DETERMINATION OF CHROMIUM IN DIFFERENT OXIDATION-STATES BY SELECTIVE ONLINE PRECONCENTRATION ON CELLULOSE SORBENTS AND FLOW-INJECTION FLAME ATOMIC-ABSORPTION SPECTROMETRY

For on-line preconcentration of Cr(III) and Cr(VI), several functionalized cellulose sorbents, a chelating resin and conventional ion-exchange resins were examined. Cellulose with phosphonic acid exchange groups was found to be superior for the preconcentration of Cr(III), but a cellulose derivative with quaternary amine groups for the preconcentration of Cr(VI). The effects of most common cations and anions present in natural waters on the sorption of both chromium forms was examined. In the optimized flow-injection manifold for a 50-ml aspirated sample volume the detection limits were calculated to be 0.78 and 1.4 mug l-1 for Cr(III) and Cr(VI), respectively. Preliminary results of the application of the developed method to the determination of chromium speciation in natural water samples are presented.