Flow Injection Analysis of Lactose in Milk Using a Chemically Modified Lactose Electrode

β-Galactosidase and glucose oxidase were immobilized with bovine serum albumin using glutaraldehyde on to a glassy carbon electrode silanized with 3-aminopropyltriethoxysilane. The laboratory-constructed lactose electrode was used for flow injection analysis to determine the lactose content in milk. Electrochemical interference could be detected by a non-enzymatic electrode (W₂) and the current was subtracted from that of the enzymatic electrode (W₁), providing an accurate measurement of the hydrogen peroxide that was enzymatically generated. The peak current was linearly related to the lactose concentration in the range 10^?4~ 1.5 × 10^?3 M (original concentration) and 40 samples/hr could be analyzed. The relative standard deviation for 10 assays was less than 2%. The proposed method was compared with the chloramine T method and the values determined by both methods were in good agreement.