Determination of dimethylselenide and dimethyldiselenide in milk and milk by-products by solid-phase microextraction and gas chromatography with atomic emission detection.

A method based on solid-phase microextraction (SPME) followed by gas chromatography with microwave-induced plasma atomic emission detection for determining dimethylselenide (DMSe) and dimethyldiselenide (DMDSe) in milk and milk by-products is proposed. Parameters affecting the SPME, such as sample volume or mass, ionic strength, adsorption and desorption times and temperatures were optimized in the headspace mode. The matrix effect was evaluated for the different samples studied, concluding that standard additions calibration was required for quantification purposes. The detection limits ranged from 70 to 110 pg mL(-1) for DMSe and from 80 to 400 pg mL(-1) for DMDSe, depending on the sample under analysis. None of the twenty-three samples analyzed contained the studied compounds at concentrations above the corresponding detection limits.