Determination of Serum Thyroxine after Dissociation from Thyroxine-Binding Globulin in Alkaline Solution and Adsorption on Dextran-Coated Charcoal

A competitive protein-binding procedure for determining serum thyroxine is described in which thyroxine is described in which thyroxine is first dissociated from serum thyroxine-binding globulins in an alkaline solution. After binding equilibration, the unbound thyroxine is separated by dextran-coated charcoal. The procedure takes only 100 mul of serum, requires no evaporation, and is sensitive and reproducible. Results by this procedure correlate well with those for a generally accepted method.