The general procedure for solid phase extraction is as follows:
1. Activating the adsorbent: Rinse the solid phase extraction cartridge with an appropriate solvent before extracting the sample to keep the adsorbent wet, which can adsorb target compounds or interfering compounds. Different modes of solid phase extraction cartridge activation use different solvents:
(1) Weak polar or non-polar adsorbents used in reversed-phase solid-phase extraction are usually rinsed with a water-soluble organic solvent, such as methanol, and then rinsed with water or a buffer solution. It is also possible to rinse with a strong solvent (such as hexane) before rinsing with methanol to eliminate impurities adsorbed on the adsorbent and their interference with the target compound.
(2) The polar adsorbent used in normal-phase solid-phase extraction is usually eluted with the organic solvent (sample matrix) where the target compound is located.
(3) The adsorbent used in ion-exchange solid phase extraction can be washed with the sample solvent when it is used for samples in non-polar organic solvents; when it is used for samples in polar solvents, it can be washed with water-soluble organic solvents After washing, rinse with an aqueous solution of appropriate pH value and containing certain organic solvents and salts.
In order to keep the sorbent in the SPE cartridge wet after activation and before sample addition, about 1 ml of the solvent for activation should be kept on the sorbent after activation.
2. Sample loading: Pour the liquid or dissolved solid sample into the activated solid phase extraction cartridge, and then use vacuum, pressure or centrifugation to make the sample enter the adsorbent.
3. Washing and elution: After the sample enters the adsorbent and the target compound is adsorbed, the weakly retained interfering compound can be washed away with a weaker solvent, and then the target compound can be eluted with a stronger solvent and collected. . Rinse and Elution As previously described, the eluent or eluent can be passed through the adsorbent by means of vacuum, pressure or centrifugation.
If the adsorbent is selected to have weak or no adsorption to the target compound and strong adsorption to the interfering compound, the target compound can also be rinsed and collected first, while the interfering compound is retained (adsorption). ) on the adsorbent, the two are separated. In most cases, the target compound is retained on the adsorbent, and finally eluted with a strong solvent, which is more conducive to the purification of the sample.