Double-isotope derivative assay of serum iodothyronines: I. Preparation of acetyl derivatives of thyroxine and triiodothyronine

In order to apply the double-isotope derivative method to assay of total serum thyroxine or triiodothyronine, the stable mono- and diacetyl derivatives of these compounds were prepared and examined for use in an assay procedure. The monoacetyl derivatives were found to be best for this purpose since they show greater stability, are more soluble in polar solvents, and are easier to purify by chemical or chromatographic means. Therefore the N-acetyl- 3H derivatives of thyroxine and triiodothyronine were used to develop an assay procedure.