Identification, Isolation, and Characterization of a Novel Degradation Impurity of Busulfan Using Preparative Chromatography, NMR, and LC-MS.

Background: Busulfan is the most effective medication for treating chronic myelogenous or granulocytic leukemia because it has cytotoxic properties that harm or kill hematopoietic cells. It cannot absorb light in the Ultraviolet range due to its structure. Because of this, it is very challenging to quantify using traditional HPLC coupled with UV/Photodiode Array detectors. So, using sodium diethyldithiocarbamate, a derivatization method was developed to quantify related impurities. A significant unknown impurity was identified in derivatized samples of busulfan and a noticeably high percentage level was discovered during routine drug testing.

Objective: We aimed to isolate, and characterize the unknown impurity observed in the samples and to identify its root cause.

Methods: Preparative HPLC was used to isolate the unidentified, derivatized impurity, and 1H NMR, 13C NMR, and MS were used to decipher its structural components.

Results: The spectral characterization data analysis showed that the unknown impurity was related to busulfan. Additionally, it was noted that the impurity developed as a result of the residual buffer used to prepare the derivatizing reagent.

Conclusion: The isolated impurity was found to be same as comparable to that found in busulfan drug substances, according to the results of the characterization tools. An alternative method of reagent preparation was optimized and deemed satisfactory because the buffer used in reagent preparation is the only factor contributing to the formation of impurities.

Highlights: Using cutting-edge analytical characterization tools, it was possible to explain the structural characteristics of an unknown impurity and discover that it was a novel impurity, which undoubtedly contributes to the comprehension of drug substance reaction properties.