A simple, sensitive and selective spectrophotmetric method is presented for the rapid determination of mercury (II) at trace levels using 2-mercapto-5-methylbenzimidazole (MMBI) as a new spectrophotometric reagent (lambdamax = 320 nm) in a slightly basic (0.04 M Britton-Robinson (BR) buffer, pH 8.0) aqueous solution. The reaction is instantaneous and the absorbance remains stable for over 24 hours. The average molar absorption coefficient was found to be 2.71 x 10(4) L mol-1 cm-1. The stoichiometric composition of the chelate is 1:1 (Hg:MMBI). Considerable excesses of copper, zinc, lead and cadmium do not interfere in the determination. The method developed allowed the determination of mercury in the range of 2 x 10-6 to 4 x 10-5 mol.L-1 with good precision, accuracy and the detection limit was 9.9 x 10-7 mol.L-1 of Hg. The method was successfully applied to fish samples and the results were evaluated and compared with classic atomic absorption spectrometry (AAS). The relative standard deviations for the samples analyzed were between 7.2 and 33% (n = 5), while the errors were between 1.63 and 11.6. The method was found to be sensitive, selective and was used for the determination of mercury in fish with satisfactory results.
mercury; fish samples; analytical methodology
