A Mass Spectrometric Approach for the Direct Analysis and Comparison of Pyrolytic Oils

Abstract

A mass spectrometric method has been developed to analyze the pyrolytic oils and allow the comparison of the chemical composition between samples originating from different sources. In the approach, the liquid oil samples are directly introduced without prior treatment into the chemical ionization source of a tandem mass spectrometer where they are vaporized in a plasma of isobutane using a temperature programmed direct insertion probe. The total ion current, which is composed mostly of parent-molecular ions, is monitored as a function of temperature by repetitively scanning the mass spectrometer. The thermograms obtained, which represent the variation of the molecular weight profile of the sample with temperature, can be used to characterize the oils and easily compare samples generated using different processes or under different experimental conditions. The identification of the individual compounds that constitute the oils and are observed in the molecular weight profiles, can be done by recording the collision activated spectrum (MS/MS) of the ion of interest after it has been mass isolated from the mixture. The approach is rapid, allows the comparison between different pyrolytic oils and is very useful and efficient to characterize these complex mixtures.