A simple, low-cost and robust capillary zone electrophoresis method with capacitively coupled contactless conductivity detection for the routine determination of four selected penicillins in money-constrained laboratories.

A simple and robust capillary zone electrophoresis method was developed and validated for the determination of amoxicillin and clavulanate, ampicillin, phenoxymethyl penicillin (Pen V) as well as flucloxacillin. Capacitively coupled contactless conductivity detection was employed as detection mode that makes CE a simple and economic tool for money-constrained laboratories. The developed method is straightforward and user-friendly. It offers good sensitivity and sufficient selectivity for the routine assay of the selected penicillins. The repeatabilities were <1.9% RSD for relative peak areas and <1% RSD for migration times for all the analytes. The method showed good linearity (R2  > 0.995) within the 80-120% range of the target concentration (0.5 mg/mL) for each antibiotic. The accuracy of the method, evaluated by standard fortification at three levels, was good for all the analytes. An extended robustness study was performed by varying ±10% of the optimum value of TRIS concentration, l-histidine concentration and temperature in a full factorial design at two levels. This was to evaluate larger than usual variability of factors on the assay value, in order to better cover potential global variance in lab conditions and equipment. Finally, the method was applied for the determination of percent (%) content of all antibiotics in available formulations.