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-2um column. More than 20 kinds of core shell columns are available in the market. Recently high stability under a basic pH condition has been requested for a core shell reversedphase as well as a fully porous C18. In this study, dense end-capping using a difunctional silyl-reagent was evaluated as an encapsulated type end-capping.

Evaluation of Stability underpH11.5 condition

Present Bonding TechniqueSunniest bonding technique including end-capping

Ratio ofreagents

Carbonloading

Elutiontime

Void incolumn

Relativeplate

Present C18A

7.2%

14 hours

1.3 mm90%

Prototype 501

A:B=2:1

7.3%

34 hours

2.7 mm83%

1 23Synthesis of hexamethyloctadecyltetrasilane (C18 reagent A)
Bonding on silica Reflux in toluene

FinalTMS

SiO
Si
Si
SiOSiSiOOSi

O OOSiSiOOOOSiO OOOSiOSiOOSi

Si
Si O
SiO

SiSiOOOOOOSi O OOSiOSiSiOOOOSi
O
O Si
Si
Si O
OO OH
OSi
OOOSi
Si
Si
OO O
O O
O
Si O
O Si O
SiO
O

Si O
Si

HO

Prototype 502

A:B=1:1

7.1%

34 hours

2.2 mm90%

Prototype 504

A:B=1:2

6.9%

34 hours

4.3 mm62%

Prototype 505

A:C=2:1

7.7%

34 hours

3.0 mm85%

Prototype 507

HOO OO

Novel Silyl-ReagentsStandard Sample
12 3

A:C=1:1

7.9%

34 hours

2.0 mm91%

Prototype 508

A:C=1:2

7.1%

20 hours

3.3 mm82%

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

1 231232132130545456765658101214Column:
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

SiMeMeSi

MeSi

MeSi SiOOMe
OMe OMe OMe

SiOOOClMeMe

MeSiClC18 reagent BO

MeMe
Si OSiOMeSiOOMe

Relative plate of butylbenzene /%MeMeMeMeMeMe Me MeMeSiSiSiOOClC18 reagent C

k6=10.4
N6=31,900

1620

22

Bonding on Silica

Company P C18 Hybrid20

Company A C18 Hybrid00

10,00020,00030,000Elution volume /mL
Mixture ratio ofreagents A and B（2:1）（1:1）(1:2)

Finally endcapping TMS

Reflux in toluene
MeMe

MeSi

ClO

MeMe
Si O

MeSiO

MeMeSi OMe
Me Me
MeSi O Si Si
MeMe
OMe
Si O
OMe
MeSi
OMe OMe OMeOSi OClMixture of reagent A and B

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

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

Prototype 513 C18

TF1=1.31

7Hydrophobicity

Steric Selectivity

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

120.391.60

1.46

Prototype 513 C18, 2.6 μm

0.39

1.59

1.44

Conclusion* The novel C18 with encapsulated type end-capping

showed almost same stability under basic pH conditions tocompare with a hybrid 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 for formic acid.

45321110323232

TF4=1.2023234

TF4=1.37

454ClSiOSiO

MeSiOSiOMeOMe

MeClMeMeSiOMeMe

MeMeSiOSiOSiOMeOSi

Mixture of reagent A and C

SiOO

44SunShell C18

Prototype 513 C18
6781

TF1=1.47

10CH3NCH3Amitriptyline

Company P C18

TF1=3.48

3

Company P C18 Hybrid 5 μm

11

TF1=1.37023

Company A C18
312Company A C18 Hybrid1132233SunShell C18

Prototype 513 C18

4Retention time/minClwww.chromanik.co.jp932

2

TF1=1.46

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Company A C18Company A C18 Hybrid

Acidic Compound

1SiCompany P C18Sample: 1=Uracil, 2=Propranolol, 3= Nortriptyline, 4=Amitriptyline

Finally endcapping TMS

MeMe Me MeMe4

Mobile phase: Acetonitrile/10mM ammonium acetate pH6.8=40/60
Flow rate: 1.0 mL/min, Temp.: 40oC

Reflux in toluene

MeMe9Retention time/min

TF1=5.24

MeMe8Company P C18 Hybrid
TF4=1.89

TF4=1.35

32

1

TF4=2.61

TF4=3.59 42Me7

Basic Compound1

TF1=1.45

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

6Mobile 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(Amylbenzene/Butylbenzene) (Triphenylene/o-Terphenyl)

SunShell C18, 2.6 μm

3Retention time/min

1

Prototype 513

22405

SunShell C18

TF1=1.21

118

Company A C18 Hybrid217

k6=10.1
N6=33,600

80

40Company A C18

TF1=1.31

160

TF1=2.07
27100

Me21Mobile 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

Hydrogen Bonding Capacity

Company P C18 Hybrid 5 μm

1Retention time/min(Caffeine/Phenol)

Stability under pH10.5 and at 60 oC

6Company P C182TF1=1.29

k6=6.8N6=28,800

441

TF1=1.24

k6=9.0N6=30,200

65SunShell C18
21.8 MPa

4721Company P C18 Hybrid 5 μm 9.3 MPa

N6=15,000

Company A C18430.6 MPa
Company A C18 Hybrid424.5 MPa

Metal Chelating Compound

Company P C18
26.1 MPak6=5.4N6=30,800

6,7 k6=4.6

Prototype 513
22.5MPa
276Mobile 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 Acid5610