Hydride generation-headspace single-drop microextraction-electrothermal atomic absorption spectrometry method for determination of selenium in waters after photoassisted prereduction

A headspace single-drop microextraction (SDME) method has been developed in combination with electrothermal atomic absorption spectrometry for determination of total inorganic Se and Se(IV). SeH2 is generated in a 40 mL volume closed-vial and trapped onto a Pd(II)-aqueous containing drop that is supported at the needle tip of a high-precision chromatographic syringe. Sample pre-treatment by UV irradiation prior to hydride generation allowed converting Se(VI) into Se(IV), hence, facilitating total Se determination. A 2IV6-2 fractional factorial design was employed for characterising the effect of relevant variables over SeH2 trapping. The variables showing the most significant effect were Pd(II) concentration in the drop and extraction time. A preconcentration factor of about 25 is achieved. The limit of detection of Se was 0.15 ng/mL using trapping onto a 3-μL drop and the precision expressed as relative standard deviation was about 3%. The limit of detection could be improved further using repeated sampling of the headspace.