MERCURY DETERMINATION BY COLD VAPOR ATOMIC-ABSORPTION SPECTROMETRY IN SEVERAL BIOLOGICAL INDICATORS FROM LAKE MARACAIBO, VENEZUELA

Two sampling sessions were carried out in Lake Maracaibo and eight sites selected in four pairs one in front of the other (El Mojan-Ancon de Iturre, Santa Cruz de Mara-Punta de Palmas, Maracaibo-Punta de Leiva and San Francisco-La Rita). Specimens of Cynoscion acoupa Maracaiboencis (curvina, n = 5), Oligoplites palometa (palometa, n = 5), Penaeus schmitti (shrimp, h = 20), and Polymesoda arctata (mussels, n = 20) were collected. For the curvina and palometa, muscle, brain, kidney, gill, liver and heart were analysed. Shrimp and mussels were analysed whole, without the shells. Samples were lyophilized and cold digested in a mixture of sulfuric, nitric and perchloric acids, potassium permanganate and hydrogen peroxide. Spectrometric determination was carried out using cold vapour atomic absorption spectrometry and sodium borohydride as reducing agent. Accuracy was tested with a National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) RM50 Albacore Tuna, and against another method. The detection limit for Hg was 53 ng l-1. Good agreement was found between results for the analysis of SRM RM50 (Hg = 0.95 +/- 0.14 mg kg-1) and the assigned value furnished by NIST (Hg = 0.95 +/- 0.10 mg kg-1). Precision and the interference were also evaluated. Mercury concentrations in brain, kidney and heart tissues of the curvina and palometa were found to be higher than those in the muscle tissue.