Evaluation of Monodispersion Silica for High Performance
Liquid Chromatography using Van Deemter Plotwww.chromanik.co.jp

HPLC2014 P-470

Norikazu Nagae* and Tomoyasu Tsukamoto
ChromaNik technologies Inc. Namiyoke, Minato-ku, Osaka Japan 552-0001*Corresponding author email: nagae@chromanik.co.jp

Abstract
The feature of a superficially porous (core shell) particle used as a highly efficient material is existence of a core, a thin porous layer and narrow particle size
distribution, which lead to higher efficiency than a totally porous particle. On the other hand, recently a monodispersion silica gel has been presented to be
the almost same particle size distribution as a superficially porous silica and to be higher performance materials than a conventional totally porous silica. In
this study, a monodispersion totally porous silica and a superficially porous silica were compared regarding theoretical plate and Van Deemter plot. As aresult of a plate measurement, a monodispersion silica showed 16% higher theoretical plate than a conventional totally porous silica, while a superficiallyporous silica indicated 47% higher. It was leaded by comparing with Van Deemter plot that only A term of Van Deemter Equation was decreased by effect ofnarrow particle distribution and both B and C terms were reduced by effect of a thickness of porous silica layer. It was elucidated that predominance ofsuperficially porous silica over totally porous silica was leaded by not only low Eddy diffusion due to narrow particle size distribution but also both low
longitudinal diffusion and short mass transfer path due to a thin porous layer.
18

Totally porous silica

16Plate Height, H (um)

HB termA term

C termu
A term : Eddy diffusion(dp is particle diameter)
B term : Longitudinal diffusion (Dm is diffusion coefficient)C term : Mass transfer

Fully porous 3 um

12

Fully proous 1.8 um
HC=0.044x52u

10SunShellCore
Shell2.6
2.7 umum(H=1.08u+6)86

HB=5/u (H=5/u + 4)

024

68

1014

Totally porous 1.8 μm

12(Conventionaldistribution)

50.044x1.82=0.14(Totally porous)

1.00x2.7=2.75(Narrow distribution)(Totally porous)

20024

68

0.044x2.72=0.32

3) C term value is in proportional to a particle size (dp) squared.

0.14

1.00x2.7=2.7

3.5(Core shell)same as 1.8um particle(Core shell)

50.044x2.72=0.32

1.33x2.7=3.6(Conventionaldistribution)

4) B·Dm is assumed to be 5 for a totally porous particle and 3.5 for a core shell particle
by plots in figure 2 and above (1) .

(Totally porous)5) C/Dm of totally porous particle is assumed to be 0.044 by plots in figure 2. The C
term value of 1.8 μm totally porous particle is assumed to be as same as that of 2.7 μm
core shell particle.
1816Totally porous 5 μm

81464

HA=2.4
HC=0.14u
HB=5/u1042002u (mm/sec)

46810

HA=2.7
HC=0.14u
HB=3.5/uu (mm/sec)

Totally porous 2.7 μm

12Totally porous 2.7 μm
Narrow particle size distribution（as same as core shell）

12

Conventional particle size distribution

10H (μm)

10850% up

1015% up
Totally porous 2.7 μm
Totally porous 2.7 μm

864200246810HA=3.6
HC=0.32u
HB=5/u66

HA=2.7
HC=0.32u
HB=5/u42002468narrow particle size distribution

Core shell 2.7 μm
Totally porous 1.8 μm

4810200u (mm/sec)u (mm/sec)

6) The coefficient A is assumed to be 1.33 and 1.00 for a conventional particle and anarrow particle size distribution particle respectively by plots in figure 2 and above (4)and (5).

121414246810U (mm/sec)

Figure 4. Van Deemter PlotTable 2. Property and chromatographic dataPhotoParticle type

Averageparticle size

Particle size
distribution

Porediameter

Efficiencya,Reduced HETPa

Retention
timebCore shell particle

2.78 μm

D90/D10=1.11

9 nm

N=20,500h=1.75

7.8 min

47% up
Monodispersion totally
porous particle

2.81 μm

D90/D10=1.09

10 nm

N=16,000h=2.22

9.6 min

N=12,200h=2.57

9.8 min

16% up
Conventional totally
porous particle

Figure 3. Difference of diffusion in column
Longitudinal direction2) The particle size distribution is narrowed , a coefficient (A) of A term decreases. The
coefficient (A) is also the same value in the case of the particle size distribution is thesame.

(Narrow distribution)

H (μm)

H (μm)

H (µm)

6H (μm)B·Dm

108161) It is assumed by Plots in figure 3 that the ratio of B/Dm value of B term between
core shell and totally porous particles is 7/10.

(C/Dm)·dp2

Core shell 2.7 μm
Narrow particle size distribution

12

Conventional particle size distribution

1014

Some assumptions and the definition of Van Deemter Equation

A·dp

1412Mobile Phase Velocity , u (mm/sec)

Figure 2. Comparison of plate height plots

1.33x1.8=2.4

Totally porous
Conventional particle size distribution
2.7 μm

B term decreases to 70%.

0Table 1. Parameter of each particle

Totally porous
Narrow particle size distribution
2.7 μmCore shell
Narrow particle size distribution
2.7 μmThe ratio of the core for a cross section of the column is around 30%.

Cores block the path ofdiffusion of a solute.

HB=3.5/u (H=3.5/u + 2.7)

2Figure 1. Van Deemter equation

Totally porous
Conventional particle size distribution
1.8 μmCore shell silica

Column: C18, 50 x 4.6 mm
Mobile phase:
Acetonitrile/water=(60/40)
Temperature: 25 oC
Sample : Naphthalene

41. F. D. Antia and C. Horvath, J. Chromatogr., 435 (1988) 1-15.

Particle

A solute diffuses both outside a particle and in a pore.

Fully porous 5 um

14

3.19 μm

D90/D10=1.48

12 nm

a: Stationary phase, C18; column dimension, 100 x 2.1 mm; mobile phase, acetonitrile/water (60/40); flow rate, 0.3 mL/min;column temperature, 25 oC; sample, butylbenzene.
b: Retention time of butylbenzeneConclusion
 A monodispersion totally porous silica showed a narrow
particle size distribution as same as superficially poroussilica.
 A narrow particle size distribution made A term of Van
Deemter Equation decrease 25% to compare with aconventional particle size distribution particle. The
coefficient (A) became from 1.33 to 1.00. As the result,an efficiency increased 15% to 16%.
 Measurement value was almost corresponded thetheoreticallycalculated
value
includingsomeassumptions.
 A core shell silica showed ca. 50% higher theoreticalplates than a conventional totally porous silica because
reducing of both B and C term values of Van Deemter
Equation was added due to a thin porous layer of theparticle.