Capillary electrophoresis on-line coupled with hydride generation-atomic fluorescence spectrometry for speciation analysis of selenium

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Abstract
A new method for speciation analysis of two inorganic selenium species was developed by on‐line coupling of capillary electrophoresis (CE) with hydride generation‐atomic fluorescence spectrometry (HG‐AFS) and on‐line conversion of Se(VI) to Se(IV). Baseline separation of Se(VI) and Se(IV) was achieved by CE in a 50 cm×75 μm inside diameter (ID) fused‐silica capillary at −20 kV using a mixture of 15 mmol·L−1 NaH2PO4 and 0.5 mmol·L−1 cetyltrimethylammonium bromide (pH 7.5) as electrolyte buffer. Se(VI) was on‐line reduced to Se(IV) by mixing the CE effluent with concentrated HCl. The precision (relative standard deviation, RSD, n=7) ranged from 0.7 to 1.3% for migration time, 6.4 to 3.7% for peak height response, and 5.9 to 6.1% for peak area for the two selenium species at the 500 μg·L−1 (as Se) level. The detection limits were 33 and 25 μg·L−1 (as Se) for Se(VI) and Se(IV), respectively. The recoveries of the two selenium species in five locally collected water samples ranged from 88 to 114%. The developed method was applied to speciation analysis of inorganic selenium species in spiked natural water samples.

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