SPE technology is a physical extraction process including liquid phase and solid phase based on the theory of liquid-solid chromatography, which uses selective adsorption, selective elution to enrich, separate and purify the sample. In daily application, SPE cartridge can also be regarded as a simple chromatographic process approximately. SPE often adopts the separation principle by liquid chromatography with selective adsorption and selective elution.
Working Procedures of SPE Cartridge The specific working procedures are as followed: make the liquid sample solution pass through the adsorbent, retain the substance under test, then choose the appropriate strength solvent to flush the impurity, and then use a small amount of solvent to quickly elute the substance under test, so as to achieve the purpose of rapid separation, purification, and concentration. It is also possible to selectively adsorb and interfere with impurities and allow the substance under test flow out, or simultaneously adsorb the substance and impurities under test, and then use a suitable solvent to selectively elute the remaining substance under test.
The capacity of SPE Cartridge The capacity of the SPE cartridge refers to the adsorption capacity of solid-phase extraction cartridge filler. The capacity of solid-phase extraction cartridges with silica gel as matrix is generally 1~5 mg/100mg, that is, the column capacity is 1%~5% of the filler mass. while the capacity of the bonded silica gel ion exchange adsorbent filler is expressed in meq/g, i.e., the capacity per gram of filler is X mg eq. Such filters typically have a capacity of 0.5~1.5 meq/g. Column capacity must be considered when selecting solid phase extraction columns because the sample matrix is usually more complex. Therefore, in considering that the column capacity should be the target compound plus the total amount of impurities that can be adsorbed cannot exceed the column capacity. Otherwise, some of the target compounds may not be adsorbed during the sample loading process, resulting in low recovery.
The Basic Operational Steps of SPE Cartridges According to different retention mechanisms of fillers, the basic operational steps of SPE cartridges are slightly different. 1. The retention of filler is the target compound The basic operation is normally divided into four steps: the first step is activation, which is for removing the impurities in the cartridge and creating a certain solvent environment. The second step is sample loading, which is using a certain solvent to dissolve the sample and moving them to the cartridge to retain the component on it. The third step is drip washing, which is for removing the disrupting chemicals to the maximum extent. The fourth step is elution, which is eluting the analyzed matter with a small volume of solvent and collect it.
2. The retention of filler is the impurity There are basically three steps for the SPE operation: the first step is activation, which is for removing the impurities in the cartridge and creating a certain solvent environment. The second step is sample loading, which is moving the sample into the cartridge. At this time, most parts of the target compound will flow out with the sample base solution. The third step is elution, which is drip washing the component and merging the fluid.