Speciation of Selenium and Arsenic Compounds by Capillary Electrophoresis With Hydrodynamically Modified Electroosmotic Flow and On-line Reduction of Selenium(VI) to Selenium(IV) With Hydride Generation Inductively Coupled Plasma Mass Spectrometric Detection

Abstract

Capillary electrophoresis (CE) with hydride generation inductively coupled plasma mass spectrometry was used to determine four arsenicals and two selenium species. Selenate (Se^VI) was reduced on-line to selenite (Se^IV) by mixing the CE effluent with concentrated HCl. A microporous PTFE tube was used as a gas–liquid separator to eliminate the ⁴⁰Ar³⁷Cl and ⁴⁰Ar³⁵Cl interference from ⁷⁷Se and ⁷⁵As, respectively. The direction of the electroosmotic flow during CE was reversed with hydrodynamic pressure, which allowed increased freedom of buffer choice. For conventional pressure injection, method detection limits for Se^IV and Se^VI based on seven replicate injections were 10 and 24 pg, respectively. Recoveries of Se^IV and Se^VI in drinking water were measured.