Solid Phase Extraction is a pretreatment technique commonly used for the extraction of analytes from complex matrices. This solid-liquid extraction method is fast and efficient, and is used to prepare a sample before assaying the analytes that make it up. Indeed, it makes it possible to extract, purify and concentrate the targeted compounds in solution or in suspension in a liquid phase by using the difference in affinity between the analyte and the interferents which will help their separation.
Solid Phase Extraction generally requires four steps.
First, the cartridge is packaged by percolating a certain volume of solvent (or more) in order to activate the support. The cartridge must imperatively remain wet before depositing the sample.
Second, the sample is loaded onto the cartridge and its percolation begins, allowing the separation of analytes and interferents. The targeted compounds adsorb on the cartridge.
Third, the cartridge is washed to remove the interferents by passing a suitable eluent leaving the analytes adsorbed.
Finally, the analytes are collected by elution with an appropriate solvent.
! Note that it is possible that the interferents adsorb on the cartridge allowing the purification of the analytes. The desorption step would therefore not be encountered in this specific case since the analytes will pass directly through the stationary phase without adsorption.
It is useful during the development of the extraction to check each washing and elution step by chromatography to avoid any loss and contamination.
A wide range of cartridges exists and the platform performs Solid Phase Extractions in normal phase, reverse phase, cation exchanger as well as the anion exchanger.