Polymer monolithic column containing embedded graphene oxide sheets for sensitive determination of carbamate insecticides by HPLC

We describe a new kind of polymer monolithic column for polymer monolith microextraction (PMME) of carbamate insecticide (methomyl, carbofuran and pirimicarb) residues from water samples. The monolith was prepared inside the tip of a micropipette via thermally initiated free-radical polymerization of methacrylic acid as the monomer, ethylene glycol dimethacrylate as the cross-linker, and graphene oxide (GO) dispersed in the mixed porogens (1-propanol and 1,4-butanediol). The resulting monolith was characterized by scanning electron microscopy and IR spectrometry. The effects of sample flow rate, sample volume, sample pH, desorption solvent and flow rate on PMME were optimized. Compared to a monolith without GO, the new monolith displays higher enrichment capacity, and is reusable and stable. Following extraction, the three carbamates were quantified by HPLC. The limits of detection (for S/N = 3) for the three carbamates are in the range of 0.3-0.7 mu ga (TM) L-1, and the intra- and inter-day precisions are < 5.7 %. The new monolith was successfully applied for the determination of the insecticides in various (spiked) environmental water samples, with recoveries in the range from 78.9 to 103.4 %.