Lidocaine metabolite formation as a measure of liver function in hepatic transplantation

Abstract

Transformation byproducts and pathways for the degradation of 2-phenylbenzimidazole-5-sulfonic acid (PBSA), a widely used organic active sunscreen agent, by UV254nm/H2O2 advanced oxidation process (AOP) were elucidated by mass spectrometry. Fourteen byproducts were identified, including environmentally hazardous benzamide (BD) and benzamidine (BZD). Beside of aromatic ring opening, desulfonation (−80 Da) and hydroxylation (+16 Da) were also two main reaction pathways. Degradation kinetics were compared with two PBSA structurally related compounds 2-phenylimidazole (2-PIZ) and benzimidazole (BZ) to estimate the application feasibility of the studied AOP. No apparent photolysis was noticed while the degradation of 1 μM pollutants in the presence of 1 mM H2O2 followed pseudo-first-order kinetics, with their observed rate constant (kobs) in the order of 2-PIZ > PBSA > BZ > BD > BZD, which is consistent with their respective second-order rate constant with hydroxyl radical. However, at high pollutant and oxidant concentrations, i.e., 50 μM and 5 mM, respectively, light attenuation contributed significantly to the change in kobs in the following manner, 2-PIZ ∼ BZ > PBSA ∼ BD > BZD. SO42− and NH4+ were the major inorganic mineral ions monitored in this study. Release of SO42− from PBSA degradation system reached 70% at 190 min. At the same time interval, NH4+ were ⩽50% for all pollutants studied. Ultimate mineralization of PBSA, 2-PIZ, BZ, BD and BZD in terms of %TOC at 190 min was found to be 23%, 38%, 45%, 57% and 62%, respectively. UV/H2O2 was shown to be efficient for the removal of organic sunscreen agents from water, however, special care toward the formation of environmentally hazardous byproducts should be considered.