Silica Supported Ionic Liquid As The Sorbent For Solid-Phase Extraction Of Sulfonylurea Herbicides

Agricultural chemicals can be used to prevent the diseases, insects and weeds to do the harm to crops and improve the yield and quality of the products. Sulfonylurea herbicides (SUs) have developed into the largest class of herbicides in the world due to their characters of high activity, high selectivity, extensive weed control and low dosage. With their increasing use in the application amount and range, more and more concerns have been raised by the public regarding their residue in the environment and crops and their poison in human health.At present, chromatography is one of the most common methods for the determination of pesticide residues. Since the SUs have the characteristics of low volatility and thermal instability, they are more suitable to be analyzed by HPLC than GC. The SUs usually exist in crops or environmental samples at trace level. Therefore, it is essential to pre-concentrate the SUs before the HPLC analysis in order to improve the detection sensitivity. Solid-phase extraction (SPE) combined with HPLC is an important technology for the trace analysis of organics. At the same time, owing to the diversity and complexity of the matrix, it is significant to develop the SPE sorbent with higher selectivity to enhance the accuracy and stability of the detection.In this paper, the silica supported ionic liquid was synthesized by the immobilization of ionic liquids via the cation and characterized. The synthesized silica supported ionic liquid was used as the SPE sorbent to combine with HPLC instrument. In the experiment, the SPE conditions including the sample pH, elution solvents and elution volume were optimized. The HPLC analysis was performed under a linear gradient program using methanol, acetonitrile and doubly deionized water as the mobile phase and obtained with the baseline separation of the12SUs. The developed SPE-HPLC method was successfully applied to simultaneous determination of the12SUs in the real environmental samples. The LODs of the selected SUs in the water sample were between2.9ng L-’and101.7ng L-1. The recoveries for the12SUs in real water samples were in the range of69.7-119.5%with the RSDs of1.5-8.4%. The LOD of each analyte in the soil was between80ng kg-1and1000ng kg-1. The recoveries for the analytes in the soil ranged from60.9%to121.3%with the RSDs of3.7-11.3%.In order to compare with the silica supported ionic liquid sorbent, the C18sorbent coupled to HPLC method for the determination of residual SUs was also developed to analyze real samples and the spiked samples. The synthesized silica supported ionic liquid sorbent possessed higher selectivity and stability for the SUs in complex samples than the conventional C18sorbent did, which showed that this new material can be developed as a potential sorbent for SPE.