SIMULTANEOUS DETERMINATION OF CHROMIUM(III) COMPLEXES AND CHROMIUM(VI) BY FAST PROTEIN ANION-EXCHANGE LIQUID-CHROMATOGRAPHY ATOMIC-ABSORPTION SPECTROMETRY

Chromium(III) complexes [oxalate and ethylenediaminetetraacetic acid ( EDTA)] and Cr-VI were separated simultaneously on a fast protein liqui d chromatography (FPLC) anion-exchange column of Mono Q HR 5/5. For se paration tris(hydroxymethyl)aminomethane (TRIS)-HCl buffer (5 X 10(-3) mol dm(-3), pH 5.5-8.5), and the same buffer with NaCl (0.5 mol dm(-3 )), were employed in gradient elution (15 min; flow rate, 1 cm(3) min( -1)). The column was regenerated (NaCl) and equilibrated (TRIS-HCl buf fer) in the following 8 min. With this procedure, Cr-III positive spec ies and kinetically labile, negatively charged Cr-III complexes such a s Cr-III-citrate passed through the column, whereas relatively stable anionic Cr-III complexes (with EDTA and oxalate), and Cr-VI were separ ated and determined by ultraviolet molecular (234 and 273 nm, respecti vely) and atomic (357.9 nm) absorption. Atomic absorption was measured 'offline' in 100 or 200 mu l eluate fractions. The method was,success fully employed for the determination of Cr-VI, Cr-III-EDTA, and Cr-III -oxalate in cabbage xylem at ng cm(-3) levels [limits of detection (LO D), 5, 3, and 80 ng cm(-3), respectively], using a 500 mu l sample loo p. In addition, chromate was monitored in Cr-VI containing nutrient so lutions during plant experiments to investigate Cr uptake by plants (L OD, 5 ng cm(-3)).