Sugars colorimetric analysis

Copper. In the presence of sulfur dioxide, copper-protein cloudiness may develop in white wines. Only small amounts of copper (about 0.3 to 0.5 mg/liter) cause cloudiness. Widespread use of stainless steel in modern wineries has reduced copper pickup, but many wineries routinely test their wines for copper. Atomic absorption spectrophotometry is the method of choice (51) although reducing sugars and ethanol interfere, and correction tables must be used (107). To reduce this interference, chelating and extracting with ketone is recommended (108). Lacking this equipment colorimetric procedures can be used, especially with di-ethyldithiocarbamate (3, 4, 6, 9,10, 22,109). Neutron activation analysis has been used for determining copper in musts (110). 

Traditional methods of analysis for determination of principal organic acids, glycerol and sugars in wine are based on enzymatic or colorimetric reactions ethanol is determined by distillation of wine and density measurement of the distillate. In Table 1.2, data of organic acids, glycerol, glucose, fructose and ethanol determined by HPFC are reported as a percentage of results obtained by the traditional methods. 

Number-average molecular weights, M, were obtained from colorimetric data from end-group analysis (reducing sugar) according to procedure described earlier (19) ... 

Doctoral Thesis, Univiersity of Hies Balears, Palma de Mallorca, Spain Dubois M, Gilles KA, Hamilton JK, Rebers PA, Smith F (1956) Colorimetric method for determination of sugars and substances. Anal Chem 28 350-356 Englyst HN, Cummings JH (1988) Improved method for measurement of dietary fibre as nonstarch polysaccharides in plant foods. J Soc Off Anal Chem 71(4) 808-814 Faichney GJ, White GA (1985) Methods for the analysis of feeds eaten by ruminatnts. Division of Animal Production, Ian Clunies Ross Animal Research laboratory, PO Box 239, Blacktown, NSW 2184, Australia... 

A number of important methods are based on the oxidation of sugars by ferricyanide ion in alkaline solution. The method is open to the same objections as the copper reduction methods, namely, the lack of a stoichiometric reaction and the dependence of the method on arbitrarily chosen conditions. The ferricyanide may be used to titrate the sugar solution directly by the use of picric acid or of methylene blue as an indicator. Or, the reduced ferrocyanide may be precipitated as the zinc salt, and the excess ferricyanide determined iodometrically. The Hagedom-Jensen method and the Hanes modification utilize the latter procedure. In the Folin-Malmros micro method, Prussian blue is formed and determined colorimetrically. Extensive application of the ferricyanide method has been made in the determination of the diastatic power of amylase preparations and in blood analysis. 

One of the major uses of colorimetric methods is in the monitoring of chromatographic columns. All the low pressure GPC columns can be connected to automated colorimetric assay systems based on any of the total sugar assay methods. There is a potential in the adoption of such systems (analogous to flow injection analysis) into HPLC systems for the specific and more sensitive (compared to RI and UV) detection of underivatized glucose oligomers. 

The hydrophobic properties of a series of 5-aIl l-, 5-alkenyl- and 5-alI yl-substituted deoxyuridines were defined from their retention behaivour on silica and reversed-phase columns. Zeatin and its riboside were determined in plant tissues by solid-phase extraction and cation-exchange h.p.l.c. Sugar and nucleoside H-phosphonates have been separated by anion-exchange h.p.l.c., and by flow injection analysis in which the components are hydrolysed, oxidised and the orthophosphate so generated is detected colorimetrically. ... 

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