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. GC–MS provided information about structural fragments and molecular mass of the unknown compound. GC–AED was used for confirmation of the occurrence of the individual elements in the structure and to enable calculation of the empirical formula. GC–FT-IR gave valuable information regarding functional groups in the molecule.