GOST 20996.12-82

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  ГОСТ 20996.12-82

GOST 20996.12−82 Selenium technical. Atomic absorption method for the determination of copper, iron, tellurium, and lead (Change No. 1)

GOST 20996.12−82*

Group B59

INTERSTATE STANDARD

SELENIUM TECHNICAL

Atomic absorption method for the determination of copper, iron, tellurium and lead

Selenium. Atom-absorbtion method of determination
for copper, iron, tellurium and plumbum

AXTU 1709

Date of introduction 1983−07−01

Resolution of the USSR State Committee on standards of 22 June 1982, N 2481 date of introduction is established 01.07.83

Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)

* PUBLISHING (July 2000) with amendment No. 1, approved in December 1987 (IUS 3−88)


This standard establishes the atomic absorption method for the determination of copper (at a mass fraction of copper from 0.003 to 0.06%), iron (if iron mass fraction of from 0.004 to 0.6%), tellurium (if the mass fraction of tellurium from of 0.004 to 0.6%) and lead (at a mass fraction of lead from 0.001 to 0.06%).

The method is based on measuring atomic absorption of copper, iron, tellurium and lead in the flame of a propane-butane-air or air-acetylene at the wavelengths of 325; of 248.3; 214,3; is 283.3 nm, respectively.

As the radiation source used for copper, iron and lead lamp hollow cathode; for tellurium — electrodeless lamp with a hollow cathode.

1. GENERAL REQUIREMENTS

1.1. General requirements for method of analysis according to GOST 20996.0−82.

2. EQUIPMENT, REAGENTS, SOLUTIONS

Atomic absorption spectrophotometer including the lamp with a hollow cathode (copper, iron, tellurium, lead), the electrodeless lamp (for tellurium) and all accessories.

Gas propane-butane GOST 20448−90.

Acetylene in cylinders GOST 5457−75.

Air, compressed under a pressure of 2·10-6·10kPa (2−6 bar).

Nitric acid GOST 4461−77 and diluted 1:1.

Hydrochloric acid by the GOST 3118−77 and diluted 1:1.

Copper GOST 859−78*.
_________________
* On the territory of the Russian Federation GOST 859−2001. — Note the manufacturer’s database.

Standard solutions of copper:

Solution a: a sample of copper weighing 1 g is placed in a conical flask with a capacity of 250−300 cm, 25−30 cm and pour themixture of nitric and hydrochloric acids (1:3), dissolve by boiling, and evaporated to dryness. The residue is twice treated with 7−10 cmof hydrochloric acid, evaporating the solution to dryness. The dry residue is dissolved in 100−120 cmof hydrochloric acid (1:1), boil to dissolve the salt, cooled and transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

1 cmof the solution contains 1 mg of copper.

Solution B: aliquot part of the 50 cmof the solution And placed in a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.1 mg of copper.

Iron according to GOST 9849−86.

Standard iron solution:

Solution a: a sample of iron weighing 1 g is placed in a conical flask with a capacity of 250−300 cm, 30−35 cm, pour themixture of nitric and hydrochloric acids (1:3), boiled and evaporated to dry salts. Pour 100−120 cmof hydrochloric acid (1:1), boil for 5−7 minutes, cooled, transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

1 cmof the solution contains 1 mg of iron.

Solution B: aliquot part of the 50 cmof the solution And placed in a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.1 mg of iron.

Tellurium.

Standard solutions of tellurium:

Solution a: a sample of tellurium weighing 1 g is placed in a conical flask with a capacity of 250−300 cm, 20−25 cm, pour themixture of nitric and hydrochloric acids (1:3), boil to dissolve the sample and evaporated to dryness. Pour 200−220 cmof hydrochloric acid, cooled and the solution transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

1 cmof the solution contains 1 mg of tellurium.

Solution B: take 50 cmof solution A and transferred to volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.1 mg of tellurium.

Lead according to GOST 3778−77*.
_________________
* Valid GOST 3778−98. — Note the manufacturer’s database.

Standard solutions of lead:

Solution a: a sample of lead weighing 1 g is placed in a conical flask with a capacity of 250−300 cm, 10−15 cm pourednitric acid and evaporated when heated to the wet state. Then pour 5−7 cmof nitric acid and transferred the solution into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

1 cmof the solution contains 1 mg lead.

Solution B: take 50 cmof solution A and transferred to volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmof a solution contains 0.1 mg of lead.

3. ANALYSIS

3.1. A portion of the selenium mass 1−5 g (depending on the mass fraction of the element and sensitivity of the instrument) is placed in a conical flask with a capacity of 250−300 cm, 40−50 cm, pour themixture of nitric and hydrochloric acids (1:3), boiled and evaporated to a volume of 3−5 cm. Pour 50−60 cmof water, boil for 5−7 minutes, cooled and transferred to volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

The resulting solution, if necessary diluted with water, selecting the appropriate aliquot part in a volumetric flask.

When the mass fraction of elements less than 0.01% should be stripped of selenium, as described in GOST 20996.7−82.

Fotometrirovanie of each object is carried out twice, washing with water pre-capillary and the spray system after each photometry for 5−10 s

Measurement conditions selected in accordance with device used.

A lot of the determined elements in the sample solution found by the calibration schedule.

(Changed edition, Rev. N 1).

3.2. Construction of calibration graphs

In a volumetric flask with a capacity of 100 cmplaced 0,2; 0,5; 1,0; 3,0; 4,0; 5,0; 6,0 cmstandard solutions Used copper, iron, lead and 0,5; 1,0; 5,0; 10,0; 15,0; 20,0 cmstandard solution tellurium. To each flask add 1−2 cmof hydrochloric acid, made up to the mark with water and mix. Measure the optical density of the obtained solutions in the beginning, middle and end of the electrophoretic samples and averaged values of the optical densities and their corresponding concentrations to build calibration graphs.

4. PROCESSING OF THE RESULTS

4.1. Mass fraction of element (a) in percent is calculated by the formula

,

where is the mass of the element found on the calibration schedule, µg/cm;

 — the total volume of solution, cm;

 — the volume of the analyzed solution after dilution, cm;

 — aliquotes volume of the solution taken for analysis, cm;

 — weight of selenium,

G.

4.2. Discrepancies in the results of two parallel measurements and the two tests should not exceed the values given in the table.

(Changed edition, Rev. N 1).

4.3. The differences in the assessment of mass fraction of copper, iron, tellurium, lead use the methods specified in GOST 20996.8−82, GOST 20996.6−82, GOST 20996.10−82, GOST 20996.3−82.

(Added, Rev. N 1).