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This study aimed at investigating the photocatalytic degradation of humic acid (HA) as a representative of natural organic matter (NOM) by using Ce-doped ZnO as a novel material. Following photocatalysis, HA degradation was characterized by specified UV-vis and fluorescence spectroscopic parameters as well as by the dissolved organic carbon (NPOC) content. Excitation-Emission Matrix (EEM) fluorescence features were also evaluated by using advanced techniques. Comparison of Ce-doped ZnO photocatalysis to TiO2 P-25 photocatalytic treatment of the HA samples was elucidated under similar experimental conditions. Kinetic modeling of the photocatalytic removal of HA expressed promising results indicating that Ce-doped ZnO could serve as an efficient catalyst for the degradation of NOM.
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Cério/química , Substâncias Húmicas/análise , Fotólise/efeitos da radiação , Raios Ultravioleta , Óxido de Zinco/química , Catálise , Cinética , Espectrofotometria Ultravioleta , Difração de Raios XRESUMO
We propose a homogenous multi-analyte immunoassay based on the quenching of quantum dot (QD) fluorescence by means of graphene. Two QDs with emission maxima at 636 and 607 nm were bound to antibodies selective for mouse or chicken immunoglobulins, respectively, and graphene functionalized with carboxylic moieties was employed to covalently link the respective antigen. The antibody-antigen interaction led graphene close enough to QDs to quench the QD fluorescence by resonance energy transfer. The addition of free antigens that competed with those linked to graphene acted as a "turn-on" effect on QD fluorescence. Fluorescence emitted by the two QDs could be recorded simultaneously since the QDs emitted light at different wavelengths while being excited at the same wavelength and proved to be linearly correlated with free antigen concentration. The developed assay allows measuring both antigens over 2-3 orders of magnitude and showed estimated limits of detection in the nanomolar range. This approach is thus a promising universal strategy to develop homogenous immunoassays for diverse antigens (cells, proteins, low-molecular-mass analytes) in a multi-analyte configuration.
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PURPOSE: Myocardial perfusion imaging contributes >20 % of the average medical radiation exposure to the population in the USA. Imaging protocols able to achieve a radiation exposure ≤9 mSv in 50 % of the studies by 2014 have been recommended. The aim of this study was to analyse the temporal evolution of administered activities in patients scheduled for dual-day (99m)Tc tracer gated single photon emission computed tomography (SPECT) and to compare different dose administration protocols in terms of patients' effective dose. METHODS: Patients evaluated from 1 July 2002 to 31 January 2012 were allocated according to the protocol adopted: group 1: fixed activity according to diagnostic reference level: 740 MBq up to 80 kg (adapted for weight <60 kg); 900 MBq 80-100 kg, 1,110 MBq >100 kg, standard filtered back-projection (FBP) reconstruction; group 2: weight-adjusted activity: 8 MBq/kg up to 1,110 MBq, standard FBP reconstruction; and group 3: 4 MBq/kg, UltraSPECT wide beam reconstruction (WBR) reconstruction. A dual-head Anger camera (GE Helix) was used. RESULTS: A total of 9,060 patients were allocated to different groups: 4,751 in group 1, 2,844 in group 2 and 1,465 in group 3. The stress + rest administered activity was 1,617 ± 180 in group 1, 1,136 ± 260 in group 2 and 682 ± 164 MBq in group 3 (all p < 0.001). Patients' effective dose was 13.7 ± 3 in group 1, 9.5 ± 2.8 in group 2 and 5.7 ± 1.6 mSv in group 3 (all p < 0.001). The 50th percentile was 12.6 in group 1, 9.1 in group 2 and 5.3 mSv in group 3. The effective dose received by the dedicated cardiologists was 2.1, 1.5 and 1.0 µSv/exam in group 1, group 2 and group 3 periods, respectively (all p < 0.001). CONCLUSION: A significant reduction over time in the administered activity for gated SPECT was achieved; accordingly, a significant reduction in patients' exposure was obtained. A simple weight-adjusted strategy with 8 MBq/kg immediately fulfils the recommendations to limit exposure. In selected group 3 patients, a stress-only strategy allows for studies with <3 mSv exposure. Thus, at least the adoption of a new reconstruction algorithm is strongly encouraged, and suggested tracer activities for cardiac gated SPECT are to be revised.
Assuntos
Tomografia Computadorizada por Emissão de Fóton Único de Sincronização Cardíaca/métodos , Doses de Radiação , Idoso , Tomografia Computadorizada por Emissão de Fóton Único de Sincronização Cardíaca/efeitos adversos , Feminino , Humanos , Masculino , Imagem de Perfusão do Miocárdio/efeitos adversos , Exposição Ocupacional/análise , Estudos Retrospectivos , Tecnécio Tc 99m Sestamibi/efeitos adversos , Fatores de TempoRESUMO
RATIONALE: A comprehensive study of the environmental fate of pollutants is more and more required, above all on new contaminants, i.e. pharmaceuticals. As high-resolution mass spectrometry (HRMS(n)) may be a suitable analytical approach for characterization of unknown compounds, its performance was evaluated in this study. METHODS: The analyses were carried out using liquid chromatography (LC) (electrospray ionization (ESI) in positive mode) coupled with a LTQ-Orbitrap analyzer. High-resolution mass spectrometry was employed to assess the evolution of the drug transformation processes over time; accurate masses of protonated molecular ions and sequential product ions were reported with an error below 5 millimass units, which guarantee the correct assignment of their molecular formula in all cases, while their MS(2) and MS(3) spectra showed several structurally diagnostic ions that allowed characterization of the different transformation products (TPs) and to distinguish the isobaric species. RESULTS: The simulation of phototransformation occurring in the aquatic environment and identification of biotic and abiotic transformation products of the two pharmaceuticals were carried out in heterogeneous photocatalysis using titanium dioxide, aimed to recreate conditions similar to those found in the environmental samples. Twenty-eight main species were identified after carbamazepine transformation and twenty-nine for clarithromycin. CONCLUSIONS: This study demonstrates that HRMS, combined with LC, is a technique able to play a key role in the evaluation of the environmental fate of pollutants and allows elucidation of the transformation pathways followed by the two drugs.
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Carbamazepina/química , Cromatografia Líquida/métodos , Claritromicina/química , Espectrometria de Massas/métodos , Poluentes Químicos da Água/química , Carbamazepina/análogos & derivados , Carbamazepina/metabolismo , Carbono , Claritromicina/análogos & derivados , Claritromicina/metabolismo , Hidroxilação , Fotólise , Poluentes Químicos da Água/metabolismoRESUMO
The paper examines the transformation of phenazone (2,3-dimethyl-1-phenyl-3-pyrazolin-5-one), a widely used analgesic and antipyretic drug, under simulated solar irradiation in pure water, using titanium dioxide, and in river water. High-resolution mass spectrometry was employed to monitor the evolution of photoinduced processes. Initially, laboratory experiments were performed to simulate drug-transformation pathways in aqueous solution, using TiO(2) as photocatalyst. Thirteen main phenazone transformation products were detected, and full analysis of their MS and MS(n) spectra identified the diverse isobaric species. All these transformation products were themselves easily degraded, and no compounds were recognized to remain until 1h of irradiation. From these findings, a tentative degradation pathway is proposed to account for the photoinduced transformation of phenazone in natural waters. These simulation experiments were verified in the field, seeking phenazone in River Po water samples.
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Antipirina/química , Antipirina/efeitos da radiação , Espectrometria de Massas/métodos , Titânio/química , Antipirina/toxicidade , Hidroxilação , Luz , Fotólise , Rios/química , Testes de Toxicidade , Água/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/toxicidadeRESUMO
Spiramycin, a widely used veterinary macrolide antibiotic, was found at traceable levels (nanograms per litre range) in Po River water (N-Italy). The aqueous environmental fate of this antibiotic compound was studied through drug decomposition, the identification of the main and secondary transformation products (TPs), assessment of mineralisation and the investigation of drug TPs toxicity. Initially, laboratory experiments were performed, with the aim of stimulating the antibacterial transformation processes followed in aquatic systems. The TPs were identified through the employment of the liquid chromatography (LC)-mass spectrometry technique. Under illumination, spiramycin degraded rapidly and transformed into numerous organic (intermediate) compounds, of which 11 could be identified, formed through five initial transformation routes. These laboratory simulation experiments were verified in situ to check the mechanism previously supposed. Po River water was sampled and analysed (by LC-high-resolution mass spectrometry) at eight sampling points. Among the previously identified TPs, five of them were also found in the river water. Three of them seem to be formed through a direct photolysis process, while the other two are formed through indirect photolysis processes mediated by natural photo sensitisers. The transformation occurring in the aquatic system involved hydroxylation, demethylation and the detachment of forosamine or mycarose sugars. Toxicity assays using Vibrio fischeri proved that even if spiramycin did not exhibit toxicity, its transformation proceeded through the formation of toxic products.
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Antibacterianos/análise , Água Doce/química , Luz , Espiramicina/análise , Poluentes Químicos da Água/química , Antibacterianos/metabolismo , Itália , Estrutura Molecular , Espiramicina/metabolismo , Poluentes Químicos da Água/análiseRESUMO
The diffusion of drug residues in wastewaters and surface waters as rivers and streams may constitute a problem for the environment, with consequences on the ecosystem and also on the human health. This paper deals with the study of the photo-induced transformation of amiloride, an orally administered diuretic agent, under simulated solar light. Direct photolysis and photocatalyzed degradation processes, using titanium dioxide as a photocatalyst, were investigated. The study involved the monitoring of the drug decomposition, the identification of intermediate compounds of the decomposition, the assessment of mineralization, as well as the evaluation of the toxicity associated to the degradation products. Amiloride underwent complete degradation within 30min of irradiation (heterogeneous photocatalysis) or 4h (homogeneous photolysis). HPLC coupled to HRMS, via ESI interface, demonstrated to be a powerful tool to identify and measure degradation products of the studied drug. By considering the photocatalytic process, the identified intermediates are formed through: (1) dechlorination and hydroxylation of the heteroaromatic ring; (2) the detachment of the guanidinic moiety; (3) cleavage of the heteroaromatic ring. The drug photomineralization was a rather slow process and after 4h of irradiation 25% of the total organic carbon (TOC) was still present. Chlorine was stoichiometrically released as chloride ions within the considered irradiation times (4h), while nitrogen was only partially converted into ammonium ions. This was due to the formation of guanidine, known to be hardly mineralized photocatalytically, and some other small molecules still containing the nitrogen. Acute toxicity, measured with a Vibrio fischery assay, showed that amiloride transformation proceeded through the formation of toxic compounds.
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Amilorida/química , Amilorida/toxicidade , Catálise , Fotólise , Espectrometria de Massas em TandemRESUMO
The photocatalytic transformation of acesulfame K - an artificial sweetener that has gained popularity over the last decades for being a calorie-free additive in food, beverages and several pharmaceutical products - was studied using three different photocatalysts, the benchmark TiO2-P25 and two other forms of synthetized titanium oxides named TiO2-SG1 and TiO2-SG2. The two latter materials were synthesized by a sol gel process in which the hydrolysis rate of titanium n-butoxide was controlled by the water formed in situ through an esterification reaction between ethanol and acetic acid. The investigation included monitoring the sweetener disappearance, identifying its intermediate compounds, assessing mineralization and evaluating toxicity. The analyses were carried out using high-performance liquid chromatography (HPLC) coupled with a LTQ-Orbitrap analyzer via an electrospray ionization (ESI) in the negative ion mode. This is a powerful tool for the identification, characterization and measurement of the transformation products (TPs); overall 13 species were identified. The use of several semiconductors has pointed out differences in terms of both photocatalytic efficiency and mechanism: the assessment of the evolution kinetics of each species (TPs, total organic carbon and inorganic ions) has brought to the elaboration of a general transformation pathway of acesulfame K. TiO2-SG2 proved to be the most efficient material in degrading the artificial sweetener and leads to the complete mineralization within 6 h of irradiation, while up to 16 h are required for TiO2-P25.
Assuntos
Modelos Químicos , Processos Fotoquímicos , Tiazinas/química , Titânio/química , Poluentes Químicos da Água/química , Catálise , Cromatografia Líquida de Alta Pressão , Cinética , Edulcorantes/análise , Edulcorantes/química , Água/química , Poluentes Químicos da Água/análiseRESUMO
The present study reports the photocatalytic transformation of stevioside, under simulated solar irradiation using TiO2 as a photocatalyst. As a tool of investigating the effect of various aqueous matrices, as well as, the initial stevioside concentration on the variation of the photocatalytic efficiency, a fully nested experimental design was employed. A significant impact on the degradation rate of the sweetener was observed: degradation rate decreases in the order distilled water>river water>lake water, attributed to the increased natural organic matter content of the respective natural water samples. Moreover, the investigation has involved the identification of intermediate compounds, as well as the assessment of mineralization and toxicity evaluation. More than one hundred unknown transformation products, most of them in the form of several isobaric species, were identified. By employing accurate mass determination, we were able to attribute an empirical formula to each species and through MSn analyses we were capable to distinguish several isobaric species. The overall transformation mechanism was assessed and involved the hydroxylation/oxidation of the molecule and the subsequent loss of the glucose units bound to the parent compound.
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In the present study, we investigated the possibility to abate Acesulfame K, a persistent emerging contaminant, in aqueous media using zinc oxide based materials. For this purpose, bare and Ce-doped zinc oxide was prepared via an easy and cheap hydrothermal process using different cerium salts as precursors. Their photocatalytic performance was evaluated in different media, namely ultrapure and river water under both UV-vis and visible light. Commercial TiO2 P25 was also employed and used as a reference photocatalyst for comparison purposes. The obtained results pointed out that cerium doped zinc oxide composites exhibit higher performance than TiO2 P25, especially under visible light and in the presence of organic matter, when the activity of the latter is greatly depressed. In particular, ZnO doped with cerium (1%) was the most effective material, and could be a promising alternative to TiO2 P25, especially in the treatment of natural waters.
Assuntos
Cério/química , Edulcorantes/análise , Tiazinas/análise , Poluentes Químicos da Água/química , Óxido de Zinco/química , Algoritmos , Catálise , Luz , Processos Fotoquímicos , Rios , Raios UltravioletaRESUMO
The addition of graphene nanoplatelets (GNP) to TiO2 nanoparticles (NPs) has been recently considered as a method to improve the photocatalytic efficiency of TiO2 by favoring charge carrier separation. Here, we show that it is possible to improve the efficiency of GNP-TiO2 composites by controlling the shape, stability, and facets of TiO2 NPs grown on GNP functionalized with either COOH or NH2 groups, while adding ethylendiamine (EDA) and oleic acid (OA) during a hydrothermal synthesis. We studied the photocatalytic activity of all synthesized materials under UV-A light using phenol as a target molecule. GNP-TiO2 composites synthesized on COOH-functionalized GNP, exposing {101} facets, were more efficient at abating phenol than those synthesized on NH2-functionalized GNP, exposing {101} and {100} facets. However, neither of these composites was stable under irradiation. The addition of both OA and EDA stabilized the materials under irradiation; however, only the composite prepared on COOH-functionalized GNP in the presence of EDA showed a significant increase in phenol degradation rate, leading to results that were better than those obtained with TiO2 alone. This result can be attributed to Ti-OH complexation by EDA, which protects GNP from oxidation. The orientation of the most reducing {101} facets toward GNP and the most oxidizing {100} facets toward the solution induces faster phenol degradation owing to a better separation of the charge carriers.
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Conventional wastewater treatment methods have shown to be unsuitable for a complete elimination of iodinated X-ray contrast agents (ICMs), which have thus been found in wastewater treatment plant (WWTP) effluent and in surface water. Once in the surface water, they could be transformed through different processes and form several transformation products that may need to be monitored as well. To this end, we studied the abatement and transformation of ICMs by combining laboratory experiments with in field analyses. We irradiated different aqueous solutions of the selected pollutants in the presence of TiO2 as photocatalyst, aimed to promote ICMs degradation and to generate photoinduced transformation products (TPs) similar to those occurring in the environment and effluent wastewater. This experimental strategy has been applied to the study of three ICMs, namely iopromide, iopamidol and diatrizoate. A total of twenty-four, ten, and ten TPs were detected from iopamidol, diatrizoate and iopromide, respectively. The analyses were performed using a liquid chromatography-LTQ-FT-Orbitrap mass spectrometer. The mineralization process and acute toxicity evolution were assessed as well over time and revealed a lack of mineralization for all ICMs and the formation of harmful byproducts. After characterizing these transformation products, WWTP effluent and surface water taken from several branches of the Chicago River were analyzed for ICMs and their TPs. HRMS with MS/MS fragmentation was used as a confirmatory step for proper identification of compounds in water and wastewater samples. All three of ICM were detected in the effluent and surface water samples, while no significant amount of TPs were detected.
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Meios de Contraste/análise , Monitoramento Ambiental , Fotólise , Águas Residuárias/análise , Poluentes Químicos da Água/análise , Chicago , Meios de Contraste/química , Diatrizoato/análise , Diatrizoato/química , Iohexol/análogos & derivados , Iohexol/análise , Iohexol/química , Iopamidol/análise , Iopamidol/química , Poluentes Químicos da Água/químicaRESUMO
We studied the aquatic environmental fate of 2-ethylhexyl 4-(dimethylamino)benzoate (OD-PABA), a widespread sunscreen, to assess its environmental persistence and photoinduced transformation. Direct photolysis is shown to play a key role in phototransformation, and this fast process is expected to be the main attenuation route of OD-PABA in sunlit surface waters. The generation of transformation products (TPs) was followed via HPLC/HRMS. Five (or four) TPs were detected in the samples exposed to UVB (or UVA) radiation, respectively. The main detected TPs of OD-PABA, at least as far as HPLC-HRMS peak areas are concerned, would involve a dealkylation or hydroxylation/oxidation process in both direct photolysis and indirect phototransformation. The latter was simulated by using TiO2-based heterogeneous photocatalysis, involving the formation of nine additional TPs. Most of them resulted from the further degradation of the primary TPs that can also be formed by direct photolysis. Therefore, these secondary TPs might also occur as later transformation intermediates in natural aquatic systems.
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Protetores Solares/química , Poluentes Químicos da Água/química , para-Aminobenzoatos/química , Catálise , Cromatografia Líquida de Alta Pressão/métodos , Meio Ambiente , Radical Hidroxila , Processos Fotoquímicos , Fotólise , Titânio/química , Água/químicaRESUMO
The aquatic environmental fate of ethylhexyl methoxy cinnamate (EHMC), one of the most used UVB filters worldwide, was studied by assessing its environmental persistence and photoinduced transformations. The role of direct and indirect photolysis was evaluated. Direct photolysis was shown to play a key role, and this process is expected to be the main attenuation route of EHMC in sunlit surface waters. In contrast, the reaction with OH radicals would be negligible and that with (3)CDOM* would at most be a secondary process. The measurement of the quantum yield of direct photolysis and of the rate constants of reaction with photogenerated transient species (or, sometimes, the use of reasonable values for the latter) allowed the prediction of the EHMC half-life time in surface waters, by means of a validated photochemical model. The predicted EHMC lifetime is of the order of hours to a few days in fair-weather summertime, and the main factors controlling the EHMC phototransformation in sunlit surface waters would be the water depth and the dissolved organic carbon (DOC) content. The formation of transformation products (TPs) was followed as well via HPLC/HRMS. Three TPs were detected in the samples exposed to UVA radiation, while one additional TP was detected in the samples exposed to UVB radiation. The detected TPs comprised 4-methoxybenzaldehyde, a hydroxylated derivative and dimeric species. Through the use of heterogeneous photocatalysis with TiO2, seven additional TPs were identified, most of them resulting from the further degradation of primary TPs formed through direct photolysis and that might be detected in aquatic systems as well. The photodegradation of EHMC in the presence of TiO2 yielded more toxic TPs than the parent compound (as determined with the Vibrio fischeri Microtox assay). The increased toxicity is partially accounted for by the formation of 4-methoxybenzaldehyde.
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Cinamatos/análise , Modelos Químicos , Processos Fotoquímicos , Fotólise , Poluentes Químicos da Água/análise , Cinamatos/química , Meia-Vida , Cinética , Raios Ultravioleta , Poluentes Químicos da Água/químicaRESUMO
UNLABELLED: Lymphoscintigraphy associated with radioguided biopsy of the sentinel node (SN) is well established in clinical practice for melanoma. In breast cancer, the SN concept is similarly valid, and lymphoscintigraphy is a useful method for localizing the axillary SN. The aim of this study was to optimize the lymphoscintigraphy technique in association with a gamma ray detecting probe (GDP) for identifying and removing the SN in breast cancer patients. METHODS: Two-hundred fifty patients with operable breast tumor underwent lymphoscintigraphy before surgery. Three different size ranges of 99mTc-labeled colloid particles (<50, <80 and 200-1000 nm) were used, with either subdermal (above tumor) or peritumoral injection. Early and late scintigraphic images were obtained in anterior and oblique projections, and the skin projection of the detected SN was marked. Sentinel nodes were identified and removed with the aid of the GDP during breast surgery; they were tagged separately. Complete axillary dissection followed. In 40 patients, a blue dye was also administered in addition to subdermal radiolabeled colloid to compare blue dye mapping with lymphoscintigraphy localization. RESULTS: Lymphoscintigraphy successfully revealed lymphatic drainage in 245 of 250 patients (98%). The axillary SN was identified in 240 patients (96%). SN biopsy correctly predicted axillary node status in 234 of 240 patients (97.5%). Lymphoscintigraphy and GDP detected the SN most easily and consistently when 200-1000 nm colloid was administered subdermally in an injection volume of 0.4 ml. Blue dye mapping was successful in 30 of 40 patients (75%). In 26 of these patients, the dye and lymphoscintigraphy identified the same node; in 4 cases different nodes were identified. None of these four patients had axillary disease. CONCLUSION: Lymphoscintigraphy is a simple procedure that is well tolerated by patients. Sentinel node identification is more reliable when large-size radiolabeled colloids are injected in a relatively small injection volume (0.4 ml). Use of a GDP greatly facilitates precise pinpointing and rapid removal of the SN.
Assuntos
Antimônio , Neoplasias da Mama/patologia , Linfonodos/patologia , Metástase Linfática/diagnóstico por imagem , Metástase Linfática/patologia , Compostos Radiofarmacêuticos , Compostos de Tecnécio , Agregado de Albumina Marcado com Tecnécio Tc 99m , Axila , Biópsia/métodos , Neoplasias da Mama/diagnóstico por imagem , Coloides , Feminino , Raios gama , Humanos , Linfonodos/diagnóstico por imagem , CintilografiaRESUMO
The photocatalytic transformation of dexamethasone and the formation of its intermediate compounds have been studied using titanium dioxide as a photocatalyst. The degradation of dexamethasone occurs easily through the formation of several hydroxy derivatives whose characterization has been made by HPLC/MS/MS. Even if both oxidative and reductive processes can be operating, only oxidative products have been identified in air saturated aqueous suspensions. A pattern of reaction pathways accounting for the observed intermediates is proposed. The obtained experimental evidence may be rationalized postulating the existence of a double initial mechanism. A single oxidation step resulting from the attack by one *OH radical leading to the formation of five hydroxy-derivatives and a concomitant attack involving two *OH radicals leading to the hydroxylation of the quinoid moiety of the molecule.
Assuntos
Dexametasona/química , Titânio , Cromatografia Líquida , Dexametasona/efeitos da radiação , Cromatografia Gasosa-Espectrometria de Massas , Indicadores e Reagentes , Luz , Espectrometria de Massas , Oxigênio/química , FotoquímicaRESUMO
A zeolitic material containing Ti chains activated by light allows a shape-selective transformation of organic compounds; the molecules that can enter into the zeolitic cavities are protected from the light-induced processes, while the other are degraded.
RESUMO
In the comparison of formamide and urea photocatalytic degradation, despite their similar structures, the final fate of bound nitrogen under illumination with TiO2 has shown a different behaviour; both the rate and the ratio of NH4+ and NO3- ion evolution seem not to be linked to the initial nitrogen oxidation state, but to the carbon oxidation state.
Assuntos
Formamidas/química , Nitratos/síntese química , Nitrogênio/química , Compostos de Amônio Quaternário/síntese química , Ureia/química , Carbono/química , Poluição Ambiental , Oxirredução , Fotoquímica , Fatores de Tempo , Titânio/química , Gerenciamento de Resíduos/métodosRESUMO
Humic substances (HS) are known to act as photosensitizers toward the transformation of pollutants in the surface layer of natural waters. This study focused on the role played by HS toward the transformation of xenobiotics in seawater, with the purpose of assessing the prevailing degradation routes. Phenol was chosen as model xenobiotic and its transformation was investigated under simulated sunlight in the presence of terrestrial or marine humic and fulvic acids, in pure water at pH8, artificial seawater (ASW) or natural seawater (NSW). The following parameters were determined: (1) the phenol degradation rate; (2) the variation in HS concentration with irradiation time; (3) the production of transformation products; (4) the influence of iron species on the transformation process. Faster transformation of phenol was observed with humic acids (HA) compared to fulvic acids (SRFA), and transformation induced by both HA and SRFA was faster in ASW than that in pure water. These observations can be explained by assuming an interplay between different competing and sometimes opposite processes, including the competition between chloride, bromide and dissolved oxygen for reaction with HS triplet states. The analysis of intermediates formed in the different matrices under study showed the formation of several hydroxylated (hydroquinone, 1,4-benzoquinone, resorcinol) and condensed compounds (2,2'-bisphenol, 4,4'-bisphenol, 4-phenoxyphenol). Although 1,4-benzoquinone was the main transformation product, formation of condensed molecules was significant with both HA and SRFA. Experiments on natural seawater spiked with HS confirmed the favored formation of condensed products, suggesting a key role of humic matter in dimerization reactions occurring in saline water.
Assuntos
Benzopiranos/química , Substâncias Húmicas , Fenol/química , Processos Fotoquímicos , Água do Mar/química , Poluentes Químicos da Água/química , Fenol/análise , Luz Solar , Poluentes Químicos da Água/análiseRESUMO
A study on the fate of two antineoplastic drugs, methotrexate and doxorubicin, in the aquatic environment is presented. The investigation involved a study of their decomposition under dark experiments, homogeneous photolysis and heterogeneous photocatalysis using titanium dioxide, the identification of intermediate compounds, as well as the assessment of acute toxicity over time. The analysis were carried out using LC (ESI positive mode) coupled with LTQ-Orbitrap analyser; accurate mass-to-charge ratios of parent ions were reported with inaccuracy below 10mmu, which guarantee the correct assignment of their molecular formula in all cases, while their MS(2) and MS(3) spectra showed several structural-diagnostic ions that allowed to characterize the different transformation products and to discriminate the isobaric species. Fourteen and eight main species were identified subsequently to doxorubicin or methotrexate transformation. The major transformation processes for doxorubicin involved (poli)hydroxylation and/or oxidation of the molecule, or the detachment of the sugar moiety. Methotrexate transformation involved decarboxylation or the molecule cleavage. Acute toxicity measurements showed that not only the two drugs exhibit high toxicity, but also their initial transformation products are highly toxic.