A method is described for characterization of size-resolved particles including the nanoparticles fraction with a diameter of 29-58 nm in roadside atmosphere.The method is based on thermal desorption (TD) of a sample followed by comprehensive two-dimensional gas chromatography (GC × GC) with novel detection capabilities, including high resolution time-of-flight mass spectrometry (HRTOF-MS) and simultaneous detection with a nitrogen phosphorous detector (NPD) and a quadrupole mass spectrometer (qMS).Increased selectivity with the GC × GC-HRTOF-MS allows a group type separation of a selected chemical class, e.g.oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs), using mass chromatography with a 0.05 Da wide window in the complex sample matrix.Also, exact mass measurements provide candidate elemental compositions as well as NIST library search results for tentative identifications of 50 compounds.