Rapid Determination of 6 Arsenic Species in Soil by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry after Ultrasound Extraction with Ascorbic Acid-Phosphate Solution

The study mentioned by the title was conducted to solve problems of the long chromatographic separation time as well as arsenite radical As(Ⅲ) being easily converted into arsenate As(V) for the determination of 6 arsenic species in soil by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The 10 mL of mixed solution of 1.6 mol·L⁻¹ phosphoric acid solution and 0.5 mol·L⁻¹ ascorbic acid solution at volume ratio of 1∶1 was added into 0.1 g of the soil sample. The mixture was extracted by ultrasound at room temperature for 6 h. The extract was diluted to 50 mL by water, and the solution obtained passed through a 0.22 μm polyethersulfone membrane. The 6 arsenic species including arsenobetaine (AsB), As(Ⅲ), dimethyl arsenic (DMA), arsenocholine (AsC), methyl arsenic (MMA) and As(V) in the filtrate was determined by HPLC-ICP-MS. In chromatographic analysis, the Dionex IonPac AG7 column (50 mm×4 mm, 10 μm) was used as the stationary phase, and mixed solutions of 3.5 mmol·L⁻¹ ammonium carbonate solution and 100 mmol·L⁻¹ ammonium carbonate solution at different volume ratios were used as the mobile phase for gradient elution. It was shown that linear relationships between values of the mass concentration and the peak area of the 6 arsenic species were kept in definite ranges, with detection limits (3S/N) in the range of 0.010-0.050 μg·L⁻¹. Test for recovery was made according to the standard addition method, giving recoveries in the range of 92.0%-110%, and RSDs (n=6) of the determined values were less than 5.0%. The proposed method was used for the analysis of 6 actual soil samples, and As (III) and As (V) were detected, with detection amounts of 0.07-0.15 µg·g⁻¹ and 3.44-8.61 µg·g⁻¹, respectively.