An on-line preconcentration system for the determination of selenium in seawater samples

Abstract

A flow injection system was developed for the preconcentration and determination of selenium in water samples by hydride generation atomic absorption spectrometry (HG-AAS). The preconcentration is based on the sorption of species formed between Se(IV) and ammonium pyrrolidinedithiocarbamate (APDC) in a minicolumn packed with polytetrafluoroethylene (PTFE) and subsequent elution with an alkaline solution of sodium borohydride. After the formation and separation of volatile hydride, this species has been transported to a quartz cell for measuring absorbance. All steps involving separation and detection were performed in an online system. The factors influencing the sorption and desorption of Se(IV) were investigated. Under optimized conditions, the method showed linearity in the range from 0.1 to 1.0 μg L⁻¹ of Se(IV). Analytical parameters of the method, such as the limit of detection (0.03 μg L⁻¹ of Se(IV)), enrichment factor (20), concentration efficiency (20 min⁻¹), consumption rate (0.54 mL) and analytical frequency (60 h⁻¹), were also determined. The accuracy of the method was tested by the determination of selenium in certified reference materials (mussel tissue and wastewater). The proposed procedure was applied for the determination of selenium in seawater samples. The results obtained by analysis of seven different samples varied between 0.21 ± 0.01 and 0.35 ± 0.05 μg L⁻¹ of Se(IV).