Determination of thyroid hormones in pharmaceutical preparations, after derivatization with 9-anthroylnitrile, by high-performance liquid chromatography with fluorescence detection

HPLC with fluorescence detection was used for the determination of low levels of liothyronine sodium and levothyroxine sodium in pharmaceutical preparations after fluorogenic derivatization. 9-Anthroylnitrile in dimethyl sulfoxide was used as a precolumn fluorogenic reagent. The 9-anthroylnitrile derivatives of liothyronine sodium and levothyroxine sodium were separated on a reversed-phase column with acetonitrile–0.02 M sodium dodecylsulfate (pH 3.5 with phosphoric acid) as the eluent. The calibration graphs were linear over a sample concentration range of 0.25–2.5 μg/ml. The detection limits for liothyronine sodium and levothyroxine sodium were 0.2 ng per injection. The proposed method was applied to the determination of thyroid hormones in pharmaceutical preparations.