Supporting Information
Dicationic imidazolium ionic liquid modified silica as a novel
reversed-phase/anion-exchange mixed-mode stationary phase for high
performance liquid chromatography
Min Sun, Juanjuan Feng*, Xiaojiao Wang, Huimin Duan, Leilei Li, Chuannan Luo**
Key Laboratory of Chemical Sensing & Analysis in Universities of Shandong
(University of Jinan), School of Chemistry and Chemical Engineering, University of
Jinan, Jinan 250022, China
*Correspondence:
Dr. Juanjuan Feng, Key Laboratory of Chemical Sensing &
Analysis in Universities of Shandong (University of Jinan), School of Chemistry and
Chemical Engineering, University of Jinan, Jinan 250022, China; E-mail:
chm_fengjuanjuan@ujn.edu.cn (J. Feng); Fax: +86-536-89736065
**Correspondence:
Prof. Chuannan Luo, Key Laboratory of Chemical Sensing &
Analysis in Universities of Shandong (University of Jinan), School of Chemistry and
Chemical Engineering, University of Jinan, Jinan 250022, China; E-mail:
chm_luocn@ujn.edu.cn (C. Luo); Fax: +86-536-89736065
Reagents
Spherical and porous silica particles of 6 µm, with 8 nm average pore diameter and
390 m2 g−1 specific surface area (BET), which were obtained from Lanzhou Institute
of Chemical Physics, Chinese Academy of Sciences (Lanzhou, China), were used as
the support. 3-Mercaptopropyltrimethoxysilane (98%) was obtained from Qufu
Chenguang Fine Chemical Co. (Shandong, China) and purified by vacuum distillation
before
use.
1-Vinylimidazole
(98%),
1,6-dibromohexane
(97%)
and
azobisisobutyronitrile (AIBN) were purchased from Shanghai Jingchun Industry Co.
(Shanghai, China). 1-Vinylimidazole and 1,6-dibromohexane were purified by
vacuum distillation before use. AIBN was purified by recrystallization in ethanol
before use. Toluene was dried by refluxing with sodium for 24 h, and then distilled
before use. Polycyclic aromatic hydrocarbons (PAHs), phenols, anilines, organic
acids, ethanol and methanol used in chromatographic separations were analytical
reagents; inorganic salts including potassium bromate, potassium bromide, potassium
nitrate, potassium iodide and potassium thiocyanate were analytical reagents. Other
organic and inorganic compounds used in experiments were of analytical grade
quality and were used without further purification.
Synthesis of dicationic imidazolium ionic liquid
Synthesis
of
1,1’-(1,6-hexanediyl)bis(1-vinylimidazolium)
bibromide
was
according to the following procedures: 1-vinylimidazole (9.42 g, 0.10 mol) was
dissolved in 40 mL acetone; 1,6-dibromohexane (7.78 g, 0.05 mol) was dissolved in
10 mL acetone and slowly added into the 1-vinylimidazole solution. The mixture was
stirred for 24 h at room temperature. The precipitate was obtained by filtering the
liquid phase. The product was purified by recrystallization in acetone three times. The
structure was confirmed by 1H NMR. 1H NMR (DMSO-d6, 400 MHz; δ, ppm, relative
to TMS): 9.429–9.436 (t, 1H), 8.180–8.189 (t, 1H), 7.891–7.899 (t, 1H), 7.236–7.297
(q, 1H), 5.909–5.954 (q, 1H), 5.408–5.435 (q, 1H), 4.151–4.187 (t, 2H), 1.792–1.826
(t, 2H), 1.265–1.300 (t, 2H).
Characterizations
1
H NMR (UNITY INOVA-400 MHz) was used to confirm the formation of
dicationic imidazolium bromide salt. Surface properties of SilprSH and Sil-DIL were
characterized by a field-emission scanning electron microscope (SEM, SUPRATM55,
Carl Zeiss, AG, Germany) and an energy-dispersive X-ray spectrometer (EDS, Oxford
INCA X-Act, England). The carbon, hydrogen and nitrogen contents of SilprSH and
Sil-DIL were determined by elemental analysis, performed on an Elementar Vario EL
cube (Hanau, Germany). The average concentration of mercaptopropyl groups and IL
groups can be calculated through the carbon content of SilprSH and nitrogen content
of Sil-DIL, respectively. The specific surface area (BET) of silica, SilprSH and
Sil-DIL was investigated on an ASAP 2010 Accelerated Surface Area and
Porosimetry System (Micromeritics, USA).
The calculating formulas are as follows:
(1) Mercaptopropyl groups on SilprSH (µmol m−2) =
(2) IL groups on Sil-DIL (µmol m−2) =
C %  106
= 2.85
36  S1
N % 10 6
= 0.25
56  S 2
(1)
(2)
where C% and N% represent the percentage of carbon and nitrogen, respectively. S1
and S2 are the specific surface area of silica (390 m2 g−1) and SilprSH (330 m2 g−1),
respectively.
Fig. S1. The EDS spectra of SilprSH (a) and Sil-DIL (b).
Fig. S2. The effect of methanol content on retention factors (k) of PAHs (a) and
anilines (b), respectively. Chromatographic conditions: mobile phase: methanol-water,
other conditions are the same as in Fig. 2.
Fig. S3. The effect of KH2PO4 concentration (a) and pH (b) of the mobile phase on
the retention factors (k) of inorganic anions containing bromate, bromide, nitrate,
iodide and thiocyanate. Chromatographic conditions: mobile phase: the solution of
KH2PO4, detection: UV at 200 nm, other conditions are the same as in Fig. 2.
Fig. S4. The chromatogram of the inorganic anions containing bromate (1), bromide
(2), nitrate (3), iodide (4) and thiocyanate (5). Chromatographic conditions: mobile
phase: 150 mmol L-1 KH2PO4 solution (pH=4.6), detection: UV at 200 nm, other
conditions are the same as in Fig. 2.