Qualitative and quantitative study of nitrogen‐containing compounds in heavy gas oil using comprehensive two‐dimensional gas chromatography with nitrogen phosphorus detection

In this work, a GCxGC-nitrogen-phosphorus detection (NPD) methodology was developed to separate and quantitate nitrogen-containing compounds in Brazilian heavy gas oil. First, the NPD performance was improved in order to achieve best GCxGC performance. The geometry of this detector was also evaluated. The use of an extended jet improved significantly the peak shape. The GCxGC separation was studied using both first and second dimension columns with different internal diameters. The use of a thicker film in both dimensions provided better performance. LODs of 0.16-8.49 pg of individual compounds were achieved. Two different extraction techniques of the neutral and basic nitrogen-containing compounds were also evaluated. The method using ion-exchange resins to separate neutral and basic nitrogen-containing compounds was more efficient than the method using modified silica. As an example, the amounts (microg/g) of each class reported were: indole (2.77), alkyl carbazoles ranging from C(0) to C(6+) (1.467), alkyl benzocarbazoles from C(0) to C(4+) (793), alkyl quinolines (31.2) and alkyl benzoquinolines (21.6) were quantitated.