Selective preconcentration of phenyl-mercury by living Escherichia coli and its determination by cold vapour atomic absorption spectrometry Original Research Article

A method is proposed for speciation of phenyl-mercury (Ph-Hg) in waters based on the retention of analyte by a living Escherichia coli strain (K-15) grown in the aqueous sample solution containing glucose as a nutrient. In the general procedure, equilibrium between the analyte in the sample and the living bacterial cells is allowed to be established. However, a theoretical model of the retention process, based on a rate-determining step in reaching the adsorption equilibrium, illustrates the feasibility of quantifying the analyte before equilibrium is reached. The Ph-Hg-biomass is separated from the solution by centrifugation and the amount of organo-mercury retained is determined directly in the biomass slurry by cold vapour atomic absorption spectrometry (CVAAS). Speciation of Ph-Hg from matrices containing other mercury species {ethyl-mercury, methyl-mercury, Hg2+, Hg(I)} and the CVAAS determination of Ph-Hg can be carried out with relative standard deviations of 2.2–5.3%. The detection limit for Ph-Hg under optimum conditions is 0.05 ng ml−1.