Preparation and evaluation of a poly(N-isopropylacrylamide) derived graphene quantum dots based hydrophilic interaction and reversed-phase mixed-mode stationary phase for complex sample analysis

The poly(N-isopropylacrylamide) (NIPAAm) was first polymerized onto the surface of graphene quantum dots (GQDs) functionalized silica as packing materials via reversible addition-fragmentation chain transfer (RAFT) polymerization reaction, which can expand the interaction modes between stationary phase and analytes. A series of characteristic methods were selected to estimate the chemical bonding results of silica, involving Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The prepared column can exhibit reversed-phase and hydrophilic interaction modes, which were demonstrated by the retention of eight kinds of target analytes with different Log P values. The column was then applied to separate banlangen granules and further verified by HPLC tandem time-of-flight mass spectrometry (HPLC/QTOF-MS). In conclusion, Sil-GQDs-PNIPAAm stationary phase improved the analysis range and performance of traditional phases, exhibiting flexible selectivity and application prospect for both hydrophobic and hydrophilic analytes.