Comparison of Direct-Deposition Supercritical Fluid and Gas Chromatography/Fourier Transform Infrared Spectra to Condensed-Phase Library Spectra

Abstract

Comparisons of spectra from direct-deposition (DD) capillary gas chromatography (GC) and supercritical fluid chromatography (SFC)/Fourier transform infrared (FT-IR) measurements of two quinones with C₂ symmetry axes and several barbiturates to spectra from condensed-phase libraries of the corresponding compounds are reported. The best spectral search results were obtained when the eluites were deposited on an amorphous substrate, such as ZnSe. A small number of polar, hydrogen-bonding compounds were found to align with each other or with a crystalline substrate. Different crystalline forms of some polymorphic analytes can also yield ambiguous identifications. These effects produce enough differences in the DD GC/FT-IR and SFC/FT-IR spectra to cause occasional incorrect identifications when the spectra are searched against KBr-disk library spectra.