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Determination of Cr(III) and Cr(VI) in Environmental Waters by Derivative Flame Atomic Absorption Spectrometry Using Flow Injection On-Line Preconcentration with Double-Microcolumn Adsorption

H-W. Sun^a,*, W-J. Kang^b, J. Ha^c, S-X. Liang^a and S-G. Shen^a

^a College of Chemistry and Environmental Science, Hebei University, Baoding, 071002, China
^b College of Public Health, Hebei Medical University
^c Hebei University of Science and Technology

The species of Cr(III) and Cr(VI) in water samples were determined by flow injection on-line preconcentration and separation on two-microcolumn system–derivative flame atomic absorption spectrometry during a collaborative analysis for certification. The Cr(III) and Cr(VI) in water samples were retained on two microcolumns with ion exchange resin and were eluted directly to nebulizer by 15% HNO₃ and 8% NH₄NO₃, respectively. The characteristic concentration (at the sensitivity grade of 2 mV min^-1 for 1 min of preconcentration time) for Cr(III) and Cr(VI) were 0.130 and 0.0985 µg l^-1, in the order which were 332- and 431-fold better than those of  FAAS, and 45- and 47-fold better than those of FI-FAAS, respectively. The relative standard deviations were 3.27% and 3.66% with corresponding detection limits (3σ) of 0.244 and 0.235 µg l^-1, respectively. The linear ranges of determinations for Cr(III) and Cr(VI) were 0~100 µgm l^-1 with correlation coefficients of 0.9984 to 0.9996. The satisfactory recovery of 94.4%~106% for Cr(III) and Cr(VI) could be obtained from water samples.

Keywords: Flow injection, On-line preconcentration, Derivative flame atomic absorption spectrometry, Chromium(III), Chromium(VI)