UV Vapor Generation for Determination of Selenium by Heated Quartz Tube Atomic Absorption Spectrometry

A new vapor generation technique utilizing UV irradiation coupled with atomic absorption for the determination of selenium in aqueous solutions is described. In the presence of low molecular weight organic acid solutions, inorganic selenium(IV) is converted by UV irradiation to volatile selenium species, which are then rapidly transported to a heated quartz tube atomizer for detection by atomic absorption spectrometry. Optimum conditions for photochemical vapor generation and interferences from concomitant elements were investigated. Identification of the volatile products using cryotrapping GC/MS analysis revealed that inorganic selenium(IV) is converted to volatile selenium hydride, selenium carbonyl, dimethyl selenide, and diethyl selenide in the presence of formic, acetic, propionic, and malonic acids, respectively. In acetic acid solution, the efficiency of generation was estimated to be 50 ± 10%. No interference from Ni2+ and Co2+ at concentrations of 500 and 100 mg L-1, respectively, was evident. A detection limit of 2.5 (mu)g L-1 and a relative sensitivity of 1.2 (mu)g L-1 (1% absorption) with a precision of 1.2% (RSD, n = 11) at 50 (mu)g L-1 were obtained.