Rapid and simplified assay for thyroid in pharmaceutical preparations by potentiometric titration

A procedure for the determination of thyroid (thyroid hormone) in pharmaceutical preparations by titration with 1 mM silver nitrate using an ion-selective electrode was developed and evaluated. Samples were combusted according to the USP procedure and analyzed with a minimum of work-up for iodine content. The results obtained by this method were compared with those obtained by the official methods. The recovery of iodide from spiked placebo samples was investigated. The method is applicable to content uniformity analyses as well as to bulk material and to the analysis of organically bound iodide in other pharmaceutical preparations such as sodium levothyroxine tablets. The method is fast, simple, accurate, applicable to automation, and is suitable for routine quality control use.