2
DONG ET AL.
Huang et al.9 reported a method of using a chiral
of (R)‐BINOL as the template on the surface of the silica
gel, and the resulting materials were employed as the CSPs
for the chiral separation of racemic BINOL by HPLC. The
influence of the pretreatment temperature, the content of the
template molecule of the SMIP‐CSPs, and the mobile phase
on the separation of the racemic BINOL were systematically
investigated.
dehydroabietic amine as a chiral resolution reagent for
separating racemic BINOL, and explored the influences of
the concentration, reaction time, and dosage on the chiral
separation of BINOL. Lv et al.10 synthesized a chiral selector,
(8S,9R)‐(−)‐N‐benzylcinchonidium chloride, for the chiral
separation of a BINOL racemate. Zhang et al.11 reported CSPs
(Lux Amylose‐2) based on starch derivatives for separating
BINOL and its derivatives by high‐performance liquid
chromatography (HPLC) with a separation factor of 1.32.
Zhan et al.12 employed polysaccharide‐based CSPs (Chiralcel
OD‐H) for chiral separating a BINOL racemate with a separa-
tion factor of 1.46. Ma et al.13 reported the chiral separation of
a BINOL racemate by utilizing an immobilized Chiralpak IC
column with a separation factor of 1.48. Gao and colleagues14
prepared a molecularly imprinted polymer monolith to realize
the chiral separation of binaphthol enantiomers by the method
of capillary electrochromatography. The influence of several
parameters on the column permeability was investigated.
The results showed that baseline separation was obtained with
a resolution of the binaphthol enantiomers that reached 1.8.
Liu et al.15 reported that they observed the chiral separation
of a series of C2‐asymmetric bi‐naphthyl compounds on the
molecularly imprinted polymers using 1,1′‐bi‐2‐naphthol as
template and postulated that the specific hydrogen bonding
interactions seemed to be the key factor to achieve the chiral
separation.
2 | MATERIALS AND METHODS
2.1 | Chemicals and reagents
Silica gel (diameter about 7 μm, pore diameter about 100 nm)
as a support medium for preparation of the surface molecu-
larly imprinted microspheres was purchased from the Japan
Daicel (Tokyo, Japan). BINOL was purchased from Sichuan
Tiancai Fine Chemical (Sichuan, China). EGDMA and acryl-
amide (AM) were purchased from Aladdin (Shanghai, China)
and distilled before use. 2,2‐Azobisisobutyronitrile (AIBN)
was purchased from Tianjin Chemical Reagent Factory
(Tianjin, China) and recrystallized from ethanol before use.
Acetonitrile, chloroform, methanol, and acetone were
purchased from Kermel (Tianjin, China). All chemical
reagents were of analytical or HPLC grade.
2.2 | Equipment
Molecularly imprinted polymers (MIPs) possess a signif-
icant amount of 3D structure cavities which afford it a
specific molecularly recognition ability.16 Molecularly
imprinted technology (MIT) has been widely studied and
applied in molecular recognition and preferential adsorption
due to this high selectivity for the template molecules.
However, this method also had some disadvantages, such as
a slow mass transfer, i.e., time‐consuming, and has a poor
chiral recognition. These are caused by the fact that most of
the imprinted holes in the MIPs are distributed inside the
material and this results in the lower adsorption and is
distributed inside the material and this results in the lower
adsorption and desorption rates during the separation proce-
dure by HPLC. The surface molecularly imprinted technol-
ogy (SMIT)17-19 shows unique advantages in comparison to
the MIT, since most of the imprinted holes are established
on the surface of the support materials; therefore, SMIP can
allow the faster mass transfer, more accessible sites, and a
more effective separation capacity for template molecules
than MIP.
All the chromatography measurements were performed by
the HPLC system (Jasco, Japan), UV (UV‐2070 Plus), chiral
detector (CD‐2095 Plus), pump (PU‐2089 Plus), column
thermostation (CO‐2060 Plus), and intelligent sampler
(AS‐2055 Plus). The morphology of the materials was
measured using a scanning electron microscope (SEM)
(JSM‐6480, Hitachi, Japan).
2.3 | Preparation of SMIP‐CSPs
All the reactions proceeded under N2 atmosphere, as
a simple experimental procedure (Scheme 1), (R)‐BINOL
(0.25 mmol,71.6 mg) as the template molecule, and AM
(0.50 mmol,35.6 mg) as the functional monomer were dis-
solved in acetonitrile (3.0 mL). A 0.8 g silica gel sample
was placed in a thick‐wall eggplant flask. In order to evenly
coat the precursor on the surface of the silica gel, 0.5 mL of
the precursor solution was gradually dropped into the flask.
The flask was then stroked on a cork mat to evenly coat the
precursor on the surface of silica gel, then the coated silica
gel was dried using rotary evaporators. After drying in a
vacuum, EGDMA (1.59 mmol, 280 μL), as the crosslink
agent, solution in acetonitrile/chloroform (1/2, v/v,3 ml), were
mixed with the coated silica gel, followed by the addition of
AIBN (0.049 mmol,8 mg) as the initiator. The flask contain-
ing the complex of BINOL and AM was placed in a water bath
In 1986, Okamoto et al. reported CSPs based on surface‐
coated silica gel particles with chiral selectors,20 and they
have now been widely used in various fields.21-25 Inspired
by this, an MIP coated silica gel (SMIP‐CSP) was prepared
in this study by the in situ copolymerization of AM with
ethylene glycol dimethacrylate (EGDMA) in the presence