Avaliação do comportamento de espécies de mercúrio em peixes após diferentes métodos de cocção

Abstract

Most of studies evaluating Hg in fish have been developed using fresh fish and the few studies involving the assessment of Hg in fish after cooking process, involve only the determination of total Hg and no clear conclusions have been reported. Considering the relatively high temperatures used for the preparation of fish and the volatile characteristics of some Hg species, this study aimed to evaluate the behavior of species of Hg (Hg2+ and CH3Hg+) after different cooking treatments in six different species of fish. Three different cooking procedures (cooking with water, frying and roasting) were evaluated, in addition to in natura samples. Moreover, the influence of three different conditions (containing salt, salt and lemon, and without seasonings) was evaluated for each treatment. All additives involved, like salt, lemon, oil and water used during the cooking procedure were collected to evaluate the mass balance of total Hg, including its possible losses. After each culinary treatment, samples were freeze-dried and ground in a cryogenic mill. For the extraction method of Hg species a solution of 0.6% (m/v) L-cysteine was used. Parameters such as time and cooking temperature and the mass and shape of sample were previously selected and optimized. Parameters of the speciation method were also evaluated such as: concentration of extractant solution, extraction time, sample weight and analyte recovery test (CH3Hg+ and Hg2+). Mercury species were identified and quantified by liquid chromatography-chemical vapor generation-inductively coupled plasma mass spectrometry (LC-CVG-ICP-MS). The accuracy was evaluated using certified reference material of dogfish muscle (DORM-2) and an agreement better than 97% with reference values was obtained for CH3Hg+ and total Hg. The relative standard deviation of the proposed method was below 5.5%. The limit detection of 1.7 and 2.3 ng g-1 as Hg for Hg2+ and CH3Hg+, respectively, were obtained. Losses of Hg species up to 33% were detected after frying procedure. However, no significant conversions between Hg species in any culinary treatment were observed.