Determination of Alcohols

In contrast, alcohol dehydrogenase (ADH) requires a coenzyme, nicotinamide adenine dinucleotide (NAD), whose reduced form (NADH) cannot be oxidized by oxygen. An electioactive species must act as a mediator u le noate NAD. A variety of substances have been tested as mediators [168], phenazine methosulfate (PMS) rapidly oxidizes NADH but is unstable, and thioglycdate and methyl violet react too slowly. Flavin mononucleotide (FMN), however, is easily oxidized at the anode by a constant current, and NAD can be regenerated. Hence, ethanol is determined using the three following reactions  

The direct electron transfer from the coenzyme NADH to the electrode can be facilitated using organic conducting salts such as NMP+TCNQ (see 3.3.l.f). These salts reduce the cofactor redox potential required, which limits any interference phenomena and fouling up of the electrodes [43]. These problems can also be overcome using an electrode with a hydrophobic membrane (p02 electrode) on which alcohol oxidase and catalase [170] can be immobilized. These enzymes catalyse the following reactions  

The catalase regenerates some of the consumed oxygen, and the response of the electrode is linear up to 25 mg/1. This electrode responds to ethanol and also to other alcohols, such as methanol, propanol, butanol and isopropanol. 

Phenol is also determined using the oxygen electrode with phenol hydroxylase, which catalyses the following reaction [171]  

The determination of cholesterol is carried out using cholesterol oxidase coupled with a platinum electrode which detects the hydrogen peroxide formed [172]. 

Ethanol is the most common toxic substance involved in medical-legal cases. It is frequently a contributory factor in accidents. Methanol content is controlled in drinking water and fermentation media. It is also a widely used solvent in paints. The determination of other aliphatic alcohols is of minor importance. 

For enzymatic alcohol measurement, alcohol dehydrogenase (ADH, EC 1.1.3.13) and alcohol oxidase (AOD, EC 1.11.1.6) from various sources have been used  

Because of the analogy of the AOD reaction to that of GOD, Clark in 1972 had already suggested an alcohol sensor based on AOD. Guilbault and Nanjo (1975a) described an H202-sensing AOD electrode with a detection limit of 0.01 mg/ml. 

The substrate specificity of AOD from different microbial sources has been studied in detail. Yeasts cultivated on methanol produce large amounts of AOD together with catalase. This AOD has a high activity towards methanol. Ethanol is oxdized more rapidly only by AOD from Basidiomycetes. AOD also reacts with other aliphatic alcohols, mercap-tans, and formaldehyde. Acetone, isopropanol, lactate, and other hy-droxyacids do not react. Because of the high catalase content of the 

Transcutaneous determination of ethanol with an oxygen electrode covered by AOD has been described by Clark (1979). Stepwise increases of the ethanol concentration in rat blood resulted in a curve reflecting the ethanol injections, returning to the initial value only after several hours. Disturbances were caused by variations in body temperature and blood pressure. In the paper cited, Clark developed the concept of a sensor for volatile enzyme substrates. 

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The determination of alcohols in essential oils depends on the conversion of these compoimds into their acetic esters, and then carrying out an ester determination as described above. 

The determination of alcohol-insoluble solids as a means for grading peas can... 

Multilamellar liposomes, absorbed on paper, containing extrapped peroxidase permit the quantitative determination of alcohol sulfates by measuring the amount of peroxidase released from the liposomes as this amount varies with the amount of surfactant [272]. 

A method developed to analyze alkylbenzenesulfonates by reverse phase ion pair HPLC with UV detection has also been applied to the determination of alcohol ether sulfates [286]. 

Katayama, M., Masuda, Y., and Taniguchi, H., Determination of alcohols by high-performance liquid chromatography after pre-column derivatization with 2-(4-carboxyphenyl)-5,6-dimethylbenzimidazole,/. Chromatogr., 585,219, 1991. 

Levels of a number of metabolites as well as a number of enzymes in body fluids are indicative of disease conditions. Many of the enzymatic reactions mentioned above have been used in solution clinical assays as well as in test strips.446,497-508 512-515 Assays for hydrogen peroxide and the enzyme peroxidase using NADH and a tetrazolium salt have been de-scribed.509,5io Assays of exogenous substances (e.g., drugs or their metabolites) also utilize this chemistry. The determination of alcohol using alcohol dehydrogenase is an example.511 As mentioned above, the assay of enzyme levels can also be achieved using tetrazolium salts.516-520... 

While additive analysis of polyamides is usually carried out by dissolution in HFIP and hydrolysis in 6N HC1, polyphthalamides (PPAs) are quite insoluble in many solvents and very resistant to hydrolysis. The highly thermally stable PPAs can be adequately hydrolysed by means of high pressure microwave acid digestion (at 140-180 °C) in 10 mL Teflon vessels. This procedure allows simultaneous analysis of polymer composition and additives [643]. Also the polymer, oligomer and additive composition of polycarbonates can be examined after hydrolysis. However, it is necessary to optimise the reaction conditions in order to avoid degradation of bisphenol A. In the procedures for the analysis of dialkyltin stabilisers in PVC, described by Udris [644], in some instances the methods can be put on a quantitative basis, e.g. the GC determination of alcohols produced by hydrolysis of ester groups. 

A device described by Sawyer and Dixon [13] was used for the determination of alcohol and acid in beer and stout. Attempts to improve the reliability of this method and to improve the signaTto-noise characteristics of the measurements prompted a critical design described by Lidzey et al. [14]. This unit overcomes many of the fluctuations in results observed with use of the first unit in this a number of possible sources of surging were indicated and these were not controlled owing to the varying conditions in the coil. In addition, the separation of the waste involatile material from the volatile phase took place outside the heated flask distillation unit. Air bubbles present in the segmented stream were also responsible for considerable surging. 

Determination of alcohol. Transfer quantitatively 50ml of previous alcoholic soln into Erlenmeyer flask, incline it at 45° and pour slowly on the side of die flask, with cooling and swirling,... 

GC is used to produce reliable results in the determination of alcohol in biologic samples. Cravey and Jain (18) have done extensive work on the blood alcohol method and their review covers the current status of methodology, including enzyme and osmomet-ric methods as well as GC. Pereira et al (19) have described the GC-MS determination of ethanol in blood using a modification of the procedure described by Jain (20). 

N. Pena, R. Tarrega, A.J. Reviejo and J.M. Pingarron, Reticulated vitreous carbon-based composite bienzyme electrodes for the determination of alcohols in beer samples, Anal. Lett., 35(12) (2002) 1931-1944. 

In short, the interethnic differences in the structure of ADH appear to have sufficient effects upon the fate of ethanol to be one of the determinants of alcoholism. Furthermore, one should not exclude the possibility that variation of ADH matters, for the fate of endogenous (89,90) or exogenous substrates (91,92). Ethanol is also metabolized by CYP2E1, but this enzyme is quantitatively less important than are the ADH (93). 

Boston, WJ ., Li, T.K. Genetic determinations of alcohol and aldehyd dehydrogenases and alcohol metabolism. Semin. Liver Dis. 1981 1 179-188... 

Table 8 Compendial applications of GC for the determination of alcohol content in raw materials and dosage forms ...

British Pharmacepoeia (BP) and European Pharmacopoeia (EP) Applications of GC for the Assay Chromatographic Purity Identification Presence of Volatile Matter, Intermediates and Related Substances Organic Volatile Impurities Determination of Water Presence of Isomers and Racemate Ratios Determination of Alcohol and Miscellaneou s Uses of GC in Pharmaceutical Raw Materials and Dosage Forms. 

One point about alcohol s acute effects is that alcohol generally acts on the body as a depressant, and its acute effects are proportional to the magnitude of the BAG. Simply put, as the BAG increases, acute effects increase in number and intensity. However, how humans experience some degree of intoxication and behave under different doses of alcohol may be modified by psychological and situational factors as well as alcohol dose and tolerance to this drug. For some behaviors these nondrug factors may be even more powerful determinants of alcohol s acute effects than drug factors. 

Suitable blood-related specimens for the determination of alcohols are serum, plasma, or whole blood. The venipuncture site should be cleansed with an alcohol-free disinfectant, such as aqueous benzalkonium chloride (Zephiran). 

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... 

A microbial FET for the determination of alcohol has been constructed by Tamiya et al. (1988). The cell membrane of Gluconobacter suboxydans, which converts ethanol to acetic acid, was attached in calcium alginate to the gate of a pH-FET and covered by a nitrocellulose layer. The differential output versus a membrane-free reference gate was linearly related to the logarithm of the ethanol concentration up to 20 mg/1. The sensor responded to propanol and butanol with similar sensitivity, but not to methanol. The response time was 10 min. Below 30°C the sensor was stable for 40 h. 

A = specific gravity of the distillate obtained in the determination of alcohol, 4 (a). 

Determine by the immersion refractometer at 20° the refraction of the distillate obtained in the determination of alcohol. If, on reference to the table under A6, the refraction shows the percentage of alcohol agreeing with that obtained from the specific gravity, it may be assumed that no methyl alcohol is present. If, however, there is an appreciable quantity of methyl alcohol, the low refractometer reading will at once indicate the fact. If the absence from the solution of refractive substances other than H2O and the alcohols is assured, this difference in refraction is conclusive of the presence of methyl alcohol. 

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