Spectrophotometric determination of certain cephalosporins using molybdophosphoric acid
Cephalexin (I), cephradine (II), cephazolin sodium (III), cefaclor (IV), cefoxitin sodium (V), cephamandole nafate (VI) and cefotaxime sodium (VII) were determined spectrophotometrically in the pure form and in pharmaceutical formulations by using molybdophosphoric acid as an oxidising agent. The molar absorptivities and Sandell sensitivities (in l mol–1 cm–1 and ng cm–2, respectively) were 2.93 × 103 and 118.5 for I, 2.48 × 103 and 140.9 for II, 7.66 × 103 and 62.2 for III, 3.23 × 103 and 119.4 for IV, 9.05 × 103 and 49.7 for V, 7.16 × 103 and 71.6 for VI, and 6.20 × 103 and 77.0 for VII. Six replicate analyses of solutions containing seven different concentrations of each of the substances examined were carried out and gave a mean correlation coefficient ⩽0.9998; the factors of the regression line equation for these drugs were calculated.
The proposed method was applied to the determination of these cephalosporins in pharmaceutical formulations and the results demonstrated that the method is equally accurate, precise and reproducible as the official methods.