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In the present study, we assessed mercury exposure of residents of different sites of Valparaiso Region (Chile) due to fish consumption and atmospheric contamination from coal-burning power plant and copper smelter. Total mercury concentration was determined in 199 hair samples and in 14 species of marine fish, purchased in the supermarket or collected in the studied fishing villages-1 in human hair samples and from 0.04 to 3.-1 in fish samples. Importantly, hair mercury concentration was significantly higher in the case of population exposed to mercury exclusively by fish consumption (e.g. Quintay and Zapallar), in comparison to the residents exposed to industrial emissions and fish consumption (e.g. Puchuncavi, Las Ventanas, Quintero). Finally, high mercury concentrations were observed in fish types commonly consumed by the residents of the fishing villages, evidencing human exposure to mercury through fish consumption.

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A new method for the extraction of methyl-, butyl-, phenyl-and octyltin compounds from soil and vegetal samples was proposed. The extraction procedure is based on an acidic solution in methanol for both matrices using a microwave system. The optimal conditions for each matrix were determined using the experimental design methodology and the respective figures of merit were evaluated. In optimal conditions, the analytes can be detected between 0.1-2.9 ng g -1 with repeatability lower than 6.5 % for both matrices. The extraction procedure was satisfactorily applied to spiked real samples, reaching recoveries ranged to 48.5-94.1% and 69-123 % for vegetal and soil samples, respectively. The proposed methodology is a promising alternative for control of organotin compounds in terrestrial ecosystems. Finally, the analytical performance of the proposed methodology was compared with published works in order to demonstrate its advantages and benefits.

In the present work, the applicability of a monolithic column was evaluated for mercury speciation analysis in certified and real fish samples. The influence of the flow and composition of the mobile phase (2-mercaptoethanol concentration and methanol content) on the retention times of iHg and MeHg was evaluated. The optimal separation conditions were achieved for a mobile phase containing 5 % methanol and 0.02 % mercaptoethanol in acetate buffer (pH 5.0) at a flow rate of 1.6 ml min-1. Different extraction conditions were studied to analyze a certified reference material with the optimized methodology and the best results (93 % recovery) were obtained for microwave-assisted extraction with a mixture of HCl 6 M + NaCl 0.5 M. Finally, the proposed method was satisfactorily applied to real fish samples collected from different markets in the central region of Chile, presenting levels ranging from 0.73-3.4 mg kg-1 .