The Interaction in SPE Cartridge
When using the SPE cartridge, many kinds of interaction can be produced during the whole process.
1. Non-Polar Interaction
The interaction between nonpolar functional group and nonpolar adsorbent on the target chemical compound is called non-polar interaction. This kind of interaction can be better reflected in the polar solvent and especially in water, so it is also called lyophobic interaction. The typical example is the interaction between phthalic acid esters and C18 in the water.
2. Polar Interaction
The interaction between polar functional groups on the target chemical compound and the adsorbent is called polar interaction. This kind of interaction can be well reflected in the weak polar solvent or nonpolar solvent.
3. Ion Interaction
The interaction between ion functional group on the ion target chemical compound and the functional group with the opposite charges on the adsorbent is called ion interaction.
4. Secondary Interaction
As for the reversed silica gel bonding adsorbent, the silicon hydroxyl which remains on the surface of particles can have polar interaction with the polar chemical compound. Also, part of the silicon hydroxyl can have ion interaction with the alkali compound after dissociation. Relate to the non-polar interaction, these interactions are on the sidelines, so we call them secondary interaction.
Solid Phase Extraction Cartridge Activated Solvent
Different modes of solid phase extraction cartridge activation use different solvents:
Weak polar or non-polar adsorbent for reversed phase solid phase extraction, usually rinsed with a water-soluble organic solvent such as methanol and then rinsed with water or a buffer solution. It can also be rinsed with a strong solvent before the methanol is rinsed to eliminate impurities adsorbed on the adsorbent and its interference with the target compound.
The polar adsorbent used in normal-phase solid-phase extraction is usually rinsed with the organic solvent (sample matrix) in which the target compound is located.
The adsorbent used in ion exchange solid phase extraction can be rinsed with a sample solvent when used in a sample in a non-polar organic solvent.
When used in a sample in a polar solvent, it can be drenched with a water-soluble organic solvent. After washing, the appropriate pH is used, and the aqueous solution can be rinsed with an aqueous solution of a certain organic solvent and salt.
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