Determination of enrofloxacin and ciprofloxacin in foods of animal origin by capillary electrophoresis with field amplified sample stacking-sweeping technique.

A simple on-line preconcentration method combining field-amplified sample stacking (FASS) with sweeping was developed and validated for the determination of enrofloxacin (ENRO) and ciprofloxacin (CIP) in multiple foods. To improve the efficiency of sweeping, gamma-cyclodextran (γ-CD) was introduced to the sample matrix. The optimal experimental conditions were as follows: running buffer (pH 8.8), (a) 20mM Tris and 80mM NaDC with 300s sample injection time, (b) 20mM Tris and 120mM NaDC with 240s sample injection time; sample matrix, 300mM Tris and 5mM γ-CD at pH 10.0; applied voltage, 15kV; detection wavelength, 270nm. With buffer condition (a), the limits of detection (LODs) for ENRO and CIP were 1.87 and 2.21ng/mL. The sensitivity was improved 376 and 406-fold for ENRO and CIP compared to conventional capillary electrophoresis (CE) method, respectively. The buffer with condition (b) has been successfully applied to the analysis of six kinds of animal foodstuffs by capillary electrophoresis with UV detector. The recoveries (85-102%) were achieved with relative standard deviations of 0.1-4.4%.