Selective Pb(II)-Imprinted Polymer for Solid Phase Extraction in the Trace Determination of Lead in Infant Formula by Capillary Electrophoresis

Abstract

A lead ion-imprinted polymer (IIP) based on methacrylic acid (MAA) and 4-vinylpyridine (4VP) as functional monomers has been synthesized by a radical precipitation method. The complex Pb-MAA-4VP was polymerized with ethylene glycol dimethacrylate as the cross-linker agent. The material was used in solid phase extraction (SPE) coupled with capillary electrophoresis (CE) for the determination of lead in infant formula samples. The physical-chemical properties of the IIP were characterized by scanning electron microscopy, IR spectroscopy, and Freundlich and Dubinin-Raduskevich models. The IIP selectivity was determined in presence of Ca(II), Mg(II), Cd(II), Cr(III) and Cu(II), which are present in the infant formula sample. The proposed methodology (SPE-CE) for the determination of lead has a limit of detection of 0.5 µg L-1 and a limit of quantification of 1.5 µg L-1, with an intra and inter-day repeatability of less than 5 % RSD in all cases. Four of twenty samples were positive for lead with concentrations ranging from 10 to 43 µg kg-1, and the results were compared with ETAAS. ANOVA demonstrated no significant difference between the results obtained by SPE-CE and ETAAS (α = 0.05 %).