Basic nitrogen compounds (N-compounds), present in middle distillates, can inhibit acidic catalysts used in hydrotreatment processes. A better knowledge of these compounds, especially the environment of the nitrogen atom, may be interesting to improve these processes. Herein, we propose a new promising methodology to couple the extraction of the basic N-compounds by flash chromatography with 2D NMR analysis. The NMR sequence heteronuclear single-quantum correlation (HSQC) allows us to visualize specific C-H correlations and, with the help of the prediction software Advanced Chemistry Development/Laboratory (PS-ACDL), eleven areas of interest have been identified. The representativeness of these areas has been validated with data from literature and with a gas oil (GO) sample analysis. These areas are specific to C-H couples in pyridine, quinoline, isoquinoline, and acridine derivatives and give a detailed fingerprint of basic N-compounds in the GO cut. Moreover, certain areas allow us to describe the close environment of the nitrogen atom and allow, for example, to differentiate isoquinoline from quinoline derivatives.