In-situ separation of chromium(III) and chromium(VI) and sequential ETV-ICP-AES determination using acetylacetone and PTFE as chemical modifiers

Electrothermal vaporization-inductively coupled plasma-atomic emission spec trometry (ETV-ICP-ES) has been used for the sequential determination of Cr( III) and Cr(VI). The method is based on the difference between the chelate reactions of the two Cr species and acetylacetone. Cr(III) chelate was sepa rated from Cr(VI) and determined with use of acetylacetone as chemical modi fier. The retained Cr(VI) in graphite tube was analyzed subsequently, after addition of polytetrafluoroethylene (PTFE) as chemical modifier. The diffe rent factors affecting the vaporization behavior of Cr(III) acetylacetonate were investigated in detail. The detection limits for Cr (III) and Cr(VI) were 0.56 and 1.4 ng mL(-1), respectively, and relative standard deviations for 0.1 mug mL(-1) Cr(III) and 0.1 mug mL(-1) Cr(VI) were 2.5% (n = 6) and 4.8% (n = 6), respectively. The linear ranges of the calibration curve for both Cr(III) and Cr(VI) covered three orders of magnitude. The proposed me thod was used to analyze water samples with satisfactory results.