Radiation induced effects on cephalosporins: an ESR study

Purpose: This paper reports experimental data on the ESR identification of four irradiated cephalosporins (cefpodoxime, cefsulodin, cefixime and cefti zoxime). ' Materials and methods: Equations to describe the ESR curves versus the dose and storage rime were developed using mathematical procedures. Results: Limits Of detection (LOD) and limits of quantification (LOQ), esti mated on the basis of the S/N ratios are 1.0 +/- 0.5 kGy and 2.5 +/- 0.5 kG y respectively. The yield of free radicals are in the range 4.6 10(19) - 2. 2 10(20) radicals mol(-1) (G values from 0.1 to 0.4). Besides a very unstab le situation (cefsulodin), the time limit of detection of free radicals aft er storage ranges from about 1 year to over 2 years. These time intervals a re comparable with the shelf-life of the antibiotics and to the time limits found for 10 other cephalosporins described previously. Apart from qualita tive detection, ESR spectrometry can be used for dose estimation. Exponenti al loss of ESR signal (first-order reaction) correlates well with the data. Conclusion: Given the sensitivity of ESR spectrometry, this experimental te chnique is promising for identification of irradiated cephalosporins.