Non-hydrolytic Sol-gel Methodology to Prepare a Molecularly Imprinted, Organic-silica Hybrid-based Stir Bar for Recognition of Sulfonylurea Herbicides

Based on a molecularly imprinted organic-silica hybrid-based stir bar, a pre-treatment methodology was developed for enrichment of nicosulfuron in aqueous samples. The molecularly imprinted organic-silica hybrid-based coating on the outer surface of a glass stir bar was prepared by in-situ polymerization using nicosulfuron as a template molecule, a-methacrylic acid as a functional monomer, methacryloxypropytrimethoxysilane as a cross-linker in the mixture of acetonitrile and trichloromethane (V/V, 7.5:1). To achieve the selective extraction of the target analyte from aqueous samples, several main parameters, including extraction time, pH value and contents of inorganic salt in the sample matrix were investigated. Evidence was also presented by the scanning electronic microscopic images of the imprinted and non-imprinted stir bars. Then, the extraction efficiency of the stir bar was tested with separate experiments and competitive sorption experiments. These results showed that using six sulfonylureas as substrates the molecularly imprinted organic-silica hybrid-based stir bar gave high selectivity for the template, nicosulfuron compared to the non-imprinted organic-silica hybrid-based stir bar. This sorption extraction was coupled to liquid chromatography ultraviolet detection allowing the determination of nicosulfuron from tap water. The method showed good recoveries and precision, 96.0% (RSD 2.7%, n=3) for tap water spiked with 0.125 nmol (25.00 mL sample), suggesting that the stir bar can be successfully applied to the pre-concentration of nicosulfuron in real aqueous samples.