Determination of 7 Metal Elements in Agricultural Soil by Automatic Graphite Digestion-Inductively Coupled Plasma Mass Spectrometry

An automatic graphite digestion-inductively coupled plasma mass spectrometry (ICP-MS) has been established for the determination of 7 elements, Cd, As, Pb, Cr, Cu, Ni and Zn in soil. The soil samples were digested with 8 mL HNO₃+5 mL HCl+5 mL HF+1 mL HClO₄ system for 3 h, with a acid driving temperature of 160 ℃. After digestion, the soil samples were quantified by Rh-Re as the internal standard and determined using the collision mode of inductively coupled plasma mass spectrometer. The results showed that the 7 elements had good correlation within a certain linear range, with correlation coefficients all greater than 0.999. The limits of detection were 0.02~0.5 mg/kg, and the limits of quantitation were 0.08~2.0 mg/kg. The relative standard deviation of the determination results of certified reference materials in soil was 0.9%~6.1%, and the relative error was −8.9%~7.6%. The spiked recoveries of the 7 elements in three typical agricultural soils, namely paddy fields, orchards, and artificial grasslands, were 85.4%~109.0%, 86.4%~102.0%, and 85.8%~99.0%, respectively. The method has a low detection limit, high precision and accuracy, and can meet the technical requirements for quality assurance and quality control of detailed investigation of pollution in agricultural soil.