Methylmercury determination in biota by solid-phase microextraction: Matrix effect evaluation

Aqueous-phase alkylation followed by, headspace solid-phase microextraction (SPME) for mercury speciation in biota, was developed a decade ago. Despite this, matrix effects in this technique have not yet been addressed. In this paper, the importance of these effects has been assessed and overcome by standard addition calibration. Furthermore, improvements were made in the extraction of methylmercury (MeHg) from biological matrixes by optimizing the matrix digestion procedure (temperature and digestion time) and the SPME parameters (aliquot volume of digested samples, extraction temperature and fibre coating), which aimed to minimize the matrix effects. Accordingly, samples were alkaline digested (KOH, 25%, w/v, 60 °C, 180 min) and an aliquot was propylated using an aqueous NaBPr4 solution, headspace SPME sampling and, finally, by using GC-pyrolysis (Py)-atomic fluorescence spectrometry (AFS) determination. The procedure developed was validated using dogfish muscle reference material NRCC DORM-2.