Development of Methods for Selenium Determination in Fish: Tools for Ecotoxicological Studies

Selenium (Se) plays a significant role in many physiological processes. During the past years the role of Se has changed, from being considered toxic to the definition of being essential in almost every cell of our body. Furthermore, Se species play a role in mercury (Hg) detoxification suggesting that the protective effect of Se against Hg is related to the amount of Se available. In this work, two methods for Se determination in fish, by HG-AFS and HG-MP AES were developed. Moreover, a green analysis was applied to evaluate them. To both methods, optimization conditions were exhaustively evaluated and validated. Excellent figures of merit were obtained, with LOD of 0.04 mg kg-1 and 0.004 mg kg-1 to HG-MP AES and HG-AFS, respectively. The developed methods fit our purpose, being adequate for the determination of Se in fish and were compared in terms of accordance with the green analytical chemistry principles using AGREE metrics. The HG-MP AES method constitutes a greener alternative (0.60) than AFS (0.46). Borriqueta porgy (Boridia grossidens) fish samples from the Uruguayan coast were analyzed. The levels of Se in the samples were between 0.15 – 0.40 mg kg-1 determined by HG-MP AES and 0.13 – 0.35 mg kg-1 with HG-AFS, being the developed methods two alternatives for the Se monitoring. Finally, an ecotoxicological study was conducted to evaluate Se protection against Hg in fish tissue. All samples presented a Se:Hg molar ratio and the Selenium Health Benefit Value above 1, suggesting the protection of Se against mercury toxicity. This work presents two developed analytical methods suitable for the determination of Se in fish samples; in addition, this is the first evaluation that presents HG-MP AES for Se determination in fish. Furthermore, this work constitutes the first to determine Se in Uruguayan coast as well as the first to evaluate the Se protection against Hg in fish tissue.