Headspace stir bar sorptive extraction combined with GC-ICP-MS for the speciation of dimethylselenide and dimethyldiselenide in biological samples

Abstract

A new method for the determination of volatile organo seleno compounds (dimethylselenide (DMSe) and dimethyldiselenide (DMDSe)) has been developed using a headspace sorptive extraction combined with capillary gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP-MS). The DMSe and DMDSe retained on the sorptive bar were desorbed by methanol and introduced into GC-ICP-MS for separation and determination. The extraction performance of various sorptive bar coatings, including poly(dimethylsiloxane) (PDMS), PDMS-poly(vinyl alcohol) (PVA), carbowax (CW)-PDMS-PVA, PDMS-β-cyclodextrin (β-CD) has been studied, and the best extraction efficiencies for DMSe and DMDSe were obtained by PDMS-PVA sorptive bar coating. The factors affecting extraction and desorption of DMSe and DMDSe were studied and the optimized operation conditions were established. The limits of detection were 33 and 7.1 ng L−1 for DMSe and DMDSe, respectively, and the correlation coefficients of 0.9986 for DMSe and 0.9998 for DMDSe were obtained in the concentration range 0.5–500 ng mL−1 and 0.025–50 ng mL−1, respectively. Repeatability, based on seven replicate determinations, expressed as relative standard deviations (RSDs), were 8.0% (CDMSe = 5 ng mL−1) and 6.1% (CDMDSe = 0.5 ng mL−1) for DMSe and DMDSe, respectively. The proposed method was applied for the analysis of DMSe and DMDSe in biological samples (garlic, onion and their juice) and a good agreement was obtained between the analytical results obtained by standard addition and external calibration methods.