A kinetic-spectrophotometric method for the determination of glucose in solutions

A kinetic-spectrophotometric method is proposed to determine glucose in solutions. Measurements were performed at 400 nm; the negative peak was obtained by subtracting the absorption spectra of myoglobin (Mb) before and after oxidation. In this method, glucose is added to a mixture of Mb and glucose oxidase. Glucose is oxidized by glucose oxidase and oxygen to gluconate and hydrogen peroxide is generated. The liberated hydrogen peroxide oxidizes the Mb heme (Fe2+) into Fe3+. The higher the glucose concentration added, the more the H2O2 generation, and the more the Mb oxidation (Fe2+ to Fe3+) and, as a result, the higher the absorbance at 400 nm (negative peak, lower absorbance value). The increments of added glucose are monitored by measuring the absorbance decay versus time (0-250 s) at 400 nm. Each glucose concentration has an accompanying unique absorbance value at 250 s. The higher the glucose concentrations, the lower the absorbance at 250 s (measured at 400 nm). The calibration curve for glucose was linear from 0.1 to 3.0 mM; the detection limit was found to be 0.025 mM. There was no interference from major substances present; the only interference was from species that react with H2O2 (ascorbic acid, uric acid, and urea) or that react with glucose (Cu2+ and Fe3+). Standard deviation in the determination was ±0.01 mM for a 1.3 mM glucose solution (n = 10). © Nauka/Interperiodica 2006.