of manganese in the rest of the calibration solutions is 0.05, respectively; 0.Yu; 0.20: 0.40; 0.60; 0.80; 1.00 mg / dm 3.
The calibration solutions are prepared on the day of use.
6.5.1.3 Preparing the device
The preparation of the device for operation is carried out in accordance with the manual (instruction) for the operation of the device.
6.5.1.4 Calibration of the device - according to 6.3.1.8 using calibration solutions according to 6.5.1.2. verification of the acceptability of the calibration characteristic - according to 6.3.1.9, control of the stability of the calibration characteristic - according to 6.3.1.10.
6.5.1.5 Preparing water samples for analysis
In a heat-resistant conical flask with a capacity of 100, 250 or 500 cm 3, add an aliquot of a water sample with a cylinder, add 1 drop of hydrogen peroxide (Section 5). 5 cm 3 of the mixed reagent (6.5.1.1) and the sample is concentrated by evaporation on a hotplate to 90 cm 3 or diluted with distilled water to the same volume. Then add 1.0 g of ammonium persulfate (section 5) and bring the solution to a boil on an electric hot plate and boil for 3 minutes.
The flask is cooled under a stream of cold water, its contents are transferred into a volumetric flask with a capacity of 100 cm 3, brought to the mark with distilled water and mixed.
Note - The recommended volume of an aliquot of the sample is 100 cm 3 with the expected value of the mass concentration of manganese in the sample from 0.05 to 1 mg / dm 3. At a lower manganese content (from 0.01 to 0.05 mg / dm 3), the volume of a / quat should be increased to 250 * 500 cm 3, and at a higher (over 1 mg / dm 3) - reduced to 20 or 25 cm 3.
6.5.1.6 Prepare a blank sample according to 6.3.1.11.5.
6.5.2 Carrying out measurements - according to 6.3.2 using the calibration characteristic according to 6.5.1.4. Distilled water is used as a reference solution.
6.5.3 Processing of measurement results - according to 6.3.3.
6.5.4 Metrological characteristics - cl 6.3.4.
6.5.5 Quality control of measurement results - in accordance with 6.3.5.
6.5.6 Registration of measurement results - according to 6.3.6.
7 Determination of manganese content using formaldoxime (method B)
7.1 The essence of the method
The essence of the method is the formation of a complex compound of manganese with al-doxyme in an alkaline medium, followed by measuring the optical density of the solution and calculating the mass concentration of manganese in the water sample. When using a device equipped with a monochromator. set the working wavelength to 455 nm. when using filter devices, select a filter that has an absorption maximum in the region of (440 ± 20) nm.
7.2 Interfering influences
Iron (II) ions form a violet complex with formaldoxime. which interferes with the determination of manganese. This influence is eliminated during sample preparation by adding solutions of sodium ethyl acetate-mintetraacetate (7.3.1). a mixed solution of hydroxylamine hydrochloride and ammonia (7.3.5) and Mohr's salt (7.3.7). containing iron (II) ions. into all calibration solutions, blank and aliquot of water sample.
The presence of 1 mg / dm 3 cobalt (which is unlikely for water within the scope of this standard) gives a response equivalent to 40 μg / dm 3 manganese.
In the presence of calcium, orthophosphate ions with a content above 2 mg / dm 3 (in terms of phosphorus) may underestimate the results. The combined presence of calcium and magnesium with a total mass concentration of more than 300 mg / dm 3 causes an overestimation of the results. These interfering influences are eliminated when preparing a water sample according to 7.3.13.
7.3 Preparation for measurements
7.3.1 Preparation of a solution of sodium ethyl diamine tetraacetate with a molar concentration of 0.24 mol / dm e
In a volumetric flask with a capacity of 1000 cm 3, half filled with water, add 90 g of Trilon B. add 19 g of sodium hydroxide and, after complete dissolution, bring to the mark with distilled water.
Note - Similarly, you can obtain the specified solution by dissolving in distilled water 109 g of tetrahydrate (CtoHwN ^ Na ^^ MjO) or 100 g of dihydrate (C, 0 H, rN.Na4O e -2HyO) tetrahydrogen salt of ethylenediaminetetraacetic acid in distilled water and bring to distilled water marks.
7.3.2 Preparation of formaldoxime solution
In a volumetric flask with a capacity of 100 cm 3 add 50 cm 3 of distilled water, add 10 g of hydroxylamine hydrochloride and after its dissolution add 5 cm 3 of an aqueous solution of formaldehyde (formalin) and bring to the mark with distilled water.
The shelf life of the solution at a temperature from 2 ° C to 8 * C is no more than 1 month.
7.3.3 Preparation of a solution of hydroxylamine hydrochloride with a molar concentration of 6 mol / dm 3
In a volumetric flask with a capacity of 100 cm 3 add 42 g of hydroxylamine hydrochloride, dissolve in distilled water and then bring to the mark with distilled water.
The shelf life of the solution at a temperature of 2 ° C to 8 ° C is no more than 1 month.
7.3.4 Preparation of ammonia solution with molar concentration of 4.7 mol / dm 3
In a volumetric flask with a capacity of 200 cm 3, add 50 cm 3 of distilled water, add 70 cm 3 of concentrated aqueous ammonia solution (section 5) and bring to the mark with distilled water.
The shelf life of the solution in a tightly closed container made of polymer material is no more than 2
7.3.5 Preparation of a mixed solution of hydroxylamine hydrochloride and ammonia
Mix equal volumes of the solutions of ammonia (7.3.4) and hydroxylamine hydrochloride (7.3.3).
The shelf life of the solution at a temperature of 2 s C to 8 ° C in a tightly closed container made of polymeric material is no more than 7 days.
7.3.6 Preparation of a solution of sulfuric acid with a molar concentration of about 3 mol / dm 3
In a heat-resistant glass with a capacity of 1000 cm 3, 750 cm 3 of distilled water is added, carefully with stirring and, if necessary, cooling add 170 cm 3 of concentrated sulfuric acid. The contents of the glass are allowed to cool, transferred to a volumetric flask with a capacity of 1000 cm 3 and brought to the mark with distilled water.
The shelf life of the solution is no more than 1 year.
7.3.7 Preparation of Mohr's salt solution of mass concentration 700 mg / dm 3
Into a volumetric flask with a capacity of 1000 cm 3 add 500 cm 3 of distilled water, add 700 mg of Mohr's salt ((NHifeFefSO ^? 6HgO], after dissolution add 1 cm 3 of sulfuric acid solution (7.3.6) and bring to the mark with distilled water.
The shelf life of the solution at a temperature of 2 ° C to 8 J C in a dark place is no more than 3 months.
7.3.8 Preparation of a sodium hydroxide solution with a molar concentration of 4 mol / dm 3
In a glass or conical flask, place from 500 to 600 cm 1 of distilled water, add 160 g of sodium hydroxide and, after complete dissolution, transfer to a volumetric flask with a capacity of 1000 cm 3 and bring to the mark with distilled water.
The shelf life of the solution in a container made of polymeric material is no more than 2 months.
7.3.9 Preparation of an initial solution of manganese with a mass concentration of 100 mg / dm 3
In a volumetric flask with a capacity of 50 cm 3 add 5 cm 3 of a standard sample of the composition of a solution of manganese (II) ions. add 0.5 ml of sulfuric acid solution (7.3.6). bring the volume in the flask to the mark with distilled water and mix.
The shelf life of the solution is no more than 3 months.
7.3.10 Preparation of a working solution of manganese with a mass concentration of 5 mg / dm 3
Into a volumetric flask with a capacity of 50 cm 3 add 2.5 cm 3 of the stock solution of manganese (7.3.9). add 0.5 ml of sulfuric acid solution (7.3.6) and make up to the mark with distilled water.
The shelf life of the solution is no more than 1 month.
7.3.11 Preparation of calibration solutions
7.3.11.1 Preparation of manganese calibration solutions in the mass concentration range from 0.05 to 1.00 mg / dm 3
Pipettes 0.0; 0.5; 1.0; 2.0; 4.0; 6.0; 8.0 and 10.0 cm 3 of the working manganese solution according to 7.3.10. add 0.5 cm 3 of a sulfuric acid solution according to 7.3.6 and bring to the mark with distilled water. The mass concentration of manganese in the working calibration solutions is, respectively, 0.00: 0.05: 0.10: 0.20: 0.40: 0.60: 0.80 and 1.00 mg / dm 3.
7 3.11.2 Preparation of calibration solutions for the mass concentration range of manganese from 0.5 to 5.0 mg / dm 3
In a row of seven volumetric flasks with a capacity of 50 cm 3 each add 0.00: 0.25: 0.50: 1.00: 1.50; 2.00 and 2.50 cm 3 of the original manganese solution according to 7.3.9. add 0.5 cm 3 of a sulfuric acid solution according to 7.3.6 and bring to the mark with distilled water. The mass concentration of manganese in the calibration solutions is 0.0, respectively; 0.5; 1.0; 2.0: 3.0: 4.0 and 5.0 mg / dm 3.
Calibration solutions are prepared before use.
7.3.11.3 Processing of calibration solutions to form a colored compound
Transfer the calibration solutions (7.3.11.1 and 7.3.11.2) into conical flasks with a capacity of 100
Into each conical flask with calibration solutions (7.3.11.1. 7.3.11.2) add 1 ml of Mohr's solution (II) (7.3.7). 2 cm 3 of ethylenediamitetraacetate solution (7.3.1) and stir, then add 1 cm 3 of formaldoxime solution (7.3.2) and immediately add 2 cm 3 of sodium hydroxide solution (7.3.8).
The contents of each flask are thoroughly mixed and after 5 - 10 minutes add to each flask, stirring its contents. 3 cm 3 of a mixed solution of hydroxylamine hydrochloride and ammonia (7.3.5). The solutions are kept at room temperature for at least 1 hour but not more than 4 hours and then measurements are carried out according to 7.3.12.
Calibration solutions that do not contain manganese (with a mass concentration of manganese equal to zero) are a blank sample for calibration.
7.3.12 Calibration of the device - according to 6.3.1.8 using calibration solutions processed according to 7.3.11.3, and establishing separate calibration characteristics for the range from 0.05 to 1.00 mg / dm 3 using cuvettes with an absorbing layer thickness of 4 to 10 cm (recommended value 5 cm) and from 0.5 to 5.0 mg / dm 3 using cuvettes with an absorbing layer thickness of 1 cm. The absorbance value of the blank sample for calibration against distilled water is used when checking the acceptability of the absorbance of the blank sample according to 7.3.14.
Checking the acceptability of the calibration characteristics in accordance with 6.3.1.9. control of the stability of the calibration characteristics - according to 6.3.1.10.
7.3.13 Preparing water samples
7.3.13.1 If the sample has not been preserved, then it is acidified in accordance with 3.3.
7.3.13.2 If the expected value of the mass concentration of manganese in the sample is not less than 0.05 mg / dm 3. then take an aliquot of the analyzed sample (3.3. 7.3.13.1) with a volume of 50 cm 3 with a cylinder and transfer it to a conical flask with a capacity of 100 cm 3.
7.3.13.3 If the expected value of the mass concentration of manganese in the water sample is less than 0.05 mg / dm 3. then take an aliquot of the analyzed water (3.3. 7.3.13.1) with a volume of 250 cm 3 with a cylinder. Place the sample in an evaporation dish and evaporate in a water bath or electric stove, if necessary in several steps, to a volume of about 30 cm 3. During evaporation on a hot plate, the sample should not boil to avoid splashing. The one stripped off sample is transferred into a conical flask with a capacity of 100 cm 3, add 2.5 cm 3 of sodium hydroxyl solution (7.3.8) and dilute to the mark with distilled water.
Make sure that after adding the sodium hydroxide solution the pH of the sample does not exceed 3 (control with universal indicator paper). If this condition is not met, then add dropwise a solution of sulfuric acid according to 7.3.6 until a pH value of less than 3 is reached.
7.3.13.4 To the sample (7.3.13.2, 7.3.13.3) add (225 ± 25) mg of potassium persulfate or sodium persulfate as an oxidizing agent (Section 5) and boil for 40 min. cool, transfer the contents of the flask into a volumetric flask with a capacity of 50 cm 3, bring to the mark with distilled water and add about 0.5 g of sodium sulfite (Section 5) to remove excess oxidant.
7.3.13.5 Transfer the sample processed according to 7.3.13.4 into a conical flask with a capacity of 100 ml.
Add 1 ml of Mohr's salt solution (7.3.7) to the contents of the conical flask. 2 cm 3 of sodium ethylenediaminetetracetate solution (7.3.1) and mix, then add 1 cm 3 of formaldoxime solution (7.3.2) and immediately add 2.5 cm 3 of sodium hydroxide solution (7.3.6) and mix thoroughly.
After 5-10 mms, add to the analyzed sample with stirring. 3 cm 3 of a mixed solution of hydroxylamine hydrochloride and ammonia (7.3.5) and incubate at room temperature for at least 1 h.
Turbid samples are centrifuged before measurements in accordance with 7.4.
7.3.14 Analysis of a blank
Distilled water is used as a blank sample, the volume of which is equal to the volume of an aliquot of the analyzed water. Prepare a blank sample for measurements according to 7.3.13 simultaneously with water samples.
If the optical density of the prepared blank sample, measured relative to distilled water, differs significantly (by more than 0.02 optical density units) from the optical density value of the blank sample for calibration (7.3.11.3). measured with respect to distilled water, the reasons for this difference should be established and eliminated. The most likely reason is contamination of the chemicals used and / or distilled water, insufficient cleanliness of the dishes.
7.4 Carrying out measurements - similarly to 6.3.2, taking into account the requirements of 7.3.12. A blank sample prepared according to 7.3.14 is used as a reference solution.
7.5 Processing of measurement results according to 6.3.3 using metrological characteristics according to table 2.
7.6 Metrological characteristics
The method provides for obtaining measurement results with metrological characteristics not exceeding the values given in Table 2. with a confidence level of P = 0.95.
table 2
|
Measurement range of mass concentration of manganese, mg / dm * |
The repeatability limit of the allowed discrepancies. obtained about uelo - 0.95) g |
Reproducibility limit acceptable discrepancy between the two results reproducibility conditions at P 0.95) R.% |
Accuracy indicator ((early * relative favorability with probability |
|
0.01 to 0.05 incl. | |||
|
St. 0.05 to 0.20 incl. | |||
|
St. 0.2 to 5.0 incl. | |||
|
* The established numerical values of the limits of the relative error correspond to numerical values expanded uncertainty (in otiositeg units) (Jet. with a coverage factor k = 2. |
|||
If the water sample was diluted (6.3.2. 7.4) then use the values of the metrological characteristics according to Table 2 for the diluted sample.
7.7 Quality control of measurement results - according to 6.3.5.
7.8 Registration of measurement results - according to 6.3.6 using metrological characteristics according to Table 2.
Bibliography
Recommendations for Interstate Standardization RMG 76-2004. State system for ensuring the uniformity of measurements. Internal quality control of the results of quantitative chemical analysis
UDC 628.1.033: 006.354 MKS 13.060.50 TN VED 220100000
Key words: drinking water, water from underground sources, water from surface sources, mass concentration of manganese, photometric methods, tests
Signed for printing 03.03.2015. Format 60x84%.
Uel. print l. 2.33. Circulation 31 copies. Zach. 1096
Prepared on the basis of the electronic version provided by the developer of the standard
FSUE STANDARTENFORM *. 123995 Moscow. Granatny lane .. 4.
2 REFERENCES
Throughout this standard, references are made to the following standards:
4 POTENTIOMETRIC METHOD
The method is based on the oxidation reaction of divalent manganese with a solution of potassium permanganate to trivalent in a neutral medium in the presence of sodium pyrophosphate.
The influence of iron, titanium, aluminum, chromium and other elements is eliminated by binding them into soluble pyrophosphate complexes.
Potassium carbonate - sodium carbonate according to GOST 4332.
Sodium peroxide.
Hydrogen peroxide in accordance with GOST 10929.
Sodium carbonate according to GOST 83, solution 50 g / dm 3.
Sodium diphosphate 10-water according to GOST 342, solution 120 g / dm 3. The solution is prepared 24 hours before use.
Bromothymol blue (indicator), solution 0.4 g / dm 3.
Metallic manganese in accordance with GOST 6008, purity not less than 99.9%; 10 g of metallic manganese is placed in a glass with a capacity of 400 cm 3, the surface layer is treated for several minutes with a mixture of 50 cm 3 of water and 5 cm 3 of nitric acid until a shiny surface is obtained. The manganese is washed six times with water, then with acetone and dried at 100 ° C for 10 minutes.
A standard solution of manganese 1 g / dm 3, prepared as follows: 1.0000 g of metallic manganese is placed in a glass with a capacity of 400 cm 3, 20 cm 3 of sulfuric acid diluted 1: 1 and 100 cm 3 of water are added. The solution is boiled for several minutes, cooled, poured into a volumetric flask with a capacity of 1000 cm 3, added to the mark with water and mixed. 1 cm 3 of the solution contains 0.001 g of manganese.
Potassium permanganate according to GOST 20490, purity not less than 99.5% and recrystallized as follows: 250 g of potassium permanganate is placed in a glass with a capacity of 1 dm 3 and 800 cm 3 of water heated to 90 ° C is poured. The solution is filtered under vacuum through a crucible with a filtering glass plate No. 3. The filtered solution is rapidly cooled in ice-water to 10 ° C with vigorous stirring and the fine-crystalline precipitate is allowed to settle. Then the solution is poured off, the crystalline mass is transferred into a crucible with a filtering glass plate No. 3 and sucked off. The recrystallization is repeated once more. The resulting crystalline mass is transferred onto glass or into a wide porcelain cup and dried in air in a place protected from light, protecting from dust. When the crystalline mass, when crushed with a glass rod, stops sticking together, it is dried at 80 - 100° C for 2 - 3 hours in a drying oven. Then transferred to a dark glass jar with a ground-in cork. The potassium permanganate purified in this way is completely non-hygroscopic.
A titrated solution of potassium permanganate 1.8 g / dm 3, prepared as follows: 1.8 g of potassium permanganate is dissolved in 1 dm 3 of water and left for 6 days, then the solution is poured through a siphon into a dark glass bottle.
The mass concentration of a titrated solution of potassium permanganate according to a standard manganese solution is set as follows: an aliquot of a standard manganese solution with a volume of 100 cm 3 is taken into a glass with a capacity of 400 - 500 cm 3 containing 150 cm 3 of a solution of sodium pyrophosphate. Set the pH of the solution to 7, as indicated in, and titrate with a solution of potassium permanganate in accordance with. In parallel, a control experiment is carried out without adding a standard manganese solution.
Mass concentration WITH of a titrated solution of potassium permanganate in grams of manganese per cubic centimeter, established by a standard solution, is calculated by the formula
WITH = ,
where T- mass of manganese in an aliquot of a standard solution, g;
Mass concentration WITH a titrated solution of potassium permanganate in grams of manganese per cubic centimeter, established by potassium permanganate, is calculated by the formula
WITH = ,
where T - weight of a sample of potassium permanganate, g;
Mass concentration WITH a titrated solution of potassium permanganate in grams of manganese per cubic centimeter, established according to a standard sample, is calculated by the formula
WITH = ,
where A - mass fraction of manganese in a standard sample,%;
T -weight of a sample of a standard sample, g;
V 1 - the volume of potassium permanganate solution consumed for titration of a standard manganese solution, cm 3;
V 2 - the volume of potassium permanganate solution consumed for titration of the control experiment solution, cm 3.
5.11.2 Potassium permanganate standardization ( )
Place 1.5 g of potassium permanganate () in a fluoroplastic or Teflon glass with a capacity of 250 - 300 cm 3, add 30 - 40 cm 3 of water and mix thoroughly. Hydrochloric acid (20 cm 3) is poured in, covered with a watch glass and heated. At the end of the reaction, the watch glass is removed and washed with water. To the cooled solution add 10 cm 3 perchloric acid () and 20 cm 3 hydrofluoric acid (
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INTERSTATE COUNCIL FOR STANDARDIZATION. METROLOGY AND CERTIFICATIONS
INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION
INTERSTATE
STANDARD
DRINKING WATER
Determination of manganese content by photometric methods
(ISO 6333: 1986, NEQ)
Official edition
Standardinform
Foreword
The goals, basic principles and procedure for carrying out work on interstate standardization are established by GOST 1.0-92 “Interstate standardization system. Basic Provisions "and GOST 1.2-2009" Interstate Standardization System. Interstate standards, rules and recommendations for interstate standardization. Rules for development, acceptance, application, updating and cancellation "
Information about the standard
1 PREPARED by Limited Liability Company "Protector" together with Limited Liability Company "Lumex Marketing"
2 INTRODUCED by the Federal Agency for Technical Regulation and Metrology. Technical Committee for Standardization TC 343 "Water Quality"
3 ACCEPTED by the Interstate Council for Standardization, Metrology and Certification (minutes of October 20, 2014 N? 71-P)
4 This standard has been developed taking into account the main provisions of the international standard ISO 6333: 1986 Water quality - Determination of manganese - Formaldoxime spectrometric method, in part of clause 7
Degree of Compliance - Non-Equivalent (NEQ)
6 By order of the Federal Agency for Technical Regulation and Metrology of November 11, 2014 No. 1539-st, the interstate standard GOST 4974-2014 was put into effect as a national standard of the Russian Federation from January 1, 2016.
10% solution of magnesium sulfate (6.3.1.2). mix again and leave until sediment of magnesium hydroxide, with which manganese is coprecipitated, to the bottom of the glass. Depending on the expected value of the mass concentration of manganese, the volume of the aliquot can be increased to 500 cm 3. In this case, the volume of the added solutions of sodium hydroxide and magnesium sulfate is changed proportionally.
If the water sample was preserved during sampling, then the volume of sodium hydroxide solution determined in accordance with 6.3.1.11.1 is added to the sample aliquot and then all the operations provided for the unconserved sample are carried out, starting with the addition of magnesium sulfate solution.
6.3.1.11.3 After settling, most of the solution is decanted over the precipitate, and the residue is filtered through an ash-free "red ribbon" filter. The filter cake is washed two to three times with distilled water and dissolved in 10 cm 3 of orthophosphoric acid solution (6.3.1.3), collecting the filtrate in a volumetric flask with a capacity of V 2 = 50 cm 3.
Wash the filter with distilled water two to three times like this. so that the total volume of the filtrate and wash water in the flask is approximately 35 cm 3. Then add 10 cm 3 of 1% silver nitrate solution (6.3.1.5) and mix. In this case, there should be no clouding of the solution due to the formation of silver chloride. About 0.3 g of ammonium persulfate or potassium persulfate is added to the solution, brought to a boil on a hotplate and kept in a boiling water bath for 10 minutes.
After cooling, the solution is brought to the mark with distilled water and the optical density is measured according to 6.3.2.
6.3.1.11.4 If, after adding the silver nitrate solution (6.3.1.5), a white precipitate or cloudiness forms, shake the flask containing the solution until then. until the precipitate gathers into lumps and the solution clears. Then the solution is centrifuged or filtered through a dry "red tape" filter into another volumetric flask with a capacity of 50 cm 3, the precipitate is washed 2-3 times with a small amount of distilled water and discarded. 0.3 g of ammonium persulfate or potassium persulfate (Section 5) is added to the filtrate with wash water. bring to a boil on a hotplate and incubate in a boiling water bath for 10 minutes. After cooling, the solution is brought to the mark with distilled water and the optical density is measured according to 6.3.2.
6.3.1.11.5 Prepare a blank sample in the same way, replacing the sample of the analyzed water with distilled water. If the water sample has been preserved (see 3.2), then before the analysis of the blank sample, add nitric acid to it in the same volume as when preserving the water sample.
6.3.2 Conduct of measurements
Measure the optical density of the sample and the blank sample prepared in accordance with 6.3.1.11 with respect to distilled water at least three times under the same conditions in which the calibration solutions were measured (see 6.3.1.8).
Calculate the arithmetic mean of the values obtained.
If the value of the optical density of the prepared sample is outside the upper limit of the range of the calibration characteristic, then the analysis of the sample is repeated by taking a smaller aliquot, or the water sample is diluted with distilled water before the start of the analysis and all operations are carried out with the diluted sample according to 6.3.1.11.1 6.3.1.11.4 ...
Dilution factor (calculated by the formula
where V is the volume of the volumetric flask used to dilute the sample, cm 3;
The volume of the sample aliquot taken for dilution, cm 3.
6.3.3 Processing of measurement results
6.3.3.1 If there is a computer (microprocessor) system for collecting and processing information, the procedure for processing the results is determined by the manual (instruction) for the operation of the device.
6.3.3.2 In the absence of a computer (microprocessor) system for collecting and processing information, the mass concentration of manganese in a water sample X. mg / dm 3 is calculated by the formula
Information about changes to this standard is published in the annual information index "National Standards", and the text of changes and amendments is published in the monthly information index "National Standards". In the event of a resehot (replacement) or cancellation of this standard, a corresponding notice will be published in the monthly 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
© Standartinform, 2015
In the Russian Federation, this standard cannot be reproduced in whole or in part. replicated and distributed as an official publication without the permission of the Federal Agency for Technical Regulation and Metrology
1 area of use............................................... .................................................. ....................................one
3 Sampling ............................................... .................................................. .................................................. ..2
4 Requirements for the conditions of measurements ............................................ ............................................ 2
5 Measuring instruments, auxiliary equipment, reagents, materials ...................................... 3
6 Determination of manganese content using oxidation to permanganate ions
(method A) .............................................. .................................................. .................................................. ......4
7 Determination of manganese content using formaldoxime (method B) .......................... 11
Bibliography................................................. .................................................. ..............................................15
INTERSTATE STANDARD
DRINKING WATER Determination of manganese content by photometric methods Drinking water. Determination ot manganese content by photometric methods
Date of introduction - 2016-01-01
1 area of use
This standard applies to drinking water, including packaged in containers. and water from underground and surface sources of drinking water supply and establishes photometric methods for determining the content of manganese in the range of mass concentrations from 0.01 to 5.00 mg / dm 3 using:
Oxidation of manganese compounds to permanganate ions after removing the interfering effect of chloride ions (method A);
Formation of a colored compound with formaldoxime (method B).
If the mass concentration of manganese exceeds 5 mg / dm 3. then the analyzed sample is diluted with distilled water, but not more than 100 times.
The methods provide comparable results.
This standard uses normative references to the following interstate standards:
GOST OIML R 76-1-2011 State system for ensuring the uniformity of measurements. Scales of non-automatic operation. Part 1. Metrological and technical requirements. Testing
4.2 Measurements of volumes of water and solutions are carried out at an ambient temperature of 15 ° C to 25 ° C.
4.3 All solutions, unless otherwise specified, should be stored at an ambient temperature of 15 ° C to 25 “C in closed containers.
4.4 Laboratories conducting tests must comply with the requirements of GOST ISO / IEC 17025.
5 Measuring instruments, auxiliary equipment, reagents, materials
Photometer, spectrophotometer, photoelectrocolorimeter, photometric analyzer (hereinafter referred to as the device), allowing to measure the optical density of a solution in the wavelength range from 400 to 700 nm with an admissible absolute measurement error of the spectral transmittance of no more than ± 2% in optical cells with a thickness of the light-absorbing layer from 1 to 10 cm.
Interstate standard sample of the composition of aqueous solutions of manganese (II) ions with a mass concentration of 1 g / dm 3 with a permissible relative error of the certified value of no more than ± 2% at a confidence level of P = 0.95.
Scales of non-automatic operation in accordance with GOST OIML R 76-1 with limits of permissible absolute error no more than ± 0.001 g.
Volumetric flasks 2-50-2. 2-100-2, 2-200-2. 2-1000-2 in accordance with GOST 1770.
Measuring cylinders 2-10-2, 2-25-2. 2-50-2. 2-100-2. 2-200-2, 2-500-2, 2-1000-2 in accordance with GOST 1770.
Pipettes, graduated 1-1-2-1, 1-1-2-2. 1-1-2-5. 1-1-2-10 or other types and designs in accordance with GOST 29227.
Household electric stove in accordance with GOST 14919.
Water bath of any type.
Mechanical or electronic stopwatch or mechanical clock according to GOST 10733. or electronic clock according to GOST 23350. or electronic-mechanical quartz clock according to GOST 26272 of any brand or timer.
Centrifuge of any type, suitable for centrifugation of liquid volumes up to 100 cm 3 and providing a rotation speed of at least 85 s "(5000 rpm)
A household refrigerator of any type, providing a temperature from 2 ° C to 8 J C.
Conical heat-resistant flasks with a capacity of 50.100.250.500.1000. 1500 cm 3 in accordance with GOST 25336.
Chemical glasses with a capacity of 1000 cm 3 in accordance with GOST 25336.
Evaporation bowls are porcelain GOST 9147 or quartz bowls in accordance with GOST 19908.
Glass sticks
Ash-free filters "red tape"
Ammonium persulphate (persulfate) in accordance with GOST 20478. analytical grade.
Magnesium sulfate 7-water in accordance with GOST 4523. x. h. or h. d. a.
Sodium hydroxide (sodium hydroxide) in accordance with GOST 4328. х. h. or h. d. a.
Orthophosphoric acid in accordance with GOST 6552, x. h. or h. d. a.
Nitric acid in accordance with GOST 4461, x. h. or h. d. a.
Sulfuric acid in accordance with GOST 4204, analytical grade.
Silver nitrate according to GOST 1277, analytical grade
Mercury sulfate oxide. p.a., mass fraction of the main substance not less than 98%
Distilled water in accordance with GOST 6709.
Potassium persulfate (persulfate) according to GOST 4146 or sodium persulfate (persulfate), analytical grade a.
Sodium sulfate (sodium sulfate) in accordance with GOST 195. anhydrous, analytical grade.
Sodium sulfite in accordance with GOST 195, anhydrous, analytical grade.
Hydrogen peroxide in accordance with GOST 10929. x. h. or h. d. a.
Disodium salt ethylenediamine-MM.1CH \ N "-tetrauceenic acid 2-aqueous (Trilon B) according to GOST 10652.
Note - It is allowed to use tetrahydrate (CioHuN; Na «Oj-4H; 0) or dihydrate (CtoHijl4.-NaiOa-2HiO) of tetrasodium salt of ethylenediaminetetrasacetic acid.
Hydroxylamine hydrochloride according to GOST 5456.
Formaldehyde (YASNO), aqueous solution (formalin) according to GOST 1625.
Ammonia water in accordance with GOST 3760. chemically pure. or according to GOST 24147, special ch.
Salt of ferrous oxide and ammonium double sulfate (Mohr's salt) in accordance with GOST 4208.
Phenolphthalein (indicator), alcohol solution with a mass fraction of 0.1% according to GOST 4919.1.
Universal indicator paper.
Note - It is allowed to use other measuring instruments, apparatus, auxiliary devices and materials with metrological and technical characteristics not worse than those specified in this standard, as well as chemical reagents of a higher qualification.
6 Determination of manganese content using oxidation to permanganate ions (method A)
6.1 The essence of the method
The essence of the method lies in the catalytic oxidation of manganese compounds with potassium persulfate or sodium persulfate to permanganate ions, followed by measuring the optical density of the solution and calculating the mass concentration of manganese in the water sample. When using an instrument equipped with a monochromator, set the operating wavelength to 525 nm. when using filter devices, choose a filter that has an absorption maximum in the region of (530 ± 20) nm.
Depending on the method for eliminating the interfering effect of chloride ions, the following method options are established:
1 using magnesium hydroxide coprecipitation;
2 with evaporation with sulfuric acid:
3 - using complexation with mercury (II).
6.2 Disturbing influences
Interfering influences are eliminated during sample preparation. Elimination of interfering influences in variant 3 is effective if the content of chloride ions in an aliquot of a sample taken for analysis does not exceed 0.1 g.
6.3 Determination of manganese content with elimination of the interfering effect of chloride ions
coprecipitation with magnesium hydroxide (option 1)
6.3.1 Preparing for measurements
6.3.1.1 Preparation of a stock solution of manganese with a mass concentration of 10 mg / dm 1
In a volumetric flask with a capacity of 100 cm, 1 cm of a standard sample of a solution of manganese (II) ions with a mass concentration of 1 g / dm 3 is pipetted, diluted with distilled water to about half of the volume of the flask, add 0.5 cm 3 of concentrated nitric acid and bring to the mark with distilled water ...
The shelf life of the solution is no more than 1 month.
6.3.1.2 Preparation of a 10% solution of magnesium sulfate
In a conical flask (or glass) with a capacity of 100 ml, 10 g of 7-aqueous magnesium sulfate is introduced and dissolved in 90 cm 3 of distilled water.
The shelf life of the solution is no more than 6 months.
6.3.1.3 Preparation of a 20% volume fraction of phosphoric acid solution
800 cm 3 of distilled water is placed in a glass with a capacity of 1000 cm 3 and 200 cm 3 of orthophosphoric acid is added carefully with stirring and, if necessary, with external cooling.
The shelf life of the solution is no more than 1 year.
6.3.1.4 Preparation of 4% sodium hydroxide solution
In a conical flask with a capacity of 100 cm 3 place 96 cm 3 of distilled water and add 4 g of sodium hydroxide After dissolving sodium hydroxide, the solution is transferred into a vessel made of polymeric material.
The shelf life of the solution is no more than 2 months.
6.3.1.5 Preparation of 1% silver nitrate solution
In a volumetric flask with a capacity of 100 cm 'add 1 g of silver nitrate, dissolve in distilled water and then bring to the mark with distilled water.
The shelf life of the solution in a dark glass container is no more than 1 month.
6.3.1.6 Preparation of calibration solutions
In conical heat-resistant flasks with a capacity of 50 or 100 cm 1 add with a pipette 0.00; 0.25; 0.50; 1.00; 2.00; 3.00; 4.00; 5.00 cm 3 stock solution of manganese (6.3.1.1). Add to each flask 10 cm 3 of a 20% volume fraction of phosphoric acid solution (see 6.3.1.3), 10 cm 3 of silver nitrate solution (see 6.3.1.5) and 0.3 g of potassium persulfate or sodium persulfate. The contents of the flasks are diluted with distilled water to about 40 cm 3, brought to a boil on a hotplate and boiled for 3 minutes.
The solutions are cooled in a stream of cold water, transferred to volumetric flasks with a capacity of 50 cm 3, brought to the mark with distilled water and mixed. The mass concentration of manganese in the prepared calibration solutions is equal to 0.00, respectively; 0.05; 0.10; 0.20; 0.40; 0.60; 0.80; 1.00 mg / dm 3.
The manganese-free calibration solution is a blank for calibration.
Calibration solutions are prepared on the day of use.
6.3.1.7 Preparing the device
The preparation of the device for operation is carried out in accordance with the manual (instruction) for the operation of the device.
6.3.1.8 Instrument calibration
Measure the absorbance of all calibration solutions and the calibration blank (6.3.1.6) three times at the wavelength specified in 6.1. in an optical cell with a thickness of the light-absorbing layer from 2 to 4 cm. using distilled water as a reference solution.
For each calibration solution, the arithmetic mean value is calculated from the obtained optical density values.
The calibration characteristic is set in the form of the dependence of the arithmetic mean values of the optical density of the calibration solutions minus the arithmetic mean of the optical density of the blank sample from the mass concentration of manganese in the corresponding solution. Wherein;
If the device is equipped with a computer (microprocessor) system for collecting and processing information. then the calibration characteristic is set in accordance with the manual (instruction) for the operation of the device;
If the device does not provide for automated calibration, then the obtained calibration characteristics are processed by the linear regression method using the software intended for this purpose. In the absence of such a possibility, the slope of the calibration characteristic b is calculated. (optical density units) dm 3 mg ". according to the formula
where the mass concentration of manganese in the th calibration solution, mg / dm 3;
A, is the arithmetic mean of the optical density of the i-th calibration solution minus the optical density of the blank sample for calibration, the unit of optical density;
I is the number of calibration solutions.
Note - The software for some devices allows you to calculate the calibration coefficient K, equal to 1 / b.
6.3.1.9 Verification of the acceptability of the calibration characteristic
The verification of the acceptability of the calibration characteristic using a computer (microprocessor) system for collecting and processing information is carried out in accordance with the manual (instruction) for the operation of the device.
If the device does not have software that provides for automated calibration, then for each calibration solution, calculate the value of the slope of the calibration characteristic Lc (optical density unit) dm 3 mg according to the formula
where A, and Cr see 6.3.1.8.
The calibration characteristic is recognized as acceptable when the conditions are met at each calibration point
where b is the value of the slope of the calibration characteristic, calculated by the formula (1), (units of optical density) dm 3 mg 1.
If this condition is not met, then the establishment of the calibration characteristic is repeated.
6.3.1.10 Control of the stability of the calibration characteristic
The stability of the calibration characteristic is monitored at least once a quarter, as well as when replacing reagents, after repair or a long downtime of the device. For control, use one or two newly prepared calibration solutions according to 6.3.1.6 (hereinafter referred to as control solutions).
Measure the optical density of the control solutions in the same way as in 6.3.1.8 and, using the calibration characteristic, from the obtained optical density values, calculate the value of the mass concentration of manganese in the control solutions.
The calibration characteristic is considered stable when the condition
1 C - C, 1 10.12, (4)
where C „iM” is the mass concentration of manganese in the calibration solution obtained with the control
measurement, mg / dm 3;
С „- the actual value of the mass concentration of manganese in the calibration solution. mg / dm 3.
If condition (4) is not met for only one control solution, then this control solution is prepared again and repeated measurements are made. The results of the repeated control are considered final. In this case, if the condition of stability of the calibration characteristic is not met. then the instrument is calibrated again.
6.3.1.11 Preparing water samples for analysis
6.3.1.11.1 If the water sample has been preserved (3.2), then determine the volume of 4% sodium hydroxide solution required to neutralize the acid.
To do this, take an aliquot of water with a volume of V \ = 100 cm 3, add 3 to 5 drops of a 1% alcohol solution of phenolphthalein and pour from a graduated pipette a 4% sodium hydroxide solution (6.3.1.4) until it does not disappear for 30 s pink in color. Record the volume of the sodium hydroxide solution consumed and, if necessary, recalculate it by the volume of the aliquot of the sample taken for the determination according to 6.3.1.11.2. Discard the aliquot used to find the volume of the sodium hydroxide solution.
6.3.1.11.2 If the water sample was not preserved during sampling, add 2 ml of a 4% sodium hydroxide solution (6.3.1.4) to a 100 ml aliquot J of the sample. mix, add 2 cm "
