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- Occurrence of chiral bioactive compounds in the aquatic environment: a reviewPublication . Ribeiro, Cláudia; Ribeiro, Ana Rita; Maia, Alexandra S.; Tiritan, Maria ElizabethIn recent decades, the presence of micropollutants in the environment has been extensively studied due to their high frequency of occurrence, persistence and possible adverse effects to exposed organisms. Concerning chiral micropollutants in the environment, enantiomers are frequently ignored and enantiomeric composition often neglected. However, enantioselective toxicity is well recognized, highlighting the need to include enantioselectivity in environmental risk assessment. Additionally, the information about enantiomeric fraction (EF) is crucial since it gives insights about: (i) environmental fate (i.e., occurrence, distribution, removal processes and (bio)degradation); (ii) illicit discharges; (iii) consumption pattern (e.g., illicit drugs, pharmaceuticals used as recreational drugs, illicit use of pesticides); and (iv) enantioselective toxicological effects. Thus, the purpose of this paper is to provide a comprehensive review about the enantioselective occurrence of chiral bioactive compounds in aquatic environmental matrices. These include pharmaceuticals, illicit drugs, pesticides, polychlorinated biphenyls (PCBs) and polycyclic musks (PCMs). Most frequently analytical methods used for separation of enantiomers were liquid chromatography and gas chromatography methodologies using both indirect (enantiomerically pure derivatizing reagents) and direct methods (chiral stationary phases). The occurrence of these chiral micropollutants in the environment is reviewed and future challenges are outlined.
- Dispersive liquid–liquid microextraction and HPLC to analyse fluoxetine and metoprolol enantiomers in wastewatersPublication . Ribeiro, Ana R.; Gonçalves, Virgínia M. F.; Maia, Alexandra S.; Ribeiro, Cláudia; Castro, Paula M. L.; Tiritan, Maria E.Sample extraction is a major step in environmental analyses due both to the high complexity of matrices and to the low concentration of the target analytes. Sample extraction is usually expensive, laborious, time-consuming and requires a high amount of organic solvents. Actually, there is a lack of miniaturized methodologies for sample extraction and chiral analyses. Here, we developed a dispersive liquid-liquid microextraction (DLLME) to extract the pharmaceuticals fluoxetine and metoprolol, as models of basic chiral compounds, from wastewater samples. Compounds were then analysed by enantioselective high-performance liquid chromatography. We monitored the influence of sample pH, extracting and dispersive solvent and respective volumes, salt addition, extracting and vortexing time. The DLLME method was validated within the range of 1-10 A mu g L-1 for fluoxetine enantiomers and 0.5-10 A mu g L-1 for metoprolol enantiomers. Accuracy ranged from 90.6 to 106 % and recovery rates from 54.5 to 81.5 %. Relative standard deviation values lower than 7.84 and 9.00 % were obtained for intra- and inter-batch precision, respectively.
- Anthropogenic pressure in a Portuguese river: endocrine-disrupting compounds, trace elements and nutrientsPublication . Ribeiro, Cláudia M. R.; Maia, Alexandra S.; Ribeiro, Ana R.; Couto, Cristina; Almeida, Agostinho A.; Santos, Mariana; Tiritan, Maria E.Natural organic compounds such as phytoestrogens and phytosterols found in various plants, as well as mycotoxins produced by fungi, can be found in aquatic environments. The aim of this study was to investigate the occurrence of three different classes of natural estrogenic compounds, i.e., phytoestrogens, phytosterols and mycotoxins, in estuarine water samples from the Ave River estuary. For that, water samples were collected at five sampling points distributed along the estuary at low tide, during 1 year, processed by solid-phase extraction (SPE) and analyzed by gas chromatography coupled to mass spectrometry (GC–MS). To correlate the presence of phytoestrogens and phytosterols in the estuarine water, local flora was collected on riverside. Trace elements content and physicochemical parameters such as nutrients and dissolved oxygen were also determined seasonally at each sampling point, to give insights for the evaluation of water quality and anthropogenic pressure. Both phytoestrogens and phytosterols showed a seasonal variation, with the highest values observed in spring and summer and the lowest in winter. Daidzein (DAID) was found up to 404.0 ng L¡1 in spring and coumestrol (COUM) was found up to 165.0 ng L¡1 in summer. The mycotoxin deoxynivalenol (DON) was ubiquitously determined with values ranging from 59.5 to 642.4 ng L¡1. Nutrients and metals distribution and concentration varied among sampling stations and seasons. This study revealed for the first time the presence of mycotoxins, various classes of phytoestrogens and stigmasterol (STG) in estuarine water from the Ave River (Portugal), and the evaluation of the water quality confirmed that this estuary is still highly impacted by anthropogenic activities.
- Enantiomeric separation of tramadol and Its metabolites: method validation and application to environmental samplesPublication . Silva, Cátia; Ribeiro, Cláudia; Maia, Alexandra S.; Gonçalves, Virgínia; Tiritan, Maria Elizabeth; Afonso, CarlosThe accurate assessment of racemic pharmaceuticals requires enantioselective analytical methods. This study presents the development and validation of an enantioselective liquid chromatography with a fluorescence detection method for the concomitant quantification of the enantiomers of tramadol and their metabolites, N-desmethyltramadol and O-desmethyltramadol, in wastewater samples. Optimized conditions were achieved using a Lux Cellulose-4 column 150 × 4.6 mm, 3 μm isocratic elution, and 0.1% diethylamine in hexane and ethanol (96:4, v/v) at 0.7 mL min-1. The samples were extracted using 150 mg Oasis® mixed-mode cation exchange (MCX) cartridges. The method was validated using a synthetic effluent of a laboratory-scale aerobic granular sludge sequencing batch reactor. The method demonstrated to be selective, accurate, and linear (r2 > 0.99) over the range of 56 ng L-1 to 392 ng L-1. The detection and the quantification limits of each enantiomer were 8 ng L-1 and 28 ng L-1 for tramadol and N-desmethyltramadol, and 20 ng L-1 and 56 ng L-1 for O-desmethyltramadol. The feasibility of the method was demonstrated in a screening study in influent and effluent samples from a wastewater treatment plant. The results demonstrated the occurrence of tramadol enantiomers up to 325.1 ng L-1 and 357.9 ng L-1, in the effluent and influent samples, respectively. Both metabolites were detected in influents and effluents.