Speciation of CrIII and CrVI in aqueous samples by coprecipitation/slurry sampling fluorination assisted graphite furnace atomic absorption spectrometry

A Pb(PDC)(2) coprecipitation separation and preconcentration combined with slurry sampling fluorination assisted electrothermal atomic absorption spectrometry with PTFE as chemical modifier has been developed for the speciation of Cr-III and Cr-VI. Base on the variation of the pH, this method can soundly separate Cr-III and Cr-VI at pH 4.0 and 9.0, respectively. The experimental conditions of the coprecipitation and GFAAS determination were investigated systematically. Under the optimum conditions, the linear range of Cr-III and Cr-VI was from 0.5 to 80 ng/ml, and detection limit was 0.02 ng/ml with the RSD of 3.2% for Cr-VI (n = 9, C = 1 ng/ml) and 3.9% for Cr-III (n = 9, C = 1 ng/ml). The proposed method has been applied for the analysis of Cr-III and Cr-VI in natural water and tea infusion samples with satisfactory recoveries.