ESR studies of paramagnetic centers in pharmaceutical materials - Cefaclor and Clarithromycin as an example

Abstract

Electron spin resonance (ESR) studies of two antibiotics, Cefaclor and Clarithromycin, have been performed in order to investigate concentration and dynamics of free radicals generated in these compounds due to thermal sterilization. For Cefaclor three combinations of temperature and heating time have been applied: 160°C, 170 °C, 180 °C for 120 min, 60 min, and 30 min, respectively, according to the pharmaceutical sterilization norm. Clarithromycin has been heated at 160 °C for 120 min. The ESR lineshape has been investigated versus microwave power ranging from 2.2 mW to 70 mW. Electron spin-spin relaxation time has been estimated from the ESR lineshape analysis. Concentrations of radicals generated due to different sterilization procedures have been compared with the purpose to select the best sterilization scheme.