Analytical advanced techniques in the molecular-level characterization of Brazilian crude oils

摘要

AbstractThe study focused on the analytical characterization at the molecular level of twenty-five Brazilian oils by applying two analytical advanced techniques: comprehensive bidimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) and negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI(?)-FT-ICR MS), using crude oil samples directly with minimal sample preparation and without any fractionation steps. First, individual compounds present in the classes were detected, identified and semi-quantified using a polar/non-polar column set, which has proved to be more effective in separating compounds. Later, the ESI(?)-FT-ICR MS was optimized for crude oil analysis and characterization of the less volatile polar compounds (oxygen-, nitrogen- and sulfur-containing compounds). Many classes were identified via GC×GC-TOFMS, such asn-alkanes, branched alkanes, alkyl-monocyclic alkanes, alkyl-bicyclic alkanes, saturated polycyclic, alkyl-benzenes, alkyl-naphthalenes, alkyl-phenanthrenes, alkyl-chrysene, alkyl-indanes, alkyl-tetrahydro-naphthalenes, pyrenes, fluorenes and sulfur compounds. The high chromatographic resolution power of GC×GC-TOFMS (for volatile compounds) with the high dynamicm/zrange of FT-ICR MS allowed the chemical characterization of the crude oils with the identification of polar, volatile and nonvolatile compound classes. ESI(?)-FT-ICR MS data suggest that many heteroatomic compounds were detected, withm/zvalues ranging from 200 to 800, resulting in percentages of assignable pe