PRECONCENTRATION OF CR(III) AND TOTAL CR IN WATERS FOR FLAME AAS IN AFLOW-THROUGH ELECTROCHEMICAL SORPTION CELL/

Chromium in water samples is determined by flame atomic absorption spe ctrometry (AAS) after the preconcentration of Cr(III) species on activ ated alumina at pH 7 in a flow system coupled on-line to the AAS instr ument. The total Cr concentration is determined after the electrochemi cal reduction of chromate ions to Cr(III) which are preconcentrated to gether with the original Cr(III) species in the sample. Both the reduc tion and the sorption are carried out in a combined cell containing a porous electrode, a layer of the sorbent and the counter electrode in series. The porous electrode is made of glassy carbon particles coated with gold. Tap, river and synthetic sea water samples were analyzed w ith this method. The detection limits are 0.5 ng/ml and 250 ng/ml for 500 ml and 1 ml sample solution, respectively.