Polymer Coated Titania for Analytical and Preparative Reversed-Phase Chromatography

Pittcon 2005CLAYTON V. MCNEFF1, BINGWEN YAN1, JOCHEN WINKLER2

1ZirChrom Separations, Inc., 617 Pierce Street, Anoka, MN 553032 Sachtleben, Duisburg, Germany

1-866-STABLE-1www.zirchrom.com

Outline• Properties of Titania

• RP Phase Stationary Phase

• Chromatographic Data

• Selectivity Comparison of Sachtopore-RP, Silica C18, ZirChrom-CARB, and ZirChrom-PBD

• Effect of Lewis Base Mobile Phase Additive on Elution of Basic Compounds

• Chemical and Thermal Stability TestingConclusion - The Sachtopore®-RP shows very similar selectivity to ZirChrom®-PBD and has excellent stability from pH 1-12 and up to 100 oC.

Element Electronic Structures

• Silicon (element 14; 2.3 g/cc; Si4+ ionic radius 0.400 Å)– Ne3s23p2

• Titanium (element 22; 4.5 g/cc; Ti4+ ionic radius 0.605 Å)– Ar3d24s2

• Zirconium (element 40; 6.5 g/cc; Zr4+ ionic radius 0.720 Å)– Kr4d25s2

All have four valence electrons so some chemistry is similar, but presence of d orbitals and very electropositive nature allow Ti and Zr (metals) to form strong electron donor-acceptor complexes (coordination chemistry).

Surface Chemistry of Titania-Based Supports for HPLC

Ti Ti

O

OTi Ti

O

OTi Ti

O

OTi Ti

O

O

O

OO

O

O

O

O HO

O H H2O O H2 H2OO H

Weak Brönsted Base: Ti Ti

O

O

O

H++ ⇔Ti Ti

O

O

O

H

Weak Brönsted Acid: OHTiOOHTiOH 2+⇔+−−

Strong Lewis Acid: Ti

O

O

O

OP

O

OO

O

⇔+ SCX modeTi

O

O

O

O

P

OO O

O -

Titania Crystal FormsAnatase (tetragonal), 300 oCRutile (tetragonal), 600 oCBrookite (orthorhombic), 850 oC.

AnataseRutile

Crystallographic data and pI values of sorbents

SiO2 TiO2 Al2O3 ZrO2Ionisation potential (V) 45.14 (Si4+) 43.27 (Ti4+) 28.45 (Al3+) 34.34 (Zr4+)Coordination number 4 6 6 7Ion radius (A) 0.41 (Si4+) 0.68 (Ti4+) 0.5 (Al3+) 0.8 (Zr4+)Ionisation potential/coordination number (V) 11.29 7.33 4.74 4.83pI of sorbent (pH) 2.2 6.6 8.1 6Porosities of test columns (%) 73 74 79 69

Polyethylene Coated Titania

Ti Ti

O

OTi Ti

O

OTi Ti

O

OTi Ti

O

O

O

OO

O

O

O

O HO

O H H2O O H2 H2OO H

PolyethyleneCH2-CH2[ ]n

22 Non-electrolyte Solutes

Benzene Toluene Ethylbenzene p-xylene Propylbenzene Butylbenzene

Br Cl

Cl

OO

O

CN NO2 NO2Cl

NO2

OBromobenzene p-Dichlorobenzene Anisole Methylbenzoate Naphathalene Acetonphenone

Benzonitrile Nitrobenzene p-Nitrotoluene p-Nitrobenzyl Chloride

O

Benzophenone

OH OH NH H

OOH OH

Cl

Benzylalcohol 3-Phenyl Propanol N-Benzyl Formamide Phenol p-Chlorophenol

Nonpolar

Polar

HB Donor

Selectivity Comparison

LC Conditions: Mobile phase, 40/60 ACN/Water; Flow rate, 1.0 ml/min.; Temperature, 30 oC; Injection volume, 5ul; Detection at 254nm.

Solute

-1.500

-1.000

-0.500

0.000

0.500

1.000

1.500

2.000

benz

yl for

mami

de

benz

yl alc

ohol

phen

ol

3-phe

nyl p

ropan

ol

p-chlo

rophe

nol

aceto

phen

one

benz

onitri

le

nitrob

enze

ne

methy

lbenz

oate

aniso

le

p-chlo

rotolu

ene

p-nitro

benz

yl ch

loride

benz

ophe

none

bromo

benz

ene

naph

thalen

ep-x

ylene

p-dich

lorob

enze

nebe

nzen

etol

uene

ethyl

benz

ene

propy

l ben

zene

butyl

benz

ene

log

(k' S

olut

e/k'

ben

zene

)

ZirChrom-PBDZirChrom-CARBSilica C18Sachtopore®-RP

κ-κ Comparison

LC Conditions: Mobile phase, 40/60 ACN/Water; Flow rate, 1.0 ml/min.; Temperature, 30 oC; Injection volume, 5ul; Detection at 254nm.Reference: Melander, W.; Stoveken, J.; Horvath, C. J. Chromatogr. 1980, 199, 35-56.

R2 = 0.992

R2 = 0.036

R2= 0.911

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

0.00 1.00 2.00 3.00 4.00 5.00k' (Schtopore RP)

k' (P

BD

, CA

RB

, C18

) Sachtopore®-RP vs ZirChrom-PBD

Sachtopore®-RP vs ZirChrom-CARBSachtopore®-RP vs Silica-C18

Chemical Stability

Exposure and Evaluation Conditions: Mobile phase, 15/85 ACN/0.1M Nitric acid, pH 1.0, or 0.01M Tetramethylammoniumhydroxide, pH 12.0; Flow rate, 1.0 ml/min.; Temperature, 30 oC; Injection volume, 5 µl; Detection at 254 nm; Column, 50 mm x 4.6 mm i.d. Sachtopore®-RP .

pH 1.0

0.0

2.0

4.0

6.0

0 1000 2000 3000 4000 5000

Column Volumes

k'

methyl benzoate

anisole

Benzonitrile

toluene

pH 12.0

0.0

2.0

4.0

6.0

0 1000 2000 3000 4000 5000

Column Volumes

k'

toluene

anisole

Benzonitrile

Methyl benzoate

Temperature Stability at 100 oC

Exposure and Evaluation Conditions: Mobile phase, 15/85 ACN/water; Flow rate, 1.0 ml/min.; Temperature, 100 oC with Metalox heater; Injection volume, 5 ml; Detection at 254 nm; Column, 50 mm x 4.6 mm i.d., Sachtopore®-RP .

0.0

1.0

2.0

3.0

0 1000 2000 3000 4000 5000 6000

Column Volumes

k'

toluene

anisole

Benzonitrile

methyl benzoate

Effect of Lewis Base Additive on Separation of Basic Drugs

Chromatographic Conditions: Column 50X4.6 mm Sachtopore®-RP, Mobile phase: 30/70 ACN/20 mM buffer (pH=7). (A) ammonium acetate, (B) ammonium fluoride, (C) ammonium phosphate. flow rate: 1ml/min, temperature: 40 oC. Wavelength: 254 nm. Solutes: (1) lidocaine, (2) quinidine, (3) tryptamine, (4) amitriptyline, and (5) nortriptyline.

min0 2 4 6 8 10 12 14 16 18

1 3

2 4

5

1 3

2

4

4

5

5

2+3

1

A

B

C

Effect of Ionic Strength on Separation of Basic Drugs

min0 2.5 5 7.5 10 12.5 15 17.5 20 22.5

45

2+3

1

1 32

45

1 32 4 5

(A) 10 mM

(B) 15 mM

(C) 20 mM

Chromatographic Conditions: Column 50X4.6 mm Sachtopore®-RP , Mobile phase: 30/70 ACN/phosphate buffer (pH=7). (A) 10 mM, (B) 15 mM, (C) 15 mM. flow rate: 1ml/min, temperature: 40 oC. Wavelength: 254 nm. Solutes: (1) lidocaine, (2) quinidine, (3) tryptamine, (4) amitriptyline, and (5) nortriptyline.

Antihistimines Separation at pH 10

-5,0

0,0

10,0

20,0

30,0

40,0

45,0

0,0 2,0 4,0 6,0 8,010,0 12,0 15,0

mAU

min

1

2

3

4

5

230 nm

NH 3 C

O

4: Diphenylpyraline

ON

C H 3

C H 3

5: Phenyltoloxamine

H

H

C O O H

C O O H

1: maleic acid

N

ON

C H 3

C H 3

C l

2: Carbinoxamine

N

NH 3 C

C H 3C l

3: Chlorphenamine

LC Cconditions: Mobile phase, 74% (50 mM H3PO4 + 5 mM KH2PO4), 26% ACN, pH 10; Flow rate, 1.0 ml/min.; Temperature, Ambient; Injection volume, 20 µl; Detection at 220 nm; Column, Sachtopore®-RP (300 Å, 3 µm, 150x4 mm).

Separation of Basic Cardiac Drugs at pH 10

-1,0

5,0

10,0

15,0

20,0

25,0

33,0

0,0 2,0 4,0 6,0 8,0 10,0 12,0 15,0

mAU

min

1

2

3

4

5

6

7

230 nm

N

N

N

N

N

H 3 C

C H 3H 3 C

1: Trapidil

O

O H

HN C H

3

C H3

H3

C O

2: Metoprolol

N

NN

N

N

N

N

NO H

O H

H O

H O

5: DipyridamoleHN

O C H 3

O

H 3 C O

ON O 2

H 3 C C H 3

3: NifedipineO

ON C H 3

C H 3

I

I

O

C H 3

4: AmiodaroneO

O

N C H 3H 3 C

7: Etafenone

NH 3 C O

H 3 C O

C N

C H 3

H 3 CC H 3

O C H 3

O C H 3

6: Verapamil

LC Cconditions: Mobile phase, 70% (10 mM Borax + 10 mM Soda), 30% ACN, pH 10; Flow rate, 1.0 ml/min.; Temperature, Ambient; Injection volume, 20 µl; Detection at 230 nm; Column, Sachtopore®-RP (300 Å, 3 µm, 150x4 mm).

Semi-Prep Separation of Pentifylline (vasodilator)

-200

0

250

500

750

1000

1250

1500

1800

0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 9,0 10,0

mAU

min

SLB16 #69 A15 UV_VIS-1280 nm

LC Cconditions: Mobile phase, (+ 10 mM Na2B4O7 + 1 mM H3BO3), pH 8.8; Flow rate, 1.0 ml/min.; Temperature, Ambient; Injection volume, 20 µl; Detection at 254 nm; Column, Sachtopore®-RP (300 Å, 3 µm, 150 x 4 mm).

Particle Sizes:3,5,10,20,40,80100 micron1 mm

Pores sizes:60, 100, 300, 500, 1000, 2000 Angstroms

Conclusions

• The Sachtopore®-RP shows similar selectivityto ZirChrom®-PBD (ODS-like for neutrals).

• The Sachtopore®-RP has excellent stabilityfrom pH 1-12 and up to 100 oC.

• The type of Lewis base buffer has a profound effect on selectivity for Sachtopore®-RP.

• Basic (amine) analytes generally undergo RP/CEX mixed-mode retention mechanism onSachtopore®-RP.

Acknowledgments

For more information and web access to the free Buffer Wizard: www.zirchrom.com

®

1-866-STABLE-1www.zirchrom.com

Dr. Jochen Winkler – Sachtleben

Dr. Bingwen Yan - ZirChrom

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