Heterogeneous enzyme immunoassay of alpha-fetoprotein in maternal serum by flow-injection amperometric detection of 4-aminophenol.

A sandwich-type heterogeneous enzyme immunoassay with flow-injection analysis for alpha-fetoprotein (AFP) in human serum has been developed. 4-Aminophenol, the product of enzymatic reaction, is detected amperometrically. The interassay CV for this electrochemical enzyme immunoassay was less than 8.2%, with a minimum detection limit for AFP of 0.163 micrograms/L. The calibration curve had a linear range of 0.316-100 micrograms/L. Studies with 48 human maternal serum samples, comparing results by this method with those by a commercial kit, showed a good correlation (r = 0.961). This procedure provides an alternative method for determining low concentrations of AFP in human maternal serum.