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A thermionic detector was evaluated for capillary supercritical fluid chromatography (SFC) of polar nitro-containing polycyclic aromatic compounds (nitro-PAC). Three modes of operation were studied. The best performance was obtained using a nitro-selective mode of detection. A number of nitro-PAC were successfully chromatographed using density programming at 101 C. Capillary column gas chromatography-mass spectrometry was used with state-of-the-art injection techniques and inert columns to analyze diesel exhaust particulate extracts. Polar normal phase HPLC fractions of a heavy-duty diesel exhaust particulate, a National Bureau of Standards (NBS) Standard Reference Material (SRM) 1650, were analyzed by capillary column GC coupled to high resolution mass spectrometry using electron impact (EI) and negative ion chemical ionization (NICI). A total of 80 polycyclic aromatic compounds, belonging to many different chemical classes, were identified. Among them, phenazine and phthalic anhydride were positively identified for the first time in diesel exhaust particulates. In addition, cyclic imides and their alkylated derivatives were tentatively identified for the first time, according to their electron impact mass spectra and exact mass measurements. Other novel polar chemical classes of PAC were evidence by NICI MS using a direct insertion probe.