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 ceftizoxime). ' 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), estimated on the basis of the S/N ratios are 1.0 +/- 0.5 kGy and 2.5 +/- 0.5 kGy 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 unstable situation (cefsulodin), the time limit of detection of free radicals after storage ranges from about 1 year to over 2 years. These time intervals are comparable with the shelf-life of the antibiotics and to the time limits found for 10 other cephalosporins described previously. Apart from qualitative detection, ESR spectrometry can be used for dose estimation. Exponential loss of ESR signal (first-order reaction) correlates well with the data. Conclusion: Given the sensitivity of ESR spectrometry, this experimental technique is promising for identification of irradiated cephalosporins.