Electrooxidation of Ethanol on Pt and PtRu Surfaces Investigated by ATR Surface-Enhanced Infrared Absorption Spectroscopy

Herein, it was investigated for the first time the electro-oxidation of ethanol on Pt and PtRu electrodeposits in acidic media by using in situ surface enhanced infrared absorption spectroscopy with attenuated total reflection (ATR-SEIRAS). The experimental setup circumvents the weak absorbance signals related to adsorbed species, usually observed for rough, electrodeposited surfaces, and allows a full description of the CO coverage with the potential for both catalysts. The dynamics of adsorption-oxidation of CO was accessed by ATR-SEIRAS experiments (involving four ethanol concentrations) and correlated with expressions derived from a simple kinetic model. Kinetic analysis suggests that the growing of the CO adsorbed layer is nor influenced by the presence of Ru neither by the concentration of ethanol. The results suggest that the C-C scission is not related to the presence of Ru and probably happens at Pt sites.

Electrooxidation of ethanol on Pt and PtRu surfaces investigated by ATR surface-enhanced infrared absorption spectroscopy

Herein, it was investigated for the first time the electro-oxidation of ethanol on Pt and PtRu electrodeposits in acidic media by using in situ surface enhanced infrared absorption spectroscopy with attenuated total reflection (ATR-SEIRAS). The experimental setup circumvents the weak absorbance signals related to adsorbed species, usually observed for rough, electrodeposited surfaces, and allows a full description of the CO coverage with the potential for both catalysts. The dynamics of adsorption-oxidation of CO was accessed by ATR-SEIRAS experiments (involving four ethanol concentrations) and correlated with expressions derived from a simple kinetic model. Kinetic analysis suggests that the growing of the CO adsorbed layer is nor influenced by the presence of Ru neither by the concentration of ethanol. The results suggest that the C-C scission is not related to the presence of Ru and probably happens at Pt sites.

From Sample Processing to Quantification: A Full Electrochemical Approach for Neutral Analyte Derivatization, Capillary Electrophoresis Separation, and Contactless Conductivity Detection

A thin-layer electrochemical flow cell coupled to capillary electrophoresis with contactless conductivity detection (EC-CE-(CD)-D-4) was applied for the first time to the derivatization and quantification of neutral species using aliphatic alcohols as model compounds. The simultaneous electrooxidation of four alcohols (ethanol, 1-propanol, 1-butanol, and 1-pentanol) to the corresponding carboxylates was carried out on a platinum working electrode in acid medium. The derivatization step required 1 min at 1.6 V vs. Ag/AgCl under stopped flow conditions, which was preceded by a 10 s activation at 0 V. The solution close to the electrode surface was then hydrodynamically injected into the capillary, and a 2.5 min electrophoretic separation was carried out. The fully automated flow system operated at a frequency of 12 analyses per hour. Simultaneous determination of the four alcohols presented detection limits of about 5 x 10(-5) mol As a practical application with a complex matrix, ethanol concentrations were determined in diluted pale lager beer and in nonalcoholic beer. No statistically significant difference was observed between the EC-CE-(CD)-D-4 and gas chromatography with flame ionization detection (GC-FID) results for these samples. The derivatization efficiency remained constant over several hours of continuous operation with lager beer samples (n = 40).

Performance and selectivity of PtxSn/C electro-catalysts for ethanol oxidation prepared by reduction with different formic acid concentrations

Carbon supported Pt-Sn catalysts were prepared by reduction of Pt and Sn precursors with formic acid and characterized in terms of structure, morphology and surface properties. The electrocatalytic activity for ethanol oxidation was studied in a direct ethanol fuel cell (DEFC) at 70 degrees C and 90 degrees C. Electrochemical and physico-chemical data indicated that a proper balance of Pt and Sn species in the near surface region was necessary to maximize the reaction rate. The best atomic surface composition, in terms of electrochemical performance, was Pt:Sn 65:35 corresponding to a bulk composition 75:25 namely Pt3Sn1/C. The reaction products of ethanol electro-oxidation in single cell and their distribution as a function of the nature of catalyst were determined. Essentially, acetaldehyde and acetic acid were detected as the main reaction products; whereas, a lower content of CO2 was formed. The selectivity toward acetic acid vs. acetaldehyde increased with the increase of the Sn content and decreased by decreasing the concentration of the reducing agent used in the catalyst preparation. According to the recent literature, these results have been interpreted on the basis of ethanol adsorption characteristics and ligand effects occurring for Sn-rich electrocatalysts. (C) 2012 Elsevier Ltd. All rights reserved.

Chemical Selectivity during the Electro-Oxidation of Ethanol on Unsupported Pt Nanoparticles

In this paper we present results on the electro-oxidation of ethanol on unsupported (carbon free) platinum nanoparticles, considering the effects of the alcohol concentration. The case of the so-called dual pathway mechanism during the electro-oxidation of ethanol showed to be influenced by the surface coverage of adsorbed carbon monoxide (COad) at unsupported platinum. The influences of adsorbed intermediates were followed by in situ infrared spectroscopy (FTIR) and by electrochemical experiments. Unsupported platinum showed that the reaction leads to the formation of CO2 and acetic acid as main products at low concentrations of ethanol (0.01 to 0.1 mol L-1). At least in this case of 0.01 mol L-1 ethanol, most formation of CO2 occurred via COad (indirect pathway). At higher concentration of ethanol, however, most CO2 was formed via a reactive intermediate such as acetaldehyde (direct pathway). In addition, in this higher concentration of ethanol, the acetic acid was produced via formation of adsorbed acetaldehyde (via acetate) at higher overpotentials. In case of the acetic acid formation, a dual pathway was identified during the electro-oxidation of ethanol at low alcohol concentrations, whereas a parallel pathway occurred without the formation of adsorbed acetate intermediates at low overpotentials. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.101203jes] All rights reserved.

Ethanol induces vascular relaxation via redox-sensitive and nitric oxide-dependent pathways

We investigated the role of reactive oxygen species (ROS) and nitric oxide (NO) in ethanol-induced relaxation. Vascular reactivity experiments showed that ethanol (0.03-200 mmol/L) induced relaxation in endothelium-intact and denuded rat aortic rings isolated from male Wistar rats. Pre-incubation of intact or denuded rings with L-NAME (non selective NOS inhibitor, 100 mu mol/L), 7-nitroindazole (selective nNOS inhibitor, 100 mu mol/L), ODQ (selective inhibitor of guanylyl cyclase enzyme, I mu mol/L), glibenclamide (selective blocker of ATP-sensitive K+ channels, 3 mu mol/L) and 4-aminopyridine (selective blocker of voltage-dependent K+ channels, 4-AP, 1 mmol/L) reduced ethanol-induced relaxation. Similarly, tiron (superoxide anion (O-2(-)) scavenger, 1 mmol/L) and catalase (hydrogen peroxide (H2O2) scavenger, 300 U/mL) reduced ethanol-induced relaxation to a similar extent in both endothelium-intact and denuded rings. Finally, prodifen (non-selective cytochrome P450 enzymes inhibitor, 10 mu mol/L) and 4-methylpyrazole (selective alcohol dehydrogenase inhibitor, 10 mu mol/L) reduced ethanol-induced relaxation. In cultured aortic vascular smooth muscle cells (VSMCs), ethanol stimulated generation of NO, which was significantly inhibited by L-NAME. In endothelial cells, flow cytometry studies showed that ethanol increased cytosolic Ca2+ concentration ([Ca2+]c), O-2(-) and cytosolic NO concentration ([NO]c). Tiron inhibited ethanol-induced increase in [Ca-2]c and [NO]c. The major new finding of this work is that ethanol induces relaxation via redox-sensitive and NO-cGMP-dependent pathways through direct effects on ROS production and NO signaling. These findings identify putative molecular mechanisms whereby ethanol, at pharmacological concentrations, influences vascular reactivity. (C) 2011 Elsevier Inc. All rights reserved.

Fermentation medium and oxygen transfer conditions that maximize the xylose conversion to ethanol by Pichia stipitis

The xylose conversion to ethanol by Pichia stipitis was studied. In a first step, the necessity of supplementing the fermentation medium with urea. MgSO(4) x 7H(2)O, and/or yeast extract was evaluated through a 2(3) full factorial design. The simultaneous addition of these three nutritional sources to the fermentation medium, in concentrations of 2.3, 1.0, and 3.0 g/l, respectively, showed to be important to improve the ethanol production in detriment of the substrate conversion to cell. In a second stage, fermentation assays performed in a bioreactor under different K(L)a (volumetric oxygen transfer coefficient) conditions made possible understanding the influence of the oxygen transfer on yeast performance, as well as to define the most suitable range of values for an efficient ethanol production. The most promising region to perform this bioconversion process was found to be between 2.3 and 4.9 h(-1), since it promoted the highest ethanol production results with practically exhaustion of the xylose from the medium. These findings contribute for the development of an economical and efficient technology for large scale production of second generation ethanol. (C) 2011 Elsevier Ltd. All rights reserved.

Liquid-Liquid Equilibrium Data for the System Lard plus Oleic Acid plus Ethanol + Water at 318.2 K: Cholesterol Distribution Coefficients

This research reports liquid liquid equilibrium data for the system lard (swine fat), cis-9-octadecenoic acid (oleic acid), ethanol, and water at 318.2 K, as well as their correlation with the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) thermodynamic equations, which have provided global deviations of 0.41 % and 0.53 %, respectively. Additional equilibrium experiments were also performed to obtain cholesterol partition (or distribution) coefficients to verify the availability of the use of ethanol plus water to reduce the cholesterol content in lard. The partition experiments were performed with concentrations of free fatty acids (commercial oleic acid) that varied from (0 to 20) mass % and of water in the solvent that varied from (0 to 18) mass %. The percentage of free fatty acids initially present in lard had a slight effect on the distribution of cholesterol between the phases. Furthermore, the distribution coefficients decreased by adding water in the ethanol; specifically, it resulted in a diminution of the capability of the solvent to remove the cholesterol.

Purification of bromelain from pineapple wastes by ethanol precipitation

Bromelain is an aqueous extract of pineapple that contains a complex mixture of proteases and non-protease components. These enzymes perform an important role in proteolytic modulation of the cellular matrix in numerous physiologic processes, including anti-inflammatory, anti-thrombotic and fibrinolytic functions. Due to the scale of global production of pineapple (Ananas comosus L.), and the high percentage of waste generated in their cultivation and processing, several studies have been conducted on the recovery of bromelain. The aim of this study was to purify bromelain from pineapple wastes using an easy-to-scale-up process of precipitation by ethanol. The results showed that bromelain was recovered by using ethanol at concentrations of 30% and 70%, in which a purification factor of 2.28 fold was achieved, and yielded more than 98% of the total enzymatic activity. This enzyme proved to be susceptible to denaturation after the lyophilization process. However, by using 10% (w/v) glucose as a cryoprotector, it was possible to preserve 90% of the original enzymatic activity. The efficiency of the purification process was confirmed by SDS-PAGE, and native-PAGE electrophoresis, fluorimetry, circular dichroism and FTIR analyzes, showing that this method could be used to obtain highly purified and structurally stable bromelain. (C) 2012 Elsevier B.V. All rights reserved.

Vehicle emissions and PM2.5 mass concentrations in six Brazilian cities

In Brazil, the principal source of air pollution is the combustion of fuels (ethanol, gasohol, and diesel). In this study, we quantify the contributions that vehicle emissions make to the urban fine particulate matter (PM2.5) mass in six state capitals in Brazil, collecting data for use in a larger project evaluating the impact of air pollution on human health. From winter 2007 to winter 2008, we collected 24-h PM2.5 samples, employing gravimetry to determine PM2.5 mass concentrations; reflectance to quantify black carbon concentrations; X-ray fluorescence to characterize elemental composition; and ion chromatography to determine the composition and concentrations of anions and cations. Mean PM2.5 concentrations in the cities of Sao Paulo, Rio de Janeiro, Belo Horizonte, Curitiba, Porto Alegre, and Recife were 28, 17.2, 14.7, 14.4, 13.4, and 7.3 mu g/m(3), respectively. In Sao Paulo and Rio de Janeiro, black carbon explained approximately 30% of the PM2.5 mass. We used receptor models to identify distinct source-related PM2.5 fractions and correlate those fractions with daily mortality rates. Using specific rotation factor analysis, we identified the following principal contributing factors: soil and crustal material; vehicle emissions and biomass burning (black carbon factor); and fuel oil combustion in industries (sulfur factor). In all six cities, vehicle emissions explained at least 40% of the PM2.5 mass. Elemental composition determination with receptor modeling proved an adequate strategy to identify air pollution sources and to evaluate their short- and long-term effects on human health. Our data could inform decisions regarding environmental policies vis-a-vis health care costs.

Similar ethanol drinking in adolescent and adult C57BL/6J mice after chronic ethanol exposure and withdrawal

BACKGROUND: Increasing evidence shows that excessive alcohol consumption during adolescence increases vulnerability to alcohol use disorders in adulthood. The aim of this study was to examine differences between adolescent and adult C57BL/6J mice in drinking behavior and blood ethanol (EtOH) concentrations (BECs) after chronic EtOH exposure and withdrawal. METHODS: Male adolescent (PND = 28 to 30) and adult (PND = 70) C57BL/6J mice were allowed to consume EtOH in a 2-bottle choice paradigm (15% EtOH vs. water) for 3 weeks (Baseline drinking, Test 1, and Test 2), which were interspersed with 2 cycles (Cycles I and II) of chronic EtOH vapor or air inhalation (16 hours) and withdrawal (8 hours). BECs were determined during both cycles. RESULTS: Chronic EtOH exposure led to increased EtOH intake during Test 1 and Test 2 in both adolescent and adult mice compared with air-exposed controls, and no differences between age groups were observed. During Cycle I adult mice showed higher BECs compared with adolescents. During Cycle II, BECs were lower in adult mice as compared to Cycle I, and BECs in adolescent mice did not change between the 2 cycles. CONCLUSIONS: Chronic EtOH exposure followed by withdrawal periods increases EtOH consumption similarly in both adolescent and adult mice, despite differences in BECs