Complementary use of gas chromatography-mass spectrometry, gas chromatography-atomic emission detection and nuclear magnetic resonance for identification of pharmaceutically related impurities of unknown structures.

The complementary use of gas chromatography-mass spectrometry (GC-MS), gas chromatography-atomic emission detection (GC-AED) and nuclear magnetic resonance (NMR) spectroscopy is demonstrated by the identification of four major by-products in a sample from an exploratory attempt to synthesise 1.3-dichloro-5-(difluoromethoxy)benzene. GC-MS was used for straightforward identification of the target compound and one of the impurities.

Gas chromatography with mass spectrometric, atomic emission and Fourier transform infrared spectroscopic detection as complementary analytical techniques for the identification of unknown impurities in pharmaceutical analysis.

An example of the complementary use of GC-MS. GC-AED and GC-FT-IR is described for efficient structure elucidation of an unknown impurity in pharmaceutical analysis. None of the analytical techniques could solve the structure of the unknown impurity alone; identification was, however, straightforward by combining the available spectroscopic information.