Extraction–spectrofluorimetric method for the determination of erythromycin and its esters in pharmaceutical formulations using manual and flow-injection procedures

Abstract

A sensitive and rapid extraction–spectrofluorimetric method for the determination of erythromycin, based on the formation of an ion pair with Erythrosine B, is described. The calibration graph resulting from the measurement of the fluorescence of the chloroform extract (10 cm³) at 560 nm with excitation at 544 nm is linear over the range 10–600 µg of erythromycin per 20 cm³ of total volume of aqueous phase, with a relative standard deviation (RSD) of 1.5% for 3.7 µg cm^–3 erythromycin. The method can be successfully adapted to an unsegmented flow system, the peak height being proportional to erythromycin concentration over the range 0.65–5.88 µg of erythromycin per 400 mm³ of sample solution injected. Up to 45 samples h^–1 can be processed with an RSD of 2.9–3.8%. Manual and flow-injection methods were satisfactorily applied to the determination of erythromycin in pharmaceutical preparations.