Ion chromatographic and voltammetric determination of heavy metals in soils. Comparison with atomic emission spectroscopy

This work deals with the comparison between three analytical techniques for the total contents analysis of heavy metals in agricultural soils polluted by copper. The soils samples are digested to clear solutions using a mixture of perchloric and hydrofluoric acids. The metals studied are copper, lead, cadmium, nickel, cobalt, zinc and manganese. Soil solutions are complex matrices and the analytical techniques investigated are ion chromatography (IC), Anodic Stripping Voltammetry (ASV) or Adsorptive Stripping Voltammetry (AdSV) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), or graphite furnace atomic absorption spectroscopy (AAS). The use of ion chromatography as analytical technique is possible using two different eluents: PDCA for the determination of zinc, cobalt and manganese and oxalic acid for the analysis of copper, nickel and manganese. Without any enrichment process we can obtain very good agreement results between ICP-AES and IC for Cu$^{2+}$, Mn$^{2+}$, Zn$^{2+}$ and Ni$^{2+}$. Good correlation are obtained between ASV and ICP-AES or AAS for Cd$^{2+}$, Pb$^{2+}$ and Zn$^{2+}$ and between AdSV and ICP-AES for Ni$^{2+}$. No good agreement is found between IC or AdSV on the one hand and ICP-AES on the other hand for cobalt