Separation of chromium (III) and chromium (VI) by capillary electrophoresis using 2,6-pyridinedicarboxylic acid as a pre-column complexation agent.
A simple method was developed for the simultaneous determination of Cr(III) and Cr(VI) by capillary zone electrophoresis (CZE), where Cr(III) was chelated with ligands to form anionic complexes. Nitrilotriacetic acid, N-2-hydroxyethylenediaminetriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, and 2,6-pyridinedicarboxylic acid (PDCA) were investigated as Cr(III) complexing ligands. Of all the ligands studied, 2,6-PDCA with Cr(III) gave the largest UV response and high selectivity for Cr(III). In addition, the condition for pre-column derivatization, including pH, concentration ratio [Cr(III)/2,6-PDCA] and the stability of Cr(III) complexes were also examined. The separation of anionic forms of Cr(III) and Cr(VI) was achieved using co-CZE with UV detection at 185 nm. The electrolyte contained 30 mM phosphate, 0.5 mM tetradecyltrimethylammonium bromide, 0.1 mM 2,6-PDCA and 15% (v/v) acetonitrile at pH 6.4. The detection limits were 2 microM for Cr(III) and 3 microM for Cr(VI) and linear plots were obtained in a concentration range of 5-200 microM. The utility of the method was demonstrated for the determination of Cr(III) and Cr(VI) in contaminated soils.
Chen
Z
Z
CSIRO Land and Water, Adelaide Laboratory, Glen Osmond, SA, Australia. zuliang.chen@adl.clw.csiro.au
Naidu
R
R
Subramanian
A
A
D002857:Chromium / Q000737:chemistry / Q000302:isolation & purification*; D019075:Electrophoresis, Capillary / Q000379:methods*; D007202:Indicators and Reagents / Q000737:chemistry*; D010848:Picolinic Acids / Q000737:chemistry*; D012680:Sensitivity and Specificity
D007202:Indicators and Reagents; D010848:Picolinic Acids; D002857:Chromium; C004860:dipicolinic acid