Method development for the simultaneous determination of methylmercury and inorganic mercury in seafood

Abstract

This paper reports the method development for the simultaneous determination of methylmercury (MeHg+) and inorganic mercury (iHg) species in seafood samples. The study focused on the extraction and quantification of MeHg+ (the most toxic species) by liquid chromatography coupled to on-line UV irradiation and cold vapour atomic fluorescence spectroscopy (LC-UV-CV-AFS), using HCl 4 mol L−1 as the extractant agent. Accuracy of the method has been verified by analysing three certified reference materials and different spiked samples. The values found for total Hg and MeHg+ for the CRMs did not differ significantly from certified values at a 95% confidence level, and recoveries between 85% and 97% for MeHg+, based on spikes, were achieved. The detection limits (LODs) obtained were 0.001 mg Hg kg−1 for total mercury, 0.0003 mg Hg kg−1 for MeHg+ and 0.0004 mg Hg kg−1 for iHg. The quantification limits (LOQs) established were 0.003 mg Hg kg−1 for total mercury, 0.0010 mg Hg kg−1 for MeHg+ and 0.0012 mg Hg kg−1 for iHg. Precision for each mercury species was established, being ≤ 12% in terms of RSD in all cases. Finally, the developed method was applied to 24 seafood samples from different origins and total mercury contents. The concentrations for Total Hg, MeHg+ and iHg ranged from 0.07 to 2.33, 0.003–2.23 and 0.006–0.085 mg Hg kg−1, respectively. The established analytical method allows to obtain results for mercury speciation in less than 1 one hour including both, sample pretreatment and measuring step.