A chromatographic-infrared method has been used for the separation and characterization of acid compound types in shale oil high-boiling distillates. Acid compound concentrates are separated by high performance liquid chromatography (HPLC) on basic alumina, and the chromatographic subfractions are analyzed by quantitative infrared spectrometry. The analyses are reproducible, and generally 90 percent or more of the material is analyzed. Major acid compound types identified in shale oils are phenols, pyrrolic nitrogen compounds, and amides. 16 references, 7 figures, 4 tables.