Chromium speciation with isotope dilution mass spectrometry

✍ Scribed by Robert Nusko; Klaus G. Heumann

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 724 KB
• Volume: 286
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(94)85074-7

✦ Synopsis

Abstraet C&II) and Cr(VI) were determined by positive thermal ionisation isotope dilution mass spectrometry (IDMS). From the spiked samples, Cr(VI) was separated from CrfIII) by extraction with the liquid anion exchanger Amberlite LA-2. Re-extraction of Cr(VI) was performed with an ammonia solution. After electrolytic deposition of chromium from both species the isotope ratio 5zCr/53Cr was determined. Detection limits of 1.2 ng g-t for CrGII) and of 2.4 ng gg' for (XVI), respectively, were achieved. A HCO;/CO, buffer solution of pH 6.4 containing CrfIII) and Cr(VI) enriched in 53Cr was used as spike solution. The stability of the chromium species in this solution was tested in model experiments with labelled radioactive 'lCr. The accuracy of the IDMS method could be shown in two interlaboratory comparisons. Several fresh and treated waste water samples with CrfIII) concentrations in the range of 2-55 ng g-' and Cr(VI) concentrations of less than 2.4 ng g-' were analysed. The results of the fresh water samples could be explained by the known geochemical behaviour of chromium in natural water systems.