Co Gamma Irradiation - A Combined Computational and Experimental Study

Radiolysis of sulfamethoxazole (SMX) was investigated in aqueous samples with different initial conditions: [SMX]0 (20 μM ÷ 140 μM), pH0 (2.0 ÷ 11.0), [H2O2]0 (0 ÷ 10 mM) and absorbed doses (D, 0.3 kGy ÷ 5.0 kGy). Five transformation products (TPs) of SMX were experimentally identified and evaluated using HPLC/UV and LC-QTOF-MS, respectively. Compared to the precursor SMX, they possess higher polarities as well as molar masses (m/z = 270304) with –OH group preferentially attached to the benzene ring. The calculated hydrophobicity abilities of SMX and its products showed a linear correlation with the corresponding chromatographic retention times. Under the considered experimental conditions, no significant effects of the initial sample compositions on the TPs’ identities were observed. It was found that the abundances of all 5 TPs increased with the increase of the absorbed doses up to about 1.0 kGy. Higher absorbed doses resulted in the decrease of their abundances, reaching the non-detectable levels at D = 5.0 kGy. Based on the combined experimental and computational results, possible transformation schemes of SMX are briefly proposed and compared to the literature.