ELECTROCHEMICAL ENZYME-IMMUNOASSAY USING SEQUENTIAL SATURATION TECHNIQUE IN A 20-MUL CAPILLARY - DIGOXIN AS A MODEL ANALYTE

Capillary enzyme immunoassay with flow-injection analysis for digoxin using the sequential saturation technique has been developed. Glass capillary tubes (10 cm x 0.53 mm i.d.) with immobilized digoxin antibody were used as the immunoassay reactor. The product of enzymatic reaction, 4-aminophenol, was detected amperometrically. The digoxin and the labeled digoxin binding reaction with the immobilized digoxin antibody were completed in 2 and 10 min, respectively. Digoxin was determined in a 20-mu l sample with a detection limit of 10 pg ml(-1) (200 fg or 260 attomoles) and a 3 orders of magnitude range.