155 research outputs found
Occurrence of Fusarium mycotoxins and their dietary intake through beer consumption by the European population
No full textSince cereals are raw materials for production of beer and beer-based drinks, the occurrence mycotoxins in 154 beer samples was topic of investigation in this study. The analyses were conducted using QuEChERS extraction and gas chromatography-tandem mass spectrometry determination. The analytical method showed recoveries for vast majority of analytes ranged from 70% to 110%, relative standard deviations lower than 15% and limits of detection from 0.05 to 8 μg/L. A significant incidence of HT-2 toxin and deoxynivalenol (DON) were found in 9.1% and 59.7% of total samples, respectively. The exposure of European population to mycotoxins through beer consumption was assessed. No toxicological concern was associated to mycotoxins exposure for average beer consumers. Despite that, for heavy beer drinkers, the contribution of this commodity to the daily intake is not negligible, approaching or even exceeding the safety levels
Mind the gap regarding the knowledge of infant exposure to mycotoxins, acrylamide, bisphenols and heavy metals through human milk
No full textBreastfeeding offers infants nutritional, immunological, neurological and emotional benefits, although some toxic compounds can also be detected in human milk and transported along this food chain, such as mycotoxins, bisphenols, heavy metals, and acrylamide. This narrative review collects data from around the world regarding the occurrence of these contaminants in human milk with a view to evaluate infant exposure to these compounds and the potential associated health risks. The factors driving the presence of these toxins in human milk are explored, as are some strategies and measures to minimize their transfer to infants. The incidence and the levels of toxic compounds reported in bibliography vary, ranging from trace levels to considerably high concentrations. The data obtained suggest that breastfed infants better tolerate exposure to toxic compounds than infants fed with milk formulas, even though in some cases the estimated daily intake may exceed the established reference values. Certain measures should be adopted to minimize the exposure of mothers and breastfed infants to toxic compounds, such as monitoring of good practices throughout the food chain and dietary control, avoiding commodities more susceptible to contamination.This preparation of this review was supported by the Spanish Ministry of Science and Innovation project (PID2020-115871RB-I00) and by the Generalitat Valenciana (Spain: projects GV/2020/020 and AICO/2021/037). N.P. was supported by the post-PhD program of the University of Valencia for the requalification of the Spanish University System from the Ministry of Universities of the Government of Spain, modality “Margarita Salas” (MS21-045)”, financed by the European Union, Next Generation EU. M.S–R was supported by the post-PhD program from the Universidad de Castilla-La Mancha and by the Ministry of Universities of the Spanish Government, modality “Margarita Salas - Complementaria” (2023-POST-21234), financed by the European Union, Next Generation EU. Finally, M.C.C. acknowledges the support of The Ramón Areces Foundation (ref. CIVP19A5918) and also, the award of the Spanish government MCIN/AEI to the IATA-CSIC as Center of Excellence Accreditation Severo Ochoa (CEX2021-001189-S/MCIN/AEI/10.13039/501100011033). M.C.C. also acknowledges the support of an H2020-ERC Starting Grant 639226 and that of the Spanish Ministry of Science and Innovation (MCIN) research grant (ref. PID2022-139475OB-I00).Peer reviewe
Determinación de herbicidas derivados de la urea en aguas y vegetales
No full textRESUMEN
La Legislación de la Unión Europea establece límites muy rigurosos para la presencia de residuos de herbicidas derivados de la urea en aguas y en alimentos. Muchos de estos herbicidas son termolábiles y se descomponen durante el análisis por cromatografía de gases (CG), si bien se pueden determinar de manera indirecta a partir de los productos de degradación.
El presente trabajo se propone como objetivos; estudiar el comportamiento de herbicidas derivados de la urea en CG con columnas capilares, evaluar su cuantificación en base a sus productos de degradación térmica, poner a punto un nuevo método de análisis en aguas y vegetales basado en la MEFS y la determinación por CG y aplicarlo al análisis de muestras reales.
Para la consecución de los objetivos, se realizó un estudio bibliográfico de las propiedades físico-químicas y de las técnicas de extracción y de determinación, un estudio de los factores que influyen en el análisis por CG y en la MEFS desde matrices acuosas, se calcularon experimentalmente las constantes de distribución aparentes fibra/agua que rigen la MEFS y se aplicó la MEFS al análisis de residuos en aguas naturales y en muestras de vegetales.
De los ensayos realizados se obtuvieron las siguientes conclusiones: Los herbicidas derivados de la urea se pueden determinar por CG con detectores de nitrógeno-fósforo, captura electrónica y espectrometría de masas a partir de sus productos de degradación térmica, formados en el inyector con buena sensibilidad y reproducibilidad.
La temperatura del inyector es el factor más importante de todos los que influyen en la degradación térmica. La inyección a 300ºC facilita la degradación completa y reproducible de los herbicidas estudiados antes de su interacción con la fase estacionaria de la columna, por lo que es la temperatura elegida para llevar a cabo el resto de los análisis. El disolvente empleado en la inyección de fenilureas es muy importante, así se forman los ésteres carbámicos análogos con metanol y etanol y los isocianatos análogos con acetonitrilo, diclorometano y acetato de etilo mientras que metabenzotiazuron forma un benzotiazol, clorsulfuron una triazina y una fenilsulfonamida con independencia del disolvente empleado.
La extracción en fase sólida con discos de octilsílice y posterior análisis de los extractos por cromatografía de gases permite la detección de los herbicidas seleccionados en aguas a concentraciones inferiores a 01 mg/L con recuperaciones speriores al 87%.
La fibra de poliacrilato muestra mejor eficacia que las de polidimetilsiloxano para la extracción de los herbicidas permitiendo con un tiempo de extracción razonable (60min) alcanzar límites de detección inferiores a 01 mg/L.
La MEFS con fibra de poliacrilato seguidas de CG permiten el análisis de los herbicidas seleccionados en aguas a concentraciones inferiores a 01 mg/L. En la MEFS, el aumento de la fuerza iónica y la dilución de la muestra disminuyen las interferencias de los ácidos húmicos en aguas y la de las partículas sólidas de origen vegetal en hortalizas, proporcionando límites de detección inferiores a los Límites Máximos de Residuos legislados para cebollas, patatas y zanahorias.
La MEFS acoplada con la cromatografía de gases permite el análisis de ureas herbicidas en muestras de hortalizas a concentraciones muy por debajo de las exigidas en los Límites Máximos de Residuos Legislados. Una doble extracción realizada a pH 4 y a pH 11, es suficiente para conocer por separado los residuos que proceden de fenilureas herbicidas y los residuos de anilinas que son sus metabolitos
La MEFS acoplada con CG no emplea disolventes y permite realizar la extracción desde muestras acuosas y la determinación de manera automática. Su aplicación en alimentos con alto contenido en agua, abre muchas posibilidades de futuro en el campo del análisis de residuos de plaguicidas en alimentos.
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SUMARY
Substituted ureas are an important group of pesticides that are used as herbicides (phenylureas and sulfonylureas) and insecticides (benzoylureas). Phenylurea herbicides (PUHs) are largely used in field applications for pre- and post-emergence weed control in a variety of crops. The main groups of phenylurea herbicides are the N-phenyl-N,N-dialkylureas, N-phenyl-N-methoxyureas and compounds containing a heterocyclic group. More recently a group of sulfonylurea herbicides (SUHs) has been developed.
Multiresidue and single residue methods generally consist of the same basic steps, but multiresidue methods allow the determination of a large number of pesticides in a single analysis, reducing thus time and cost of analysis. The Maximum Admissible Concentration (MAC) of pesticides in drinking water, defined by European Community Directive as 0.1 mg L-1 for individual pesticides and 0.5 mg L-1 for the sum of pesticides posed certain demands to the analytical methods for pesticide residue determination.
Gas chromatographic conditions for determining eight phenylurea æchlortoluron, diuron, fluometuron, isoproturon, linuron, metabenzthiazuron, metobromuron and monuronæ and one sulfonylurea æchlorsulfuronæ herbicides were assessed. Degradation products of herbicides formed in the injector were used for identification. Most phenylureas formed their respective carbamic acid methyl esters, metabenzthiazuron formed an aminobenzothiazol and chlorsulfuron formed an aminotriazine plus a phenylsulfonamide.
On-column injections of standards at different temperatures (from -30ºC to 400ºC) using columns with four stationary phases (BPX70, BPX35, BP10 and BPX5) were evaluated to identify the best chromatographic behaviour. The best suited column was BP10-30m. The effect of other factors such as injection mode, injector design, sample volume and the solvent used were also investigated. Instrument detection limits (IDLs) ranged from 0.05 ng for chlorsulfuron to 3 ng for monuron with the NPD and, from 0.01 ng for chlorsulfuron to 5 ng for metabenzthiazuron with the ECD. The RSDs (n=4) were lower than 4% at the 12-25 ng level.
The method was applied to analyse surface waters extracted with C18 Empore disks with recoveries higher than 85%. Down to 0.1 mg·L-1 of each herbicide could be determined. Chlortoluron was found (11.4 mg·L-1) in a water sample and its presence was confirmed by gas chromatography-mass spectrometry.
Degradation products of chlorsulfuron, chlortoluron, diuron, fluometuron, isoproturon, linuron, metabenzthiazuron, metobromuron, and monuron formed in the gas chromatographic injector were used for identification of their respective herbicide. The spectra of the derived compounds were obtained with a quadrupole mass spectrometric detector working in scan mode (20-450 amu). The solvent used for phenylurea herbicide injection (ethanol, methanol, dichloromethane, and acetonitrile) had influence on the generated compounds. When methanol and ethanol were used as solvents, the major products formed from phenylureas were carbamic acid esters. When acetonitrile or dichloromethane were used, the main derivatives were phenylisocyanates. However, chlorsulfuron and metabenzthiazuron generated a triazine plus a phenylsulfonamide and a benzothiazolamine respectively regardless of the assayed solvent. Linuron and diuron showed the same behaviour and gave degradation products with the same mass spectra. The thermal reactions occurred instantaneously in the injector block favoured by the high selected temperature (300ºC).
The derived compounds from urea herbicides can be determined using a BP10-30m column and a Selected Ion Registering (SIR) program based on two to three m/z ions as a way to sensitively detect the presence of urea herbicides in environmental extracts. With standards in methanol the instrumental detection limits ranged from 0.1 pg for chlorsulfuron (detected as 2-chlorobenzensulfonamide) to 1 pg for monuron and metobromuron (both detected as their analogous carbamic acid methyl esters). The RSD were below 9 % at the 5 ng·L-1 level. The response was linear (r > 0.9986) within the 5 ng·L-1 to 25 mg·L-1 range. The unequivocal identification of some phenylurea herbicides was not always possible because some herbicides having analogous structures such as diuron and linuron gave the same derivative.
Under the proposed conditions matrix effects were low enough to permit calibration with samples proceeding from ecological (non-pesticide treated) crops. Twelve commercial samples of each carrots, onions and potatoes were analyzed and only three samples of potatoes contained residues of linuron at levels below MRL
Low cost manufacturing of light trapping features on multi-crystalline silicon solar cells : jet etching method and cost analysis
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 127-128).An experimental study was conducted in order to determine low cost methods to improve the light trapping ability of multi-crystalline solar cells. We focused our work on improving current wet etching methods to achieve the desired light trapping features which consists in micro-scale trenches with parabolic cross-sectional profiles with a target aspect ratio of 1.0. The jet etching with a hard mask method, which consists in impinging a liquid mixture of hydrofluoric, nitric and acetic acids through the opening of hard mask, was developed. First, a computational fluid dynamics simulation was conducted to determine the desired jet velocity and angle to be used in our experiments. We find that using a jet velocity of 3 m/s and a jetting angle of 45° yields the necessary flow characteristics for etching high aspect ratio features. Second, we performed experiments to determine the effect of jet etching using a photo-resist mask and thermally grown silicon oxide mask on multiple silicon substrates : , , and multi-crystalline silicon. Compared to a baseline of etching with no jet, we find that the jet etching process can improve the light trapping ability of the baseline features by improving their aspect ratio up to 65.2% and their light trapping ability up to 38.1%. The highest aspect ratio achieved using the jet etching process was 0.62. However, it must be noted that the repeatability of the results was not consistent: significant variations in the results of the same experiment occurred, making the jet etching process promising but difficult to control. Finally, we performed a cost analysis in order to determine the minimum efficiency that a jet etching process would have to achieve to be cost competitive and its corresponding features aspect ratio. We find that a minimum cell efficiency of 16.63% and feature aspect ratios of 0.57 are necessary for cost competitiveness with current solar cell manufacturing technology.by Amine Berrada Sounni.S.M.in Technology and PolicyS.M
A Review of the Mycotoxin Enniatin B
No full textMycotoxin enniatin B (ENN B) is a secondary metabolism product by Fusarium fungi. It is a well-known antibacterial, antihelmintic, antifungal, herbicidal, and insecticidal compound. It has been found as a contaminant in several food commodities, particularly in cereal grains, co-occurring also with other mycotoxins. The primary mechanism of action of ENN B is mainly due to its ionophoric characteristics, but the exact mechanism is still unclear. In the last two decades, it has been a topic of great interest since its potent mammalian cytotoxic activity was demonstrated in several mammalian cell lines. Moreover, the co-exposure in vitro with other mycotoxins enhances its toxic potential through synergic effects, depending on the concentrations tested. Despite its clear cytotoxic effect, European Food Safety Authority stated that acute exposure to ENNs, such as ENN B, does not indicate concern for human health, but a concern might be the chronic exposure. However, given the lack of relevant toxicity data, no firm conclusion could be drawn and a risk assessment was not possible. In fact, very few studies have been carried out in vivo and, in these studies, no adverse effects were observed. So, research on toxicological effects induced by ENN B is still on-going. Recently, some studies are dealing with new advances regarding ENN B. This review summarizes the information on biochemical and biological activity of ENN B, focusing on toxicological aspects and on the latest advances in research on ENN B
Micotoxinas en plantas medicinales y zumos. Estrategias para su mitigación
No full textEn la presente Tesis Doctoral se ha realizado una revisión bibliográfica para evaluar la presencia de micotoxinas emergentes de Fusarium en plantas medicinales en la materia en crudo, así como en forma de infusiones y cápsulas, así mismo se ha explorado sus posibles efectos beneficiosos y perjudiciales. Por otro lado, se ha llevado a cabo una revisión acerca del posible efecto de los tratamientos no térmicos HPP y PEF en la reducción de los contenidos de micotoxinas.
Así mismo, se han desarrollado y validado diferentes procedimientos analíticos para la determinación de micotoxinas en productos frescos, plantas medicinales y tés (en crudo o listos para su consumo) y zumos. La metodología empleada se ha basado en la determinación por cromatografía líquida y cromatografía de gases acopladas a espectrometría de masas en tándem. Por lo que respecta a la extracción de micotoxinas, se ha empleado el método QuEChERS para el análisis de matrices sólidas (plantas medicinales en diferentes formas) y el método DLLME para el análisis de muestras líquidas (infusiones de plantas medicinales y tés y zumos). La determinación analítica empleada ha sido validada en cuanto a exactitud, precisión, linealidad y límites de detección y cuantificación de acuerdo con la normativa europea.
Los resultados obtenidos tras analizar las plantas medicinales y los tés, revelan mayores contenidos de micotoxinas en crudo y en las cápsulas que en las infusiones resultantes, con contenidos que en ocasiones puntuales han sobrepasado los 1000 µg/kg y con incidencias inferiores al 34%. En las infusiones listas para el consumo los contenidos en general no han sobrepasado 100 µg/L con incidencias inferiores al 20%. En los zumos, AOH y PAT, han sido las micotoxinas detectadas con mayores incidencias, del 29 y 18%, respectivamente y mayores contenidos, con concentraciones medias de las muestras positivas de 207 y 28.18 µg/L, respectivamente.
La evaluación de la exposición a micotoxinas considerando los resultados obtenidos y los datos de consumo, revela un riesgo bajo a través del consumo de infusiones de plantas medicinales y tés, con porcentajes de IDT inferiores al 4% incluso considerando a los grandes consumidores (3 tazas/día). En cuanto a la evaluación del riego a través del consumo de cápsulas se observa un riesgo bajo en general, aunque en algunos suplementos como boldo, cardo mariano y cola de caballo se alcanzan porcentajes considerables de las IDT de hasta un 22.2%. Respecto a la evaluación del riesgo a través del consumo de zumos se alcanza un porcentaje considerable de la IDT para OTA (35.29%) y PAT (13.80%) (escenario upper bound) en niños considerando una ingesta de 200 mL diarios.
El procesamiento de los alimentos produce una reducción en los contenidos de micotoxinas y a una degradación parcial de éstas. Durante la preparación de las infusiones de plantas medicinales con tratamiento térmico se ha observado una reducción media de micotoxinas (AFs, ZEA, ENNs y BEA) del 74% al 100%, observándose una baja tendencia de las micotoxinas a migrar desde la materia prima a las infusiones resultantes. Respecto a los tratamientos no térmicos de procesado de los alimentos, como PEF y HPP, se han obtenido porcentajes de reducción que oscilan entre un 43 a 53% para micotoxinas emergentes de Fusarium en zumos y entre un 56 a 70% en smoothies tras el procesado mediante PEF. Para las AFs se han obtenido porcentajes de reducción en un rango más amplio, desde un 16 a 84% tras el tratamiento por PEF. Tras la aplicación del tratamiento HPP se han observado menores porcentajes de reducción (8-29%).
Tras el tratamiento por PEF se han identificado varios productos de degradación mediante el análisis por LC-ESI-qTOF-MS. La obtención de productos de degradación de las micotoxinas tratadas, que se han originado por la pérdida de fragmentos aminoacídicos estructurales como HyLv, Val, Ile o Phe para ENNs y BEA confirma la reducción del efecto del tratamiento por PEF. Para la AFB2, se ha identificado un producto de degradación resultado de la adición de grupos OH - y H + a los dobles enlaces y de la pérdida del grupo metileno (-CH2). Se ha determinado la toxicidad in silico de los productos de degradación mediante el servidor Pro Tox-II, obteniéndose menor toxicidad que los compuestos originales, a excepción de los productos de degradación obtenidos para la ENNB.
Los datos de la evaluación de la estabilidad de ENNB en el tracto gastrointestinal humano durante la digestión in vitro muestra su baja estabilidad en este medio y una degradación significativa del compuesto original. Así mismo, se han identificado 5 productos de degradación de ENNB mediante UHPLC-HRMS, que pueden atribuirse a la oxidación y apertura del anillo depsipéptido.In this Doctoral Thesis, a bibliographic review has been carried out to evaluate the presence of Fusarium emerging mycotoxins in medicinal plants as raw materials, infusions and tablets. Their possible beneficial and harmful effects have also been explored. On the other hand, a review has been carried out about the possible effect of non-thermal treatments HPP and PEF on mycotoxin contents reduction.
Likewise, different analytical procedures have been developed and validated for the determination of mycotoxins in fresh products, medicinal plants and teas (in the form of raw material or ready to eat) and juices. The methodology used has been based on the determination by liquid chromatography and gas chromatography coupled to tandem mass spectrometry. Regarding the extraction of mycotoxins, QuEChERS method has been used for the analysis of solid matrices (medicinal plants in several forms) and DLLME method for the analysis of liquid matrices (medicinal plants, tea beverages and juices). The analytical determination used has been validated in terms of accuracy, precision, linearity and limits of detection and quantification in accordance with European regulations.
The results obtained after analyzing medicinal plants and teas, revealed higher mycotoxin contents in the raw material and tablets than in the resulting beverages, with contents that occasionally have exceeded 1000 µg/kg, with incidences lower than 34%. In ready-to-drink beverages, in general the contents have not exceeded 100 µg/L with incidences lower than 20%. In juices, AOH and PAT, are the mycotoxins detected with the highest incidences, 29 and 18%, respectively, and contents, with mean concentrations of positive samples of 207 and 28.18 µg/L, respectively.
The evaluation of mycotoxin exposure considering the results obtained and the consumption data revealed a low risk through the consumption of medicinal plant and tea beverages, with TDI percentages lower than 4%, even considering high consumers (3 cups/day). Regarding the evaluation of the mycotoxin exposure through the consumption of tablets, low risk is observed in general, although in some supplements such as boldo, milk thistle and horsetail, considerable percentages of TDI (up to 22.2%) are reached. Regarding risk assessment through the consumption of juices, a considerable percentage of the TDI is reached for OTA (35.29%) and PAT (13.80%) (upper bound scenario) in children considering an intake of 200 mL daily.
Food processing lead to a reduction in mycotoxin contents and partial degradation. During the heat treatment of medicinal plant beverages preparation, an average reduction of mycotoxins (AFs, ZEA, ENNs and BEA) is obtained from 74% to 100%, observing a low tendency of mycotoxins to migrate from raw materials to the resulting infusions. Regarding non-thermal treatments of food processing (PEF and HPP), reduction percentages ranging from 43 to 53% are obtained for emerging Fusarium mycotoxins in juices and between 56 to 70% in smoothies after PEF processing. For AFs, reduction percentages are obtained in a wider range, (from 16 to 84%). After the application of the HPP treatment, lower reduction percentages are observed for both emerging mycotoxins and AFs (8-29%).
After PEF treatment, several degradation products have been identified by LC-ESI-qTOF-MS analysis. The degradation products obtained for the treated mycotoxins, which have been originated from the loss of structural amino acid fragments such as HyLv, Val, Ile or Phe for ENNs and BEA confirms the reduction effect of the treatment by PEF. For AFB2, a degradation product resulting from the addition of OH - and H + groups to the double bonds and the loss of a methylene group (-CH2) has been identified. In silico toxicity of the degradation products has been assessed by the Pro Tox-II server. Toxicity has decreased except for the degradation products obtained for the ENNB.
Evaluation of ENNB in the human gastrointestinal tract during in vitro digestion shows few stability in this medium and a significant degradation of the original compound. Likewise, 5 ENNB degradation products have been identified by UHPLC-HRMS, which can be attributed to oxidation and opening of the depsipeptide ring
Some methods to address the problem of unbalanced sentiment classification in an arabic context
No full textAn empirical study to address the problem of Unbalanced Data Sets in sentiment classification
No full textMigrant Necropolitics at the Table: Civilized Cannibalism in Mahi Binebine\u27s \u3cem\u3eCannibales\u3c/em\u3e
No full textIn Cannibales, the Maghrebi Francophone author Mahi Binebine revisits the encounter between the so-called “cannibals” and the European colonizer in the context of illegal immigration where bodies become commodities exchangeable for social improvements creating a different form of cannibalism. It is no longer the usual dichotomy between the civilized and the savage that is at work but rather a “civilized” European imperialist who feeds himself on a migrant’s flesh. This article argues that this representation works as a “colonial fragment” from the past but contextualized in today’s globalization. Binebine’s morbid depiction of an ambivalent postcolonial cannibalistic encounter translates as a representation of migrants in terms of cannibalistic necropolitics. The illegal migrant has no choice but to be swallowed by a narcissistic exocannibalism which seeks to incorporate what it feeds on to a total unity suggesting a bleak future not only for illegal migrants but for globalization as possibly devouring itself
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