Highly selective determination of methylmercury with methylmercury-imprinted polymers

Methylmercury-imprinted and non-imprinted polymers were prepared by formation monomer complex of methylmercury with (4-ethenylphenyl)-4-formate-6-phenyl-2,2′-bipyridine and thermally polymerizing with divinylbenzene (crosslinker) in the presence of 2,2′-azobisisobutyronitrile as initiator and subsequently leached with the acidic thiourea solution (1.0 mol L−1 of thiourea and 4.0 mol L−1 of HCl). In the same way, non-imprinted copolymers were prepared without methylmercury chloride added. The separation and preconcentration characteristics of the polymers for methylmercury were investigated by batch and column procedures. The results demonstrated that the methylmercury-imprinted polymers had higher adsorption capacity (170 μmol g−1 of dry microbeads) and good selectivity for methylmercury compared to non-imprinted polymers. The distribution ratio (D) values of the methylmercury-imprinted polymers increased for methylmercury with respect to both D values of Hg(II), Cu(II), Zn(II), Cd(II) and non-imprinted polymers. The relatively selective factor (αr) values of CH3Hg+/Hg(II), CH3Hg+/Cu(II), CH3Hg+/Zn(II), and CH3Hg+/Cd(II) are 24.0, 46.7, 50.7, and 40.2, which are greater than 1. The methylmercury-imprinted polymers can be used at least twenty times with recoveries no less than 95%. Based on the packed columns with methylmercury-imprinted polymers, a highly selective solid-phase extraction (SPE) and preconcentration method for methylmercury was developed. The metal ion imprinted polymer solid-phase extraction (MIIP-SPE) preconcentration procedure showed a linear calibration curve within concentration range from 0.093 to 22 μg L−1. The detection limit and quantification limit were 0.041 and 0.093 μg L−1 (3σ) for cold vapor atomic absorption spectrometry (CVAAS). The relative standard deviation of the 10 replicate determinations was 3.5% for the determination of methylmercury in human hair sample. Determination of methylmercury in certified human hair sample (IAEA-086) and soil certified reference material (CRM 580) demonstrated that the interfering substances in matrix had been almost removed during preconcentration. The methylmercury-imprinted polymers were good enough for methylmercury determination in matrixes containing components with similar chemical property such as Hg(II), Cu(II), Zn(II), and Cd(II).