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UBC Theses and Dissertations

HPLC analysis of digoxin and digitoxin : development of methods for dosage form assay and separation of potential impurities and metabolites Desta, Belachew


The objective of this investigation was to develop quantitative isocratic HPLC methods for the analysis of digoxin and digitoxin. An HPLC system that employs a reverse-phase column, UV detection at 220 nm and solvent systems consisting of various proportions of water, methanol, isopropanol and dichlormethane was developed for the separation of digoxin, digitoxin and their potential degradation products and metabolites. HPLC separations of the above compounds by isocratic, solvent switchover and gradient elution modes were carried out in chromatographic times of 27, 16 and 13 minutes, respectively. For purposes of monitoring the separation of dihydro metabolites of digoxin, a 100% fluid recovery system was developed for use in the HPLC analysis of digoxin and its metabolites after fluorogenic post-column derivatization using the air-segmentation process. As an evidence of selectivity, the isocratic HPLC systems were utilized for the separation of a mixture of ten closely related steroids and the isolation of digitoxin from Digitalis purpurea leaf. The isocratic HPLC systems were found to be applicable for the quantitative analysis of digoxin and digitoxin in their respective dosage forms. The HPLC assay of digoxin and digitoxin dosage forms was carried out in less than forty-five minutes. These methods were found to be precise, accurate, sensitive enough for single tablet assay, and capable of simultaneously monitoring the potential degradation products or metabolites of digoxin and digitoxin. A comparison of the assay of digoxin and digitoxin dosage forms by HPLC and USP methods indicated that: (a) the precision and accuracy of both methods were comparable and within acceptable limits; (2) analysis by HPLC can be completed in less than forty-five minutes whereas the USP methods require over four hours; and (3) the HPLC methods have the advantages of higher sensitivity, selectivity and simplicity over the USP methods. The HPLC methods were used for the stability study of digoxin and digitoxin in their respective dosage forms. Lanoxin and digitoxin tablets were found to be stable under all the conditions of storage used in this study. Natigoxin tablets, Lanoxin injection and elixir were found to be subject to varying degrees and patterns of degradation. On the basis of the stability results it was observed that the assortment of pathways that may be involved at different conditions and times of storage'would make it difficult to estimate digoxin shelf-life from data obtained by accelerated aging. From the results of this investigation, it was concluded that the isocratic HPLC methods were suitable for the assay of digoxin and digitoxin dosage forms as well as for purposes of stability testing and simultaneous monitoring of degradation products or metabolites. This abstract represents the true contents of the thesis submitted.

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