Avaliação e monitoramento dos subprodutos da fotodegradação de fármacos e disruptores endócrinos em meio aquoso por espectrometria de massas de alta resolução

Abstract

The occurrence of organic contaminants in the environment has become a subject of interest in recent years. Among the many classes of compounds that comprise this large group, drugs have received particular concern. The objective of the present study is therefore to identify and monitor recalcitrant by-products resulting from the degradation of several drugs from different therapeutic classes (ibuprofen, bezafibrate, diclofenac, sulfamethoxazole, ethinylestradiol, and the endocrine disruptor bisphenol A) in aqueous medium. Two distinct processes, direct photolysis (employing UV-A and UV-Cradiations) and photocatalysis (using the TiO2/UV-A and TiO2/UV-C systems), were investigated herein. The first step of the present work consisted of the evaluation of the effectiveness of these procedures in the degradation of the selected drugs. Hence, aliquots were collected directly from the reaction vessel after assorted exposure times (from 0 to 120 minutes) and analyzed by liquid chromatography coupled to highresolution mass spectrometry (LC-HRMS) to evaluate the removal efficiency. To evaluate the degradation efficiency, total organic carbon (TOC) measurements were also performed. In a second stage, the same aliquots were analyzed by direct infusion mass spectrometry aiming at identifying resulting by-products. The analyses were conducted by electrospray ionization in the positive and negative modes. Ecotoxicitytests using brine shrimp (Artemia Salina) were also conducted with each aliquot collected. These assays were carried out in triplicate to estimate the toxicity of the byproducts. The experimental results showed that the UV-C, UV/C-TiO2 and UV/A-TiO2 systems were efficient in removing all compounds, excepting ethinylestradiol, the most recalcitrant of them. Despite the high removal rates, degradation rates were lower,indicating the formation and persistence of degradation products generated under these conditions. The behavior of each by-product as a function of exposure time to the degradation systems was also appraised. Finally, the tests against Artemia Salina demonstrated that some recalcitrant by-products possess higher toxicity than theprimary precursor.