GB/T 16415-2008Determination of selenium in coal -- Hydride generation-atomic absorption method (English PDF)

4.3 Sodium borohydride solution. 18 g/L. Weigh 1.8 g of sodium borohydride and

dissolve it in 100 mL of 5 g/L sodium hydroxide solution. Prepare the solution before use.

4.4 Selenium standard stock solution. 1 mg/mL. Weigh 0.1000 g of high-purity

selenium into a 100 mL beaker, add 5 mL of nitric acid, heat at low temperature until dissolved, continue heating to drive out nitrogen oxides, cool, transfer to a 100 mL volumetric flask, dilute to the mark with water, and shake well.

Commercially available certified reference materials can also be used as selenium standard stock solutions.

4.5 Selenium standard intermediate solution. 10 µg/mL. Pipette 1 mL of the selenium

standard stock solution (4.4) into a 100 mL volumetric flask, dilute to the mark with the blank solution (6.2.2), and shake well.

4.6 Selenium standard working solution. 0.2 µg/mL. Pipette 1 mL of the selenium

standard intermediate solution (4.5) into a 50 mL volumetric flask, dilute to the mark with the blank solution (6.2.2), and shake well.

4.7 Nitrogen. The purity is above 99.9%.

4.8 Acetylene. High-purity acetylene.

5.4 Atomic absorption spectrophotometer. with absorption peak area integration and

peak height measurement functions.

5.5 Light source. Selenium hollow cathode lamp or selenium electrodeless discharge

lamp.

5.6 Automatic hydride generator. It is capable of automatic washing, liquid metering and liquid addition, with an accuracy of 0.5%.

5.7 Electric heating plate. It can maintain the temperature at 60 °C~90 °C.

6.1 Preparation of sample solution

6.1.1 Accurately weigh 1 g of air-dried coal sample with a particle size of less than 0.2 mm (accurate to 0.0002 g) (when Ad of the coal sample is greater than 40.00% or St,d is greater than 8.00%, or Sed is greater than 15 µg/g, weigh 0.5 g of coal sample), place it in a porcelain crucible pre-filled with 1.5 g of Aldrin, mix the coal sample and aldrin evenly, and then evenly cover it with about 1.5 g of Aldrin.

6.1.2 Place the crucible in a cold muffle furnace, slowly raise the temperature to 500 °C and heat at this temperature for 1 hour. Then raise the temperature to 800 °C and heat at this temperature for another 3 hours. Remove the crucible and cool to room temperature.

6.1.3 Crush the calcined sample and transfer it to a 150 mL beaker containing 20~30 mL of hot water. Add 5 mL of hydrochloric acid to the crucible to dissolve the remaining residue, then pour it into the beaker. Wash the crucible with 15 mL of hydrochloric acid three times (5 mL each time), and transfer the wash solution to the beaker. Stir the solution. After cooling, transfer the entire solution to a 100 mL volumetric flask, dilute to the mark with water, and shake well.

NOTE. Some samples may contain solid residue, but it will not affect the test results.

6.2 Preparation of blank solution

6.2.1 Weigh 15 g of aldrin into a 100 mL evaporating dish. Place the dish in a cold muffle furnace, slowly raise the temperature to 500 °C, and heat at this temperature for

1 hour. Then raise the temperature to 800 °C and continue heating for 3 hours. Remove the evaporating dish and cool to room temperature.

6.2.2 Transfer the ignited aldrin to a beaker containing 100~150 mL of hot water.

Dissolve the residue in the dish with 25 mL of hydrochloric acid, transfer it to the beaker, and rinse the residue into the beaker with water. Rinse the evaporating dish with 75 mL of hydrochloric acid three times (25 mL each time) and transfer the solution to the beaker. Stir until the aldrin is completely dissolved. Cool to room temperature, transfer to a 500 mL volumetric flask, dilute to the mark with water, and shake well. Transfer it to a plastic bottle for storage.

6.3 Preparation of standard solutions

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