The Development of an Indirect Enzyme Linked Immunoassay for Abscisic Acid

An indirect method of enzyme-linked-immunosorbent-assay (ELISA) is reported for abscisic acid (ABA), utilising a thyroglobulin-ABA conjugate for coating wells. The assay can use commercially available monoclonal antibodies, is sensitive to as little as 20 picograms ABA per well, and is much more conservative of antibody than direct methods. The most dilute ABA standards did not retain their antigenicity during storage, so ABA standard sets were diluted immediately prior to use. The indirect ELISA was used successfully to estimate ABA concentrations in developing cotyledons of Pisum sativum L., after only little preliminary purification. It was validated for this tissue through the use of gas chromatography-electron capture detection (GC-EC), and capillary GC-selected ion monitoring (GC-MS-SIM) using [(2)H(6)]ABA as an internal standard. Full spectrum GC-mass spectrometry was also used to verify that ABA was present in a sample assayed quantitatively by both ELISA and GC-MS-SIM.