Glucose, colorimetric determination

Colorimetric determination of the produced a-D-glucose. Acarbose is added to inhibit unspecific a-glucosidases present in leukocytes [33]. 

The Enzymatic Colorimetric Determination of Glucose Sigma Chemical Company St. Louis, 1979 Technical Bulletin No. 510. 

Figure E2.2.1 Principle of the colorimetric determination of glucose using GOPOD reagent.

S91 Wilsey, C., Kurchacova, E. and Ide, R. (1984). A solid-phase reagent strip test for the colorimetric determination of serum glucose on the Seralyzer reflectance photometer. Clin. Chem. 30, 969, Abstr. 149. 

The data in this table were obtained during a colorimetric determination of glucose in blood serum. 

Uric acid is usually determined by measuring its ultraviolet absorption at 292 nm. However, the amount of uric acid in blood is small and the absorption is not specific. So, after the measurement, the uric acid is destroyed by adding the enzyme uricase. The absorbance is measured again. The difference in absorbance is due to the uric acid present. Since only uric acid wiU be decomposed by uricase, the method becomes specific. A similar procedure for the colorimetric determination of uric acid involves the oxidation of uric acid with molybdate to form molybdenum blue, a molybdenum(V) compound. In principle, uric acid could be determined as glucose was, but impurities in uricase preparations usually rapidly destroy the very small amount of hydrogen peroxide produced. 

The response of a colorimetric test for glucose was checked with the aid of standard glucose solutions. Determine the correlation coefficient from the following data and comment on the result. 

More-specific methods are available for identifying and quantitating the typical, amino sugar component of heparin (and some heparan sulfate species), namely, 2-deoxy-2-sulfoamino-D-glucose. Most of these methods are based on conversion of these residues into 2,5-anhydro-D-mannose by deamination with nitrous acid (see Section VIII,2). The 2,5-anhydro-D-mannose residues may be determined either colorimetrically,52-54 or fluorimetrically.55... 

Normal Rabbits. Six male, white rabbits (2.5 - 3.0 kg) were housed individually. Animals were fasted overnight for 16 hours (with access to water) prior to each experiment to reduce the gastrointestinal content and absorption variability. After treatment with either a control dose or experimental insulin in poly(acrylic acid) resin dose, a one week washout period was required before the next experiment. The protocol called for blood samples to be taken from an indwelling ear catheter at -1, -.5, -.25, +.5, +1, +1.5, +2, +3, +4, +5 and +6 hours. Serum glucose levels were determined by an oxidase colorimetric method using the Sigma 510 Glucose Kit. 

Note that instruments 1-4 were photometric devices with less then 0.01 absorbance accuracy evaluated against reference neutral filters at 546 nm and A = 1.000, traceable to INM. The bandwidth provided by the interference filters equipping the absorption photometers was within the range of 4-10 nm. Instrument 5 was a 10 nm bandwidth photometric device with less than 1.0% absorbance linearity, evaluated at 405 nm and 500 nm, against liquid absorbance RMs type 16.02 and 16.03 [5], Enzymatic colorimetric methods for determination of glucose and urea were used. The o-cresoftalein colorimetric method was used for calcium determination. 

A valuable series of comparative experiments was performed by Schwim-mer and Olcott151 on the reaction of glycine with D-glucose, D-fructose, D-glucose 6-phosphate, D-fructose 6-phosphate, and D-fructose 1,6-diphosphate in the presence and absence of a phosphate buffer at pH 6.5. The rate of browning at 70° (over 18 hours) was determined colorimetrically at 420 mp. An increase in the rate of browning was observed for the hexose 6-phosphates, as compared with the unsubstituted sugars. Similarly, the... 

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