Solid Phase Extraction
Solid Phase Extraction (SPE)
Solid Phase Extraction is a fast and efficient sample preparation technique for cleanup or concentration for analysis, HPLC, GC, TLC, UV, IR and an excellent tool for method development.
Main steps of the SPE procedure
1. Conditioning of the adsorbent
Conditioning of the adsorbent is necessary in order to ensure reproducible interaction with the analyte. Conditioning, also called solvation, results in a wetting of the adsorbent and thus produces an environment which is suitable for adsorption of the analyte. Nonpolar adsorbents are usually conditioned with 2 – 3 column volumes of a solvent, which is miscible with water (methanol, THF, -propanol etc.), followed by the solvent in which the analyte is dissolved (pure matrix, e. g. water, buffer). Polar adsorbents are conditioned with nonpolar solvents. After the conditioning step, the adsorbent bed must not run dry to maintain solvation (deconditioning).
2. Sample application (adsorption)
Sample application can be performed with positive or negative pressure with a flow rate of ~3 ml/min. Sample volumes vary from a few milliters up to liters.
3. Washing of the adsorbent
Washing of the adsorbent is usually achieved with a special wash solution; however, in some cases it may not be necessary. If the polarity difference between the wash solution and the eluent is very large, or if both are not miscible, drying of the adsorbent bed after washing is recommended to improve elution and recovery.
Elution with a suitable eluent should not be too fast. The elution speed depends on the column or cartridge dimensions and the quantity of adsorbent (about 1 ml/min).