Speciation of inorganic and organolead compounds by gas chromatography-atomic absorption spectrometry and the determination of lead species after pre-concentration onto diphenylthiocarbazone-anchored polymeric microbeads

Poly(EGDMA-HEMA) microbeads were prepared by suspension copolymerization of ethyleneglycol dimethacrylate (EGDMA) and hydroxyethylmethacrylate (HEMA) using poly(vinylalcohol), benzoyl peroxide and toluene as the stabilizer, t he initiator, and the diluent, respectively. A chelating ligand, diphenylth iocarbazone (dithizone), was then attached. The microbeads were characteriz ed by FT-IR and elemental analysis. The affinity microbeads containing 118. 9 mu mol dithizone g(-1) polymer were used in the adsorption/desorption of some selected lead species, Pb(II), (CH3)(2)PbCl2, (C2H5)(2)PbCl2, (CH3)(3) PbCl, and (C2H5)(3)PbCl from aqueous media containing different amounts of these species (5-200 mg 1(-1)) at different pH values, 2.0-8.0. Adsorption rates were high, and adsorption equilibrium was reached in approximately 45 min. The detection limits of the lead species onto the dithizone-anchored affinity microbeads from solutions containing a single species was 0.28 ng ml(-1) for Pb(II), 0.12 ng ml(-1) for (CH3)(3)PbCl, 0.24 ng ml(-1) for (C2H 5)(3)PbCl, 0.18 ng ml(-1) for (CH3)(2)PbCl2 and 0.30 ng ml(-1) for (C2H5)(2 )PbCl2 on a weight basis for lead. The same behavior was observed during co mpetitive adsorption that is adsorption from a mixture. The affinity order of the lead species was Pb(II) > (CH3)(2)PbCl2 > (CH3)(3)PbCl2 > (C2H5)(3)P bCl > (C2H5)(2)PbCl2 for competitive adsorption. Dithizone-anchored microbe ads were found to be suitable for repeated use of more than five cycles, wi thout noticeable loss of adsorption capacity. For the speciation of organol ead compounds, ionic alkyllead compounds were derivatized by n-butyl Grigna rd reagent and the speciation was performed using a gas chromatography-atom ic absorption spectrometry coupled system. Detection limits were improved a t least 180-fold with this preconcentration approach using the dithizone-an chored microbeads. (C) 2000 Elsevier Science B.V. All rights reserved.