Simultaneous assays of glucose, urate, and cholesterol in blood serum by amperometric flow injection analysis

Glucose, uric acid, and cholesterol in serum were assayed simultaneously in a flow injection system by using a 16‐way switching valve and a parallel configuration of three immobilized enzyme reactors. Nafion film‐coated and Nafion/cellulose acetate film‐coated platinum electrodes were used to selectively detect the hydrogen peroxide generated enzymatically in the enzyme reactors, without any interferences from electroactive species such as L‐ascorbate and proteins present in the serum. The signal current was linearly related to the glucose concentration in the range of 5–700 mg/dL, to the urate concentration in the range of 1–80 mg/dL, and to the cholesterol concentration in the range of 5–100 mg/dL. The precision (coefficient of variation) was better than 2.8% for the simultaneous assay of the three species in human control serum. The assay speed was up to 32 samples per hour.