Investigation of Related Impurities in Metadoxine by a Reversed Phase High Performance Liquid Chromatography Technique

A new reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed for the separation and identification of impurities present in metadoxine. Herein, we report that one of the impurities eluted from the metadoxine sample is 4-deoxypyridoxine hydrochloride (4-DPH). In HPLC analysis, the retention time (RT) of 4-DPH was observed to be at 13.5 min in both the reference and metadoxine samples and the relative retention time (RRT) was 1.71. The presence of 4-DPH in a metadoxine sample was also confirmed by a chromatogram obtained by spiking the 4-DPH standard into the sample. Furthermore, the elution and mass of impurity 4-DPH in metadoxine was proven by LC-mass spectroscopy studies. This method highlights the presence of another unknown impurity that has so far not been observed in earlier methods of metadoxine evaluation. Hence, the developed method achieved superior resolution between metadoxine and impurities and thereby facilitates the production of a purer metadoxine drug.