The determination of liothyronine and thyroxine in thyroid preparations

Abstract
A procedure is described for determining liothyronine and thyroxine in thyroid substances. This involves stepwise hydrolysis with barium hydroxide, extraction of combined iodinated amino-acids by n-butanol, separation and isolation of liothyronine and thyroxine by paper chromatography, subsequent ignition of their separated chromatograms by oxygen flask combustion and estimation of evolved iodine in benzene solution by spectrophotometric absorption at 295 mμ. The method is suitable for routine quality control of thyroid products.