The purpose of this study was to evaluate the influences of digestion temperature on the extraction of heavy metals from soil using the standard method established by Korean Ministry of Environment (KMES). A total of 7 heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn) in soil samples were extracted at varying digestion temperatures [(66 ± 2.0)^oC, (73 ± 1.9)^oC, (80 ± 1.3)^oC, (85 ± 1.7)^oC, (92 ± 2.0)^oC, (98 ± 1.7)^oC]. As, Cd, Cu, Pb and Zn concentrations remained relatively constant over the temperature range, but Ni and Cr concentrations greatly varied with the digestion temperature. The extent of variation in extraction efficiencies as compared to the concentration obtained at 66^oC was in following order; Ni (7.09% ~ 35.42%) > Cr (4.79% ~ 25.40%) > Zn (3.99% ~ 17.52%) > Cu (2.22% ~ 19.34%) > As (3.54% ~ 8.26%) > Cd (–5.08% ~ 1.08%) > Pb (–4.71% ~ –1.70%). The accuracy for certified reference materials at the digestion temperature of 80 and 85^oC was 98.7% ~ 105.8%. Therefore, digestion temperature of 80^oC ~ 85^oC is suggested to obtain reliable and reproducible data when the standard method by Korean Ministry of Environment is employed to analyze multiple heavy metal components in soil samples.

Keywords: KMES, Auqa regia, Digestion temperature, Soil, Heavy metals