Large-volume sample stacking for the analysis of seven beta-lactam antibiotics in milk samples of different origins by CZE.
A method for the simultaneous determination of eight beta-lactam antibiotics (nafcillin, cloxacillin, oxacillin, dicloxacillin, ampicillin, amoxicillin, and penicillin G) in fortified milk samples of different origins has been proposed by using CZE with diode-array detection (CZE-DAD). Optimum separation was obtained on a 64.5 cm x 75 microm bubble cell capillary using 175 mM Tris buffer with 20% ethanol at pH 8.0. Methylparaben has been used as an internal standard (IS). Taking into account the lack of sensitivity of the UV-Vis detection, a solvent extraction/SPE method was applied for off-line preconcentration and sample cleanup, and also an on-line preconcentration methodology, such as large-volume sample stacking (LVSS) with polarity switching, was developed, providing LODs ranging from 2 to 10 microg/L. The method permits the quantification of these residues below the levels established in milk by the EU Regulation. Satisfactory recoveries ranging from 86 to 93% were also obtained in milk samples of different origins.
Bailón-Pérez
M Isabel
MI
Department of Analytical Chemistry, Faculty of Sciences, Campus Fuentenueva, University of Granada, Granada, Spain.
García-Campaña
Ana M
AM
Cruces-Blanco
Carmen
C
Del Olmo Iruela
Monsalud
M
D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis*; D019075:Electrophoresis, Capillary / Q000379:methods*; D005504:Food Analysis / Q000379:methods; D005506:Food Contamination / Q000032:analysis*; D008452:Maximum Allowable Concentration; D008892:Milk / Q000737:chemistry* / Q000592:standards; D047090:beta-Lactams / Q000032:analysis*
D000900:Anti-Bacterial Agents; D047090:beta-Lactams