Application of the ratio spectra derivative spectrophotometry to the analysis of cephradine and clavulanic acid in binary mixtures

A new spectrophotometric method has been applied for resolving binary mixtures of cephradine (CED) and clavulanic acid (CA). The method is based on the use of the first derivative of the ratio spectra obtained by dividing the amplitudes, at appropriate wavelengths, of the absorption spectra of the mixtures by those of a standard solution of clavulanic acid for determining cephradine and a standard solution of cephradine for determining clavulanic acid. Beer's law is obeyed for cephradine concentrations up to 56.0 mg/l and for clavulanic acid concentrations up to 32.0 mg/l. The recovery values of cephradine and clavulanic acid in their 6:1 and 1:4 (m/m) mixtures were satisfactory.