1.1 ,This test method covers an analytical scheme using the gas chromatography/mass spectrometry (GC-MS) to determine the hydrocarbon types present in middle distillates 170 ,°,C to 365 ,°,C boiling range, 5 ,% to 95 ,% by volume as determined by Test Method D86, including biodiesel blends with up to 20 ,% by volume of fatty acid methyl ester (FAME). The detailed hydrocarbon composition, total aromatic hydrocarbon and polycyclic aromatic hydrocarbon contents can be determined. The hydrocarbon types include: paraffins, noncondensed cycloparaffins, condensed dicycloparaffins, condensed tricycloparaffins, alkylbenzenes, indans or tetralins, or both, C_nH_2n-10 (indenes, etc.), naphthalenes, C_nH_2n-14 (acenaphthenes, etc.), C_nH_2n-16 (acenaphthylenes, etc.), and tricyclic aromatics. The content of FAME in biodiesel blends can also be determined by GC.