Circular dichroism spectroscopy: An efficient approach for the quantitation of ampicillin in presence of cloxacillin

Ampicillin exhibited a negative and a positive cotton effects on the circular dichroism (CD) spectra in the wavelength range of 200-280 nm. Cloxacillin showed a positive cotton band peaking at 228 nm. Three sensitive, precise and accurate CD spectroscopic methods have been developed for the determination of ampicillin and cloxacillin. Method A was used for the determination of ampicillin in presence of cloxacillin by measuring ellipticity at 206 nm. Method B and C were employed to determine ampicillin and cloxacillin based on evaluation of ellipticity at 233 nm and 228 nm, respectively. Methods A, B and C showed linearity in the concentration range of 10-40 mu g mL(-1), 5-40 mu g mL(-1) ampicillin and 10-80 mu g mL(-1) cloxacillin, respectively. The method A was successfully applied to the determination of ampicillin in commercial dosage forms containing equivalent amount of cloxacillin. (C) 2016 Elsevier B.V. All rights reserved.