Quantitative determination of carbohydrates

Colorimetric Methods. Numerous colorimetric methods exist for the quantitative determination of carbohydrates as a group (8). Among the most popular of these is the phenol—sulfuric acid method of Dubois (9), which rehes on the color formed when a carbohydrate reacts with phenol in the presence of hot sulfuric acid. The test is sensitive for virtually all classes of carbohydrates. Colorimetric methods are usually employed when a very small concentration of carbohydrate is present, and are often used in clinical situations. The Somogyi method, of which there are many variations, rehes on the reduction of cupric sulfate to cuprous oxide and is appHcable to reducing sugars. 

Moreover, since the application of a particular starch hydrolysate product depends on its molecular weight (distribution) and/or oligosaccharide composition, analyses of these materials are a necessity to the applications chemist whilst the health and nutrition conscious public demands quantitative determination of carbohydrates in food. 

A procedure recommended for the quantitative determination of carbohydrates in solution Involved reduction (NaBD i), permethylation (DMSO-NaOH powder - Mel), and analysis by g.c. or g.c.-m.s. The derlvatlzatlon could be conducted in the same vial, and improved accuracy over other methods was claimed. The method was applied to... 

Reactions of Carbohydrates with Strong Acid, and the Qualitative and Quantitative Determination of Carbohydrates... 

Thereafter, approximate quantitative determinations of the carbohydrate content of the microbubble glycopeptide surfactant were made through the use of degradative enzymes. Table 4.3 summarizes the results from polyacrylamide (slab) gel electrophoresis of glycopeptide surfactant treated with P-N-acetyl-hexosaminidase, both alone and with endoglycosidase H. The... 

Kennedy, J. F., Melo, E. H. M., Crescenzi, V., Dentini, M., and Matricardi, P. (1992). A rapid quantitative determination of pectin and carboxymethyl cellulose in solution using poly(hexamethylenebiguanidinium) chloride. Carbohydr. Polym. 17 199-203. 

Enzymic Methods for Determination of D-Glucose. Quantitative Determination of D-Glucose by Oxidation with D-Glucose Aerodehydrogenase, L. Hough and J. K. N. Jones, Methods Carbohydr. Chem., 1 (1962) 400-404. 

The benzyl acetate (18) is quantitatively determined by capillary column gas chromatography (GC). Benzyl butanoate (20), formed from butanoic acid (19) concurrently with the formation of benzyl acetate (18), serves as the internal standard (Mansson 1983). Since 1 mol of acetic acid (14) is converted to 1 mol of benzyl acetate (18), the total hydroxyl content of the lignin preparation can be determined by quantitative determination of the benzyl acetate (18). The Mansson procedure is a modification of the Bethge-Lindstrom method for determinating O-acetyl groups in acetylated carbohydrates (Bethge and Lindstrom 1973). 

Methylation by diazomethane is a simple method for derivatization of relatively acidic compounds [e.g., phenols (pA = 9-10) or carboxylic acids (pi = 4.4 0.2)]. The application of this reagent for methylation of aliphatic alcohols requires additional acid catalysis. Methyl iodide is the most convenient reagent for synthesis of permethylated derivatives of polyols (including carbohydrates) and phenols. Dimethyl sulfate [(01130)2802] can be used in basic aqueous media for methylation of phenols, but the yields of methyl ethers, in this case, are not enough for quantitative determinations of initial compounds by GC. 

G Gellerstedt, J Li. An HPLC Method for the Quantitative Determination of Hexeneuronic Acid Groups in Chemical Pulps. Carbohydr Res 294 41-51, 1996. 

Although the determination of both the configuration and the conformation of carbohydrates involves the same general considerations, the quantitative nature of the latter requires a rather more fundamental approach. Accordingly, the following discussion is divided into two main sections the first refers to the development and applications of nuclear magnetic resonance to stereochemical problems, and deals mainly with substituent resonances the second discusses in some detail the Karplus relationship and the determination of carbohydrate conformations. 

Water has been determined in starch hydrolyzates by dissolving the sample in methyl sulfoxide and measuring the ratio of the peak heights for water and sulfoxide by using a column of Porapak Q. Other applications include the quantitative determination of 5-(hydroxymethyl)-2-furaldehyde, which is a carbohydrate degradation-product the analysis of the thermal degradation-products of carbohydrates has been re-... 

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