A method for determination of xylose utilizing glucose dehydrogenase.

A method is described for xylose determination on the Ciba-Corning 550 Express that utilizes the slower enzymatic action of glucose dehydrogenase (GDH) on D-xylose, after prior removal of glucose. Glucose oxidase is added to serum or urine and incubated for 120 min at 37 degrees C. After incubation, a perchloric acid filtrate of the specimen is added to the GDH reagent in the presence of NAD, the amount of NADH produced being proportional to the amount of xylose present. Absorbances at 340/380 nm are read at 180 s and 600 s after the reagent is added. The standard curve is linear to 7.50 mmol/L and the method showed day-to-day imprecision (CV%) of 2.7 (n = 18), 1.8 (n = 17), and 2.2 (n = 17) at concentrations of 0.62, 1.18, and 2.60 mmol/L, respectively. Recoveries ranged from 99 to 106% for sera and 96 to 100% for urines. Good correlation was obtained when tested against established automated ferricyanide and p-bromoaniline methods.