Application of wet vs. microwave digestion for trace element determination in soil, vegetable, nuts, and grain samples by ICP-OES

In this study, the ICP-OES determination of the trace elements Co, Cr, Cu, Fe, Mn, Ni, Se, and Zn in soil, vegetable, nuts and grain samples from Sakarya, Turkey, was evaluated after wet and microwave digestion. Element concentrations found in the soil samples were 0.6-1.7 μg g^-1 (Co), 4.2-8.5 μg g^-1 (Cr), 2.5-8.5 μg g^-1 (Cu), 46.2-69.9 Mg g^-1 (Mn), 4.7-7.6 Mg g^-1 (Ni), and 5.3-9.4 μg g^-1 (Zn); in the vegetable samples 0.2-1.1 μg g^-1 (Cu), 27.2-114.6 μg g^-1 (Fe), 3.8-6.5 Mg g^-1 (Mn), and 2.1-8.9 μg g^-1 (Zn); and in the dried food samples 0.04-0.94 μg g^-1 (Co), 0.24-5.64 μg g^-1 (Cr), 2.55-15.92 μg g^-1 (Cu), 4.82-37.55 μg g^-1 (Fe), 1.12-30.17 μg g^-1 (Mn), 0.43-2.27 μg g^-1 (Ni), 0.03-0.94 μg g^-1, (Se) and 2.93-20.91 μg g^-1 (Zn). The accuracy of the method was verified using certified reference materials NIST CRM 7001 Light Sandy Soil and NIST SRM 1515 Apple Leaves digested by wet ashing and microwave digestion. The microwave digestion method offered best results and was successfully carried out for all samples. The results agreed well with the literature values.