Speciation analysis of chromium(III) and (VI) in natural water samples by graphite furnace atomic absorption spectrometry

The paper reports procedure: of speciation determination of chromium in wat er samples. A comparison of three methods for the sample pretreatment prior to speciation determination of chromium by GFAAS method is made. The most efficient method, ie. chelation with ammonium pyrrolidinedithiocarbamate, f ollowed by solvent extraction with methylisobutylketone was used to determi ne Cr(VI). Cr(total) was determined directly from the acidified sample and Cr(III) - as the difference between Cr(total) and Cr(VI). The concentration s of chromium in natural waters were: Cr(total) - from 1.75 to 3.00 mu g l( -1), Cr(III) - from 0.80 to 2.00 mu g l(-1) and Cr(VI) - from 0.057 to 1.60 mu g l(-1). Chromium determination was performed by the GFAAS technique us ing multiple injections; chromium detection limit is 0.057 mu g l(-1).