As a rule, soil contains small percentages of chromium that originate chiefly from rock weathering processes, although anthropogenic sources also exist. The speciation analysis of trivalent – Cr(III) – and hexavalent chromium – Cr(VI) – is important, because the former is a trace element and the latter is highly toxic. The two chromium species are separated as Cr(III)-EDTA-complex and chromate on the Metrosep A Supp 4 - 250/4.0 column. Mass spectrometric isotope dilution analysis (SIDMS) is used for quantification.