Selective measurement of chromium(VI) by fluorescence quenching of ruthenium

A flow injection method is described for the selective measurement of chrom ium(VI) in aqueous solutions. This method is based on the dynamic quenching of ruthenium(II) fluorescence. The detection limit is 0.43 ppm and 40 samp les can be analyzed per hour. Selectivity is demonstrated over ferrous, nic kel, cupric and zinc cations and no effect is observed from sulfate, chlori de, berate and phosphate. Some interference quenching was measured for cyan ide and nitrate, but the method is more responsive to chromium(VI) by facto rs of 10.2 and 82, respectively. The effects of solution pH, carrier stream flow rate and ruthenium concentration are demonstrated. Results indicate t he method is suitable for measuring chromium(VI) in effluents from electrop lating baths. (C) 1999 Elsevier Science B.V. All rights reserved.