title: Determination of 5-nitroimidazole residues in milk by capillary electrochromatography with packed C18 silica beds.
abstract: This work presents a novel methodology for analysing 5-nitroimidazole residues in milk samples by capillary electrochromatography using lab-made packed columns, produced by carrying out a high pressure packing procedure using acetone as driving solvent and C18 silica uncapped particles (5 µm particle size) as packing material. Column frits resulted from sintering the proper stationary phase by heating the packed material for 20s with a nichrome ribbon (80% Ni-20% Cr, 28 cm × 2 mm × 0.2 mm, electric resistance 1.3 Ω) connected to a 7 V AC power supply. Lab-made C18 silica packed capillaries (40 cm x 50 µm i.d.) were employed for the determination of 5-nitroimidazole drugs. Milk samples were treated by a salting-out assisted liquid-liquid extraction followed by a solid phase extraction with Oasis®HLB cartridges prior to their injection. Samples were hydrodynamically injected into the column for 120 s at 11.5 bar. Afterwards eight 5-nitroimidazole compounds were separated in isocratic mode under an applied voltage of 27 kV and a temperature of 30 °C. The selected mobile phase consisted of a mixture 60:40 acetonitrile:ammonium acetate (2.5 mM, pH=5). Separation was monitored at 320 nm and it was performed in less than 15 min. The method was characterized in terms of linearity (R(2)≥0.993) and precision (repeatability, RSD≤12.2% and reproducibility, RSD≤14.5%), obtaining detection limits lower than 29 µg/L for all compounds under study.
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, E-18071 Granada, Spain.
authors.forename: Maykel
authors.initials: M
authors.lastname: Hernández-Mesa
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, E-18071 Granada, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Lara
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, E-18071 Granada, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Cruces-Blanco
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, E-18071 Granada, Spain. Electronic address: amgarcia@ugr.es.
authors.forename: Ana M
authors.initials: AM
authors.lastname: García-Campaña
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis*; D053801:Capillary Electrochromatography; D005506:Food Contamination / Q000032:analysis; D057230:Limit of Detection; D059625:Liquid-Liquid Extraction; D008892:Milk / Q000737:chemistry*; D009593:Nitroimidazoles / Q000032:analysis*; D015203:Reproducibility of Results; D012822:Silicon Dioxide / Q000737:chemistry; D052616:Solid Phase Extraction
chemical_list: D000900:Anti-Bacterial Agents; D009593:Nitroimidazoles; D012822:Silicon Dioxide; C052587:4-nitroimidazole
keywords: 5-Nitroimidazoles; Capillary electrochromatography; Milk; Packed capillary columns; Slurry pressure packing