Hydroxylierung In der Zuschrift auf S.10460 beschreiben O. Shoji, Y. Watanabe etal. die Verwendung von bestimmten Aminosäurederivaten fur die Aktivierung von CytochromP450BM3 zur direkten ...Hydroxylierung von Benzol zu Phenol.
•Artificial BC formation from biological materials during hot sample digestion.•Risk of overestimating BC content at high organic carbon weight.•BPCA method not suitable for organic rich material ...with low BC content.•BC assessment should be based only on BPCAs with 5 and 6 carboxyls.
For the assessment of black carbon (BC), its oxidation to benzene polycarboxylic acids (BPCAs) is an established method. However, doubts about biological precursors remain and not all published data were obtained at low carbon concentration. We hypothesised that a considerable proportion of BC may be produced during sample treatment in the presence of a high amount of organic carbon (OC). We therefore tested whether and to which degree (i) BC-free material from stems of Zea mays L. (maize straw) and leaves of Capsicum annuum L. (bell pepper), as well as (ii) cyclic and non-cyclic carbon forms (chlorophyllin, ellagic acid and β-carotene) afford BPCAs when method protocols are overloaded with a sample above the recommended amount of 5mg OC. The results showed that small amounts (<2g/kg OC) of BPCAs with three and four carboxyl groups may be formed even at low sample weight (<5mg OC), thereby falsely representing biological BC production. When this threshold was exceeded, all BPCA forms were detected. The artificial BPCA production yield in g OC increased with increasing amount of OC (R2⩾0.81), adding up to 8.7g/kgOC (19.7gBC/kgOC) artificial production. We therefore strongly recommend that a threshold of 5mg OC sample concentration be maintained in future studies and that future BC assessments be restricted to BPCAs with five and six carboxyl groups. This constrains the application of the BPCA method for organic rich samples and for samples expected to contain a relatively low amount of BC.
•The MOF-14-based QCM has an excellent sensitivity (1200 Hz@80 ppm) and selectivity to benzene, as well as ultra-low detection limit (150 ppb) and good stability.•It has always been a tough problem ...to detect the most toxic benzene vapor. For the first time, We have produced a high selective benzene sensor.•Through computational simulation, we found the selective response of MOF-14 to benzene is related not only to the interaction between ligands and detection molecules, but also to the steric hindrance effect of adsorption process.
As one of the BTEX (benzene, toluene, ethylbenzene, xylene) from living environment, benzene has the greatest carcinogenic, anesthetic and neurotoxic effects. At the same time, due to its chemical inertness and nonpolar characteristics, benzene is also the most difficult to detect in BTEX. Herein, based on QCM (quartz crystal microbalance) platform, MOF-14, a metal-organic framework, is first employed to detect benzene vapor by the host − guest interaction of MOF with benzene molecule, as well as Lewis acid-base interaction. By comparing with other three types of MOF materials, it was found that the effect of the ligand on the adsorption is greater than that of the metal point of junction. On the other hand, the different steric hindrance effects in BTEX restrict their adsorption capacity. Thus, the MOF-14 modified QCM sensor exhibits high sensing performance to benzene vapor with a detection limit at the level of 150 ppb. Our studies also indicate that the sensor shows good selectivity to oppose various kinds of interfering gases. Even toluene has a structure similar to that of benzene, it also can be distinguished. And the measurements on repeatability and long-term stability are both approved for the excellent reliability of the MOF-14 modified QCM sensor. By using computational simulation, we explored that why benzene and toluene can be distinguished by MOF-14 modified QCM sensor. This work extended the usages of MOF based QCM for high performance benzene sensing.
A gasolina é uma mistura complexa de substâncias, dentre elas estão hidrocarbonetos como o benzeno, tolueno, etilbenzeno e xilenos (BTEX), sendo esses compostos emitidos para a atmosfera, com ...destaque ao benzeno, por ser comprovadamente carcinogênico. Objetivamos avaliar as concentrações de BTEX no ar de postos de revenda de combustíveis no Município do Rio de Janeiro, Brasil, e calcular o risco de câncer associado a estas exposições. Foram realizados dois tipos de amostragem (fixa e móvel) adaptadas da metodologia nº 1.501 do Instituto Nacional de Segurança e Saúde Ocupacional (Estados Unidos), em seis postos de revenda de combustíveis na Zona Oeste da cidade. A amostragem fixa foi feita próxima às bombas de combustível, enquanto a móvel foi realizada através da coleta do ar na zona respiratória dos trabalhadores (frentistas), conforme estes se deslocavam pelo posto. As amostras foram analisadas por cromatografia gasosa com detecção por ionização em chama. Com os resultados das amostragens foram feitos os cálculos de risco à saúde, usando os indicadores Quociente de perigo (HQ) e Risco de câncer (CR), para avaliar os possíveis efeitos não-carcinogênicos e carcinogênicos, respectivamente, nos trabalhadores dos postos de revenda de combustíveis. As concentrações ambientais para a maioria dos compostos BTEX foram abaixo dos limites preconizados, menos para o benzeno, um composto carcinogênico, que apresentou concentrações muito acima dos limites, levando a altos valores de risco de câncer. Os resultados demonstraram que há riscos à saúde dos trabalhadores de postos de revenda de combustíveis, principalmente o risco de desenvolver câncer, devido à exposição excessiva ao benzeno.
Gasoline is a complex mixture of substances, including aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylenes (BTEX). These compounds are emitted into the air, with the special relevance of benzene since it is provenly carcinogenic. The study aimed to assess BTEX concentrations in filling stations in the city of Rio de Janeiro, Brazil, and to calculate the cancer risk associated with such exposures. Two types of sampling were performed (stationary and mobile), adapted from methodology n. 1,501 (U.S. National Institute for Occupational Safety and Health) for aromatic hydrocarbons, in six filling stations in the West Zone of Rio de Janeiro. Stationary sampling was done near the fuel pumps, while mobile sampling was done in the breathing zone of the workers (station attendants) as they moved around the station. The samples were analyzed with gas chromatography flame ionization detector. The sampling results were used to calculate the health risk, using the indicators Hazard quotient (HQ) and Cancer risk (CR) to assess the possible non-carcinogenic and carcinogenic effects, respectively, in filling station workers. Environmental concentrations for the most of the BTEX compounds were below the recommended limits, except for benzene, a carcinogenic compound, which displayed concentrations far above the limits, leading to high cancer risk values. The results showed that there are health risks for filling station attendants, especially the risk of developing cancer from excessive exposure to benzene.
La gasolina es una mezcla compleja de sustancias, entre ellas existen hidrocarburos como el benceno, tolueno, etilbenceno y xilenos (BTEX), emitiéndose estos compuestos a la atmósfera, donde se destaca el benceno, al tratarse de un carcinogénico comprobado. Los objetivos fueron evaluar las concentraciones de BTEX en el aire de puestos de reventa de combustibles, en el municipio de Río de Janeiro, Brasil, así como calcular el riesgo de cáncer asociado a estas exposiciones. Se realizaron dos tipos de muestra (fija y movible), adaptadas de la metodología nº 1.501 del Instituto Nacional de Seguridad y Salud Laboral (EE.UU.), en seis puestos de reventa de combustibles de la zona oeste de la ciudad. La muestra fija se realizó cerca de las bombas de combustible, mientras que la móvil se hizo mediante tomas de aire en la zona respiratoria de los trabajadores (de la gasolinera), a medida que estos se desplazaban por el lugar de trabajo. Las muestras se analizaron por cromatografía gaseosa con detección por ionización en llama. Junto a los resultados de las muestras, se realizaron cálculos de riesgo para la salud, usando los indicadores Cociente de peligro (HQ) y Riesgo de cáncer (CR), con el fin de evaluar los posibles efectos no-carcinogénicos y carcinogénicos, respectivamente, en los trabajadores de los puestos de reventa de combustibles. Las concentraciones ambientales para la mayoría de los compuestos BTEX estuvieron por debajo de los limites preconizados, menos en el caso del benceno, un compuesto carcinogénico, que presentó concentraciones muy por encima de los límites, llevando a altos valores de riesgo de cáncer. Los resultados demostraron que existen riesgos para la salud de los trabajadores de puestos de reventa de combustibles, principalmente, riesgo de desarrollar cáncer, debido a la exposición excesiva al benceno.
Zusammenfassung
Die menschliche Aufnahme von Benzol soll aufgrund dessen gesundheitsgefährdenden Potentials minimiert werden. Benzol gelangt hauptsächlich über die Atemluft in den menschlichen ...Körper; hingegen ist die Aufnahme über die Nahrung eher gering. In Getränken mit Kirschgeschmack wurde jedoch Benzol gefunden, und es wurde vermutet, dass der Geruchsstoff Benzaldehyd die Ursache für die beobachteten Benzolverunreinigungen war. Benzaldehyd wird beispielsweise zur Aromatisierung von Getränken mit Kirschgeschmack eingesetzt. Es zeigte sich, dass nur Licht die Bildung von Benzol aus Benzaldehyd förderte. Es wurde vermutet, dass die Benzolgehalte in kommerziellen Kirschsaft‐Erfrischungsgetränken auf das zugesetzte, bereits mit Benzol verunreinigte Aroma zurückzuführen sind. Daher scheint es nötig, die Benzolbildung in benzaldehydhaltigen Aromen zu unterbinden, indem man diese Produkte vor Licht schützt, beispielsweise durch den Gebrauch von getönten Glasgefäßen bei Produktion, Lagerung und Verkauf.
Summary
The exposure of humans to benzene should be minimized due to its health risk. Humans are mainly exposed by the air they inhale. The dietary intake is relatively low. However, benzene has been detected in drinks with added cherry flavor, and it was suggested that benzene could be formed from the odorant benzaldehyde. Benzaldehyde is used, for example, for flavoring beverages with cherry flavor. It was found that in particular irradiation with light increased benzene formation. It was assumed that benzene detected in commercial cherry juice soft drinks may be added as contaminant of the flavoring containing benzaldehyde. Thus, to avoid benzene formation, flavorings containing benzaldehyde should be protected from light by using amber glass vials during production, storage, and sale.
The synthesis of aryl fluorides has been studied intensively because of the importance of aryl fluorides in pharmaceuticals, agrochemicals, and materials. The stability, reactivity, and biological ...properties of aryl fluorides can be distinct from those of the corresponding arenes. Methods for the synthesis of aryl fluorides, however, are limited. We report the conversion of a diverse set of aryl iodides to the corresponding aryl fluorides. This reaction occurs with a cationic copper reagent and silver fluoride. Preliminary results suggest this reaction is enabled by a facile reductive elimination from a cationic arylcopper(III) fluoride.
•ZIF-8 and ZIF-71 with the pore sizes of 0.34nm and 0.48nm were successfully coated on ZnO nanorods surface, respectively, which came from vertically oriented ZnO nanorod arrays.•It was found that ...the pore size is critical for enhancing the selectivity of the ZnO@ZIF nanorod array sensors for the detected gas whose molecular kinetic diameters are smaller than the pore size of ZIF.•Sensors based on ZnO@ZIF-71 NRs have a pre-concentrated role for ethanol and acetone, and obviously enhanced their response.
Recently, a metal-organic framework (MOF) coating method has been reported for improving the poor gas selectivity of metal oxide semiconductor (MOS) gas sensor. However, the correlation between MOF’s pore size and the size of gas molecule is not fully discussed, as well as gas-sensing properties to gases with similar molecular size. In this paper, two zeolitic imidazolate frameworks (ZIFs) with different pore sizes (∼3.4Å for ZIF-8, ∼4.8Å for ZIF-71) are synthesized on the surface of ZnO nanorod arrays to form a ZnO@ZIF core-shell structure, where ZIFs act as gas molecule sieve membrane that shields ZnO from gas molecules larger than the pore size of ZIFs. Hydrogen, ammonia, ethanol, acetone and benzene (molecular size in the range of 2.89–5.85Å) are selected as testing gases. The ZnO@ZIF-8 sensor exhibited a clear response to smaller molecules of hydrogen and ammonia rather than larger molecules of ethanol, acetone and benzene. While the ZnO@ZIF-71 sensor only exhibited inhibited response to benzene, which has the largest molecular size. These results indicate that the selectivity of ZnO gas sensor can be regulated by surface MOF coating with specific pore size. But this pore size depending selectivity regulation method is insufficient effective for targeting gases with similar molecular sizes, which may be improved by further modification on MOF materials for selective adsorption in our future work.
PDF
