Octadecylimidazolium ionic liquids-functionalized carbon dots and their precursor co-immobilized silica as hydrophobic chromatographic stationary phase with enhanced shape selectivity

In this work, 1-vinyl-3-octadecylimidazolium bromide ionic liquids ([C 18 VIm]Br) and their derived carbon dots (ImC 18 CDs) were prepared, [C 18 VIm]Br and ImC 18 CDs were grafted on the silica to obtain Sil-ImC 18 and Sil-ImC 18 CDs, respectively, and they were also co-grafted on silica which named Sil-ImC 18 /CDs. Compared with Sil-ImC 18 and Sil-ImC 18 CDs columns, Sil-ImC 18 /CDs column exhibited enhanced selectivity for separation of tetracyclic/tricyclic polycyclic aromatic hydrocarbon (PAH) isomers, and butylbenzene isomers in reversed-phase liquid chromatography, which may be due to the synergistic effect between ImC 18 CDs and [C 18 VIm]Br, the π-π interaction between imidazolium and analytes, etc. Meanwhile, the retention behavior of Sil-ImC 18 /CDs was further evaluated and compared with the commercial C 18 column using different classes of analytes, including standard test mixtures of Tanaka, Engelhardt, SRM869b, SRM870. The results demonstrated that co-grafted column exhibited superior separation performance. And this column was applied to determine the contents of calycosin-7-glucoside, ononin , calycosin and formononetin in the extract of Radix Astragali, which were found that the concentration was 0.25 mg mL −1 , 0.15 mg mL −1 , 0.13 mg mL −1 and 0.30 mg mL −1 , respectively.