GOST 741.14-80
STATE STANDARD OF THE USSR
COBALT
METHODS FOR DETERMINATION OF CADMIUM
COBALT
Methods for the determination of cadmium
GOST 741.14−80
Group B59
AXTU 1709
(code AXTU introduced by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Replace GOST 741.14−69
The validity of
from July 1, 1981
on 1 July 1986
This standard establishes the atomic absorption and photometric methods for determination of cadmium.
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 741.1−80.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
2. ATOMIC ABSORPTION METHOD
(from 0.0002 to 0.005%)
2.1. The method is based on measuring atomic absorption of cadmium in the flame acetylene-air at a wavelength of 228,8 nm.
(p. 2.1 as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
2.2. Equipment, reagents, solutions
Spectrophotometer of atomic absorption with background correction.
A radiation source for cadmium.
Acetylene according to GOST 5457−75.
Nitric acid GOST 3118−77, a solution of 1:1.
Cobalt GOST 123−78 stamps TO; a solution of nitrate of cobalt: a portion of the cobalt with a mass of 10.00 g was dissolved in 70 cm3 of nitric acid, evaporated to wet salts, cooled and poured 15 — 20 cm3 of water, heated to dissolve salts. The resulting solution was transferred to a volumetric flask with a capacity of 100 cm3 and topped to the mark with water.
1 cm3 of the solution contains 0.1 g of cobalt.
Cadmium of high purity according to GOST 22860−77.
(paragraph six as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
A standard solution of cadmium.
Solution A: 1,000 g of cadmium dissolved in 30 cm3 of nitric acid solution 1:1, evaporated to 3 — 5 cm3, cooled, quantitatively transferred to a volumetric flask with a capacity of 1 dm3, made up to the mark with water and mix thoroughly.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
1 cm3 of solution A contains g of cadmium.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Solution B: 10 cm3 of solution A is transferred to a volumetric flask with a capacity of 100 cm3, made up to the mark with water and mix.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
1 cm3 of solution B contains g of cadmium.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Solution In: 10 cm3 of solution B is transferred to a volumetric flask with a capacity of 100 cm3, made up to the mark with water and mix.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
1 cm3 of the solution In g contains cadmium.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
2.3. Analysis
A portion of the cobalt with a mass of 5,000 g at a mass fraction of from 0.0002 to 0.002%, and 1,000 g when the mass fraction of from 0.002 to 0.005% was dissolved in 50 30 cm3 of nitric acid solution 1:1, evaporated to wet salts, cooled slightly, pour 15 — 20 cm3 of water, heated to dissolve the salts.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
The resulting solution was cooled, transferred to a volumetric flask with a capacity of 100 cm3, made up to the mark with water and mix.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Atomic absorption of cadmium in the analyzed solutions is measured parallel to the calibration solutions and the control solutions experience in flame acetylene-air at a wavelength of 228,8 nm.
The concentration of cadmium in the sample solution found by the calibration schedule, adjusted for the concentration of cadmium in solution in the reference experiment.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
2.4. In a volumetric flask with a capacity of 100 cm3 is placed 50 cm3 of a solution of nitrate of cobalt, and then 0; 0,50; 1,00; 2,50; 5,00; 7,50; 10,00 cm3 of a standard solution In, which corresponds to (0; 0,05; 0;10; 0,25; 0,50; 0,75; 1,00) g/cm3 of cadmium and topped to the mark with water. The resulting solutions sprayed into the flame of acetylene-air in accordance with clause 2.3.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
According to the obtained values of atomic absorption and relevant to them mass concentrations of cadmium build a calibration curve adjusted for the value of atomic absorption of the calibration solution containing no cadmium.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
According to the obtained values of optical density of solutions and their corresponding masses of cadmium build the calibration graph.
2.5. Construction of calibration curve for the mass concentration of cadmium from 0.002 to 0.005%
In a volumetric flask with a capacity of 100 cm3 is placed 0; 1; 2,5; 5,0; 7,5; 10 cm3 of a standard solution In that corresponds to 0; 0,010; 0,025; 0,050; 0,075; 0,100 mg of cadmium, made up to the mark with water and mix. Then do as described in section 2.4.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
2.6. Processing of the results
2.6.1. Mass fraction of cadmium (X) in percent is calculated by the formula
,
where With is the concentration of the analyzed solution found by the calibration schedule, g/cm3;
V — volume fotometricheskogo solution, cm3;
m — weight of cobalt, g.
(paragraph 2.6.1 as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
2.6.2. Allowable absolute discrepancies in the results of parallel measurements characterizing the convergence of the method (d), and the results of two analyses that characterize the reproducibility of the method (D), shall not exceed the values given in the table.
─────────────────────────────┬────────────────────────────────────
Mass fraction of cadmium, % │ allowable Absolute differences,
│ %
├──────────────────────┬─────────────
│ d │ D
─────────────────────────────┼──────────────────────┼─────────────
From 0,00010 0,00020 to incl.│Of 0.00006 │0,00008
SV. 0,00020 «0,00050» │0,00010 │0,00012
«0,0005» 0,0012 «│0,0002 │0,0002
«0,0012» 0,0020 «│0,0003 │0,0003
«0,0020» 0,0050 «│0,0004 │0,0004
(paragraph 2.6.2 as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
3. PHOTOMETRIC METHOD
(with a mass fraction of from 0.0001 to 0.002%)
3.1. The essence of the method
The method is based on measurement of absorption of complex compounds of cadmium with dithizone at a wavelength of 510 nm after prior separation by extraction of chloride complex of cadmium chloroform solution tribenzylamine with subsequent Stripping.
(clause 3.1 as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
3.2. Apparatus, reagents and solutions
Spectrophotometer or photoelectrocolorimeter of any type.
(in edition of Changes N 2, approved. By the decree of Gosstandart of the USSR from
Nitric acid GOST 4461−77, a solution of 3:2 and 0.5 M solution.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
Hydrochloric acid by the GOST 3118−77, 2 M solution.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Tartaric acid according to GOST 5817−77, a solution of 20 g/dm3.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Ammonia water according to GOST 3760−79, diluted 1:200.
Sodium hydroxide according to GOST 4328−77, a solution of 400 g/dm3.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Potassium cyanide, solutions of 10 and 0.5 g/dm3 in sodium hydroxide solution 400 g/dm3.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Potassium-sodium vinocity according to GOST 5845−79, a solution of 250 g/dm3.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Hydroxylamine hydrochloric acid according to GOST 5456−79, a solution of 200 g/dm3.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Rectified ethyl alcohol according to GOST 18300−72.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Thymol blue, solution 1 g/dm3 in the ethanol solution of 200 g/dm3.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Tribenzylamine, a solution of 80 g/dm3 in chloroform.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Chloroform according to GOST 20015−74 distilled.
Ditson (diphenylthiourea) according to GOST 10165−79, solutions of 0.4, 0.08 and 0.04 g/dm3 in chloroform.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
To prepare the solution of dithizone 0.4 g/dm3 is the sample weight of 0.04 g dissolved in 40 cm3 of chloroform, transferred to separating funnel with a capacity of 500 cm3, poured 200 cm3 of ammonia, diluted 1:200, vigorously stirred 1 — 2 minutes (ditson color water layer in orange color), drained the organic layer into another separatory funnel with a capacity of 200 cm3 and repeat the extraction with 50 cm3 of ammonia, organic layer discarded. The aqueous layer is attached to the water layer in the first separating funnel and washed with 10 — 15 cm3 of chloroform.
(in edition of Changes No. 1, promulgated by the Decree of Gosstandart of the USSR from
To the aqueous solution poured 100 cm3 of chloroform, acidified with hydrochloric acid until the color changes of the water layer from orange to greenish-blue and shaken until the discoloration of the water layer. The organic layer decanted into a separating funnel with a capacity of 200 cm3, washed with water and filtered through a dry filter into a flask made of dark glass. The solution is stored at 5 — 7 °C. To prepare the solution of dithizone 0.08 g/dm3 40 cm3 of a solution of dithizone 0.4 g/dm3 diluted to 200 cm3 of chloroform.
(in edition of Changes No. 1, promulgated by the Decree of Gosstandart of the USSR from
For preparation of a solution of 0.04 g/dm3 20 cm3 of a solution of dithizone 0.4 g/dm3 diluted to 200 cm3 of chloroform.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Cadmium GOST 1467−77.
Standard solutions of cadmium.
Solution A: 1 g of cadmium dissolved in 30 cm3 of nitric acid, diluted 3:2 in a beaker with a capacity of 400 cm3, evaporated to 3 — 5 cm3, cooled, poured 10 cm3 of hydrochloric acid and again evaporated. Evaporation repeated two more times, each time priliva 10 cm3 of hydrochloric acid. To the cooled residue poured 170 cm3 of hydrochloric acid. Quantitatively transferred to a volumetric flask with a capacity of 1 dm3, made up to the mark with water and mix thoroughly.
(in edition of Changes No. 1, promulgated by the Decree of Gosstandart of the USSR from
1 cm3 of solution contains gof cadmium.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Solution B: 10 cm3 of solution A is transferred to a volumetric flask with a capacity of 100 cm3, made up to the mark with 2 M hydrochloric acid solution and stirred.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
1 cm3 of solution contains gof cadmium.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
Solution In: 5 cm3 of solution B is transferred to a volumetric flask with a capacity of 250 cm3, made up to the mark with 2 M hydrochloric acid solution and stirred.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
1 cm3 of solution contains gof cadmium.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
3.3. Analysis
A portion of the cobalt with a mass of 1 g are dissolved in 20 cm3 of a mixture of hydrochloric and nitric acids 3:1 on a moderately heated stove, the solution was evaporated to obtain a wet salts. Evaporation with the addition of 10 cm3 of hydrochloric acid is repeated three times. The third time the solution is gently evaporated on the warm plate dry. The dry residue is dissolved in 10 cm3 of 2 M hydrochloric acid solution, transferred to a separatory funnel with a capacity of 150 — 200 cm3, wash Cup 1 cm3 of 2 M hydrochloric acid, add an equal volume of aqueous solution of tribenzylamine (strictly respecting the proportions), and shake vigorously 1 min. the Organic phase was transferred to another separatory funnel with a capacity of 200 cm3. To aqueous phase add an equal volume of water the volume of the solution of tribenzylamine and shake for 1 min. the Organic extracts connect. To the aqueous phase add 5 cm3 of chloroform, shake 20 s, the chloroform layer attached to the organic phase, and the aqueous layer discarded.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
For Stripping of cadmium to the combined organic phase add 15 cm3 of 0.5 M nitric acid solution, shake the funnel for 1 min. the Organic layer decanted into a clean separatory funnel. Reextract retain.
(as amended by Change No. 1, promulgated by the Decree of Gosstandart of the USSR from
To the organic layer poured 10 cm3 of 0.5 M solution of nitric acid, shake the separatory funnel 1 minute, the organic layer is discarded and water is attached to the first portion of the recovered. To United recovered to add 2 — 3 drops of thymol blue indicator and carefully neutralize with sodium hydroxide solution until yellow color. Stirring the solution after each addition of the reagent, pour 1 cm3 of the solution Vinokurova potassium-sodium, 5 cm3 of a solution of potassium cyanide 10 g/dm3, 1 cm3 of a solution of hydroxylamine and 15 cm3 of a solution of dithizone 0.08 g/dm3, the funnel is shaken vigorously for 1 min and poured the chloroform layer into a clean separatory funnel containing 25 cm3 of cooled to 5 — 7 °C tartaric acid. Repeat the extraction with 10 cm3 of dithizone and poured the organic phase in the separatory funnel with tartaric acid. The aqueous phase is discarded.
(in edition of Changes No. 1, promulgated by the Decree of Gosstandart of the USSR from
Separatory funnel containing tartaric acid and the combined organic extracts, vigorously shaken for 2 min, the Chloroform layer discarded. By shaking with tartaric acid dithizonate cadmium is destroyed and vacated dition is extracted with chloroform. The aqueous layer is washed with 5 cm3 of chloroform, which is discarded. To aqueous phase add 0,25 cm3 of a solution of hydroxylamine, 10 cm3 of a solution of dithizone 0.04 g/dm3, 5 cm3 of a solution of potassium cyanide 0.5 g/dm3 and shaken 1 min in a Solution containing pink dithizonate cadmium, filtered through a cotton swab in a volumetric flask with a capacity of 25 cm3. The extraction is repeated 2 — 3 times with 5 cm3 of a solution of dithizone, filtering the organic phase to the same volumetric flask (the last portion of chloroform should be colorless).
(in edition of Changes No. 1, promulgated by the Decree of Gosstandart of the USSR from
The volume of solution in a volumetric flask was adjusted to the mark with chloroform and measure the light absorption of the solution at a wavelength of 510 nm.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
As a comparison, using a solution of chloroform.
The mass of cadmium in the sample solution found by the calibration schedule-adjusted mass of cadmium in solution in the reference experiment.
(as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
3.4. Construction of calibration curve
In a separating funnel with a capacity of 100 cm3 taken 0; 0,50; 1,00; 2,00; 5,00; 6,00; 8,00; 10,00 cm3 of a standard solution In, which corresponds to (0; 0,001; 0,002; 0,004; 0,010; 0,012; 0,016; 0,020) g of cadmium, the volume was adjusted solution with a solution of hydrochloric acid to 10 cm3, poured an equal volume of a solution of tribenzylamine continue in accordance with clause 3.3.
As a comparison, using a solution of chloroform. According to the obtained values of absorption and their corresponding masses of cadmium build a calibration curve adjusted for the value of the light absorption of the calibration solution containing no cadmium.
(p. 3.4 as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
3.5. Processing of the results
3.5.1. Mass fraction of cadmium (X) in percent is calculated by the formula
,
where is the mass of cadmium was found in the calibration schedule g;
m — weight of cobalt, g.
3.5.2. Allowable absolute discrepancies in the results of parallel measurements characterizing the convergence of the method (d), and results of primary and repeated tests, characterizing the reproducibility of the method (D), shall not exceed the values given in the table.
(p. 3.5.2 as amended by Changes No. 2, approved. By the decree of Gosstandart of the USSR from
