Flow-injection- and sequential-injection immunoassay for triiodothyronine using acridinium ester chemiluminescence detection Original Research Article

This study describes the development of a competitive immunoassay for triiodothyronine (T3) comparing a flow-injection- and a modified sequential-injection technique. The detection is carried out by chemiluminescence using an acridinium ester as a label for the antigen. Both immunoreaction and chemiluminescence reaction take place in a flow-cell packed with immobilized antibodies. The sequential-injection technique was applied with and without flow-reversal. The detection limits for all types of assays were in the low fmol range (0.4 ng ml−1), whereby, with the flow-reversal mode, a slight improvement of the detection limit was observed. The relative standard deviation for the flow-injection- and the sequential-injection mode were 4.4–7.9% and 2.2–5.5%, respectively. The total assay time was 7–9 min, depending on the mode.