Abstract:

Molecularly imprinted microspheres (MIPMs) for binding and recognition of nicosulfuron (NS) (NS-MIPMs) were prepared by precipitation polymerization. Methacrylic acid (MAA) was used as the functional monomer, trimethylolpropane trimethacrylate (TRIM) as the linking agent, 2,2-azobisisobutyronitrile (AIBN) as the initiator and chloroform as the porogenic solvent. The preparation conditions were optimized, and MIPMs exhibited the best adsorption capacity when the molar ratio of NS/MAA/TRIM/AIBN was 1:4:4:1 and the volume of the porogenic solvent was 90 mL. An ultraviolet-visible (UV-Vis) spectrophotometer was employed to study the mechanism of the interaction between NS and MAA, and the results showed that the NS-MAA complexes of 1:1 molar ratio were obtained in the pre-polymerization phase. The rebinding capacity of MIPMs was evaluated according to adsorption kinetics and adsorption isotherm of the imprinted microspheres. The Scatchard plot revealed that the template polymer system has a two-site binding behavior and the MIPMs exhibited the maximum rebinding to NS at 11370.5 μg/g. The MIPMs were then used as adsorbents in a solid phase extraction (SPE) column and the optimum loading, washing and eluting conditions for the MIPMs were established. Additionally, a rapid method for the determination of NS residues in soil was developed using an NS-MIPMs SPE column. The analyte was extracted using acetonitrile and phosphate buffer, cleaned-up by an NS-MIPMs SPE column and analyzed by HPLC. The results showed that good linearity was observed in the range of 0.01-1 mg/L for NS, with a correlation coefficient of 0.9986. The recovery tests were performed at the spiked levels of 0.02-1 mg/kg, and the recoveries were in the range of 82.2%-86.3% with the relative standard deviations of 1.9%-4.3%. The advantages of the proposed method are that it is easy to operate, reliable and applicable to analyze the NS residues in soil samples.

Key words: adsorption, molecularly imprinted polymers (MIPMs), nicosulfuron, precipitation polymerization, solid phase extraction (SPE)