Feasibility of analysis of polar compounds by high performance liquid chromatography with Fourier transform infrared spectroscopic detection

Abstract

High performance liquid chromatographic separations employing on-line flow cell Fourier transform infrared spectroscopic detection were developed for polar compounds including phenols, alcohols, amines and azaarenes. Detection by FTIR gave information concerning hydrogen bonding and solvent effects occurring during the separations in addition to giving structural information about eluted species to aid in identification. Both analytical size and microbore normal phase columns were employed. Such experimental considerations as column overload, injected minimum detectable quantities, the use of analytical vs. microbore columns and flow cell pathlength were examined. The developed HPLC-FTIR systems were applied to the analysis of several coal liquefaction samples for heteroatom content. Confirmatory and additional information concerning the samples were provided by field ionization mass spectrometry, gas chromatography/ mass spectrometry and reversed phase liquid chromatography employing UV detection. An equation relating reversed phase retention times to structural parameters was developed and applied to the analysis of the coal-derived samples. Two process solvents were found to contain primarily alkyl-substituted phenols in addition to azaarenes such as pyridine and quinoline. Some non-distillable coal-derived samples were found to contain azaarenes such as alkyl quinolines. Evidence was also found concerning the presence of hydroxypyridine type compounds and the incorporation of process solvent molecules into the coal structure during liquefaction.