Identification and characterization of process related impurities in chloroquine and hydroxychloroquine by LC/IT/MS, LC/TOF/MS and NMR

The focus of this study is identification and characterization of major unknown impurities in chloroquine (CQ) and hydroxychloroquine (HCQ) bulk drug samples using liquid chromatography/ion trap mass spectrometry (LC/IT/MS) and liquid chromatography/time of flight mass spectrometry (LC/TOF/MS). The newly developed LC/MS method was employed for the analysis of both the drugs. The analysis revealed the presence of two impurities in each of the drugs. The impurities are designated as CQ-I, CQ-II (for chloroquine); HCQ-I and HCQ-II (for hydroxychloroquine). Three of the impurities, CQ-II, HCQ-I and HCQ-II were unknown have not been reported previously. Accurate masses of the impurities were determined by using Q-TOF mass spectrometer and fragmentation behavior was studied by an ion trap mass spectrometer. Based on the spectrometric data and synthetic specifics the structures of CQ-II, HCQ-I and HCQ-II were proposed as 1,4 pentanediamine, N4(7-chloro-4-quinolinyl), N4-chloromethyl, N4-ethylamine; 2-(4-(7-chloroquinolin-4-ylamino) pentylamino) ethanol and [[4-[(7-chloro-4-quinolyl) amino] N-pentyl] N-chloromethyl-N-ethylamino] ethanol respectively. The impurities were isolated by semi-preparative HPLC and structures were confirmed by NMR spectroscopy. The formation and through characterization of known CQ-I impurity is also discussed.