Simultaneous determination of methyl- and ethyl-mercury by solid-phase microextraction followed by gas chromatography atomic fluorescence detection

A method for trace level determination of organomercury species in different biota matrixes by using aqueous-phase propylation followed by headspace solid-phase microextraction (HS-SPME) and gas chromatography (GC) coupled to pyrolysis-atomic fluorescence spectrometry (Py-AFS) detection has been optimized. To maximize peak area and symmetry factors of methylmercury (MeHg) and ethylmercury (EtHg) analyzed as propyl derivatives, carrier and make-up flow rates were optimized by a user-defined experimental design. A multiple response simultaneous optimization was applied using the desirability function to achieve global optimal operating conditions. They were attained at 2 and 6 mL min−1 as carrier and make-up gas flow rates, respectively. In addition, pyrolyser temperature was also optimized, yielding the best value at 750 °C. Limits of detection and quantification at the optimum conditions were 0.04 ng g−1 and 0.13 ng g−1 for both, MeHg and EtHg. The developed analytical procedure was validated with a certified reference material (DORM-2) and applied to the determination of organomercury incurred in waterfowl egg and fish samples.