Octadecylamine and serine-derived carbon dots-modified silica gel for reversed phase/hydrophilic interaction liquid chromatography

In order to meet the demand for the separation of complex samples, the development of mixed-mode chromatographic stationary phases has become one of the research priorities in chromatographic separation. In this work, carbon dots, Ser-OCDs, with amino, hydroxyl, carboxyl and alkyl chains were synthesized for the first time and modified on silica gel for RPLC/HILIC mixed-mode chromatography. The stationary phase, Sil-Ser-OCDs, enables the effective separation of hydrophobic and hydrophilic compounds such as alkylbenzenes, polycyclic aromatic hydrocarbons, nucleosides, bases and sulfonamides with better separation selectivity and higher column efficiency compared to classical C18 column. Polycyclic aromatic hydrocarbons, nucleosides, bases and sulfonamides can all be separated in less than 10 min, Moreover, the column efficiency (theoretical plates, N) of butylbenzene was even as high as 124,024 plates m−1. By investigating the effects of column temperature and concentration of buffer salt solution on retention and constructing the van't Hoff equation, hydrogen bonding, π-π conjugation, electrostatic repulsion, partitioning and hydrophobic interactions were found to be the main retention interactions. Sil-Ser-OCDs column was eluted for a long time at pH 3 and 8, and the relative retention remained basically unchanged, which proved that the stability of the column was excellent. This work broadens the variety of chromatographic stationary phase materials, at the same time, indicates that carbon dots have promising applications in mixed-mode chromatography.