Determination of 18 Elements in Soil by Combined System of Super Microwave Digestion and Automatic Heavy Metal Analysis

A combined system of super microwave digestion and automatic heavy metal analysis was applied to determination of 18 elements (Li, Be, V, Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Cd, Sb, Tl, Pb, Bi, U) in soil. The soil of 0.1 g was taken and loaded on the above combined system to automatically complete acid addition, digestion, dilution and determination as the following steps:1 mL of water was added to wet the sample, then 1.5 mL of nitric acid, 0.5 mL of hydrochloric acid, and 0.5 mL of hydrofluoric acid were added, and the mixture was heated to 260℃ by program temperature and kept for 30 min; after cooling, depressurization, and dilution with water, inductively coupled plasma mass spectrometry was used for determination. It was shown by the results, the mass concentrations of 18 target elements were linearly related to their corresponding signal intensity ratios between target element and internal standard element of Rh in definite ranges, with detection limits (3s) in the range of 0.001-0.300 μg·L^-1; the proposed method was used for the analysis of standard substances for soil composition analysis (GSS-2, GSS-13 and GSS-27), and the determined values were in the uncertainty ranges of the certified values, with RSDs (n=6) of the determined values in the range of 1.3%-5.3%. The amount of acid used for digestion was only 50% of that of HJ 803-2016, and the method had a high degree of automation and rapid analysis, which was suitable for the analysis of large batches of soil samples.