SPECIATION OF CHROMIUM BY THE DETERMINATION OF TOTAL CHROMIUM AND CHROMIUM(III) BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

A method for the determination of chromium(III) and total chromium was studied. Chromium(III) was chelated with 0.1 mol l-1 quinolin-8-ol in methanol, extracted with isobutyl methyl ketone and determined by electrothermal atomic absorption spectrometry. The effects of the pH, extraction and heating time and amounts of reagents required for the extraction were studied. The detection limit of this method was 12 ng l-1. Different modifiers (nitric acid, magnesium nitrate and sodium tungstate) for the determination of total chromium were also investigated and a method for preconcentration on a graphite tube with hot injection using magnesium nitrate was optimized. The detection limit for the determination of total chromium using this procedure was 29 ng l-1. The precision obtained for different amounts of chromium(III) and total chromium were 2.8-6.2 and 2.2-4.3%, respectively. The graphite furnace programmes, the accuracy and the interferences for both procedures were also studied.