Investigation of C18 Bonding Chemistry on Novel Hybrid Organic/Inorganic Particles John E. O’Gara, Daniel P. Walsh, Alan R. Pelissey, Bonnie A. Alden, Christina A. Gendreau, Pamela C. Iraneta, and Thomas H. Walter Waters Corporation, 34 Maple Street, Milford, MA 01757-3696 USA Summary: A novel hybrid organic/inorganic particle is compared to a classical high purity silica with respect to C18 silane bonding chemistry. Monofunctional, trifunctional, and embedded polar group C18 silanes were bonded onto both materials under similar reaction conditions. Bonded phase data are presented that characterize the differences and similarities between the two substrates. In addition, chromatographic data are presented for each bonded phase, where capacity factor and peak shape were measured using a set of neutral, polar, and basic test analytes. © Waters Corporation, 1999

!"#$%&'()*+,--.+/+0123+!1%43'&3+5 677"8&1)37*+948:

Hybrid Organic/Inorganic Particle Technology •Hybrid Organic/Inorganic materials contain both organic and inorganic components •The hybrid particles described here were synthesized from Si(OEt)4 and CH3Si(OEt)3: O O Si O CH3Si(OEt)3

+ 2 Si(OEt)4

O CH3 Si O

SiO2(CH3SiO1.5)0.5

O O Si O O

;+Hybrid particles combine: •efficiency and mechanical strength of silica •extended pH range and absence of base tailing of organic polymers

© Waters Corporation, 1999

Characteristics & Surface Structure: Hybrid vs. Silica Supports •Characteristics of Silica and Hybrid Supports: Hybrid* 5.0 173, 174 0.72, 0.69 145, 140 6.9, 6.6 2, 1 8, 3 4, 1

Avg. Particle Diameter, µm 2 Specific Surface Area, m /g 3 Pore Volume, cm /g Avg. Pore Diameter, Å Carbon Content, % w/w Aluminum Content, ppm w/w Iron Content, ppm w/w Sodium Content, ppm w/w

Silica 5.0 325 0.84 92 0.0 0 4 0

* Two Hybrid Lots Used. Second entry used for Embedded Carbamate Bonding.

•Surface Structure of Silica and Hybrid Supports:

CH3

OH

CH3

CH3

OH

© Waters Corporation, 1999

OH

CH3

OH

OH

CH3

OH

CH3

OH

OH

Monofunctional C18 Phase Data Surface Reaction #1: C18 Bonding R

R

OH

OH CH3

∆

OH

+

Cl

OH

Si

C18H37

O

Base Cat., Toluene

OH

CH3

R

R

OH

OH

CH3 Si

C18H37

CH3

Surface Reaction #2: Trimethylsilyl Bonding R

R

OH

CH3

O

Si

OH

CH3

R

∆

C18H37

Base Cat., Toluene

CH3

+

Cl

OH

%C From: Base Particle C18 Ligand TMS Ligand Total %C C18 Surface 2 Conc.µmol/m ) © Waters Corporation, 1999

Si

CH3

OH

CH3

O

Si

OH

CH3

C18H37

R

CH3

O

Hybrid Phase R = CH3 6.9 8.0 0.3 15.2

Silica Phase R = OH 0.0 19.2 0.3 19.5

2.16

3.19

Si(CH3)3

Trifunctional C18 Phase Data Surface Reaction #1: C18 Bonding R

Bidentate Ligand Species Shown

R

OH

OH

Cl OH

+

Cl

OH

Si

C18H37

∆

OH

O

Base Cat., Toluene

Cl

Si

O

C18H37

R

R

OH

OH

Surface Reaction #2: Trimethylsilyl Bonding R

R

OH OH

O O

Si

OH

CH3 + Cl Si

C18H37

CH3

∆ Base Cat., Toluene

CH3

O

R

R

OH

O

%C From: Base Particle C18 Ligand TMS Ligand Total %C C18 Surface 2 Conc.µmol/m ) © Waters Corporation, 1999

OH

O Si

C18H37 Si(CH3)3

Hybrid Phase R = CH3 6.9 8.0 0.8 15.7

Silica Phase R = OH 0.0 18.4 0.8 19.2

2.42

3.51

Embedded Carbamate C18 Phase Data Surface Reaction #1: Embedded Carbamate C18 Bonding R

R

OH

OH

CH3

OH

+ Cl Si

OH

EC C18H37

∆ Base Cat., Toluene

CH3

R OH

EC = -(CH2)3

O OH

CH3 Si

EC C18H37

CH3

R

O O C NH

OH

Surface Reaction #2: Trimethylsilyl Bonding R

R

OH O

CH3 Si

OH R

OH

∆

EC C18H37

Base Cat., Toluene

CH3

CH3 +

O OH

Cl Si CH3

R

CH3

O

OH

%C From: Base Particle C18 Ligand TMS Ligand Total %C C18 Surface 2 Conc.µmol/m ) © Waters Corporation, 1999

CH3 Si

EC C18H37

CH3 Si(CH3)3

Hybrid Phase R = CH3 6.6 8.1 0.1 14.8

Silica Phase R = OH 0.0 21.2 0.3 21.5

1.81

3.14

Monofunctional C18 Chromatograms Hybrid / Monofunctional C18

1

0.25

1. Uracil 2. Propranolol 3. Butyl paraben 4. Dipropyl phthalate 5. Naphthalene 6. Acenaphthene 7. Amitriptyline

2 3

4

AU

5

7

6

T=1.3

0.00 0

10

Time (min)

20

Silica / Monofunctional C18

1 0.25

2 3 4

T = 1.8

AU

5 6

7

0.00 0

10

20 Time (min)

© Waters Corporation, 1999

30

Trifunctional C18 Chromatograms Hybrid / Trifunctional C18

1

0.25

1. Uracil 2. Propranolol 3. Butyl paraben 4. Dipropyl phthalate 5. Naphthalene 6. Acenaphthene 7. Amitriptyline

2 3 AU

4

7

5

6

T = 1.3

0.00 10 Time (min)

0

1

0.15

23

20

Silica / Trifunctional C18 4

T = 2.6 AU

5 6 7

0.00 0

10

20 Time (min)

© Waters Corporation, 1999

30

Embedded Carbamate C18 Chromatograms 1

Hybrid / C18 Carbamate

0.22

2 1. Uracil 2. Propranolol 3. Butyl paraben 4. Dipropyl phthalate 5. Naphthalene 6. Acenaphthene 7. Amitriptyline

T = 1.1

4 3 AU

7

5

6

0.00 10 Time (min)

0

Silica / C18 Carbamate

1

0.15

20

4 2

5

T = 1.5

3

AU

7

6

0.00 0

© Waters Corporation, 1999

10 Time (min)

20

Chromatographic Testing Conditions • 65:35 MeOH/20 mM KH2PO4/K2HPO4, pH 7.00 • Flow Rate: 1.0 mL/min • Temperature: 23.4 ± 0.1 ºC

Analytes 1) Uracil

2) Propranolol, pKa = 9.6

3) Butyl paraben

O NH N H

CH3 CH2 NH2 CH CH3 CH +

O

O CH2

HO

O C O C4H9

OH

4) Dipropyl phthalate

5) Naphthalene

O O CH2CH2CH3 O CH2CH2CH3 O

7) Amitriptyline, pKa = 9.4

HC

© Waters Corporation, 1999

+ CH3 CH2CH2 NH CH3

6) Acenaphthene

Chromatographic Data Ligand & Analyte

Monofunctional C18

Hybrid Phase R = CH3

Silica Phase R = OH

Retention Factor k (USP Tailing)

1. Uracil

-----

-----

2. Propranolol

1.64 (0.8)

2.01 (1.6)

3. Butyl paraben

2.74

2.67

4. Dipropyl phthalate

4.94

5.25

5. Naphthalene

5.22

6.37

6. Acenaphthene

11.90 (1.1)

15.64 (1.0)

7. Amitriptyline

16.54 (1.3)

20.02 (1.8)

Trifunctional C18 1. Uracil

-----

-----

2. Propranolol

1.55 (0.9)

2.28

3. Butyl Paraben

2.63

2.90

4. Dipropyl phthalate

4.81

5.79

5. Naphthalene

5.24

6.72

6. Acenaphthene

11.70 (1.1)

15.99 (1.3)

7. Amitriptyline

15.23 (1.3)

21.56 (2.6)

Embedded Carbamate C18 1. Uracil

-----

-----

2. Propranolol

1.17 (1.0)

1.78 (1.6)

3. Butyl Paraben

2.63

3.27

4. Dipropyl phthalate

3.22

3.67

5. Naphthalene

4.47

6.45

6. Acenaphthene

9.56 (1.1)

15.19 (1.1)

7. Amitriptyline

7.97 (1.1)

10.21 (1.5)

© Waters Corporation, 1999

Conclusions Hybrid vs. Silica Based C18 Bonded Phases • For all three ligands lower C18 surface concentrations were obtained on the Hybrid particles due to their reduced surface silanol concentration • Hybrid C18 Phases showed reduced analyte retentions on all three phases due to the lower surface area of the particle and the lower C18 surface concentrations • Hybrid C18 Phases showed similar efficiency and selectivity as the corresponding Silica phases • Hybrid C18 Phases showed reduced tailing factors for basic analytes, due to their reduced surface silanol concentration Note: XTerra™ packings based on Hybrid Particle Technology are now available from Waters Corporation

© Waters Corporation, 1999