Determination of arylamines and aminopyridines in pharmaceutical products using in-situ derivatization and liquid chromatography–mass spectrometry

Arylamines and aminopyridines form a class of potentially genotoxic impurities (PGIs) that can be present at trace levels in active pharmaceutical ingredients (APIs). A generic method was developed that allows the analysis of a selected set of these solutes at sub-ppm level relative to the drug substance. A highly concentrated solution of the pharmaceutical compound is analyzed by LC–MS using a single quadrupole mass spectrometer in the selected ion monitoring (SIM) mode. Since a number of target compounds show little or no retention in the reversed-phase LC setup, a fast and simple derivatization procedure using hexylchloroformate was applied. The amide derivatives of the PGI result in a higher molecular weight (more specific ion for SIM) and better chromatographic behavior. The methodology, consisting of a dual run on respectively a non-derivatized and a derivatized sample, was validated and applied to a selection of pharmaceutical substances. The method was found to be sufficiently sensitive and robust and is applicable in a QA/QC environment.