Methylmercury and inorganic mercury determination in blood by using liquid chromatography with inductively coupled plasma mass spectrometry and a fast sample preparation procedure

Despite the necessity to differentiate chemical species of mercury in clinical specimens, there are a limited number of methods for this purpose. Then, this paper describes a simple method for the determination of methylmercury and inorganic mercury in blood by using liquid chromatography with inductively coupled mass spectrometry (LC–ICP-MS) and a fast sample preparation procedure. Prior to analysis, blood (250 μL) is accurately weighed into 15-mL conical tubes. Then, an extractant solution containing mercaptoethanol, l-cysteine and HCl was added to the samples following sonication for 15 min. Quantitative mercury extraction was achieved with the proposed procedure. Separation of mercury species was accomplished in less than 5 min on a C18 reverse-phase column with a mobile phase containing 0.05% (v/v) mercaptoethanol, 0.4% (m/v) l-cysteine, 0.06 mol L−1 ammonium acetate and 5% (v/v) methanol. The method detection limits were found to be 0.25 μg L−1 and 0.1 μg L−1 for inorganic mercury and methylmercury, respectively. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from the National Institute of Standards and Technology (NIST). The proposed method was also applied to the speciation of mercury in blood samples collected from fish-eating communities and from rats exposed to thimerosal. With the proposed method there is a considerable reduction of the time of sample preparation prior to speciation of Hg by LC–ICP-MS. Finally, after the application of the proposed method, we demonstrated an interesting in vivo ethylmercury conversion to inorganic mercury.