GB/T 13079-2022Determination of total arsenic in feeds (English PDF)

4.2 Reagents or Materials WARNING

---handle all kinds of strong acids with caution. Dilute and use them in a fume hood. When using perchloric acid, be careful not to burn it to dryness, and be careful of explosion.

4.3 Instruments and Equipment

4.3.1 Spectrophotometer. with a wavelength accuracy of 2 nm.

4.3.2 Analytical balance. with an accuracy of 0.0001 g.

4.3.3 Electric drying oven. with a temperature control accuracy of 5 C.

4.4 Sample In accordance with GB/T 20195, prepare the sample of at least 200 g. Make it all pass through the analysis sieve with a pore size of

0.425 mm, thoroughly mix it, put it into a closed container and set it aside.

4.5.2.1 Preparation of standard series of solutions Accurately transfer-take

0.00 mL,

10.00 mL of the arsenic standard intermediate solution (4.2.20), respectively place them in arsenic reaction bottle, and use water to dilute to 30 mL. Add 10 mL of hydrochloric acid (4.2.3), mix it well, and follow the steps specified in 4.5.2.2, starting from the addition of 2 mL of potassium iodide solution (4.2.12).

4.6 Test Data Processing The total arsenic content w1 in the specimen, which is expressed in mass fraction and (mg/kg), is calculated in accordance with Formula (1).

4.7 Precision The ratio of the absolute difference between the two independent determination results obtained under repeatability conditions and their arithmetic mean, and the arithmetic mean shall comply with the requirements of Table 1.

5.2 Reagents or Materials WARNING

---handle all kinds of strong acids with caution. Dilute and use them in a fume hood. When using perchloric acid, be careful not to burn it to dryness, and be careful of explosion. Unless otherwise specified, use only analytically pure reagents.

5.2.1 Water. GB/T 6682, Grade-1.

5.2.2 Nitric acid. guaranteed reagent.

5.2.3 Hydrochloric acid. guaranteed reagent.

5.2.4 Sulfuric acid. guaranteed reagent.

5.2.5 Hydrogen peroxide.

5.2.6 Magnesium oxide. Total Arsenic Content (w1)/(mg/kg) Relative Deviation/%

5.2.7 Magnesium nitrate.

5.2.8 Potassium hydroxide. guaranteed reagent.

5.2.9 Potassium borohydride. guaranteed reagent.

5.3 Instruments and Equipment

5.3.1 Atomic fluorescence spectrophotometer.

5.3.2 Analytical balance. with an accuracy of 0.0001 g.

5.4 Sample Same as 4.4.

5.5 Test Procedures

5.5.4 Instrument reference conditions The instrument reference conditions are as follows:

5.5.5 Determination Adjust the atomic fluorescence spectrophotometer to the optimum working condition, successively determine the fluorescence intensity value of the standard series of solutions, blank solution and specimen solution. Take the concentration of the standard series of solutions as the x-coordinate and the fluorescence intensity value as the y-coordinate to draw a standard curve, with a correlation coefficient of r 0.995.When the fluorescence value of the specimen solution exceeds the linear range of the curve, reduce the dispensing volume of the specimen solution, in accordance with

5.5.3 and 5.5.4, re-perform the determination. In order to ensure good repeatability of the determination results, it is recommended that the number of sequences for each determination should not exceed 30 (including the number of curve sequences).

5.6 Test Data Processing The total arsenic content w2 in the specimen, which is expressed in mass fraction and (mg/kg), is calculated in accordance with Formula (2).

6.2 Reagents or Materials WARNING

---handle all kinds of strong acids with caution. Dilute and use them in a fume hood. When using perchloric acid, be careful not to burn it to dryness, and be careful of explosion.

6.2.1 Water. GB/T 6682, Grade-1.

6.2.2 Nitric acid. guaranteed reagent.

6.2.3 Hydrochloric acid. guaranteed reagent.

6.2.4 Sulfuric acid. guaranteed reagent.

6.2.5 Hydrogen peroxide.

6.2.6 Magnesium oxide.

6.3 Instruments and Equipment

6.3.1 Inductively coupled plasma mass spectrometer.

6.3.2 Analytical balance. with an accuracy of 0.0001 g.

6.3.5 Adjustable electric furnace.

6.3.6 Graphite digestion instrument. equipped with matching polytetrafluoroethylene digestion tube.

6.3.7 Microwave digestion instrument. equipped with matching polytetrafluoroethylene digestion tube.

6.3.8 High-pressure digestion tank. equipped with matching polytetrafluoroethylene digestion inner tube.

6.5.3 Instrument reference conditions and interference elimination method

6.5.3.1 Instrument reference conditions The instrument reference conditions are as follows:

6.5.4 Determination Adjust the instrument to the optimum working condition, add the internal standard working solution (6.2.17) online, use 5% nitric acid solution for zero-adjustment, and successively determine the signal intensity of arsenic (75As) in the standard series of solutions (6.2.18), blank test solution (6.5.2) and specimen test solution (6.5.2). Take the concentration of the standard series of solutions as the x-coordinate and the signal intensity as the y-coordinate to draw a standard curve, with a correlation coefficient of the standard curve r 0.999.When the response value of the specimen solution exceeds the linear range of the curve, the acid concentration of the standard series of solutions can be appropriately diluted and determined, so as to ensure that the response value of the specimen solution is within the linear range of the curve.