ONLINE THERMAL LENS SPECTROMETRIC DETECTION OF CR(III) AND CR(VI) AFTER SEPARATION BY ION CHROMATOGRAPHY

The applicability of thermal lens spectrometry for the on-line detecti on of trivalent and hexavalent chromium species after high-performance ion chromatographic (HPIC) separation was investigated. A collinear d ual-beam thermal lens spectrometer was utilized to detect Cr species s eparated as anions on a Dionex HPIC CS5 column. Precolumn derivatizati on of Cr(III) by pyridine-2,6-dicarboxylic acid and postcolumn derivat ization of Cr(VI) by diphenylcarbazide were necessary for the efficien t separation and on-line detection of both Cr species. Under the propo sed experimental conditions, i.e. 200-mu l sample loop and an argon io n laser operating at 514.5 nm, providing 160 mW power at the sample si te, detection limits of 30 and 0.3 ng/ml for Cr(III) and Cr(VI), respe ctively, were achieved.