Effect of interference on amperometric glucose biosensors with cellulose acetate membranes

A new enzyme electrode concept featuring glucose oxidase (GOD) immobilized on fine carbon powder in a fluid state and a cross‐linked GOD enzyme layer has been developed. This enzyme electrode has been tested in vitro at 37°C and has a lifetime of 3 months after which it can be recharged with fresh enzyme. In vitro interference tests carried out on this sensor used with cellulose acetate membranes are described. Sulfur‐free EDTA‐treated cellulose acetate membranes (molecular weight cutoff at 1000) were used, some of which were coated with positively and negatively charged hydrogel layers. The sensors showed a stable and linear response to glucose concentrations >300 mg/dL, in the presence of glucose alone in the phosphate buffer medium and in the presence of interferences. The effects of ascorbic acid, bilirubin, creatinine, L‐cysdne, glycine, uric acid, and urea on the amperometric signal of the sensor were studied. The cellulose acetate membrane coated with the negatively charged hydrogel layer provided good protection for the enzyme electrode, especially in the presence of uric acid, bilirubin, and L‐cystine.