Novel cation selective exhaustive injection-sweeping procedure for 5-nitroimidazole determination in waters by micellar electrokinetic chromatography using dispersive liquid-liquid microextraction
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- 作者：Maykel Herná ; ndez-Mesa ; Diego Airado-Rodrí ; guez ; Carmen Cruces-Blanco ; Ana M. Garcí ; a-Campañ ; a ; amgarcia@ugr.es" class="auth_mail
- 关键词：5-Nitroimidazoles ; Dispersive liquid&ndash ; liquid microextraction ; Cation selective exhaustive injection ; Sweeping ; Micellar electrokinetic chromatography
- 刊名：Journal of Chromatography A
- 出版年：9 May, 2014
- 年：2014
- 卷：1341
- 期：Complete
- 页码：65-72
- 全文大小：1229 K
文摘
A novel method consisting of cation-selective exhaustive injection and sweeping (CSEI-sweeping) as on-line preconcentration followed by a micellar electrokinetic chromatography (MEKC) separation has been developed for the determination of 5-nitroimidazoles (5-NDZ) in environmental waters. Moreover, dispersive liquid-liquid microextraction (DLLME) has been proposed for first time as sample treatment technique prior to CSEI-sweeping-MEKC. DLLME was applied to 5 mL of sample. Dibromomethane (1156 渭L) and 2-butanol (1363 渭L) were employed as extractant and dispersive solvents, respectively. Salting-out effect was achieved by the addition of 16% (w/v) NaCl to the samples. After DLLME and organic solvent evaporation, the residue was redissolved in a low conductivity solvent (5 mM phosphoric acid with 5% of methanol) and electrokinetically injected at 9.8 kV for 632 s in a bare fused-silica capillary (57.2 cm, 50 渭m I.D.). Prior to the injection, the capillary was rinsed with 50 mM phosphate buffer pH 2.5, followed by a plug of a higher conductivity buffer (100 mM phosphate pH 2.5, 50 mbar, 264 s) and a plug of water (50 mbar, 2 s). Separation was carried out applying 鈭?0 kV at 20 掳C in 44 mM phosphate buffer pH 2.5, containing 8% tetrahydrofuran and 123 mM sodium dodecyl sulfate. Analytical signals were monitored at 276 nm. Validation was performed in river and well waters, obtaining satisfactory results in terms of linearity, precision (% RSD generally lower than 10%) and trueness (recoveries higher than 70% in almost all cases). LODs ranged from 0.61 to 2.44 ng/mL. The combination of this microextraction technique with the proposed capillary electrophoresis methodology supposes a simple, sensitive and cheap alternative for 5-NDZ analyses, in accordance with the aims of green chemistry.