Novel Imprinted Polymer for the Preconcentration of Cadmium with Determination by Inductively Coupled Plasma Mass Spectrometry

摘要

A novel Cd(II)-imprinted polymer was prepared with chemical immobilization approach by using N-methacryloyl-L-histidine as a vinylated chelating agent for on-line solid phase extraction of Cd(II) for determination by inductively coupled plasma mass spectrometry. Cd(II)-monomer complex was synthesized and copolymerized via bulk polymerization method in the presence of ethyleneglycoldimethacrylate cross-linker. The resulting polymer was leached with 1.0 mol L⁻¹ HNO3 to generate the cavities in the polymer for Cd(II) ions. The experimental conditions, including load pH, solution flow rate, and eluent concentration for effective sorption of Cd(II) were optimized using a minicolumn of the imprinted polymer. A volume of 5.0 mL sample 5 μg L⁻¹ Cd(II) solution at pH 6.5 was loaded onto the column at 2.0 mL min⁻¹ by using a sequential injection system (FIALab 3200) followed by elution with 1.0 mL of 0.75 mol L⁻¹ HNO3. The relative selectivity coefficients of the imprinted polymer for Cd(II) were 38.5, 3.5, 3.0, 2.5 and 6.0 in the presence of Cu(II), Ni(II), Zn(II), Co(II) and Pb(II), respectively. Computational calculations revealed that the selectivity of the imprintedpolymer was mediated by the stability of Cd(II)-N-methacryloyl-L-histidinecomplex which was far more stable than those of commonly used monomers, such as4-vinyl pyridine, methacrylic acid and vinylimidazole. The detection limit (3s)and relative standard deviation (%) were found to be 0.004 μgL⁻¹ and 3.2%, respectively. The method wasvalidated by analysis of seawater certified reference material (CASS-4) andsuccessfully applied to the determination of Cd(II) in coastal seawater andestuarine water samples.