Paper spray analysis of crude oil samples: comparing traditional characterization schemes with mass spectrometric outcomes

Crude oil constitutes one of the most complex mixtures in the world and its characterization is challenging yet absolutely essential in any upstream related production context. Traditionally, this has been addressed in fractionation of the oil into saturates, aromatics, resins and asphaltenes; the SARA protocol. We have employed this conventional approach on three crude oils to compare results with mass spectrometric analysis in paper spray ionization mode where the crude does not enter inlets nor does it adhere to interfaces and therefore leaves no memory effects. Thus, it has proven to be an extremely convenient method for oil characterization as crude normally tends to damage analytical equipment by contamination. We have found that the densities of the three crude oils align very well with their SARA analyses in the sense that more saturates (alkanes) correspond to less dense oils. The paper spray ionization mass spectrometry handles the oil that consists of mostly saturates poorly and results in ill-defined peak shapes. A few peaks stand out and are most likely highly polar production compounds that are more easily ionized. On the other hand, the oils with aromatic components result in nice spectra and coupling the paper spray to HRMS clearly reveals the alkyl-aromatics. The combined results show that paper spray provides a fast valuable, non-contaminating route to oil characterization that provides actual structural insights; something that the traditional oil characterization methods can never be brought to do. We also show that production-relevant surfactants are readily characterized with paper spray. Thus, with some development it will facilitate the characterization of residual production chemicals in light crudes and guide the refining process.