N-Methylimidazolium ionic liquid-functionalized silica as a sorbent for selective solid-phase extraction of 12 sulfonylurea herbicides in environmental water and soil samples

A novel material for solid-phase extraction (SPE) was synthesized by chemical immobilization of a functionalized N-methylimidazolium ionic liquid on silica gel. Cartridges packed with the synthetic material were successfully applied to the pre-concentration of trace-level thifensulfuron-methyl, metsulfuron-methyl, chlorsulfuron, sulfometuron-methyl, rimsulfuron, ethametsulfuron, tribenuron-methyl, bensulfuron-methyl, prosulfuron, pyrazosulfuron, chlorimuron-ethyl and primisulfuron from environmental water and soil samples. The 12 sulfonylurea herbicides (SUs) obtained a good resolution in less than 50 min using HPLC with a UV detector. The recovery studies using the ionic liquid-functionalized silica as a sorbent were performed by three consecutive extractions of water and soil samples at two spiked levels. The average recovery for each analyte was in the range of 53.8–118.2% for the water samples and 60.9–121.3% for the soil sample, with RSDs lower than 11.3% in all cases. The ionic liquid-functionalized silica cartridges showed higher selectivity for the SUs than commercially available C18 cartridges did.