GOST 23957.1-2003

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  ГОСТ 23957.1-2003

GOST 23957.1−2003 Zinc. Atomic absorption method for the determination of lead, cadmium, antimony, iron and copper

GOST 23957.1−2003

Group B59

INTERSTATE STANDARD

Zinc

ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF LEAD, CADMIUM,
ANTIMONY, IRON AND COPPER

Zinc.
Atomic-absorption method for determination of lead, cadmium, antimony,
iron and copper

ISS 77.120.60
AXTU 1709

Date of introduction 2005−07−01

Preface

1 DEVELOPED by Eastern research mining and metallurgical Institute of nonferrous metals (VNIItsvetmet), the Interstate technical Committee for standardization MTK 504 «Zinc, lead"

2 INTRODUCED by Committee on standardization, Metrology and certification of the Ministry of industry and trade of the Republic of Kazakhstan

3 ACCEPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 24 dated 5 December 2003) was a standards Bureau MGS N 4774

The standard was accepted by voting:

4 by Order of the Federal Agency for technical regulation and Metrology dated December 9, 2004 No. 101-St inter-state standard GOST 23957.1−2003 introduced directly as a national standard of the Russian Federation from July 1, 2005

5 REPLACE GOST 23957.1−80

1. Scope

This standard establishes the atomic absorption method for the determination of lead, cadmium, antimony, iron and copper in the zinc when the mass fraction of, %:

lead — from 0.002 to 3.0;

cadmium — from 0.001 to 0.3;

of antimony, from 0.01 to 0.05;

iron from 0.001 to 0.2;

of copper, from 0.0005 to 0.07.

The method is based on measuring the absorption of the analytical lines of the determined elements with the introduction of the analyzed solution and compare solutions in the flame acetylene-air.

Zinc previously transferred into solution by acid decomposition.

2 Normative references

The present standard features references to the following standards:

GOST 8.315−97 State system for ensuring the uniformity of measurements. Standard samples of composition and properties of substances and materials. The main provisions of the

GOST 859−2001 Copper. Brand

GOST 1089−82 Antimony. Specifications

GOST 1467−93 Cadmium. Specifications

GOST 1770−74 laboratory Glassware measuring glass. Cylinders, beakers, flasks, test tubes. General specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3640−94 Zinc. Specifications

GOST 3778−98 Lead. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 5457−75 Acetylene, dissolved and gaseous. Specifications

GOST 5817−77 tartaric Acid. Specifications

GOST 6709−72 distilled Water. Specifications

GOST 9849−86 iron Powder. Specifications

GOST 17261−77 Zinc. Method of spectral analysis.

GOST 24231−80 non-ferrous metals and alloys. General requirements to selection and preparation of samples for chemical analysis

GOST 25086−87 non-ferrous metals and their alloys. General requirements for methods of analysis

GOST 25336−82 Glassware and equipment laboratory glass. The types, basic parameters and dimensions

GOST 29169−91 (ISO 648−77) oils. Pipette with one mark

GOST 29227−91 (ISO 835−1-81) oils. Pipettes are graduated. Part 1. General requirements

3 General requirements

3.1 General requirements for the method of analysis according to GOST 25086.

3.2 Sampling and sample preparation — according to GOST and GOST 3640 24231.

3.3 Mass fraction of the elements define two parallel portions of the sample.

3.4 the accuracy of the analysis is controlled by standard models, developed and approved by GOST 8.315, or by additives, or by comparing the analysis results obtained according to standard or other certified methods, with the error not exceeding the error of the controlled technique, not less than once a month, and when changing reagents, solutions or after a long break.

3.5 accuracy of the analysis of standard samples is checked by analysis of standard sample simultaneously with sample analysis. Analysis of the samples considered accurate if the result of the analysis of a standard sample differs from the certified characteristics by no more than , where is the accuracy evaluation of standard sample, %; -the permissible discrepancy between the results of the analysis, %.

3.6 To control the accuracy of the analysis by the method of additions determine the mass fraction of the analyzed component in zinc after adding aliquotes part of a standard solution of the component to the sample prior to analysis.

Weight additives is chosen so that the analytical signal component is increased two to three times compared to the analytical signal without the additive.

The mass percent of additives calculated as the difference between the mass fraction of the component in the samples with the additive and without additive .

The analysis is believed to be accurate, if the found Supplement different from that introduced not more than , where and is permitted discrepancies in the results of the analysis of the sample and the sample with the additive, respectively, %.

3.7 During the inspection, the accuracy of the analysis by comparing the results obtained by different standardized or certified methods, the analysis is considered accurate if the difference between the results does not exceed , where and - the permissible discrepancy of the results of the analysis, the value of which is regulated in a controlled and specific control methods of analysis.

3.8 safety Requirements — according to GOST 17261.

3.8.1 To prevent entering the working area of harmful substances released during the spraying of the analyzed solutions in the flame and bad acting on the body in quantities exceeding the maximum allowable concentration, the burner of the atomic absorption spectrophotometer should be located inside the exhaust device is equipped with a protective screen.

3.8.2 the analysis of zinc used reagents and materials which have a deleterious effect on the human body: lead, hydrochloric and nitric acid, acetylene and ammonia.

Preparation of samples for analysis must be carried out in cabinets equipped with local suction device.

3.8.3 in the use and operation of compressed, liquefied and dissolved gases in process analysis, you need to follow the rules of device safe operation of vessels working under pressure, approved by the relevant national authorities.

4 Apparatus, materials and reagents

Spectrophotometer atomic absorption of any brand.

The air is compressed under pressure from 2·10to 6·10PA (2 to 6 ATM.) depending on the device.

Acetylene in cylinders GOST 5457.

Conical flasks or beakers according to GOST 25336 capacity of 200, 250 cm.

Flasks volumetric with one mark not lower than 2nd accuracy class according to GOST 1770, with a capacity of 50, 100, 200, 250, 500 and 1000 cm.

Pipette with one mark according to GOST 29169.

Graduated pipettes according to GOST 29227.

Distilled water according to GOST 6709.

Nitric acid according to GOST 4461 and a solution of 1:3.

Lead according to GOST 3778 grade not lower than S2.

Cadmium GOST 1467.

Zinc GOST 3640 not below grade CV, solution 100 g/l; prepared by dissolving 50 g of zinc in a minimum amount of nitric acid and transferred to volumetric flask with a capacity of 500 cm.

Antimony GOST 1089 not below grade Su00.

Tartaric acid according to GOST 5817 and a solution of 400 g/DM.

Hydrochloric acid according to GOST 3118 and a 1:10 solution.

Copper according to GOST 859 not below the mark M0 or electrolyte.

Iron powder restored brand MLB-1 according to GOST 9849.

Solutions of known concentration.

Solution a: 1,000 g of metallic lead in the form of chips is dissolved in 40 cmof a solution of nitric acid under heating, cooled and transferred to volumetric flask with a capacity of 500 cm, was adjusted to the mark with water and mix.

1 cmof the solution contains 2 mg of lead.

Solution B: 1,000 g of cadmium metal was dissolved in 15 cmof nitric acid, transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix.

1 cmof the solution contains 1 mg of cadmium.

Solution: 1,000 g of crushed in an agate mortar metallic antimony and 15 g of tartaric acid dissolved in 15 cmof nitric acid under heating, cooled, transferred to a volumetric flask with a capacity of 500 cm, was adjusted to the mark with water and mix.

1 cmof solution contains 2 mg of antimony.

Solution G: 1,000 g of iron dissolved in 20 cmof nitric acid under low heat, transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix.

1 cmsolution G contains 1 mg of iron.

Solution D: 0.400 g of copper (pre-washed in a solution of hydrochloric acid 1:10 for removal of the oxide film) was dissolved in 10 cmof nitric acid, transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix.

1 cmof solution D contains 400 mcg of copper.

Solution E: 10 cmstandard solutions A, B, C, G, D transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix.

1 cmof solution E contains 200 mg of lead and antimony, 100 mcg of cadmium and iron, 40 mg of copper.

Solution W: 10 cmof solution E is transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix.

1 cmof solution F contains 20 micrograms of lead and antimony, 10 ág of cadmium and iron, 4 micrograms of copper.

Solutions comparison, containing from 0.2 to 200 mg/cmof the identified elements, is prepared from standard solutions A, B, C, D, e, F and g in accordance with table 1.


Table 1 — comparison of Solutions

For every 100 cmof solution comparison added to 10 cmof nitric acid solution. The basis of these solutions the comparison is distilled water. The first four solution comparison (table 1) is prepared in two ways: 1) on the basis of distilled water (for analysis of solutions from the sample 1,000 g); 2) based on the solution of the zinc mass concentration of 50 g/DM(for analysis of solutions from the sample of 2,500 g). To do this in a volumetric flask with a capacity of 100 cmstand 50 cm, and in measuring flask with a capacity of 200 cm — for 100 cmof solution zinc. Simultaneously cook two test solution of zinc mass concentration of 50 g/DM, which determine the (chemical, spectrographic or atomic absorption method), the mass concentration determined by the impurity for the purpose of adjusting the concentration in solution comparisons, prepared on the basis of zinc.

Note — it is permitted to use other reagents and materials subject to the achievement of metrological characteristics, not inferior to the established in this standard.

5 analysis

Zinc enters the analysis in the form of chips.

For samples with a mass fraction of lead is less than 0.01%, cadmium, and iron less than 0.005%, copper less than 0.001% of the weight of the portion must be equal to 2,500 g. For all other samples — 1,000 g.

Allowed to use other sample and dilution analyzed solutions if provided the necessary accuracy of the analysis.

The charge of zinc is placed in a Pyrex glass conical flask or beaker with a capacity of 200−250 cm, pour 2.5 cmof a solution of tartaric acid (for samples in which determine antimony), 30 cmof nitric acid (1:3) when mounting a mass of 2,500 g or 15 cm — when mounting a mass of 1,000 g and dissolved by heating. Is evaporated to wet salts, poured 12 cmof nitric acid (1:3), heated to dissolve the salts, cooled and transferred to volumetric flask with a capacity of 50 cm. Simultaneously with each of the batches of 1,000 and 2,500 g carried out two test experience for inclusion in the results of the analysis of the amendments on the content of lead, cadmium, antimony, iron and copper in the used reagents.

Analyze the solutions obtained by the decomposition of the samples with a mass fraction of lead of 1% and above, diluted five times: 10 cmof the analyzed solution is placed in a volumetric flask with a capacity of 50 cm, pour 3 cmof nitric acid was adjusted to the mark with water and mix.

Analyzed solutions and solutions comparison sprayed in the flame of acetylene-air and measure the atomic absorption of the determined elements analytical lines with wavelengths given in table 2.


Table 2 — Analytical lines of the determined elements

In nanometers

When working with the solutions obtained by the decomposition of hitch weight 2,500 g, use solutions comparison, prepared on the basis of zinc. In other cases, use the solutions of a comparison made on the basis of water.

Measurement conditions selected in accordance with device used.

Work on a calibration schedule or by «limiting solutions». The method of «limiting solutions» is to register the analytical signals of the determined elements in the analyzed solution and the two solutions comparisons, one of which has a smaller and the other larger analytical signal than the analytical signal of the designated elements in the analyzed solution.

When using atomic absorption spectrometer complete with computer processing of results of measurements of analytical signals and calculating results of the analysis provided by software and held in automatic mode without operator intervention.

6 processing of the results

6.1 Mass fraction of the element , % calculated by the formula

, (1)

where is the mass concentration of the analyzed element in the sample solution, µg/cm;

 — the volume of the analyzed solution taking into account the dilution factor, cm;

 — the weight of the portion of the sample, mg;

 — conversion factor from mg to µg.

The calculations must take into account the contents of the determined elements in the control solution, it is the content of the analyzed element in the sample is subtracted zinc concentration in the control solution.

The result of the analysis taking the arithmetic mean of two parallel definitions in case of positive result of the control of convergence.

6.2 Allowable differences in the percent of the results of two parallel measurements (-convergence) and the results of the two tests (- reproducibility), accuracy of analysis results (a) shall not exceed the values given in table 3.


Table 3 — Standards of control and accuracy of the analysis results (at a confidence probability =0,95)

Percentage

The permissible discrepancy between two parallel definitions , %, and two analyses of the same sample , %, for the intermediate mass fraction is calculated by the formula:

, (2)

, (3)

where is the relative standard deviation of repeatability (of results of two parallel measurements);

 — the relative standard deviation of reproducibility (of results of two analyses of the same sample);

 — the average of results of two parallel determinations;

 — the arithmetic mean of the two analysis results;

=2,77 when =2, =0,95;

=2,77 when =2, =0,95.

The intermediate error values of the analysis results , the allowable discrepancy of the results of two parallel measurements and the two results of the analysis of the same sample can be determined by linear interpolation.