Application Note P12.0 SPE Extraction using SiliaPrep ... - Silicycle

Application Note P12.0
SPE Extraction using SiliaPrep Carboxylic Acid (WCX)
Si
SiliaPrep Carboxylic Acid (Si-CAA) is primarily used as a weak cation exchanger (WCX) in solid phase extraction
(SPE) and in HPLC. It is the cation exchanger preferred over SiliaPrep Tosic Acid (Si-SCX) or SiliaPrep
Propylsulfonic Acid (Si-SCX-2) when performing “Catch and Release” purification of compounds bearing a
permanent positive charge such as tetraalkylammoniums. Using SCX or SCX-2 in this case could make the
release of the compound of interest difficult not to say irreversible due to the strong interaction between
the two strong ions. SiliaPrep Carboxylic Acid has a pK a of 4.8* and it can also be used in ion exchange chromatography
(IEC).
SiliaPrep
This is a recommended general sample preparation method using the SPE SiliaPrep Carboxylic Acid. You will
find below tips for the choice of solvent that you should use to establish your SPE method development:
EXTRACTION PROCEDURE
SPE Cartridge type:
Analyte structure:
• SiliaPrep Carboxylic Acid (PN: SPE-R70030B-xxx)
Note: Consult SiliCycle catalog for the choice of cartridge volume
and sorbent bed weight possibilities (-xxx).
• Cationic analytes (ie: 4° amine)
Note: Use Strong Cation Exchanger (SiliaPrep Tosic Acid or SiliaPrep
Propylsulfonic Acid) for the extraction of 1°, 2° or 3° amine.
• Sample solution pH adjustment
Tips:
- Solution pH neutral or acid (pH < 7) or
- Two pH units less than analyte pK a
Sample pre-treatment:
Procedure:
- Adjust the sample solution pH using buffered solution to
reach the pH at wich the analyte is all charged (related to the
pK a )
Precautions:
- The salt concentration should not be too high (< 30-50 mM).
- The analyte retention strength is related to the facility of the
counter ion to be replaced by the sorbent counter ion
(SiliaPrep Carboxylic Acid have an hydrogen counter ion).
See the chart below.
info@silicycle.com, www.SiliCycle.com
Tel.: 1 418.874.0054, Toll-free: 1 877.SILICYCLE (North America only)

Si
Sample pre-treatment (con’t):
Counter ion strength
Anion Strenght Cations
OH
F
Acetate
Formate
HPO 4
HCO 3
Cl
Br
Citrate
Tosylate
Weaker
Stronger
Li
H
Na
NH4
K
Mg
Fe
Ca
Cu
Pb
Ag
Ba
SiliaPrep
SPE extraction using SiliaPrep
Carboxylic Acid:
Analytical method :
• Column conditioning step
- Solvent: Methanol, acetonitrile or THF (1-2 column volume)
- Flow rate: 2-4 mL/min
• Column equilibration step
- Solvent: Buffered solution used for the sample preparation
(1 column volume)
- Flow rate: 2-4 mL/min
• Sample loading
- Load directly the prepared sample on the top of the
cartridge
- Flow rate: same rate as the cartridge volume
1 mL SPE Cartridge : 1 mL/min
3 mL SPE Cartridge : 3 mL/min
6 mL SPE Cartridge : 6 mL/min, etc.
• Interferences washing step
- Solvent: Buffured solution (1-2 column volume)
- Flow rate: 1-2 mL/min
Note: For lipophilic interferences washing, add 10-20 % of
methanol or acetonitrile to the buffer.
• Analyte elution step
- Solvent: Strong base in polar organic solvents and/or used
a high concentration of strong counter ion as displacer
(2-4 column volume)
- Flow rate: 1 mL/min
Note: A drying step (under vacuum) can be done before the analyte
elution step.
• Related to the application
*The pK a represents the pH at which the proportion of protonated and deprotonated molecules is equal (1:1).
info@silicycle.com, www.SiliCycle.com
Tel.: 1 418.874.0054, Toll-free: 1 877.SILICYCLE (North America only)