Determination of inorganic and organic mercury compounds by capillary gas chromatography coupled with atomic absorption spectrometry after preconcentration on dithizone-anchored poly(ethylene glycol dimethacrylate-hydroxyethylmethacrylate) microbeads

Poly(EGDMA-HEMA) microbeads were prepared by suspension polymerization of ethylene glycol dimethacrylate EGDMA) and hydroxyethyl methacrylate (HEMA). Poly(vinyl alcohol), benzoyl peroxide and toluene were used as stabilizer, initiator, and diluent, respectively. A chelating ligand, dithizone, was then attached. The microbeads were characterized by FTIR spectrometers and elemental analysis. The affinity microbeads containing 118.9 mu mol dithizone g(-1) polymer were used for the adsorption/desorption of inorganic mercury [Hg], methyl mercury chloride [CH3HgCl] and ethyl mercury chloride [C2H5HgCl] from aqueous media at concentrations in the range 5-1000 mu g l(-1) and various pH values (2.0-8.0). Adsorption rates were high, and adsorption equilibria were reached in about 30 min. The maximum adsorption of mercury species onto the dithizone-anchored microbeads from their individual solutions was 138 mg g(-1) for Hg(Tr), 221 mg g(-1) for CH3HgCl and 207 mg g(-1) for C2H5HgCl. The same behavior was observed during competitive adsorption in the case of the adsorption from their mixture. The affinity order of mercury species was CH3HgCl > C2H5HgCl > Hg(II). Dithizone-anchored microbeads are suitable for repeated use for more than 5 cycles without noticeable loss of adsorption capacity. Speciation of organomercurials was performed using a Gas chromatography-atomic absorption spectrometry coupled system. Detection limits were increased at least 120-fold with this preconcentration approach using the dithizone-anchored microbeads. (C) 1998 Elsevier Science B.V. All rights reserved.