Preconcentration of Cr(III) and total Cr in waters for flame AAS in a flow-through electrochemical/sorption cell

Chromium in water samples is determined by flame atomic absorption spectrometry (AAS) after the preconcentration of Cr(III) species on activated alumina at pH 7 in a flow system coupled on-line to the AAS instrument. The total Cr concentration is determined after the electrochemical reduction of chromate ions to Cr(III) which are preconcentrated together with the original Cr(III) species in the sample. Both the reduction 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 with this method. The detection limits are 0.5 ng/ml and 250 ng/ml for 500 ml and 1 ml sample solution, respectively.