Abstract

M. C. Mehra, C. Pelletler and K. Ayikoe

An ion chromatographic approach is proposed for microanalysis of Cr, Mo, W, As and Se oxyanions in an aqueous system. The ions CrO42-, MoO4, WO42-, AsO43- And SeO42- are chromatographable on a low capacity polymer based analytical column. Quantification in an isocratic mode in //g range is feasible with 4-amino-2- hydroxybenzoic acid as mobile phase. At 4 mM in pH 6.5-6.8 range with 1 -1.5 mL/min flow rate all anions except CrO42- are analyzable by indirect spectrophotometry at 320 nm, while at 370 nm it is quantifiable in direct spectrophotometric mode. Speciation of Cr6+ and Cr3+ is feasible through prior oxidative conversion of Cr3+ to absorbing hexavalent CrO42- form by refluxing it in slightly alkaline medium with hydrogenperoxide. Analytical sensitivity for Cr3+ converted as chromate at 0.04 ppm compares favourably with the Atomic absorption spectrophotometry.

Ion chromotography; UV- visible detection; chromate; molybdate; tungstate; arsenate and selenate ions; microanalysis.

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