Ferricyanide reducing sugars

Since L-sorbose is a reducing sugar a number of methods for its determination, based on this property, have been reported. Titration with the ceric sulfate, potassium ferricyanide reagent showed a fructose to sorbose ratio of 1.1,86 Cupric citrate87 as well as cupric tartrate87 reagents appear to be equally useful. 

Application and Principle This procedure is used to determine the amylase activity of barley malt and other enzyme preparations. The assay is based on a 30-min hydrolysis of a starch substrate at pH 4.6 and 20°. The reducing sugar groups produced on hydrolysis are measured in a titrimetric procedure using alkaline ferricyanide. 

This method for determining reducing sugars (7) is based on the reduction of ferricyanide ions in alkaline solution by a reducing sugar. The ferrocyanide produced can then react with a second mole of ferricyanide producing the ferric-ferrocyanide (Prussian blue) complex. Potassium... 

In the saccharogenic type of assay, enzyme activity is measured by the amount of reducing sugar formed. Any of the traditional substances for measuring reducing substances can be used, e.g. ferricyanide. 

Reducing sugars may be determined (87,231,237) by using a modified Fehling solution and Nelson s arsenomolybdate reagent (190). Potassium ferricyanide is used similarly and the ferrocyanide, produced by oxidation of the reducing sugar, is converted to Prussian blue which is estimated photometricaUy (178). 

It is difficult to correlate reducing sugar units based on different analytical methods. Hahn (63) determined the reducing values for enzymic digests of hyaluronic acid by the Somogyi, the Hagedorn-Jensen, and the hypoiodite methods (108). The results obtained with the copper sulfate and hypoiodite methods were 60 and 36% lower, respectively, than those obtained with the ferricyanide method. 

Reducing power of sugars is the basis of a number of classical analytical methods. Iodine, alkaline ferricyanide and other reagents have been used for analytical purposes. 

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. 

A method of blood sugar estimation based on the ability of glucose to reduce ferricyanide to ferrocyanide. The ferricyanide remaining is determined iodometrically. 

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