Capillary enzyme immunoassay with electrochemical detection for determining indole-3-acetic acid in tomato embryos

An amperometric immunoassay for indole-3-acetic acid (IAA) in tomato embryo s: was developed. The antibody against IAA was covalently bound to the chem ically modified inner surface of a 22 mu L silica capillary. The competitiv e binding of methylated IAA and an IAA alkaline phosphatase conjugate for a limited amount of antibody was accomplished in the silica capillary in 20 m in. The enzymatic product p-aminophenol, produced from p-aminophenyl phosph ate, was determined by flow injection analysis with amperometric detection. A detection limit for IAA of 3 pg/mu L was obtained. The average concentra tion of IAA in mature embryos measured by this method is 0.37 +/- 0.03 mu g /g. Although isotope dilution GC-SIM-MS can achieve the same detection limi t, the sample analysis is not feasible in such a complicated matrix and fur ther purification and separation are required.