Thermal analysis coupled to ultra-high resolution mass spectrometry enables the detailed temperature resolved chemical characterization of the evolved gas mixtures on the molecular level. It can be used as complementary technique to direct infusion experiments or GC-APCI. Additional information is gained due to higher temperatures feasible with the thermo balance, e.g. pyrolysis fragments can give structural information about larger molecular entities. APCI is a sensitive technique for detecting the polar and medium-polar species released during the heating process. We have shown that TG-APCI FT-MS can be applied for various petroleum samples from different distillation ranges. Ultra-high resolution was needed to differentiate between the chemical species in the complex evolved mixture.