Determination of Total Mercury in Fish Tissue Using a Low-Cost Cold Vapor Capacitively Coupled Plasma Microtorch Optical Emission Microspectrometer: Comparison with Direct Mercury Determination by Thermal Decomposition Atomic Absorption Spectrometry

A method for total Hg determination in fish tissue using cold vapor capacitively coupled plasma microtorch optical emission spectrometry was evaluated. The low-cost miniaturized analytical system includes a low power plasma microtorch (10 W) and low Ar consumption (150 ml min−1) and a QE65Pro microspectrometer as detector. Lyophilized fish tissues were microwave-assisted digested in HNO3–H2O2 mixture, brought in 5 % (v/v) HCl, then Hg vapor was chemically generated with 20 % SnCl2 solution stabilized in 15 % (v/v) HCl. The figures of merit of the proposed method were evaluated by analyzing certified reference materials and test samples and compared to those of the well-established thermal decomposition atomic absorption spectrometry method. The analytical characteristics (limits of detection and quantification, precision, and accuracy) comply with requirements for Hg determination in seafood set out in Decisions 2007/333/EC and 2002/657/EC. The limits of detection and quantification of the proposed method were 3 and 9 μg kg−1 Hg in dry mass, similar to those in thermal decomposition atomic absorption spectrometry. The precision was between 1.8 and 5.5 % for concentrations in the range 0.18–0.76 mg kg−1 Hg, while the accuracy was 99.7 ± 3.0 %. The significance tests revealed no difference between the results obtained by the two methods. The proposed miniaturized spectrometric equipment could be the subject of prototyping as low-cost instrumentation for designed applications in seafood control.