Voltammetric Determination of Cr(VI) in Cr(VI)- and Cr(VI)+Mn(IV)-Spiked Reference Soil Samples as a Function of Incubation Time and Extraction Procedures

In-house reference soils were spiked with Cr(VI) or with Cr(VI) plus Mn(IV), incubated at constant humidity and temperature for different periods of time, extracted with distilled water, neutral phosphate buffer or carbonate/hydroxide solutions and tested for Cr(VI) by an adsorptive cathodic stripping voltammetric method. The extraction by carbonate/hydroxide was not satisfactory, likely because of electrode poisoning by some organic compounds. The results showed that extractions by water or neutral phosphate buffer are fully compatible with the AdCSV analysis of Cr(VI). The proposed procedure can be used to detect Cr(VI) in soil extracts down to microg/kg level.