An artifactual solution degradant of pregabalin due to adduct formation with acetonitrile catalyzed by alkaline impurities during HPLC sample preparation

Publication date: 25 October 2019Source: Journal of Pharmaceutical and Biomedical Analysis, Volume 175Author(s): Jinsheng Lin, Xiaofei Liu, Jing Wang, Dan Li, Wenquan Zhu, Wenbin Chen, Xianhua Zhang, Qiangming Li, Min LiAbstractDuring the HPLC related substances testing of pregabalin API, an unknown peak was observed at a level exceeding the identification threshold. Preliminary investigation revealed that this impurity is not a process impurity but rather an artifactual solution degradant or “ghost peak” during the HPLC analysis. By using a strategy that combines LC-PDA/UV-MSn with mechanism-based stress studies, the unknown peak was rapidly identified as a covalent adduct formed between pregabalin and acetonitrile (the latter is a component of the HPLC sample diluent), which is structurally an ethylamidine derivative of pregabalin. It appeared that the formation of this solution degradant was catalyzed by alkaline impurities during the sample preparation. This plausible mechanism was verified by a mechanism-based forced degradation study, in which a base was added into the sample diluent and consequently, the pregabalin-acetonitrile adduct was produced extremely efficiently at a level of ˜92%. Subsequently, the structure of the solution degradant was confirmed as an ethylamidine derivative of pregabalin through characterization by 1D and 2D NMR; the formation of the ethylamidine moiety is apparently via a nucleophilic attack on the cyano group of acetonitrile by the am...
Source: Journal of Pharmaceutical and Biomedical Analysis - Category: Drugs & Pharmacology Source Type: research