High-performance liquid chromatographic assay for sodium levothyroxine in tablet formulations: content uniformity applications

Sodium levothyroxine was quantitated in 25-300 micrograms/tablet formulations. The procedure consisted of pulverization of a suitable sample, extraction into acetonitrile-water (40:60, v/v) containing 0.05% o-phosphoric acid, and injection onto a bonded-phase cyanopropyl column; the effluent was monitored by UV detection at 225 nm. Spiked placebo recovery studies demonstrated the linearity of the method over the range of 80-120% of the label claim. Stability studies indicated that no degradation products or excipients interfered with the quantitation of the intact drug. Data demonstrating the accuracy and precision of this assay are presented, and the method was applied to the measurement of single-tablet content uniformity.