Simultaneous Determination of Cephradine and Cephalexin in Serum by Derivative Synchronous Fluorescence Spectroscopy

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Abstract
The second-derivative synchronous fluorescence spectroscopic technique was applied to the simultaneous assay of cephradine and cephalexin in serum in developing a method based on the formation of the corresponding hydrolysis products of these compounds by treatment in an alkaline medium. Both the conventional and the synchronous fluorescence spectra of these hydrolysis products were completely overlapped, making it impossible to resolve the mixture. However, an appropriate selection of the instrumental variables affecting the second-derivative synchronous fluorescence spectra allowed the simultaneous determination of both compounds in a single scan. The calibration graphs run were linear in the range 0.025-5.0 .mu.g mL-1 for cephradine and 0.01-15.0 .mu.g mL-1 for cephalexin. Mixtures of cephradine and cephalexin in ratios between 1:3 and 10:1 were satisfactorily resolved and allowed the application of the proposed method to the analysis of human serum.