Stability Evaluation of Core Shell C18 with
Encapsulated Type End-Cappingwww.chromanik.co.jp

Norikazu Nagae* and Tomoyasu Tsukamoto
ChromaNik Technologies Inc. Namiyoke, Minato-ku, Osaka Japan 552-0001*Corresponding author email: nagae@chromanik.co.jp
A column packed with core shell particles has been widely used on HPLC and UHPLC because it showed not only
excellent column efficiency but also lower back pressure than sub-2 um column. More than 20 kinds of core shellcolumns are available in the market. Recently high stability under a basic pH condition has been requested for a coreshell reversed- phase as well as a fully porous C18. In this study, dense end-capping using a difunctional silyl-reagent wasevaluated as an encapsulated type end-capping.

Present Bonding TechniqueStandard Sample

Evaluation of Stability underpH11.5 condition

Sunniest bonding technique including end-capping
Synthesis of hexamethyloctadecyltetrasilane (C18 reagent A)

Ratio ofreagents

Carbonloading

Elutiontime

Void incolumn12

Relativeplate

2.7 mm83%

Prototype 502

A:B=1:1

7.1%

34 hours

2.2 mm90%

290%

Prototype 504

A:B=1:26.9%

34 hours

4.3 mm62%

Prototype 505

A:C=2:17.7%

34 hours

3.0 mm85%

Prototype 507

A:C=1:17.9%

34 hours

2.0 mm91%

A:C=1:2

7.1%

20 hours

3.3 mm82%

Reflux in toluene

Prototype 513

A:D=1:1

7.8%

50 hours

1.0 mm90%

Durable test condition
Column dimension: 150 x 4.6 mm
Mobile phase:
CH3OH/50mM Sodium phosphatebuffer =10 / 90 (pH11.5)
Flow rate: 1 mL/min
Temperature: 40 ºC

Measurement condition
Mobile phase:
CH3CN/H2O=70/30
Flow rate: 1 mL/min
Temperature: 40 ºCSample: 1 = Butylbenzene

O111Si

OSi

OSi
OO

Si
O

Si O

SiOO OOOOSi

SiOOSi

Si
OOO

Si

Si O

O O

O O Si

Si

OO OH
O
Si
SiOOOOSi
Si
Si
HOO O
OO O
O O
Si
O
Si
OOSi
Si
Si
OOOO
O Si
Si
OOOOO
O

Si O

SiO

OOSi
Si

Si

O

23475k6=6.8
N6=28,800

664546810127k6=10.1
N6=33,6006147

k6=10.4
N6=31,900

5Prototype 513
22.5MPa2k6=9.0
N6=30,200

6

SunShell C1821.8 MPa

3751618202224

Retention time/min

Column:Company P C18, 2.6 μm 150 x 4.6 mm
Company P C18 Hybrid, 5 μm 150 x 4.6 mm
Company A C18, 2.7 μm 150 x 4.6 mm
Company A C18 Hybrid, 2.7 μm 150 x 4.6 mm
SunShell C18, 2.6 μm 150 x 4.6 mm
Prototype 507 C18, 2.7 μm 150 x 4.6 mm

Mobile phase: CH3OH/H2O=75/25
Flow rate: 1.0 mL/min
Temperature: 40 ºC
Sample: 1 = Uracil, 2 = Caffeine, 3 = Phenol, 4 = Butylbenzene
5 = o-Terphenyl, 6 = Amylbenzene, 7 = Triphenylene
5Hydrogen Bonding Capacity(Caffeine/Phenol)

7

Hydrophobicity

Steric Selectivity(Amylbenzene/Butylbenzene) (Triphenylene/o-Terphenyl)

Company A C18 2.6 μm

0.48

1.54

1.20

Company P C18 Hybrid 5 μm

0.40

1.45

1.02

Company A C18, 2.7 μm

0.42

1.57

1.25

Company A C18 Hybrid, 2.7 μm

0.42

1.58

1.19

SunShell C18, 2.6 μm

0.39

1.60

1.46

Prototype 513 C18, 2.6 μm

0.37

1.59

1.44O

Stability under pH10 and at 50 oC
Relative plate of butylbenzene/%

Si234 hours

1.3 mm1Company P C18 Hybrid 5 μm 9.3 MPa

N6=15,000

7.3%

14 hours

SiO

46,7 k6=4.6

A:B=2:1

7.2%

Prototype 508

Si5Company P C1826.1 MPa

k6=5.4N6=30,800

6

Prototype 501

ABonding on silica

Si31 230HO4

Company A C1843 30.6 MPa
2 Company A C18 Hybrid
43 24.5 MPa

Present C18

Final TMS

75100

Novel Silyl-Reagents

Metal Chelating Compound

80

Prototype 507
402

TF1=1.29

MeMe

MeSiClO

MeMe
SiO

MeSiOSiSiSi

MeOOMeOMe OMe OMe

MeMe

MeSiCl

C18 reagent BOMeMeSiOSiOSiOMeOOO

C18 reagent C

5,000

10,00015,00020,00025,000

Finally endcapping TMS

SiClMeMeSiOMeSiO

MeMeSi Si
OMeMeMe
SiMeO
MeOMe
SiOMeOMeSi
OMe OMe OMeO
SiOClSiO

Mixture of reagent A and B

Relative plate of butylbenzene /%MeMe2MeCl

MeMe
SiO

MeMe
SiO

MeSi

MeMe Me MeMeMeOMe
MeMeSi
Si Si
O
MeSi
OMeO
MeMe
SiClOOOMeSiOMeOSiOClSi

Mixture of reagent A and C

415680

1Finally endcapping TMS

3260

327891

TF4=1.20

2323

TF4=1.37

Prototype 513

40Company P C18 Hybrid
200145Company P C18Company P C18 Hybrid
TF4=1.89

TF4=1.35

32

TF4=2.61

TF4=3.59 4

32

1432

14Company A C18

4

Company A C18 Hybrid
4SunShell C18

4

Prototype 513 C18678910Retention time/min

Company A C18 Hybrid

CH3NCH3Mobile phase: Acetonitrile/10mM ammonium acetate pH6.8=40/60
Flow rate: 1.0 mL/min, Temp.: 40oC0Reflux in toluene

3Mobile phase: CH3CN/20mM H3PO4=10/90
Flow rate: 1.0 mL/min, Temperature: 40 ºC
Detection: UV@250nm
Sample: 1 = 8-Quinolinol (Oxine), 2 = Caffeine

1000Mixture ratio ofreagents A and C（2:1）（1:1）(1:2)

Prototype 513 C18

TF1=1.31

Retention time/min

oStability under pH10.5 and at 60 C

Reflux in toluene

Me2

11Me

SunShell C18

TF1=1.21
1

Measurement condition
Column dimension: 50 x 2.1 mm
Mobile phase:
CH3CN/H2O=60/40
Flow rate: 0.2 mL/min
Temperature: 40 ºC
Sample: 1 = Butylbenzene

21

Basic CompoundBonding on Silica

Mixture ratio ofreagents A and B（2:1）（1:1）(1:2)

Company A C18 Hybrid

a: Value cited in company brochure or literature

Durable test condition
Column dimension: 50 x 2.1 mm
Mobile phase:
CH3OH/20mM Sodium borate/
10mM NaOH=30/21/49 (pH10)
Flow rate: 0.4 mL/min
Temperature: 50 ºC

Cl2

TF1=1.310Si

Si

Company A C18

1KinetexCompanyc18
P C18 (pH1.5-10)aMeMe Me MeMeSi2

TF1=2.07

Elution volume/mL
MeCompany P C18 Hybrid 5 μm

1typeUltracore
Company CC18C18 (pH1.5-10)a20

Company P C181PoroshellCompany AHPH-C18
C18 (pH1-12)a Hybrid0Me

TF1=1.24600Me

2

110,000

20,00030,000

Amitriptyline

Sample: 1=Uracil, 2=Propranolol, 3= Nortriptyline, 4=Amitriptyline

Elution volume /mL
Durable test condition
Column dimension: 50 x 2.1 mm
Mobile phase:
CH3OH/10mM Ammonium
bicarbonate (pH 10.5)=30/70
Flow rate: 0.8 mL/min
Temperature: 60 ºC

Acidic Compound

Measurement condition
Column dimension: 50 x 2.1 mm
Mobile phase:
CH3CN/H2O=60/40
Flow rate: 0.2 mL/min
Temperature: 40 ºC
Sample: 1 = Butylbenzene1TF1=1.47

32Company P C18
32

TF1=3.48

Company P C18 Hybrid 5 μm

1132

TF1=1.45

Company A C182

TF1=5.24Conclusion* The novel C18 with encapsulated type end-capping showed almost same stability under basic pH conditions to compare with ahybrid type C18.
* The novel C18 with encapsulated type end-capping showed a good peak shape for a metal chelating compound, acidic
compounds and basic compounds although the other hybrid type C18 showed a poor peak shape for formic acid.
* It was guessed that an amine remained on the silica surface like a by-product of a silyl-reagent leaded a poor peak shape forformic acid.

3Company A C18 Hybrid1123

TF1=1.46
TF1=1.37
0112SunShell C18

3

Prototype 513 C18234Retention time/min

Mobile phase: CH3CN/0.1% H3PO4=2/98
Flow rate: 1.0 mL/min, Temperature: 40 ºC
Detection: UV@210nm
Sample: 1 = Formic acid, 2 = Acetic acid, 3 = Propionic Acid

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