Sample Stacking and On-Line Derivatization for the Analysisof Ampicillin and Amoxicillin by Microemulsion Electrokinetic Chromatography

Abstract

A novel method using microemulsion electrokinetic chromatography (MEEKC) combining the preconcentration technique called reversed electrode polarity stacking mode (REPSM) with subsequent on-line derivatization has been developed for the quantitative determination of ampicillin and amoxicillin. It was found that the derivatization of antibiotics with 2,3-naphtalenedicarboxaldehyde (NDA) is accelerated greatly in microemulsion media, compared to the standard derivatization procedure, no heating being required. Various parameters that affect the ratio of derivatization, such as temperature, mixing and reaction time, concentration of NDA solution, and plug length were investigated and optimized. The combination of RESPM technique with the following derivatization allows the detection limits of ampicillin and amoxicillin to be decreased by a factor of 300 or more. The potential of the developed method was demonstrated by the determination of these antibiotics in a biological sample through the analysis of urine.