Speciation of chromium in mineral waters and salinas by solid-phase extraction and graphite furnace atomic absorption spectrometry

A simple GF-AAS method for speciation analysis of chromium in mineral waters and salinas was developed. Cr(VI) species were separated from Cr(111) by solid-phase extraction with APDC (ammonium pyrrolidinedithiocarbamate). The APDC complexes were formed in the sample solution under proper conditions, adsorbed on Diaion HP-2MG resin and the resin was separated from the sample. After elution with concentrated nitric acid Cr(VI) was determined by GF-AAS. Total chromium was determined by GF-AAS directly in the sample and Cr(111) concentration was calculated as the difference between those results. The detection limit of the method defined as 3 s of background variation was 0.03 mu g l(-1) for Cr(VI) and 0.3 mu g l(-1) for total chromium. RSD for Cr(VI) determination at the concentration of 0.14 mu g 1(-1) was 9%, and for total chromium at the concentration of 5.6 mu g l(-1) was 5%. The recovery of Cr(VI) was in the range of 94-100%, dependently on type of the sample. The investigation of recovery of the spiked Cr(VI) showed that at concentration levels near 1 mu gl(-1) and lower recovery may be reduced significantly even by pure reagents that seem to be free from any reductants. (c) 2005 Elsevier B.V. All rights reserved.