Coupling of LC and FT-IR: Impurity Profiling of Testosterone Undecanoate

Abstract

Reversed-phase liquid chromatography (RP-LC) was coupled to Fourier transform infrared spectrometry (FT-IR) with the use of a spray jet assembly to eliminate the solvent and to deposit the effluent on zinc selenide. The usefulness of the LC/FT-IR system in impurity profiling is demonstrated for the steroid drug testosterone undecanoate (TU). FT-IR transmission spectra of components of the steroid sample separated by LC are identified directly by library search or are interpreted to yield structural information. The study also shows the occasional similarity of the spectra of testosterone enanthate (TE) and testosterone decanoate (TD), two possible impurities of TU. This phenomenon, which can hinder identification, is attributed to the fact that TE and TD can both be either in a crystalline or in an amorphous state.