Ethanol concentration determination

To determine the concentration of ethanol in cognac a 5.00-mF sample of cognac is diluted to 0.500 F. Analysis of the diluted cognac gives an ethanol concentration of 0.0844 M. What is the molar concentration of ethanol in the undiluted cognac ... 

Provided a suitable internal standard is available, this is probably the most reliable method for quantitative GLC. For example, the concentration of ethanol in blood samples has been determined using propan-2-ol as the internal standard. 

Ethanol concentration in the fermentation broth is determined by using gas chromatography (HP 5890 series II with HP Chemstation data processing software, Hewlett-Packard, Avondale, PA) with a Poropak Q Column, and a Hewlett-Packard model 3380A integrator. A flame ionisation detector (FID) is used to determine ethanol. The oven temperature is maintained at 180 °C, and the injector and detector temperature are maintained at 240 °C. The sample taken from the fermentation media has to be filtered and any internal standard must be added for analysis based on internal standard methods otherwise, the area under the peak must be compared with known standard samples for calculation based on external standard methods. 

Many dehydrogenase enzymes catalyze oxidation/reduction reactions with the aid of nicotinamide cofactors. The electrochemical oxidation of nicotinamide adeniiw dinucleotide, NADH, has been studied in depthThe direct oxidation of NADH has been used to determine concentration of ethanol i s-isv, i62) lactate 157,160,162,163) pyTuvate 1 ), glucose-6-phosphate lactate dehydrogenase 159,161) alanine The direct oxidation often entails such complications as electrode surface pretreatment, interferences due to electrode operation at very positive potentials, and electrode fouling due to adsorption. Subsequent reaction of the NADH with peroxidase allows quantitation via the well established Clark electrode. 

An OFRR of approximately 75 pm in outer diameter (OD) is produced by rapidly pulling a capillary preform (Polymicro Technologies, Phoenix, AZ) under heat, followed by HF etching to further reduce the wall thickness to around 4 pm. The OFRR pulling system is home-built and has been detailed in Chap. 14. The wall thickness is determined from measuring the bulk RI sensitivity using different concentrations of ethanol water mixture with known RI44. 

Because the initial oxygen concentration determines the relative abundance of specific abstracting radicals, ethanol oxidation, like methanol oxidation, shows a variation in the relative concentration of intermediate species according to the overall stoichiometry. The ratio of acetaldehyde to ethene increases for lean mixtures. 

Determination of the Michaelis constant for the cofactor NAD (A nad) was carried out by measuring the initial rate of the reduction of NAD as a function of its concentration at a constant concentration of ethanol. All the solutions were prepared in 0.1 M phosphate buffer pH 7.55. 

In order to estimate the ethanol/water composition as a function of x, a novel method (described in the Experimental section) was utilized, employing a membrane "plug" of assembled filter membranes. The steady-state ethanol concentrations determined for the experiment in which pure ethanol was in the donor chamber and saline in the receiver are presented in Figure 4. Further studies are needed to validate these results. Errors due to evaporation losses are believed to be of the order of 10%. 

Since a permeability coefficient of 2 x 10 cm/sec was used in our theoretical calculation for case B, this is equivalent to a single porosity value for all calculations with Equation 6. For any given set of ethanol concentration at the boundary, the appropriate ethanol concentration distance profile was calculated from the experimentally determined profile for the pure ethanol/water system and taken as that of the system. For any given set of ethanol concentrations at the boundaries the appropriate portion of the experimentally determined ethanol concentration distance profile, was calculated from the experimentally determined profile for the pure ethanol/water system. For any given ethanol concentration distance profile, the corresponding solubility profile of 3-estradiol was obtained by interpolation of experimental solubility data (Figure 2). 

Example Ethanol is separated from a mixture of organic compounds by gas chromatography. The concentration of each component is proportional to its peak area. However, the chromatograph detector has a variable sensitivity from one run to the next. Is an internal standard required to determine the concentration of ethanol ... 

The ethanol concentration in the medium of a Saccharomyces cerevisiae cultivation can be monitored from its content in the gas phase by directly recording the current from a chemical MOS sensor [28]. The accuracy of such a measurement was significantly improved by using an electronic nose with five sensors in the array and recognizing the response pattern with ANN [29, 30]. The sensors were a combination of MOS and MOSFET sensors selected from a PCA loading plot. Data sets from three cultivations were used to train the ANN. When the trained net was applied on new cultivations the ethanol was predicted with a mean square error (RMSE) of 4.6% compared to the off-line determined ethanol (Fig. 6). With only one sensor the RMSE was 18%. 

The uptake of cocaine to hair after preliminary exposure to various acidic and basic solutions is shown in Figure 10. Three sets of experiments were performed. In the first experiment, hair was exposed to base (0.1 M sodium carbonate, pH 12) for 3 h and then washed extensively with water rmtil the water was neutral. This was then followed by two phosphate buffer rinses at pH 5.3 for 10-min periods. The hair was then exposed to 5 pg/mL of cocaine, containing a radioactive tracer, in phosphate buffer at pH 5.3 for 1 h. After exposure the excess cocaine was removed with three water rinses of 10 min each and the hair was dried. Then the hair was decontaminated with ethanol and six phosphate washes, digested, and the cocaine concentration determined by scintillation counting as per previously described procedures. Approximately twice as much cocaine was incorporated into the hair pretreated by exposure to base as compared to hair not subjected to any pretreatment. In the second experiment, hair was pretreated with 0.1 M HCl, then treated as in the first experiment. In this case approximately one sixth as much cocaine was incorporated as the control. In the third experiment, hair was pretreated with 5% acetic add and treated as in the... 

Somnolence was reported in a 27-year-old subject following an overdose of opipramol a maximum serum concentration of 0.115 pg/ml was determined ethanol was also detected (O. L. Pedersen et ai, Eur. J. clin. Pharmac., 1982, 23, 513-521). 

A detailed study of the photooxygenation of hexene isomers showed that, depending on the reaction temperature (25c or 50 C). the allylic hydroperoxides are produced E selectively38, in diastereomeric ratios from 78 22 to > 99 1. In cases with a high alkene concentration in ethanol as solvent and rose bengal as sensitizer, the product ratios are determined after 5-10% conversion. 

The organism Lymomonos mpbilis is used to convert carbohydrates to ethanol. Glucose (formula CeH Oe, mol. wt. 180 g/grnol) in a 100 g/L feed solution is converted to ethanol and carbon dioxide in a fermentation tank. The problem is to determine the final molar concentration of ethanol in the product stream and the number of liters of carbon dioxide gas... 

Statutory laws for driving under the influence of alcohol were originally based on the concentration of ethanol in venous whole blood. Because the collection of blood is invasive and requires intervention by medical personnel, the determination of alcohol in expired air has long been the mainstay of evidential alcohol measurements.There is also growing clinical interest m the determination of breath alcohol at the point-of-care. The fundamental principle for use of breath analysis is that alcohol in capillary alveolar blood rapidly equilibrates with alveolar air in a ratio... 

The most convenient way of determining ethanol concentration is by measuring the density and temperature of the solution and relating this to concentration by the use of appropriate tables. The concentration by volume determined in this way can then be related to the British proof system, or to the Sikes scale for specification on the bottle. 

Plot given of pKg vs EtOH concentration (almost linear from 90% down to 18%), however precipitation of diclofenac at EtOH% <50% needed approximate treatment of the titration curves value from extrapolation to 0% EtOH. Also, there was an approximately linear plot of apparent pK and die reciprocal of the dielectric constant, which led to a similar value. The dissociation constants of diclofenac sodium in ediyl alcohol... were determined using the titration mediod. The acid dissociation constant of the drug was decreased by the increase in die concentration of ethanol in... 

Methanol is analyzed by GC-FID. In blood it is determined by an enzymic method based on its conversion to formaldehyde by alcohol oxidase and the oxidation of formaldehyde to formic acid by the enzyme formaldehyde dehydrogenase. The presence of a toxic concentration of ethanol may give a high positive value. Methanol in air is estimated by passing 1 -4 L of air over silica gel absorbent, desorbing the analyte into water. 

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