Application of time‐of‐flight mass spectrometry to the analysis of phototransformation products of diclofenac in water under natural sunlight

Abstract

Exact mass capabilities of time-of-flight (TOF) mass spectrometry along with other mass spectrometric techniques have been evaluated to elucidate a complete range of dichlofenac phototransformation products. Photolysis experiments with diclofenac in water under direct solar irradiation were performed to characterise the main phototransformation products generated and to determine their stability. Photolysis experiments were performed in both demineralised water and reconstructed standard freshwater. Samples were extracted before analysis by solid phase extraction (SPE) with Oasis HLB and MAX cartridges. Separation and identification of the transformation products were accomplished by the combined use of gas chromatography-mass spectrometry (GC/MS) and liquid chromatography coupled with time-of-flight mass spectrometry (LC/TOFMS). Both techniques provided complementary information that enabled the identification of 13 phototransformation products. Six of them were identified by GC/MS through the structural information provided by the full scan mass spectra obtained under electron impact (EI) ionisation and the confirmation of the molecular mass provided by positive chemical ionisation (PCI) analyses. Accurate mass measurements obtained by LC/TOFMS provided the elucidation of seven polar transformation products. The low mass error observed (<2 ppm) enabled the assignment of highly probable empirical formulas as well as identification of a process dimerisation route. The photoproducts identified demonstrated that photolysis of diclofenac occurs by two main routes. One is the consequence of the initial photocyclisation of diclofenac into carbazole derivatives. The other route goes through the initial decarboxilation of diclofenac and further oxidation of the alkyl-chain, which are typical photolytic process reactions. The main photoproduct identified was 8-chloro-9H-carbazole-1yl-acetic acid.

Photolysis and TiO2-catalysed degradation of diclofenac in surface and drinking water using circulating batch photoreactors

“…The pH of the RW samples was not significantly affected throughout the course of the irradiation (Table 2), which suggests a buffering capacity of natural freshwater as already proposed by Agüera and co-workers. [57] In contrast to previous findings, a higher magnitude of degradation was attained with our experimental set-up. The composition of the chosen freshwater samples, irradiance levels of sunlight and the type of photoreactor all contributed to these differences.…”

Ecotoxicity of carbamazepine and its UV photolysis transformation products

“…However, systematic ecotoxicity testing of treatment transformation products is complicated by the complexity of the relevant degradation pathways and the large numbers of intermediate compounds of varying stability which can be formed (e.g. Agüera et al, 2005;Kosjek et al, 2009;Calza et al, 2012;Li et al, 2012). Moreover, degradation pathways may differ depending on the particular wastewater treatment regime or natural degradation pathway in question (e.g.…”

Evaluation of Performance of Hybrid Photolysis-DCMD and Photocatalysis-DCMD Systems Utilizing UV-C Radiation for Removal of Diclofenac Sodium Salt From Water

“…al. 30 reported the presence of the red-brown color during the photolysis of DCF under exposure to natural sunlight. They attributed the observed phenomenon to the formation of dimer compounds which are distinguished by the presence of acidic groups and the absence of chlorine atoms.…”