Direct Insertion Probe−Mass Spectrometry: A Useful Tool for Characterization of Asphaltenes

The direct insertion probe−mass spectrometry (DIP−MS) technique, routine analysis for labile and polar samples, is based on the introduction of samples directly into the ionization chamber, followed by their vaporization and eventual ionization by electronic impact. In this work, a new application of the DIP−MS technique to the analysis of asphaltenes, a complex mixture derived from the n-pentane-insoluble fraction of crude oil, is proposed and described. They can be detected without previous separation, as a function of their boiling point and volatility, by programming a suitable probe temperature ramp that behaves as a fractional distillation. Particular attention is devoted to the data processing that allows for a deeper evaluation of the mass spectra according to the vaporization propensity of the single compounds. Differences are evidenced between the samples on the basis of the evolution of their mass spectra.