Abstract
The photodegradation of the most prescribed glucocorticoids (GCs) was studied under relevant environmental conditions in the presence of suspended TiO2. The considered drugs included cortisone (CORT), hydrocortisone (HCORT), betamethasone (BETA), dexamethasone (DEXA), prednisone (PRED), prednisolone (PREDLO), and triamcinolone (TRIAM). The experiments were carried out at concentrations (50 µg L−1) close to the real ones in freshwater samples (tap and river) under simulated and natural sunlight, and their decomposition took place very efficiently under natural sunlight. The reactions were monitored by high-pressure liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). According to a pseudo-first-order decay, all drugs underwent degradation within 15 min, following different paths with respect to the direct photolysis. The observed kinetic constants, slightly lower in river than in tap water, varied from 0.29 to 0.61 min−1 with modest differences among GCs in the same matrix. Among main matrix macro-constituents, humic acids (HAs) were the most interfering species involved in GCs degradation. The photogenerated primary products were identified by HPLC-ESI-MS/MS, allowing to elucidate the general photochemical path of GCs. Finally, a comparison with literature data obtained using different advanced oxidation processes (AOPs) highlights the treatment efficiency with TiO2/solar light for removing such persistent aquatic contaminants.
Highlights
The role of glucocorticoids in biochemistry is difficult to exaggerate
The present study proves that TiO2 -assisted photocatalysis effectively removes various
Degradations occurred within 15 min for all GCs, and they were found to be from one to two orders of magnitude higher than direct photolysis, in the case of CORT and HCORT that scarcely absorb solar light
Summary
The role of glucocorticoids in biochemistry is difficult to exaggerate. The many possible configurations and the various chemical functions present explain the variety of reactions they catalyze in the cell and the sophisticated machinery that, starting from the regulation of glucocorticoid secretion by the hypothalamic-pituitary-adrenal (HPA), governs virtually all of the physiological processes, such as metabolism, immune and cardiovascular functions, skeletal growth, reproduction, and cognition [1,2]. Glucocorticoids (GCs) can inhibit immunological, inflammatory, and allergic processes in our body in response to an outer stimulus Since their coming in the 1950s, many synthetic molecules have been synthesized to increase pharmacological activity and reduce side effects [3]. The yearly number of prescribed GCs largely exceeds that of estrogens and androgens [4], their use as doping agents and prophylactic in husbandry was banned by the World Anti-Doping Agency and by the Council Directive 96/22/EC, respectively [5,6] Their occurrence in freshwaters, mainly as the initial drugs or slightly metabolized compounds, suggests that urban wastewater treatment plants (WWTPs) cannot remove them quantitatively [7]. Some tens of ng per gram have been found in sewage sludge samples [9,18] These concentrations are high enough to cause a negative eco-toxicological impact on various aquatic organisms, as demonstrated by the plethora of papers devoted to this issue. The sunlight TiO2 -photocatalytic efficiency for GCs removal was highlighted and compared with other advanced oxidation processes recently proposed [30,31,32,33,34,35,36]
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