Determination of Chromium, Copper, Zinc, Cadmium, Lead and Nickel in Soil by ICP-MS with Microwave Digestion

A method for the determination of chromium, copper, zinc, cadmium, lead and nickel in soil by inductively coupled plasma mass spectrometry (ICP-MS) with microwave digestion was developed. Soil sample of 0.200 0 g was digested by microwave in 6 mL of nitric acid, 2 mL of hydrochloric acid and 2 mL of hydrofluoric acid. After digestion, the solution was exposed to remove acid to about 2 mL at 150 ℃, and 2 mL of perchloric acid was added to continue to remove acid until the solution was stiff and viscous. The residues were dissolved in water, and 1% (φ) nitric acid solution was added to make its volume up to 50 mL. ICP-MS was used to analyze the sample. As shown by the results, linear ranges of the standard curves of 6 heavy metal elements were all within 50 μg·L^-1, with detection limits (3s) in the range of 0.001-0.26 μg·L^-1. Recovery test was made on blank samples by standard addition method, giving results in the range of 94.3%-103%, and RSDs (n=6) of the determined values ranged from 1.3% to 2.8%. This method was applied to the analysis of soil samples from 8 drinking water sources. The soil accumulation index was used to evaluate the soil samples with the soil background value of Hubei province as reference. The results showed that the soil samples of 7 places were not polluted, and the soil sample of 1 place was slightly polluted.