Critical evaluation of three analytical techniques for the determination of chromium(VI) in soil extracts

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Abstract
Three different analytical techniques [1,5-diphenylcarbazide spectrophotometry, chelating ion-exchange chromatography (Chelex-100), and ion-pairing reversed-phase high-performance liquid chromatography (RP-HPLC) combined with electrothermal atomic absorption spectrometry (ETAAS)] were critically evaluated for the determination of CrVI in soil extracts. Spectrophotometry was not applicable to the analysis of most soil extract samples owing to its high limit of detection (LOD = 30 ng cm–3), and the possibility of the instantaneous reduction of CrVI under the acidic conditions employed. A Chelex 100 column, although adequately sensitive (LOD = 1.5 ng cm–3), is inclined to give higher results as inhert and moderately labile CrIII complexes partially passed through the resin together with CrVI. In addition, very small particles (–3). It might also give high chromate results if negatively charged CrIII complexes form ion pairs with tetrabutylammonium phosphate and their elution partially coincided with that of CrVI. Fulvate ligands showed this type of interference. Reversed-phase HPLC is not suitable for analysis of extracts obtained from soils with freshly added tannery waste owing to the effects of the undestroyed tannery waste matrix. This study showed that each method investigated was vulnerable to some type of interference.

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