Solid-phase extraction column is a sample preparation method based on chromatographic separation, which is a more widely used and mature sample pretreatment method in recent years. Solid phase extraction includes both the solid phase (a solid adsorbent with a certain functional group) and the liquid phase (sample and solvent). Because SPE sorbents have different functional groups, specific compounds can be adsorbed and retained on the extraction column.
The role of the solid-phase extraction column:
Separation enrichment. Instrumental analysis is performed only after the target is separated from a large number of sample matrices, the sample matrix is removed, and the sample is transformed into a form acceptable to the instrument. Solid-phase extraction is suitable for both the isolation and matrix removal of target compounds in small volume samples, as well as the enrichment of trace target compounds in large volume samples.
Cleanse. One of the main purposes of sample preparation is to remove components or impurities from the sample that interfere with the instrument or analysis.
Convert solvents. There is no emulsification problem in solid-phase extraction, and no direct interaction between organic solvents and aqueous phases occurs.
There are currently two main ways to combine the ** of solid-phase extraction columns:
One is to use a switching valve to connect the column to the column, and let the chromatographic mobile phase transfer all the samples enriched on the column to the column (directly).
The other is the indirect method, which uses the same purification method as offline solid-phase extraction. Once the sample components are collected, 10-20 microliters of the components are injected into the chromatography column using the injector built into the extractor.
Second-order solid-phase extraction. It first uses indirect solid-phase extraction as a stage of sample purification, and the components are modified by solvent and then enriched by direct solid-phase extraction. In this second-order** solid-phase extraction, the majority of the sample interferences are removed first. The extraction columns used are the same as those used for ordinary off-line solid-phase extraction, and can be of type C18, ion exchange, graphitized carbon black, affinity chromatography, etc. The role of second-order solid-phase extraction is enrichment and further purification. Because the sample is already relatively clean, the second-order lifetime is significantly extended.