Novel cation selective exhaustive injection-sweeping procedure for 5-nitroimidazole determination in waters by micellar electrokinetic chromatography using dispersive liquid-liquid microextraction.
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 5mL of sample. Dibromomethane (1156μL) and 2-butanol (1363μL) 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 (5mM phosphoric acid with 5% of methanol) and electrokinetically injected at 9.8kV for 632s in a bare fused-silica capillary (57.2cm, 50μm I.D.). Prior to the injection, the capillary was rinsed with 50mM phosphate buffer pH 2.5, followed by a plug of a higher conductivity buffer (100mM phosphate pH 2.5, 50mbar, 264s) and a plug of water (50mbar, 2s). Separation was carried out applying -30kV at 20°C in 44mM phosphate buffer pH 2.5, containing 8% tetrahydrofuran and 123mM sodium dodecyl sulfate. Analytical signals were monitored at 276nm. 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 2.44ng/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.
Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, E-18071 Granada, Spain.
Maykel
M
Hernández-Mesa
Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, E-18071 Granada, Spain.
Diego
D
Airado-Rodríguez
Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, E-18071 Granada, Spain.
Carmen
C
Cruces-Blanco
Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Av. Fuentenueva s/n, E-18071 Granada, Spain. Electronic address: amgarcia@ugr.es.
Ana M
AM
García-Campaña
D002412:Cations / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical / Q000295:instrumentation / Q000379:methods; D020374:Chromatography, Micellar Electrokinetic Capillary; D004784:Environmental Monitoring / Q000191:economics / Q000379:methods*; D059627:Liquid Phase Microextraction; D009593:Nitroimidazoles / Q000032:analysis*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis
D002412:Cations; D009593:Nitroimidazoles; D014874:Water Pollutants, Chemical; D014867:Water; C052587:4-nitroimidazole
5-Nitroimidazoles; Cation selective exhaustive injection; Dispersive liquid–liquid microextraction; Micellar electrokinetic chromatography; Sweeping