N-Doped Graphene Oxide Quantum Dots as a Novel Stationary Phase for Capillary Electrochromatography

N-doped graphene quantum dots are carbonaceous smart nanomaterials that play a promising role in analytical chemistry methods, especially as sensors, high-performance liquid chromatography, and gas chromatography stationary phases. However, their application in electromigration methods was limited to the role of absorbing probes for indirect detection or a pseudostationary phase, while their high surface area and functionality present broader opportunities to increase analytical capabilities of the capillary electrochromatography method. The current work explores their ability to form a stationary phase on the inner walls of a fused-silica capillary for the capillary electrochromatography alone and with the following surfactant modification. It reports stability, the working pH range, efficiency, and selectivity of the novel capillary coating obtained with its further surfactant modification using imidazolium ionic liquids. The stationary phase was applied to separate a mixture of neutral and charged analytes, namely aromatic amino acids and steroid hormones, and the coating applicability to real samples was demonstrated with the food supplement analysis.