title: Identification and structural elucidation of an unknown impurity in carbamazepine active pharmaceutical ingredient by liquid chromatography-tandem mass spectrometry and semi-preparative chromatographic isolation.
abstract: Two impurities were detected in the HPLC analysis of crude carbamazepine active pharmaceutical ingredient. One of the impurities of the order of 0.5% was found to be unknown and has not been reported previously. A LC-MS compatible reverse phase isocratic method was developed and tandem mass spectrometry was performed using electrospray ionization source and ion trap mass analyzer. Isolation of unknown impurity was performed by semi-preparative HPLC followed by characterization using nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (FT-IR) and elemental analysis (CHNS) confirmed its structure as tetrabenzo[b,f,b'f']azepino[4',5':4,5]thieno[2,3-d]azepine-3,9-dicarboxamide. A plausible mechanism for the formation of this impurity is proposed.
authors.affiliation: Jubilant Life Sciences Ltd., Analytical Research Department, R&D Centre, C-26, Sector-59, Noida 201301, Uttar Pradesh, India. saji thomas@jubl.com
authors.forename: Saji
authors.initials: S
authors.lastname: Thomas
authors.forename: Chandra S
authors.initials: CS
authors.lastname: Mathela
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Agarwal
authors.forename: Saroj Kumar
authors.initials: SK
authors.lastname: Paul
mesh_terms: D000927:Anticonvulsants / Q000032:analysis*; D002220:Carbamazepine / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D056148:Chromatography, Reverse-Phase; D004340:Drug Contamination; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared; D053719:Tandem Mass Spectrometry; D013678:Technology, Pharmaceutical / Q000379:methods*
chemical_list: D000927:Anticonvulsants; D002220:Carbamazepine