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A new method was developed for the determination of eight triazine herbicide residues in cereal and vegetable samples by on-line sweeping technique in micellar electrokinetic capillary chromatography (MEKC). Some factors affecting analyte enrichment and separation efficiency were examined. The optimum buffer was composed of 25 mM borate, 15 mM phosphate, 40 mM sodium dodecylsulfate (SDS) and 3% (v/v) of 1-propanol at pH 6.5. The separation voltage was 20 kV and the sample was injected at 0.5 psi for 240 s. The detection wavelength was set at 220 nm with the capillary temperature being at 25 °C. Under the optimized conditions, the enrichment factors were achieved from 479 to 610. The limits of detection (LODs, S/N = 3) ranged from 0.02 to 0.04 ng/g and the limits of quantification (LOQs) of eight triazine herbicides were all 0.1 ng/g. The average recoveries of spiked samples were 82.8-96.8%. This method has been successfully applied to the determination of the triazine herbicide residues in cereal and vegetable samples., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A new MEKC method with large-volume sample stacking and polarity switching was developed for on-line preconcentration and detection of sulfonylurea herbicide (SUH) residues in cereals, including nicosulfuron (NS), thifensulfuon (methyl) (TFM), tribenuron-methly (TBM), sulfometuron-methyl (SMM), pyrazosulfuron-ethyl (PSE), and chlorimuron-ethyl (CME). In order to achieve a high resolution and enrichment factor, several parameters were optimized, such as the pH of the running buffer, the concentration of the BGE and the SDS, the separate voltage, the sample size, the pH, and the electrolyte concentration of the sample. The optimal running buffer was composed of 30 mM borate and 80 mM SDS at pH 7.0. The borate concentration in the sample was 30 mM and the pH value of the sample was the same as that of the running buffer. The concentrating voltage and the separating voltage were -15 kV and 15 kV, respectively. The sample size was 1.455 kPa × 780 s (33.11 cm). Under the optimum conditions, for NS, TFM, TBM, SMM, PSE, and CME, the enrichment factors were 613, 642, 835, 570, 709, and 599; the LODs were 0.29-0.50 ng/g, 0.22-0.36 ng/g, 0.60-0.89 ng/g, 0.39-0.72 ng/g, 0.28-0.56 ng/g, and 0.31-0.57 ng/g; the LOQs of six SUHs were all 5 ng/g; the average recoveries of the spiked sample were 86.68-92.99%, 80.73-93.65%, 81.49-94.40%, 82.97-95.1%, 82.96-98.84%, and 80.41-92.94%, respectively., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)