Study On Preparation For A Nicosulfuron-imprinted Polymer Stir Bar By Non-hydrolytic Sol–gel Method And Its Performances

Stir bar sorptive extraction (SBSE) introduced by Sandra′s group (Baltussen E et al.,1999) is a very elegant enrichment technique for complex samples. Up to now,the coating materials in SBSE mainly are PDMS and sol-gel material. However,these coating layers are short of high selectivity on target molecules and have low sample capacity. Molecular imprinting is a method that can prepare polymer material with predetermined selectivity towords a certain guest molecules. Take advantage of the shape,size,recognition site inside the molecularly imprinted polymer corresponding to the template molecules,the selectively recognization for the TM was realized through the recognition effects for template molecule..Sulfonylureas are a class of herbicides used for crops protection and have been widely used to control weeds. However,the sulfonylurea-herbicide residue is highly phytotoxic to some rotational plants at only 1% or even less of the originally applied amount. The present methods for the determination of sulfonylurea-herbicides include HPLC-UV,HPLC-MS, capillary electrophoresis,gas chromatography,and immunoassay . All pretreatments of these methods need tedious and time-consuming procedures,and require large amounts of organic solvents. Therefore,it is necessary to develop more efficient and robust pretreatment methods to meet the need for detecting these herbicides. Because of the above-mentioned causes,the following studies are done in this paper.1. In the study,a new stir bar coated with nicosulfuron-imprinted polymer monolith (MIPSB) was prepared in situ polymerization with the functional monomer methacrylic acid and the cross-linking monomer methacryloxypropytrimethoxysilane. The binding mechanism of the template and the functional monomer was studied in acetonitrile. The structural properties of the MIP were also studied.2. A glass stir bar was prepared by in-situ polymerization using nicosulfuron as a template molecule,α-methacrylic acid as a functional monomer,methacryloxypropytrimethoxysilane as a cross-linker in the mixture of acetonitrile and trichloromethane. The imprinted stir bar was used for 100 times for extraction NS in an aqueous sample without losing its extraction efficiency.3. Morphologies of the MIPSB or NMIPSB were visualized with scanning electron microscopy (SEM); To achieve the selective extraction of target analytes from aqueous samples,several main parameters,including extraction time,pH value and contents of inorganic salt in the sample matrix were investigated. Separate and competitive sorption experiments showed that using several 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 an imprinted stir bar-HPLC method allowing the determination of trace nicosulfuron from the sample matrix. The method showed good recoveries and precision. In the optimized conditions,real samples were treated using MIPSB-HPLC. The results suggest that the imprinted stir bar can be successfully applied to the preconcentration of nicosulfuron s in real samples. The method showed good recoveries and precision, 96.0% (RSD 2.7%,n=3).