Factors affecting accuracy and time requirements of a glucose oxidase-peroxidase assay for determination of glucose.

Accurate and rapid assays for glucose are desirable for analysis of glucose and starch in food and feedstuffs. An established colorimetric glucose oxidase-peroxidase method for glucose was modified to reduce analysis time and evaluated for factors that affected accuracy. Time required to perform the assay was reduced by approximately 40% by decreasing incubation time and removing steps that do not affect absorbance. Although linear regressions of absorbance and glucose concentrations of standard solutions exceeded R2 of 0.9997, evaluation of sum of squared residuals, root mean squared error, and significance of the quadratic term indicated that the curves were approximately quadratic in form. Inadequate equilibration of glucose anomers did not appear to be the issue. Historic data suggest that the standard curve is inherently nonlinear. Quadratic curves predicted standard solution glucose concentrations more accurately than did linear forms; overestimations at the midpoint of the curve averaged 0.04, 0.48, and 0.92% for quadratic and linear equations calculated from 5 standard solutions and a linear equation calculated from the 0 and most concentrated standard solution, respectively. A hydrophilic antioxidant at levels no greater than 10 micromol ascorbic acid/0.10 g air-dried sample did not affect absorbance values.