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 pi-pi 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.