Applications of TiCl3 as a Diagnostic Reagent for the Detection of Nitro- and N‑Oxide-Containing Compounds as Potentially Mutagenic Impurities Using Ultrahigh-Performance Liquid Chromatography Coupled with High-Resolution Mass Spectrometry

The ICH has strict guidelines for limiting the presence of potentially mutagenic impurities (PMIs) in marketed drugs. Therefore, it is important to fully characterize and quantitate all possible PMIs that could arise during the process of synthesizing and developing a drug. Two important and prevalent examples of PMIs are compounds containing N-oxide and nitro functional groups. TiCl3 derivatization is an established method for determining the presence or absence of N-oxide metabolites by reduction to the corresponding amine. In this study, we demonstrate a novel application of TiCl3 reduction combined with high-resolution UHPLC/HRMS to analyze PMIs. The results indicate that a variety of N-oxide- and nitro-containing compounds can be readily characterized by this facile platform method. In addition, we show that this chemical derivatization method can be utilized to enhance the ionization of nitro-containing compounds for LC/MS analysis.