Use of an ionic liquid-based surfactant as pseudostationary phase in the analysis of carbamates by micellar electrokinetic chromatography.

The applicability of an ionic liquid-based cationic surfactant 1-dodecyl-3-methyl-imidazolium tetrafluoroborate (C12 MImBF4 ) as pseudostationary phase in MEKC has been evaluated for the analysis of 11 carbamate pesticides (promecarb, carbofuran, metolcarb, fenobucarb, aldicarb, propoxur, asulam, benomyl, carbendazim, ethiofencarb, isoprocarb) in juice samples. Under optimum conditions (separation buffer, 35 mM NaHCO3 and 20 mM C12 MImBF4 , pH 9.0; capillary temperature 25°C; voltage -22 kV) the analysis was carried out in less than 12 min, using hydrodynamic injection (50 mbar for 7.5 s) and detection at 200 nm. For the extraction of these CRBs from juice samples, a dispersive liquid-liquid microextraction (DLLME) procedure has been proposed, by optimization of variables affecting the efficiency of the extraction. Following this treatment, sample throughput was approximately 12 samples per hour, obtaining a preconcentration factor of 20. Matrix-matched calibration curves were established using tomato juice as representative matrix (from 5 to 250 μg/L for CBZ, BY, PX, CF, FEN, ETH, ISP, and 25-250 μg/L for ASL, ALD, PRC, MTL), obtaining quantification limits ranging from 1 to 18 μg/L and recoveries from 70 to 96%, with RSDs lower than 9%.