Selective enrichment and determination of nicosulfuron in water and soil by a stir bar based on molecularly imprinted polymer coatings

A new molecularly imprinted stir bar was prepared using nicosulfuron, a sulfonylurea herbicide, as a template. To achieve the selective and direct extraction of a target analyte from aqueous samples, several main parameters, including extraction time, pH value and contents of inorganic salt in the sample matrix, were investigated. Competitive sorption experiments showed that using six sulfonylureas as substrates the imprinted stir bar gave high selectivity and imprinted effect on the template nicosulfuron in comparison with the non-imprinted stir bar. Evidence was also presented by the scanning electronic microscopic images of the imprinted and non-imprinted stir bars. This resulted in a combined imprinted stir bar–HPLC-UV method allowing the determination of trace nicosulfuron from the sample matrix. Based on a signal to noise ratio of 3, the detection limits were 0.75 nM for the tap water and 12.0 nmol kg−1 for the soil. The method showed good recoveries and precision, 93.4% (RSD 1.5%, n = 3) for 100 mL of tap water spiked with 2.0 nmol and 81.3% (RSD 2.6%, n = 3) for 10 g of soil spiked with 0.80 nmol, suggesting that the imprinted stir bar can be successfully applied to the preconcentration of nicosulfuron in real samples.