In-capillary microextraction using monolithic polymers: Application to preconcentration of carbamate pesticides prior to their separation by MEKC

In the present work we report a novel procedure for in-capillary microextraction using a monolithic polymeric sorbent. In the proposed methodology, sample treatment takes place in the CE instrument but in a different capillary from that used for the electrophoretic separation. Polymers based on butyl methacrylate and divinylbenzene formed in situ inside a capillary column were assayed. The best results were found with the divinylbenzene-based polymers. The usefulness of the proposed procedure was checked for the determination of carbamate pesticides (Methomyl, Asulam, Carbendazim, Aldicarb, Carbetamide, Propoxur, Pirimicarb, Carbaryl, Carbofuran and Methiocarb) and three of their degradation compounds (Aldicarb sulphoxide, 2-isopropoxyphenol and alpha-naphthol) using MEKC. The optimization of the MEKC is reported, a good separation of the 13 analytes being obtained in less than 6 min. The analytical method using in-capillary microextraction was validated in terms of linearity, repeatability, precision (RSD <= 18% for 50 mu g/L), and LODs (1-16 mu g/L), and it revealed the usefulness of this in-capillary preconcentration procedure for the determination of analytes of intermediate polarity.