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

Abstract

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 μmol dithizone g −1 polymer were used for the adsorption/desorption of inorganic mercury [Hg], methyl mercury chloride [CH 3HgCl] and ethyl mercury chloride [C 2H 5HgCl] from aqueous media at concentrations in the range 5–1000 μg 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(II), 221 mg g −1 for CH 3HgCl and 207 mg g −1 for C 2H 5HgCl. The same behavior was observed during competitive adsorption in the case of the adsorption from their mixture. The affinity order of mercury species was CH 3HgCl > C 2H 5HgCl > 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.