High-performance liquid chromatographic assay of erythromycin and its esters using electrochemical detection.

A high-performance liquid chromatographic analysis of erythromycin and its esters in plasma, urine and saliva is presented. A diethyl ether extract of sample was chromatographed on a reversed-phase column and components of the column effluent were monitored by electrochemical detection at +0.9 V (vs. Ag/AgCl). The method sensitivity limit was 10 ng with inter-day coefficients of variation from 3.2 to 10.3%. In order to assess precisely the relative concentrations of erythromycin esters (ethylsuccinate or estolate) and their active by-product erythromycin base, it is necessary to adopt measures preventing their continuous hydrolysis in biological fluids and during sample preparation.