Materials and Methods

A new coupled redox procedure has been de-veloped for the determination of glucose in 4 151 of plasma or serum. The photometric endpoint is formation of the violet.blue Fe2+.5.pyridyl benzo-diazepin-2-one chelate, for which the absorbance at 580 nm is linear with glucose concentration from 25 to 300 mg/100 ml. Results obtained by the present technique and those obtained by the o-toluidinemethod and a glucose oxidase method agree well. The mean recovery of glucose added to plasma is 96.6 % (range: 92.1-99.6%). Additional Keyphrases coupled redox reaction ferricyanide iron ligand chetate In two recent reviews (1, 2) in which reductimetric methods for plasma or serum glucose analysis were critically evaluated, those alkaline ferricyanide tech-niques involving measurement of the amount of ferro-cyanide formed were preferred for several reasons. The methods are precise. The reagent is simple and, when properly stored, relatively stable. Most importantly, ferrocyanide is less readily reoxidized than Cul+ in the analogous cuprimetric analysis. The principal limitation in existing methods involving photometric measurement is the need to convert the weakly absorbing ferrocyanide to the unstable Prussian blue. This report presents a new and sensitive method for determination of glucose in 4 ILl of plasma or serum, and is based on the following coupled ferricyanide redox reactions Glucose + [Fe(CN)6] ’-. Gluconic acid + [Fe(CN)g]4 [Fe(CN)g]4 + Fe3-- [Fe(CN)g] + Fe2 Fe2 + ligand- * (Fe2+/3)ligand chelate The ligand, a 5-pyridyl benzodiazepin-2-one deriva-tive, chelates Fe2 to form a stable, brilliant violet-blue solution (3), the A580 em of which is linear with glucose concentration. We gave an abbreviated de-scription of this procedure earlier (4), and described an automated adaptation of this technique (5)