GB/T 22105.2-2008Soil quality - Analysis of total mercury, arsenic and lead contents in soils - Atomic fluorescence spectrometry - Part 2: Analysis of total arsenic contents in soils (English PDF)

1 Scope

This part of GB/T 22105 specifies the atomic fluorescence spectrometry method for the determination of total arsenic content in the soil.

This part applies to the determination of total arsenic content in the soil.

The detection limit of the method of this part is 0.01 mg/kg.

2 Principles

After the arsenic in the sample is heated and digested, thiourea is added to reduce the pentavalent arsenic to trivalent arsenic, and then potassium borohydride is added to reduce it to arsine, which is introduced into the quartz atomizer by the argon gas for atomization and decomposition into atomic state arsenic; under the excitation of the emitted light of the special arsenic hollow cathode lamp, atomic fluorescence is produced, and the intensity of the generated fluorescence is proportional to the content of the measured element in the sample. Compared with the standard series, the content of arsenic in the sample is obtained.

3 Reagents

Unless otherwise specified, the reagents used in this part are analytical reagents, and the test water is deionized water.

3.1 Hydrochloric acid (HCl): rho=1.19 g/mL, guarantee reagent.

3.2 Nitric acid (HNO3): rho=1.42 g/mL, guarantee reagent.

3.3 Potassium hydroxide (KOH): guarantee reagent.

3.4 Potassium borohydride (KBH4): guarantee reagent.

3.5 Thiourea (H2NCSNH2): analytical reagent.

3.6 Ascorbic acid (C6H8O6): analytical reagent.

3.7 Arsenic trioxide (As2O3): guarantee reagent.

3.8 (1+1) aqua regia: Take 1 part of nitric acid (3.2) and 3 parts of hydrochloric acid (3.1), mix well, and then dilute one time with water.

3.9 Reducing agent [1% potassium borohydride (KBH4) + 0.2% potassium hydroxide (KOH) solution]: Weigh 0.2 g potassium hydroxide (3.3), put it into a beaker, dissolve with a small amount of water; weigh 1.0 g of potassium borohydride (3.4), put it into potassium hydroxide solution, dissolve it and dilute to 100 mL with water; prepare this solution for current use.

3.10 Carrier liquid [(1+9) hydrochloric acid solution]: Take 50 mL of hydrochloric acid (3.1), add water to make up to 500 mL, and mix well.

3.11 Thiourea solution (5%): Weigh 10 g of thiourea (3.5), dissolve it in 200 mL of water, and shake well. Prepare this solution for current use.

3.12 Ascorbic acid (5%): Weigh 10 g of ascorbic acid (3.6), dissolve it in 200 mL of water, and shake well. Prepare it for current use.

3.13 Arsenic standard stock solution: Weigh 0.6600 g of diarsenic trioxide (3.7) (it has been dried at 105 °C for 2 h), and put it into a beaker; add 10 mL of 10% sodium hydroxide solution, heat to dissolve, and transfer to a 500 mL volumetric flask after cooling; dilute to the mark with water, and shake well. The concentration of arsenic in this solution is 1.00 mg/mL (the able organizations can directly purchase standard stock solutions from the department recognized by the country).

3.14 Arsenic standard intermediate solution: Pipette 10.00 mL of arsenic standard stock solution (3.13) into a 100 mL volumetric flask, dilute to the mark with (1+9) hydrochloric acid solution (3.10), and shake well. The concentration of arsenic in this solution is 100 µg/mL.

3.15 Arsenic standard working solution: Pipette 1.00 mL of arsenic standard intermediate solution (3.14) into a 100 mL volumetric flask, dilute to the mark with (1+9) hydrochloric acid solution (3.10), and shake well. The concentration of arsenic in this solution is 1.00 µg/mL. […]

4 Instruments and equipment

4.1 Hydride generation atomic fluorescence spectrometer.

4.2 Arsenic hollow cathode lamps.