Study on Quantitative Analysis Method for Several Heavy Metals in Soil Sample by Inductively Coupled Plasma-Mass Spectrometry

Three different systems including HNO₃-HF, HNO₃-HF-HCl and HNO₃-HF-H₂O₂ were used to dissolve soil standard material of GBW 07405 with microwave and a PTFE sealed tank on electric heating plate respectively. The heavy metal elements of Cr, Ni, Cu, Zn, As, Cd and Pb in soil samples were quantitatively measured by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Influence of the reagents, mainly HNO₃, HCl and HF, for the digestion and matrix effect of the soil sample in the quantitative analysis of heavy metals of Cr, Ni, Cu, Zn, As, Cd and Pb are investigated in this paper. The results show that the reagents influence the quantitative analysis of Cr, Ni, Cu, Zn, As Cd and Pb to various extents and the depression effects caused by the soil matrix were observed for all the digestion systems. Digestion with the PTFE sealed tank on electric heating plate was prior to the microwave digestion as the blanks and the detection limits were lower for all the elements and the different isotopes of the same element. The results of Cr, Ni, Cu, Zn, As, Cd and Pb were especially consistent with the standard values within uncertainties for the digestion system of HNO₃-HF-HCl for the chosen isotopes of ⁵²Cr, ⁶⁰Ni, ⁶⁵Cu, ⁶⁶Zn, ⁷⁵As and ²⁰⁶Pb. This method meets the requirements of the quantitative analysis of the heavy metals Cr, Ni, Cu, Zn, As, Cd and Pb for large soil sample batches. This work can efficiently and accurately provide the scientific basis for risk assessment and maintenance for topsoil.