Glucose, enzymatic determination

A second principle used widely for glucose analysis, is that of the oxidation of glucose enzymatically, mediated by the action of glucose oxidase with the formation of gluconic acid and hydrogen peroxide (22). In this procedure it is the hydrogen peroxide which is usually assayed for determination of glucose. This method suffers from the action of inhibitors which occur, particularly with patients in a diabetic coma and these need to be removed. 

Tubular electrodes. Blaedel et al.161 were the first to introduce the TBE, a tubular electrode. It was constructed by melting a Pt cylinder in a glass capillary (see Fig. 5.25), the total length of Pt being 25.5 mm and its diameter 0.75 mm. The authors originally used it for an enzymatic determination of glucose by means of differential amperometry based on the following sequential reactions"12 ... 

Glucose was determined by the glucose oxidase-peroxidase method. Cellobiose (liberated enzymatically from methylcellotrioside) was determined in a coupled assay using cellobiose dehydrogenase from Sporotrichum thermophile (4). 

Wu M, Lin Z, Durkop A, Wolfbeis OS. Time-resolved enzymatic determination of glucose using a fluorescent europium probe for hydrogen peroxide. Analytical and Bioanalytical Chemistry 2004, 380, 619-626. 

The glucose was determined enzymatically (Yellow Springs Instruments). The response time of the complete analyzer system was ca. 37 min, of which 5 min are due to the transfer distance of 3 m between the reactor, filtration module and analyzer system. The continuous air segmented flow analyzers have the disadvantage that after 3-4 days operation, microorganisms growth was detected in the non aseptic analyzer system. 

Day 1 Reduction of Carbohydrates with Sodium Borohydride and Enzymatic Determination of Glucose... 

Incubate the reaction in a 50°C oven for 30 min. During this incubation, you may proceed with the Enzymatic Determination of Glucose, below. 

Blood glucose and blood urea nitrogen (BUN) are probably the two most frequently performed clinical tests. In the procedures described in Table 24.2, the total of all reducing sugars is measured, and so results tend to be high. But these methods have been adopted as standard ones for many years. The enzymatic determination of glucose (Chapter 22) is an established method, and dedicated enzymatic glucose analyzers are now widely used. 

Figure 11.3 depicts the cell used by the automatic potentlometrlc Instrument devised by Malmstadt and Pardue [6] for ths enzymatic determination of glucose based on reaction-rate measurements. The chemistry involved Is... 

Fig. 11.3 Concentration cell for the kinetic enzymatic determination of glucose. (1) Thermometer (2) reference stirring rod (3) reference electrode (4) sample stirring rod (5) sample electrode. (Reproduced from [6] with permission of the American Chemical Society).

Delanghe, J., J. Bellon, M. De Buyzere, G. Van Daele, and G. Leorux-Roels.1991. Elimination of glucose interference in enzymatic determination of inulin. Clinical Chemistry 37 2017-2018. 

P. Roehrig, C. M. Wolff, and J. P. Schwing, Repetitive Enzymatic Determination of Glucose with Regeneration and Recycling of Coenzyme and Enzymes. Anal. Chim. Acta, 153 (1983) 181. 

R. Appelqvist, G. Marko-Varga, L. Gorton, A. Torstensson, and G. Johansson, Enzymatic Determination of Glucose in a Flow System by Catalytic Oxidation of the Nicotinamide Coenzyme at a Modified Electrode. Anal. Chim. Acta, 169 (1985) 237. 

Hanson, R.B. and Snyder, I., 1979. Enzymatic determination of glucose in marine environments improvement and note of caution. Mar. Chem., 7 353—362. 

A second application of the stopped-flow technique is for kinetic measurements. In this application, the flow is Slopped with the reaction mixture in the flow cell where the changes in the concentration of reactants or products can be monitored as a function of time. The stopped-flow technique has been used for the enzymatic determination of glucose, urea, galactose, and many other substances of interest in clinical chemistry. 

Glucose was determined independently by the method of Borel et al ( ) and enzymatically (23). 

The enzyme glucose oxidase is used for quantitative and enzymatic determination of the glucose in food and other materials. The enzyme glucose oxidase test is widely used because it is cheap, stable, and by its specificity well established for glucose. 

Fig.4. (top) Reaction scheme for the enzymatic determination of starch as executed in the FIA manifold shown below, where AMG refers to amyloglucosidase and GDH to glucose dehdrogenase, both of which enzymes are immobilized on porous glass in separate packed-bed reactors. The detection of the generated NADH is facilitated amperometrically by means of a modified electrode at 0 mV vs. Ag/AgCl, 0.1 M KCl. Flow rates are given in ml/min injected volume 30... 

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