Surfactant-sensitized spectrophotometric determination of Hg(II) in water samples using 2-(2-thiazolylazo)- p-cresol as ligand and cetylpyridinium chloride as cationic surfactant

摘要

A new, reliable, surfactant-sensitized method is describedfor the spectrophotometric determination of total and dissolvedinorganic mercury at trace levels. The method is based on the ternarycomplex formation of Hg(II) with 2-(2-thiazolylazo)-p-cresol and acationic surfactant, cetylpyridinium chloride, at pH 9.5. Thedetection and quantification limits of the method with surfactant were6 and 19 mu g L^{-1}, while those of the method without surfactantwere 22 and 67 mu g L^{-1}, respectively. The method obeys Beer'slaw at up to approximately 10 mg L^{-1} Hg(II) in an aqueoussurfactant medium. The relative errors and relative standarddeviations of the method were 2.2% and 3.2%, while those of thedirect method were 11% and 4.4% (1.0 mg L^{-1}, n = 10), respectively.The accuracy and reliability were examined by the recoveries of spikedsolutions at 3 and 5 mg L^{-1} for the determination of mercury in tapwater, drinking water, dental unit wastewater, and artificiallyprepared model water samples. It was found that the results were verygood and comparable for both the present method and the modifieddithizone method, which was used as an independent reference method.Speciation studies for binary mixtures containing Hg(I) plus Hg(II)ions at known concentration ratios were also conducted.