Simultaneous detection of selenium by atomic fluorescence and sulfur by molecular emission by flow-injection hydride generation with on-line reduction for the determination of selenate, sulfate and sulfite

An inductively coupled plasma atomic fluorescence spectrometry (ICP-AFS) instrument, was modified so that it was capable of monitoring transient chromatographic or flow-injection profiles and that sulfur molecular emission and selenium atomic fluorescence could be monitored simultaneously in an argon–hydrogen diffusion flame on a glass burner. The analytes were introduced as hydrogen selenide and hydrogen sulfide, generated on a flow-injection manifold. Selenate was reduced to hydride-forming selenite by microwave-assisted on-line reaction with hydrochloric acid, and sulfate, or sulfite, was reduced to hydride-forming sulfide by a mixture of hydriodic acid, acetic acid and sodium hypophosphite. The effects of the nature of reducing agent, flow rate, microwave power and coil length were studied. The limit of detection (3 s) for selenium was 10 μg L−1, and for sulfide was 70 μg L−1 (200-μL injection volume). The calibration was linear for selenium up to 2 mg L−1 and to 10 mg L−1 for sulfide. The throughput was 180 h−1. The three sulfur species could be differentiated on the basis of reactivity at various microwave powers.