Browsing by Author "Toledo-Neira, Carla"

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    Fast simultaneous electrochemical detection of Bisphenol-A and Bisphenol-S in urban wastewater using a graphene oxide-iron nanoparticles hybrid sensor
    (2023) Pina, Samuel; Sepulveda, Pamela; Garcia-Garcia, Alejandra; Moreno-Barcenas, Alejandra; Toledo-Neira, Carla; Salazar-Gonzalez, Ricardo
    In this work, a novel and sensitive electrochemical sensor was developed for the simultaneous determination of low concentration levels of Bisphenol-A (BPA) and Bisphenol-S (BPS) in a secondary effluent from a wastewater treatment plant and surface water. The sensor design involved the utilization of a glassy carbon electrode that was modified with hybrid iron nanoparticles and a nanostructure of graphene oxide. The synthesized material displayed a stable heterostructure, facilitating efficient electronic transfer and exhibiting impressive electro-catalytic capacity. Furthermore, the sensor successfully detected anodic signals of BPA and BPS with a peak separation of 0.28 V, confirming its excellent performance. For method optimization, a chemometric tool based on a Central Composite Face (CCF) design response surface was employed. The optimized conditions yielded an analytical curve with a linear range of 15.0 to 120.0 mu mol L-1 for BPA, represented by the equation Iap (mu A)=-0.088 + 0.044 (mu A L mu mol-1) [cBPA], and 20.0 to 70.0 mu mol L-1 for BPS, represented by the equation Iap (mu A)=-0.367 + 0.025 (mu A L mu mol-1) [cBPS]. The detection and quantification limits for BPA were established at 12.05 and 36.51 mu mol L-1, respectively. Similarly, for BPS, the corresponding values were determined to be 11.63 and 35.24 mu mol L-1. The electrochemical method developed was validated by comparing it with the high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) technique. Notably, the electrochemical method demonstrated to be successful in the simultaneous detection and quantification of BPA and BPS in a secondary effluent and surface water.
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    hr Hydrophobic deep eutectic solvent as extractant phase for determining six carcinogenic polycyclic aromatic hydrocarbons in tea and coffee infusion samples
    (2023) Mesias-Salazar, Angela; Rebolledo-Robles, Kevin; Salazar-Gonzalez, Ricardo; Bravo, Manuel A.; Lucena, Rafael; Toledo-Neira, Carla
    In this work, an analytical methodology was developed for determining polycyclic aromatic hydrocarbons (PAHs) in tea and coffee samples. The new analytical methodology uses a hydrophobic deep eutectic solvent (DES), consisting of a thymol and lidocaine mixture, for the extraction of the analytes under dispersive liquid-liquid microextraction. The extraction procedure was optimized considering several variables (extraction phase composition, sample volume, vortexing and centrifugation time). Under optimum conditions, an using ultrahigh-performance liquid chromatography with fluorescence detection as instrumental technique, the limits of detection were 39 and 53 ng & BULL;L-1 in tea and coffee samples, respectively. The precision expressed as relative standard deviation was better than 6.3 %.The relative recoveries were in the 60.7-85.2 % interval. The proposed method was successfully applied to the analysis of tea and coffee samples. The levels found for the six carcinogenic PAHs are between 10-45 & mu;g & BULL;L-1 for tea infusions and 6-31 & mu;g & BULL;L-1 for coffee infusions. The methodology is defined as an excellent green method with a score of 80 using the analytical Eco-scale.
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    Removal of contaminants of emerging concern by solar photo electro-Fenton process in a solar electrochemical raceway pond reactor*
    (2023) Campos, Sebastian; Lorca, Javier; Vidal, Jorge; Calzadilla, Wendy; Toledo-Neira, Carla; Aranda, Mario; Miralles-Cuevas, Sara; Cabrera-Reina, Alejandro; Salazar, Ricardo
    This work proposes the degradation of different contaminants of emerging concern (CECs) present in a secondary effluent from a municipal wastewater treatment plant in a solar electrochemical raceway pond reactor (SECRPR), applying the solar photo electro-Fenton (SPFE) process. Tap water and a secondary effluent were enriched with 100 mu g L-1 of 7 CECs to study the degradation of these compounds by the SPEF process in a SEC-RPR. Among the results obtained, an elimination over 96% and 90% of 5 CECs (progesterone, estradiol, ibuprofen, diclofenac and estrone) was achieved, while sulfamethazine and carbamazepine were eliminated by 73, 37% and 80, 66% after 1 h of treatment, respectively. In turn, a secondary effluent that already achieved the minimum organic load standards established by Chilean regulations was treated in a SEC-RPR by applying different electrochemical advanced oxidation processes (EAOPs). However, regardless of the applied treatment (SPEF, electro-Fenton and electro-oxidation/H2O2), it was possible to further reduce the organic content and even mineralize it. These experiments were performed at pH 3, with Na2SO4 0.05 mM, Fe2+ 0.05 mM and applying a current density of 20 mA cm-2. The SPEF process implemented in a SEC-RPR is presented as an excellent alternative for the treatment of municipal wastewater, due to the large contact area between the effluent and UV radiation, in addition to the continuous and homogeneous generation of H2O2, which allows for the production of hydroxyl radicals in solution, favoring the degradation and mineralization of pollutants.
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    Study of degradation of norfloxacin antibiotic and their intermediates by natural solar photolysis
    (2023) Rivera-Vera, Camilo; Munoz-Lira, Daniela; Aranda, Mario; Toledo-Neira, Carla; Salazar, Ricardo
    In this work, the photolysis of the antibiotic norfloxacin (NOR) and the formation of its photodegradation products were studied using UV and solar radiation. Their extraction was also assessed in Milli-Q water and secondary effluents from a wastewater treatment plant. The photolysis of NOR was chromatographically monitored. The structure of each degradation product is related to the reaction of NOR with reactive oxygen species (ROS), as confirmed using radical quenchers and mass spectrometry. Additionally, the feasibility of extracting NOR and its degradation products was assessed using a commercial solid phase extraction system. Photolysis results showed the formation of five degradation products, generated under exposure to both types of radiation. The decays in NOR concentrations for the solar and UV treatments were adjusted to pseudo first-order kinetics with apparent constant values of k(solar) = 1.19 x 10(-3) s(-1) and k(UV) = 3.84 x 10(-5) s(-1). Furthermore, the superoxide radical was the main participant species in the formation of the degradation products P3, P4, and P5. Species P1 and P2 do not need this radical for their formation. The presence of NOR in water opens the possibility of its photolysis by solar radiation. This work contributes to the understanding of the mechanisms that mediate its photodegradation, in addition to studying potential options for its determination and its photodegradation products in the sample treatment.