Development of heart-cutting multidimensional gas chromatography coupled to time of flight mass spectrometry for silicon speciation at trace levels in gasoline samples

To improve the understanding of hydrotreatment (HDT) catalyst poisoning by silicon species, these molecules must be characterized in petroleum products using powerful analytical systems. Heart-cutting gas chromatography coupled to time of flight mass spectrometry (GC–GC/TOFMS) method equipped with a Deans switch (DS) system was developed for the direct characterization of target silicon compounds at trace level (μg kg−1) in gasoline samples. This method was performed to identify silicon compounds never characterized before. After the selection of the second dimension column using GC–GC–FID, GC–GC/TOFMS was performed. The calibration curves obtained by the GC–GC/TOFMS method were linear up to 1000 μg kg−1. Limits of detection (LOD) were ranging from 5 to 33 μg kg−1 in spiked gasoline. The method provided sufficient selectivity and sensitivity to characterize known silicon compounds thanks to their specific ions and their retention times. The analysis of a naphtha sample by GC–GC/TOFMS has shown the presence of cyclic siloxanes (Dn) as major compounds of PDMS thermal degradation with the occurrence of linear siloxanes, especially hexamethyldisiloxane (L2), which was never characterized in petroleum products but already known as severe poison for catalyst.

► A GC–GC/TOFMS was developed for the characterization of silicon compounds.
► Silicon species, potentially poisons, were identified at trace levels.
► A real advance for silicon speciation to understand catalyst poisoning.