Simultaneous determination of lactose and glucose in milk using two working enzyme electrodes

Lactose and glucose concentrations were determined simultaneously by using a measuring-cell containing lactose and glucose electrodes made by mixing beta-galactosidase/glucose oxidase and glucose oxidase, respectively, with carbon paste. The glucose electrode responds to glucose alone, while the lactose electrode measures the sum of glucose and lactose. Lactose concentration was calculated by subtracting the glucose concentration from the reading of the lactose electrode. The present dual-working electrode system permitted the determination of lactose and glucose concentrations simultaneously from a single measurement over a linear range of 0.1-2.5 mM. Furthermore, it enabled the determination of lactose concentration in milk in the presence of glucose to be carried out more precisely and with a higher degree of sensitivity than the conventional calorimetric method.