In SPE solid phase extraction products, the eluent is critical to the entire column passing process. Welch materials provides different eluent options for different types of columns, so that customers can better choose suitable products.
When examining the selection of elution solvent, the polarity index of the solvent, the choice of solvent and the elution strength can be started. The larger the polarity index of the solvent, the stronger the solvent ability for polar compounds.
Choice of eluent for reversed-phase solid-phase extraction
In reversed-phase solid-phase extraction, an organic solvent with high solubility of the target compound is generally selected as the elution solution.
According to the structure and functional group of the target compound, and according to the principle of similar compatibility, elution solvents with similar polarities can be selected.
For highly polar SPE columns, a non-polar solvent should be selected for elution.
For weakly nonpolar SPE columns, a weakly nonpolar solvent should be selected for elution.
Selection of eluent for ionic solid phase extraction column
For anion exchange columns:
Anionic compounds can be eluted from the anion exchange column when one of the following conditions is met.
- The pH of the elution solvent is two units higher than the PKa of the anion exchange functional group of the adsorbent
- The pH of the elution solvent is two units lower than the target PKa
- The elution solvent is a buffer with high anionic strength
- The eluent is a highly selective anion
For cation exchange columns:
- The pH of the elution solvent is lower than the PKa of the anion-exchange functional group of the adsorbent (pH=PKa+lg[A-]/[HA] The smaller the PKa, the stronger the acidity, and the larger the PKa, the lower the acidity) by two units
- The pH of the elution solvent is two units higher than the target PKa
- The elution solvent is a buffer with high cation strength
- The eluent is a highly selective cation
Selection of normal phase solid phase extraction column eluent
In the normal phase solid phase extraction column, the selection of the eluent can be considered according to the elution strength of the solvent.
Normal phase silica gel column: methanol, tetrahydrofuran, isopropanol, acetonitrile, isopropanol, etc.