Determination of thyroxine hormone by luminol chemiluminescence

A chemiluminescence (CL) flow system for determination of thyroxine (Thy) is presented. It is based on the catalytic effect of cobalt(II) on the CL reaction between luminol and hydrogen peroxide. The iodinated chemical structure of Thy causes a heavy atom effect. The luminol CL signals show significant quenching by Thy. The calibration graph for Thy is linear for 15–70 (mu)g ml^-1 and the 3(sigma) detection limits are 27 (mu)g ml^-1 for D-Thy and 23 (mu)g ml^-1 for L-Thy.