Determination of selenite, selenate and selenocyanate in waters by ion chromatography-hydride generation-atomic fluorescence spectrometry (IC-HG-AFS)

Dissolved inorganic selenium (Se) speciation in environmental and industrial waters is determined by ion chromatography-hydride generation-atomic fluorescence spectrometry (IC-HG-AFS). The three species selenite (Se(IV)), selenate (Se(VI)) and selenocyanate (SeCN) are separated by anion-exchange chromatography on a Dionex AS-16 column using gradient elution with NaOH (17.5–100 mmol L−1). Prior to HG-AFS detection, selenate is pre-reduced on-line to selenite by reaction with 5.8 mol L−1 HBr at 100 °C. From a 1 mL sample, detection limits of 26, 33 and 34 ng L−1 were achieved for Se(IV), Se(VI) and SeCN, respectively. The reproducibility of standard solutions, as well as of native and spiked real-world samples, was on the order of 5–10%. Spike recoveries for a wide variety of real-world samples are quantitative for all three species. The method was validated by good agreement between the measured speciation patterns for SRM 1643d and two real-world samples with the certified or measured total Se concentrations, respectively. The method was applied to determine Se speciation in a petroleum refinery waste water, where SeCN was the only detected species, and in a gold mine waste water, where smaller fractions of Se(IV) and Se(VI) were encountered besides the major species SeCN.