Study On Degradation Mechanism And Pathway Of Gamma Radiation Degrade Oxytetracycline

The wide spread use of antibiotics has brought much benefits to human and production, but it also caused the pollution of the environment problem. Gamma irradiation are advanced oxidation degradation method, this paper studied the oxytetracycline degradation by it. Study on the influence factors of the degradation rate of oxytetracycline, products detected after gamma irradiation, degradation pathways and mechanism of oxytetracycline. With degradation mechanism and the path is clear, will provide theoretical basis for the degradation of oxytetracycline to more effective.Gamma irradiation can effectively degrade oxytetracycline in the aqueous of water. In p H=7, irradiation dose=4k Gy conditions, 10mg/L oxytetracycline solution reached a degradation rate of 95.6%. The higher the initial solution concentration, the lower the irradiation degradation rate; degradation rate reducing when the p H of the solution increasing; the greater the gamma irradiation dose, the higher the degradation rate.Gamma irradiated samples test by LC-ESI-MS, found a multiple of degradation products. The retention times are 19.35min、18.84min、21.45min、30.05min、23.06 min and 22.38 min. MS scanning found that the parent ion peaks of M/Z are 461, 447, 433 279 443 and 218. According to the mass spectrometry, M/Z461 is oxytetracycline itself; oxytetracycline molecule loss one or two methyl group come into being M/Z447 or M/Z433; M/Z279 is due to the M/Z433 off M(154); M/Z218 is a thickening rings molecule, caused by open-loop degradation of OTC and containing a ester structure.Quantitative calculation software-Gaussian 03 calculated the property of OTC molecules and its degradation products molecules. We found NPA charge, atomic bond order, Wiberg bond order and energy. Free radicals generated by gamma irradiation susceptible to OTC molecules and products molecules. Those functional groups on the thickening rings are vulnerable to attack and degrade, chemical bond at the connection of carbon cycles are not stable, easy to fracture.Detailed analysis of the electron transfer process of OTC and degradation products, structural rearrangement of atoms within the molecule by the MS results and calculation date. Put forward two main pathways of OTC degradation: one pathway is M/Z461�'M/Z447�'M/Z433 to M/Z279; the other pathway is M/Z461�'M/Z443(a) ?M/Z443(b) to M/Z218.