Determination of Available Cd in Soil by ICP-MS with Constant Temperature Shaker Extraction

A method for the determination of available Cd in soil by inductively coupled plasma mass spectrometry (ICP-MS) with constant temperature shaker extraction was proposed. Soil sample was put into a enamel dish and spread out to about 2 cm of thickness for drying naturally. After grinding and passing through a 2 mm nylon sieve, 5.00 g of soil sample was placed in a 50 mL-plug centrifuge tube, and 25 mL of extraction agent was added. The above solution was extracted by constant temperature shaker with extraction temperature of 20-25 ℃, horizontal oscillation frequency of 200 r·min^-1 and extraction time of 100 min. After extraction, the sample solution was centrifuged and filtered with 0.45 μm water microporous membrane. The first 5-6 mL of filtrate was discarded, and the subsequent filtrate was collected. The subsequent filtrate (5.00 mL) was transferred to a 25 mL-colorimetric tube, and 1% (φ) nitric acid solution was used to fix volume. ICP-MS was used for analysis according to the working conditions of the instrument. As shown by the results, linear relationship between value of mass concentration of Cd and its response value was kept in the range of 0.50-100 μg·L^-1, with detection limit (3.143s) of 0.001 mg·kg^-1. Soil national standard substances were determined, and the determined values were within the ranges of certified values, with RSDs (n=6) of the determined values in the range of 3.1%-5.0%. This method has been applied to the analysis of actual soil samples, and compared with GB/T 23739-2009. The results showed that there was no significant difference between the two methods with value of t_0.05,8 of 1.145.