An analytical method which distinguishes between primary, secondary and tertiary amines has been developed. Trifluoroacetic anhydride, with 4-pyrrolidinopyridine as a catalyst, is used to form di- and mono-trifluoroacylated derivatives of primary and secondary aromatic amines, respectively. Tertiary aromatic amines such as quinoline do not react. GC/MS is then used to analyze the derivatized samples. Retention indices and response factors (relative to 4-fluoroaniline) are reported for >50 pure compounds known or expected to be present in fossil fuel base fractions. Also, results from the analysis of base fractions from mildly hydrotreated SRC II coal liquids and petroleum-derived light cycle oils will be reported.