Determination of Total Mercury in Sushi Samples Employing Direct Mercury Analyzer

Abstract

In this study a simple, fast, and low-chemical-consuming method was evaluated for the determination of total mercury in sushi samples by thermal decomposition amalgamation atomic absorption spectrometry (TDA-AAS) using a direct mercury analyzer (DMA). A small portion of fresh sushi sample (60 mg) is combusted in nickel or quartz containers, and the released mercury is trapped in a gold amalgamator, being desorbed at high temperatures and measured in an atomic absorption cell. The method accuracy was evaluated using certified reference materials (CRM) rice flour (NIST SRM 1568b), fish protein (NRC DORM-4), peach leaves (NIST SRM 1547), and oyster tissue (NIST SRM 1566b), and the method accuracy varied between 94 and 112 % for all the CRM. Analytical curves were prepared using 0.5 % nitric acid solutions (v/v) for low (0.5 to 50 μg kg⁻¹) and high concentrations (100 to 1000 μg kg⁻¹) and the correlation coefficients were above 0.999. The detection and quantification limits were 0.4 and 1.4 μg kg⁻¹, respectively. The method was applied to 30 sushi samples of tuna, salmon, and kani from Campinas City, São Paulo State, Brazil, and the results ranged from 6.2 to 761, 1.5 to 4.0, and <1.4 to 13.5 μg kg⁻¹, respectively. High amounts of total mercury were found in samples of tuna sushi, and tuna was the ingredient that most contributed to dietary Hg exposure.