Simultaneous determination of contents and ratio of salt-forming compounds by ¹H qNMR

¹H quantitative nuclear magnetic resonance (¹H qNMR) is an easy, fast analytical method．This method was used to simultaneously determine both contents and ratio of tenofovir alafenamide and fumarate in salt-forming drugs tenofovir alafenamide fumarate (TAF)．¹H NMR sample was prepared using deuterated dimethyl sulfoxide (DMSO-d₆) as solvent．Content of TAF and fumarate were calculated after comparison of peak integrations of sample with internal standard．A linear relationship was found between TAF and fumarate in the range of 0.91-1.24．Content of TAF and fumarate from ¹H qNMR was estimated to be 100.06 % and 10.90 %, respectively．These data were consistent with the mass balance method．This ¹H qNMR method provides accurate and rapid determination of ratio and absolute content of multi-component, salt-forming API．