Mercury Determination and Speciation in Surface Waters after Preconcentration with Nanosized Ion-imprinted Polymer Gels

Abstract

Hg(II) ion-imprinted polymer (Hg(II)-IIP) gels are prepared by copolymerization of methacrylic acid (functional monomer), trimethylolpropane trimethacrylate (crosslinking agent) and 2,2'-azo-bis-isobutyronitrile (initiator) in the presence of Hg(II) complexes with chelating agent 1-pyrrolidinedithiocarboxylic acid (Hg-PDC) or PDC only.  The composition, structure and morphology of the particles obtained are characterized by using elemental analysis, FTIR and  SEM. The separation and preconcentration characteristics of the Hg(II)-IIPs for inorganic mercury are investigated by batch procedure.  The optimal pH interval for the quantitative sorption is 5─7. The adsorbed Hg(II) is easily eluted by 0.1 M thiourea in 0.1 M HCl. The selectivity of the Hg(II)-IIPs toward inorganic mercury (Hg(II)) ion is confirmed through comparison of the competitive  adsorptions of CH₃Hg⁺, Cd(II), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II) and Zn(II) and high values of the selectivity and distribution coefficients are calculated. Experiments performed for selective determination of inorganic mercury in river and sea water samples showed that the interfering matrix does not influence the extraction efficiency of Hg(II)-IIPs. The detection  limit for inorganic mercury is 0.006 µg/L (3 s), determined by cold vapor atomic adsorption spectrometry. The relative standard deviation varied in the range 6─-12 % for Hg(II) and CH₃Hg⁺ levels at 0.03 to 1 μg/L. The new Hg(II)-IIPs are  tested and applied for the speciation of Hg in waters: inorganic mercury is determined selectively in nondigested water sample, while total mercury e.g. sum of inorganic and organic mercury, is determined in digested sample.