Method Development and Application for Analysis of Heavy Metals in Soils by Microwave-assisted Digestion and Extraction

In this work, total heavy metals (Cd, Cu, Pb and Zn) concentrations and corresponding speciation extraction of the certified reference material (soil GBW07445) were analyzed by flame atomic absorption spectrometry (FAAS) with microwave-assisted digestion (MAD) and microwave-assisted extraction (MAE). The experiments were optimized to improve efficiencies with smaller amount of reagents in less time. The interactions between variables such as holding time and temperature were investigated with central composite designs (CCDs). In the total content determination, the relative errors were 9.38%, 5.38%, 2.83% 1.95% for Cd, Cu, Pb and Zn, respectively and the relative errors of Cd, Cu, Pb and Zn in each extraction procedure were in the range of 5.88%-16.7%, 0%-12.5%, 1.24%-12.5% and 1.18%-11.0%, respectively. The relative standard deviations (RSD, n=3) were all below 10%. The results of sample analysis were also stated. All the experiments illustrated that the proposed methods were suitable for heavy metal analysis in soils.