1. Large scale production of C18 bound porous silica monolith
stationary phase of enhanced separation performance in liquid
chromatography
Synthesis of partially sub- 2µm Ground Silica monolith particles
PEG,Mn20,000+Urea+TMOS+0.01N Acetic acid
(Under ice cold conditions)
Multi steps heating of the mixture at 40C˚ and 120C˚
for 48 h respectively, then drying at 70C˚
Grinding and Calcination at 550C˚ for 72 h
A microscopic view of silica monolith particles
(A) and SEM images of C18-bound silica monolith particles
with different magnification (B, C, D). The scale bars are 2,
20, 10, and 2 μm for A, B, C, and D, respectively.
A
A B
D
BB
C
Experimental
Results & Discusions
Solute A a B b C a
Phenol 17400±400 27000±500 46872±800
Acetophenone 17400±650 26900±600 41503±900
4-Methyl-2-
nitroaniline
19000±700 29700±900 36034 ±1100
Benzene 18300±300 23800±900 42504±800
Toluene 19200±450 24600±600 38675 ±1400
Average 18300 26400 41100
Comparison of N-values for the column of current study with those of the phase of
previous study and commercial C-18.
A. Commercial Lichorsorper RP18
(5 µm).
B. Monolithic silica (previous study,
[1]), C18 bound, 3-5 µm.
C. Monolithic silica (current study),
C18 bound, sub 2 µm.
Current study Previous study [1]
d(0.1)a d(0.5)b d(0.9)c d(0.1)a
d(0.5)b
d(0.9)c
Number
based
0.776 1.214 2.481 0.855 1.348 2.984
Volume
based
1.463 3.233 6.230 2.346 4.185 8.541
Particle size distribution of bare silica monolith
particles
Comparison of BET/BJH data between current
and previous studies of monolith particles
Bare silica
particles
C18-bound
silica particles
A B C A B C
Pore size
(Å) 343 212 296 -- 146 216
Pore volume
(cm3
/g) 1.06 0.83 0.75 -- 0.53 0.63
Surface area
(m2
/g) 136 283 126 -- 161 115
Acknowledgments
This research was supported by the Basic Science Research program through the National Research Foundation of Korea (NRF) funded by the Ministry
of Science, ICT & Future Planning (2012 R1A1A2006066).
References [1]. Lee, S. M.; Zaidi, S. A.; Cheong, W. J. Bull. Korean Chem. Soc.2010, 31, 2943-2948.
[2].Han,K. M. and Cheong, W. J. Bull. Korean Chem. Soc.2008, 29(11), 2281-2283
[3]. Ali, F.; Cheong, W. J.; Al Othman, Z.A.; Al Majid, A. M. J. Chromatogr. A. 2013, 1303, 9-17.
The plots of BJH adsorption pore size
distribution of the bare silica monolith
particles (closed circle) and the C18-bound
silica monolith particles (open circle).
Figure Number based and volume based particle size
distribution of bare silica monolith particles.
Abstract
Conclusion
Partially sub-2-micron porous silica monolith particles of relatively uniform size have
been prepared successfully in large scale by sol gel process followed by grinding and
calcination at 550˚C. These particles were derivatized with a C18 reagent
(chlorodimethyl octadecylsilane) in anhydrous toluene under reflux and end-capped
with a misture of HMDS (hexamethyl disilazane) and TMCS (trimethyl chlorosilane).
The C18 bound phase was packed in a glass-lined stainless steel micro-column (1.0 mm
ID and 300 mm length) with a slurry packer under high pressure. The separation
efficiency as high as 130,000 N/m were achieved for a test mixture containing benzene
and its four derivatives using 60/40 acetonitrile/ water (v/v %) with 0.1% TFA at a flow
rate of 25 µL/min. The separation efficiency of current stationary phase is better than
that of common commercial C-18 phases.
Partially sub-2 µm silica monolith particles have been synthesized in relatively large scale in comparison to those of our previous
studies. Those particles were chemically modified with C-18 alkyl ligand and end-capped.
The resultant stationary phase after packing in a micro column (1.0 mm x 300 mm) showed better separation efficiency compared to
those of our previous studies for the same column dimensions. This study may be regarded as a step advance towards the realization
of future disposable micro-columns.
0 5 10 15 20 25 30 35
min
C
B
A
a. Column dimensions and mobile phase compositions: 1.0 mm ID X 300 mm and 60/40
acetonitrile/water, 0.1% TFA, 214nm.
b. Column dimensions and mobile phase composition: 0.5mm ID X 300mm and 70/30 acetonitrile/water,
0.1% TFA, 214nm.