Spectroscopic features of radiolytic intermediates induced in gamma irradiated sulfatiazole: an ESR study.
ABSTRACT Sulfonamides are used as active ingredients in different drugs to treat infections caused by bacteria. Sulfatiazole (STZ) is one of the commonly used sulfonamides as antibacterial agent in drugs, which constitute potential candidates for radiosterilization. However, the crucial point in this respect is to monitor the amount and characteristic features of the radiolytic intermediates produced after irradiation. Electron spin resonance (ESR) spectroscopy is extensively used for this purpose due to its high sensitivity toward intermediates exhibiting radicalic nature. Thus, the aim of the present work is to investigate the spectroscopic and kinetic features of the species having unpaired electrons induced in gamma irradiated STZ at room and different temperatures in the dose range of 5-50kGy using ESR spectroscopy. Spectra of irradiated STZ consisted of many resonance peaks in the studied dose and temperature ranges. Heights of the peaks measured with respect to the base line were used to monitor microwave, temperature, time-dependent features of the radical species contributing to the experimental ESR spectra. Four tentative species of different spectroscopic and structural features assigned as A, B, C and D were found well explaining the experimental ESR spectra of gamma irradiated STZ. Comparison between the principal IR bands of unirradiated and gamma irradiated samples showed no detectable changes and appearance of new bands.
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ABSTRACT: The effects of ionizing radiation generated by a beam of electrons, in that doses varied from 25-800 kGy, on the physico-chemical properties of sulfamethoxazole (SMX) in solid state have been studied at room temperature and in the air atmosphere. The changes appearing after the irradiation were detected and evaluated by the spectroscopic methods (UV, IR, MS, EPR), chromatography (TLC and HPLC) and SEM, XRD and DSC. Already the lowest dose of 25 kGy was found to change the color of SMX from white to pale cream; such change became more intense with our increasing the irradiation dose. Products of radiodegradation and decreases in the drug content were detected by TLC and HPLC only after irradiation with 400 kGy. Since the SMX radiolysis products (sulfanilamide and sulfanilic acid) are colorless compounds, it is supposed that the color results from trapping of free radicals in the crystal lattice; the concentration of free radicals was 1.04 × 10(15) spin/g. Our results indicate that the radiolysis of SMX in the solid state caused by e-beams involves breaking of the S-N and N-C bonds. The mean radiolytic yield of this process is G((-SMX)) = 1.89 × 10(-7) mol/J, whereas the yield of formation of the two products of radiolysis is close and equal to 2.18 × 10(-8) mol/J (sulfanilamide) and 2.13 × 10(-8) mol/J (sulfanilic acid).Analytical Sciences 01/2011; 27(2):203-8. · 1.57 Impact Factor
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ABSTRACT: In the present work, effects of gamma radiation on solid meropenem trihydrate (MPT), which is the active ingredient of carbapenem antibiotics, were investigated by electron spin resonance (ESR) spectroscopy. Irradiated MPT presents an ESR spectrum consisting of many resonance peaks. Heights measured with respect to the spectrum baseline of these resonance peaks were used to explore the evolutions of the radicalic species responsible for the experimental spectrum under different conditions. Variations of the denoted 11 peak heights with microwave power, sample temperature and applied radiation doses and decay of the involved radicalic species at room and at high temperatures were studied. On the basis of the results derived from these studies, a molecular model consisting of the presence of four different radicalic species was proposed, and spectroscopic parameters of these species were calculated through spectrum simulation calculations. The dosimetric potential of MPT was also explored and it was concluded that MPT presents the characteristics of normal and accidental dosimetric materials.Radiation Effects and Defects in Solids 11/2006; 161(11):653-664. · 0.60 Impact Factor