Selective high performance liquid chromatography imprinted-stationary phases for the screening of phenylurea herbicides in vegetable samples

Molecularly imprinted polymers (MIPs) for the determination of phenylurea herbicides have been synthesized by polymerisation of the appropriated reagents mixture within the pores of preformed spherical silica particles leading to a silica-MIP composite material. Subsequently, the silica matrix was etched away resulting in MIP beads which can be considered the "mirror image" of the original silica mold. The MIP particles were packed in stainless steal HPLC columns (125mmx4.6mm I.D.) and the materials were evaluated as imprinted-stationary phases for phenylurea herbicides. The imprinting effect of the originated specific binding sites for the selective recognition of phenylurea herbicides was clearly demonstrated. An efficient separation of a mixture of phenylurea herbicides in two groups, with or without a methoxy group in the chemical structure, was achieved and well shaped and defined peaks were obtained. Finally, the optimum imprinted column (prepared using linuron as template, 2-(trifluoromethyl)-acrylic acid as monomer, 72h of polymerisation time and the subsequent dissolution of silica matrix) was used for the LC-UV screening of phenylurea herbicides directly from vegetable sample extracts without any previous clean-up step at low concentration level in less than 10min.