Evaluation of a molecularly imprinted polymer as in-line concentrator in capillary electrophoresis

Molecularly imprinted polymers (MIPs) have been evaluated as sorbent for the construction of an in-line solid phase extraction concentrator in capillary electrophoresis to be applied in the monitoring of triazine herbicides: atrazine and its three metabolites, desethylatrazine, desisopropylatrazine and desethyldesisopropylatrazine. Initially, the electrophoretic separation of these compounds was optimized. The electrolyte consists of an aqueous solution of 75 mM phosphoric acid (H3PO4) adjusted to pH 2.1 and containing 0.7 mM cetyltrimethylammonium bromide. After the fabrication and assembly of the concentrator into the capillary, these optimal CE conditions were applied to evaluate the performance of this device. Efficiencies of 40 000-55 000 plates could be achieved and the separation time was around one hour. Different parameters affecting the in-line molecularly imprinted solid-phase extraction in capillary electrophoresis such as composition and volume of the elution plug were optimized. The method was evaluated in terms of linearity, precision and limits of detection and quantification. MIPs were compared with Oasis hydrophilic-lipophilic-balance (HLB) particles for the in-line coupling of solid-phase extraction and capillary electrophoresis. The superior selectivity of MIPs is demonstrated through direct injection of a urine sample spiked with 10 mu g/mL atrazine, desethylatrazine, desisopropylatrazine and desethyldesisopropylatrazine. Recoveries were between 92 and 102% compared with an aqueous solution.