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 industria l waters is determined by ion chromatography-hydride generation-atomic fluo rescence spectrometry (IC-HG-AFS). The three species selenite (Se( IV)), se lenate (Se( VI)) and selenocyanate (SeCN) are separated by anion-exchange c hromatography 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-lin e to selenite by reaction with 5.8 mol L-1 HBr at 100 degreesC. 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 quantit ative for all three species. The method was validated by good agreement bet ween the measured speciation patterns for SRM 1643d and two real-world samp les with the certified or measured total Se concentrations, respectively. T he method was applied to determine Se speciation in a petroleum refinery wa ste water, where SeCN was the only detected species, and in a gold mine was te water, where smaller fractions of Se(IV) and Se(VI) were encountered bes ides the major species SeCN.