Determination of Binary Mixtures of Beta-Lactam Antibiotics by Ratio-Spectra Fourth-Derivative Spectrophotometry

ABSTRACT

Ratio - spectra fourth - derivative spectrophotometry has been developed for simultaneous determination of the beta-lactam antibiotics ampicillin sodium and dicloxacillin sodium. The amplitude in the fourth derivative of ratio - spectra at 223.5 nm was selected to determine ampicillin and those at 207 and 225 nm to determine dicloxacillin.

Calibration graphs are linear up to 40 μg/ml of ampicillin and 30 μg/ml of dicloxacillin, r ranging from 0.9998 to 0.9999. Limits of detections (LOD) are 0.83 μg/ml for ampicillin and 0.59 and 0.27 μg/ml for dicloxacillin. The procedure is rapid, simple and does not require any preliminary separation or treatment of the samples.

The method was successfully applied for determining the two antibiotics in laboratory mixtures and in pharmaceutical products with good accuracy and precision, and it is proposed for routine quality control purposes.

Keywords::

• Derivative spectrophotometry
• ratio-spectra measurements
• ampicillin
• dicloxacillin
• beta-lactam antibiotics