A simple HPLC method for the dissolution studies on levothyroxine sodium tablets

Abstract

A simple method for the analysis of dissolution samples of levothyroxine sodium was developed. The procedure consists of filtration of the dissolution sample and direct injection of the sample onto the HPLC column. Although levothyroxine sodium is present at low concentrations (20–50 ng/ml) in the dissolution samples, its detection and quantitation was possible due to the large volumes of injection onto the HPLC column of up to 2 ml and also due to the enhanced sensitivity of up to 6 times by UV monitoring at 225 nm instead of at 254 nm. Large volumes of injection of up to 2 ml are possible due to ‘sample enrichment’ of the amino acid due to the strong adsorption property of the amino acid on the reverse-phase material of the column or precolumn packing material. The usefulness of the procedure was demonstrated by the analysis of various brands and dosage strengths of the above tablet.