Multi-throughput dynamic microwave-assisted leaching coupled with inductively coupled plasma atomic emission spectrometry for heavy metal analysis in soil

Abstract

A rapid and simple multi-throughput dynamic microwave-assisted leaching combined with inductively coupled plasma atomic emission spectrometry determination has been proposed for the simultaneous determination of Cu, Mn, Zn and Pb in soil. The approach combines the advantages of microwave and dynamic leaching technique, and up to five samples could be treated at the same time within 15 min. Nitric acid aqueous solution (20%, w/w) was employed as leachant at a flow rate of 1.5 mL min⁻¹. The leaching condition was optimized systematically and the leaching efficiencies were above 95% for Cu, Mn, Zn, Pb and lower for Cr, Cd, Ni and Co, compared to the conventional method. The leaching efficiencies of Cr, Cd, Ni, and Co could be enhanced to above 60% when a soak process was appended. Relative standard deviations of intra- and inter-day of Cu, Mn, Zn, and Pb were in the range of 1.7–6.3% and 5.0–6.9%, respectively. The proposed method was more rapid than the conventional digestion method and could be an alternative approach for the analysis of heavy metals in complex solid samples. The relatively closed system may have a broad prospect for leaching volatile elements, such as As, Se and Hg if combined with compatible detecting instrumentation.