ION-CHROMATOGRAPHIC SPECIATION OF CHROMIUM WITH DIPHENYLCARBAZIDE-BASED SPECTROPHOTOMETRIC DETECTION

Two different ion chromatographic procedures were developed for the sp eciation of different oxidation states of chromium with use of anion-e xchange column Hamilton PRP-X100, phthalate mobile phase and spectroph otometric detection based on post-column reaction of Cr(VI) with diphe nylcarbazide. Due to element-specific detection such a determination c an be carried out with retention of Cr(VI) and elution of Cr(III) in t he void peak. In the second procedure developed, Cr(III) is complexed with DCTA, and the obtained complex is also retained on an anion-excha nge column. For 200 mu l sample volume the estimated limits of detecti on were for the first procedure 2.5 and 1.8 ng/ml for Cr(III) and Cr(V I), respectively, whereas for the second one 4.5 and 1.5 ng/ml for Cr( III) and Cr(VI), respectively. In the method with complexation of Cr(I II) a better resolution of analytes was obtained and this method was a pplied for chromium speciation in spiked river waters. The obtained re sults show also a potential of the developed method for more detailed speciation of chromium, including complexes of various stability.