Finding a relationship between the composition and the emulsifying character of asphaltenes through FTICR-MS

In this work, n-heptane insoluble fractions (asphaltenes) from six crude oils were analyzed by means of Fourier-transform ion cyclotron resonance mass spectrometry (FTICR MS) using both positive Atmospheric Pressure Photo Ionization (+) APPI and negative Electro- Spray Ionization (-) ESI in order to understand their water-oil emulsion stabilization capability on a molecular level basis. Through (+) APPI it was possible to obtain an overview of samples composition. By sorting as nitrogen sulfur and oxygen containing compounds, it was possible to compositionally distinguish the asphaltenes. Through (-) ESI, several differences were also observed by grouping the classes as oxygen (NxOy+NxOySz+Oy+OySz) and non oxygen containing classes (Nx+NxSz). The interactions of these two groups of compounds must be considered in order to understand the water-oil emulsion stability. It implies that the cores where nitrogen and sulfur are part may interact via π-π stacking, while the oxygen containing compounds may interact either via hydrogen bonding or via dipole forces with the aromatic aggregates (highly polarizable), forming potentially surface active aggregates. Thus, the rate between these two families of compounds may determine the surfactant character of asphaltenes at the water-oil interface. Bearing this in mind, an emulsion stability coefficient was proposed based on the relative abundances of some families of compounds detected by (-) ESI-FTICR-MS to explain the crude oils’ tendency to form emulsions.

Thermal Desorption Combined with Atmospheric Pressure Photo Ionization for the Analysis of Volatile Compounds and its Possible Applications

We report an approach to study volatile organic compounds based on thermal desorption combined with atmospheric pressure photo ionization. The approach allows the sequential evaporation of different fractions of the sample, which simplifies the mass spectrum. We have applied the developed method for the detection of petroleum in vegetable oil. We have shown that in the negative mode, ions of fatty acids corresponding to vegetable oil dominates, while in the positive mode under relatively low temperature the light fraction of petroleum rapidly evaporates making it easy detectable.