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Functionalised and Reverse Phase Silica Gels
What is the ideal stationary phase?
Organic synthesis has been applied on the development of pharmaceutical compounds, materials for optoelectronic devices and architecturally challenging natural products. The structural diversity of these products is matched only by the breadth in their chemical and physical properties; thus, it is impossible to engineer a single stationary phase that can separate any molecule from its crude synthetic mixture.
Fortunately, surface functionalisation of the polar silanol (Si-OH) groups on silica gel has given rise to a new generation of sorbents for chromatographic, synthetic and scavenging applications. Indeed, silica has been modified to discriminate molecules on the basis of polarity, acidity, hydrophobicity, charged moieties, capacity to form hydrogen bonds, presence of fluorine atoms and the degree of unsaturation. Post-reaction harvesting of your precious compounds has never been more precise!
Our sorbent selection chart (available in windows metafile format) indicates how appropriate stationary phases can be identified based on the properties of your synthetic compound(s).
Synthesis of functionalised silica gels
Functional moieties are grafted on the surface silanol groups of regular silica gel as shown in Figure 1 (1). End-capping of the residual OH groups (2) affords protection against solvent dissolution; thus, end-capped SiliaBond® stationary phases are compatible with polar solvents including methanol.
Figure 1 – Surface functionalisation of regular silica gel, followed by end-capping
SiliaBond® stationary phases for column chromatography
SiliCycle Inc. is a pioneer in the development of functionalised silica gels, gathered under the name SiliaBond®, for use in synthesis and purification. The backbone of all SiliaBond® products is regular stationary phase silica having particle size 40 – 63 µm and pore size 60 Å.
The following tables provide specific information on the SiliaBond® sorbents. All SiliaBond® functionalised sorbents are available in Flash, SPE and 96 well plate format.
Please contact us with enquiries concerning purchases, to order a hard copy of SiliCycle's catalogue or to request a quote. For information on the use of SiliaBond® sorbents as solid-supported reagents and scavengers please follow the appropriate links.
Acids, Bases and Ion Exchangers
| Manufacturer |
SiliCycle® Inc. |
| Availability |
from 10 g to 25 kg |
| Particle Size |
40 - 63 µm (mesh 230 - 400) |
| Pore Size |
60 Å |
| Specific surface area |
500 m2/g |
|
Product Code |
Name |
Structure |
R70030B |
SiliaBond®
Carboxylic Acid |
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- Weak cation exchanger used in ion-exchange chromatography, SPE and HPLC
- Ideal sorbent for the “catch and release” purification of compounds bearing a permanent positive charge (e.g. tetraethylammonium groups)
- Can be used as a scavenger of amines and carbonates, and for the quench of alkoxides and organometallic reagents
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R51230B |
SiliaBond® Propylsulfonic Acid |
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- Strong cation exchanger used in ion-exchange chromatography and solid phase extraction (SPE) of amines (SiliCycle 2008 catalogue, page 68)
- Can be used as a solid-supported acid catalyst or a scavenger of basic molecules
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R60530B |
SiliaBond®
Tosic Acid |
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- Stationary phase for ion-exchange chromatography1,2 and cation exchanger for the “catch and release” purification of amines (SiliCycle 2008 catalogue, page 69)
- Can be used as a solid-supported acid catalyst3 or a scavenger of basic molecules, borohydrates and metal complexes (including those of Ni and Ag)
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R52030B
R52130B |
SiliaBond® Amine
SiliaBond® Amine (nec) |
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- Normal phase sorbent that is retentive towards basic molecules; also available in non-endcapped (nec) format for additional retention of polar or cationic compounds
- Used in the separation of peptides, drugs and metabolites from physiological fluids; purification of sugars; separation of steroids,4 cholesterol and triglycerides;5 and as a weak anion exchanger for the purification of strong acids
- Scavenges electrophiles and metals6 (Zn, Pb, Cu, Co, Rh3+, Ru, Cd, Hg and Cr3+)
- Can be used as a catalyst for Knoevenagel7 and Claisen8 reactions
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R76530B |
SiliaBond® Diethylamine |
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- Stationary phase for ion-exchange chromatography; weak anion exchanger for SPE
- Ideal sorbent for the “catch and release” purification of compounds bearing a permanent negative charge (e.g. salts of sulfonic acids)
- Can be used in organic synthesis as a solid-supported tertiary amine
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R65530B |
SiliaBond®
TBA Chloride (nec) |
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- Stationary phase for ion-exchange chromatography
- Strong anion exchanger for SPE or “catch and release” purification of weak acids
- Useful in the “catch and release” purification of weak acids (due to additional steric hindrance, its selectivity is different to that of SiliaBond® Amine or TMA Chloride)
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R66530B |
SiliaBond®
TMA Chloride (nec) |
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- Stationary phase for ion-exchange chromatography2,9
- Strong anion exchanger for SPE or “catch and release” purification of weak acids
- Since Cl- is bound strongly to the ammonium atom, activation of the exchanger may be required (SiliCycle 2008 catalogue, page 69)
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References
1) J. Chromatogr., 1976, 117, 269
2) J. Chromatogr., 1976, 123, 109
3) J. Org. Chem., 1989, 54, 5437
4) J. Chromatogr., 1987, 392, 464
5) J. Chromatogr., 1988, 434, 395
6) Chem. Commun., 2000, 1145
7) Tetrahedron Lett., 1988, 29, 2261
8) Molecular Diversity, 1998, 3, 161
9) J. Chromatogr., 1976, 119, 25
Reverse Stationary Phases
| Manufacturer |
SiliCycle® Inc. |
| Availability |
from 10 g to 25 kg |
| Particle Size |
40 - 63 µm (mesh 230 - 400) |
| Pore Size |
60 Å |
| Specific surface area |
500 m2/g |
|
Product Code |
Name (SiliaBond®) |
Structure |
R30030B
R30130B
R30230B
R30430B |
C18 (23% C)
C18 (23% C; nec)
C18 (17% C)
C18 (11% C) |
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- SiliaBond® C18 exhibits the highest degree of hydrophobicity and greatest retention of non-polar analytes; although it is often referred to as the traditional matrix for reverse phase chromatography, it is relatively non-selective because it interacts with the widest range of organic molecules
- Also available in non-endcapped format for use in ion-pairing chromatography
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R31030B
R31130B |
C8 (12% C)
C8 (12% C; nec) |
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- SiliaBond® C8 is a reverse phase matrix of moderate degree of hydrophobicity
- Often used instead of SiliaBond® C18 when shorter retention times are required
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R32030B
R32130B |
C4 (8% C)
C4 (8% C; nec) |
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- SiliaBond® C4 exhibits less retention towards non-polar compounds than the SiliaBond® C18 and SiliaBond® C8 sorbents
- Useful in ion-pairing chromatography and for the separation of large biomolecules
- Works best for structures that possess hydrophilic moieties or in cases where a hydrophobic region is buried within a 3D structure
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R33030B |
C1 (5% C) |
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- SiliaBond® C1 exhibits the lowest commercial degree of hydrophobicity
- Useful for the separation of large biomolecules with extensive hydrophobic regions
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R53030B |
Adamantane (16% C) |
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- The polarity of SiliaBond® Adamantane is comparable to that of the C18 sorbent, though additional steric bulk imparts unique separation parameters
- Often referred to as SiliaBond® C12
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R38030B
R38130B |
Cyano (7% C)
Cyano (7% C; nec) |
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- The polarity of SiliaBond® Cyano marks the separation between the polar and non-polar phases, hence it is used in both normal and reverse phase chromatography
- In normal phase chromatography it is the least retentive of the polar sorbents, while in reverse phase chromatography it is the least retentive of the non-polar sorbents
- Useful when dealing with extremes in the polarity scale – SiliaBond® Cyano reduces the retention time and improves peak shapes
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R61530B |
Cyclohexyl (10% C) |
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- SiliaBond® Cyclohexyl is a reverse phase sorbent of medium polarity, often employed in cases where the C8 and C4 counterparts fail to achieve separation
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R34030B
R34130B |
Phenyl (9% C)
Phenyl (9% C; nec) |
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- SiliaBond® Phenyl is a reverse phase sorbent of medium polarity, having retention times that are comparable to those of SiliaBond® C8
- Exhibits unique selectivity for aromatic or fatty acid functionalised molecules
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Normal Stationary Phases
| Manufacturer |
SiliCycle® Inc. |
| Availability |
from 10 g to 25 kg |
| Particle Size |
40 - 63 µm (mesh 230 - 400) |
| Pore Size |
60 Å |
| Specific surface area |
500 m2/g |
|
Product Code |
Name (SiliaBond®) |
Structure |
R38030B
R38130B |
Cyano (7% C)
Cyano (7% C; nec) |
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- The polarity of SiliaBond® Cyano marks the separation between the polar and non-polar phases, hence it is used in both normal and reverse phase chromatography
- In normal phase chromatography it is the least retentive of the polar sorbents, while in reverse phase chromatography it is the least retentive of the non-polar sorbents
- Useful when dealing with extremes in the polarity scale – SiliaBond® Cyano reduces the retention time and improves peak shapes
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R35030B |
Diol (nec) |
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- SiliaBond® Diol is a polar sorbent for normal phase chromatography and aqueous size exclusion chromatography (SEC)
- It can potentially separate structural isomers via formation of Hydrogen bonds
- Since its surface is covered with organic moieties it absorbs less water than regular silica – this is useful when working in the normal phase in the presence of water
- Also used in the solid phase extraction of drugs & metabolites from physiological fluids, and in the scavenging of boronic acids (SiliCycle 2008 catalogue, page 75)
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R23530B |
Silver Nitrate (nec) |
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- Chromatography with silver nitrate is a well known and established method for the separation of non polar compounds that possess centres of unsaturation1-4
- SiliaBond® Silver Nitrate can separate mixtures of unsaturated molecules including alkenes, lipids, steroids & terpenes via interactions between Ag ions and π-bonds
- It is compatible only with anhydrous solvents and cannot be used with DMF/DMSO
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R67030B |
Urea |
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- Used to adsorb cationic surfactants5 and as a polar sorbent for chromatography
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References
1) Tetrahedron, 2001, 57, 425
2) J. Chromatogr. A, 1995, 715, 372
3) J. Chromatogr., 1968, 38, 535
4) Microchem. J., 1965, 9, 227
5) Tenside Surf. Det., 2000, 37, 381
Fluorous Stationary Phases
| Manufacturer |
SiliCycle® Inc. |
| Availability |
from 10 g to 25 kg |
| Particle Size |
40 - 63 µm (mesh 230 - 400) |
| Pore Size |
60 Å |
| Specific surface area |
500 m2/g |
|
Product Code |
Name (SiliaBond®) |
Structure |
R63730B |
Fluorochrom (7% C; nec) |
|
- SiliaBond® Fluorochrom presents the highest level of fluorine available on the market and has a proprietary structure
- It is used primarily in the purification of fluorine-containing molecules
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R67530B |
Pentafluorophenyl (9% C) |
|
- In comparison to other fluorous phases, SiliaBond® Pentafluorophenyl exhibits the highest selectivity for aromatic molecules
- It is used in the separation of molecules that bear F atoms, but is also applicable in the purification of non-fluorous compounds1-3 including Taxol and its derivatives
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R63530B |
Tridecafluoro (10% C) |
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- SiliaBond® Tridecafluoro is used in the chromatography and solid phase extraction of fluorous molecules4; it has a fluorine content between that of SiliaBond® Fluorochrom and SiliaBond® Pentafluorophenyl
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References
1) J. Chromatogr., 1990, 511, 79
2) J. Nat. Prod., 1998, 61, 57
3) J. Chromatogr. B, 1997, 696, 99
4) Org. Lett., 2007, 9, 2285
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