Multifrequency EPR study of radicals formed under the influence of gamma-irradiation and mechanical activation in calcium gluconate

Abstract

In the present study, samples of calcium gluconate were examined using electron paramagnetic resonance (EPR) spectroscopy. The samples were exposed to gamma-ray irradiation and mechanical activation. It has been found that the most effective method for studying radicals in calcium gluconate samples is EPR spectroscopy in the X- and W-bands and quantum chemical calculations. The EPR spectra of calcium gluconate irradiated with gamma-ray consist of four types of radicals. We also compared the EPR spectra of high-purity mechanically activated calcium gluconate with the spectra of the officinal (in the pelleted form) samples. The EPR spectra of the mechanically activated officinal calcium gluconate are more complex, containing at least two components. It was concluded that, in this case, excipients act as inhibitors of recombination reactions for certain types of radicals. The EPR spectra of the mechanically activated calcium gluconate were compared with those of the irradiated samples and assumptions were made about the nature of the formed radicals. The spectrum of mechanically activated calcium gluconate in the W band matches the high-frequency line observed in irradiated calcium gluconate, indicating that the radical's local environment remains unchanged and resistant to both mechanical activation and irradiation.