Introduction to Solid Phase Extraction(SPE)
Solid phase extraction(SPE) cartridges provide rapid and efficient purification and concentration for pre-analytical stocks. To obtain the best analytical results for these products, you need to pay attention to the following four aspects:
1.Physical and chemical properties of the samples. Characteristics: Influencing factors such as the relative polarity of the analyte relative to the medium, charged functional groups, solubility, molecular weight, etc., determine the binding strength of the analyte to the packed bed.
2. Choose the appropriate retention method: There are two possible methods: First, the analyte is not retained with the packed bed, and the interferent is retained, thus purifying the sample. Second, the analyte remains in the packed bed, while the interfering material does not remain or elutes from the packed bed prior to elution of the sample. When the sample needs to be concentrated, the commonly used method is the second method.
3. Choose the right filler and packed bed size: Different filler types offer different selectivity. The type of packing should maximize the structural differences between the analyte and the interferent in the sample. Selecting fillers with the right selectivity results in the highest recoveries and highest purity samples and extracts. When the size of the packed bed is not optimized, there is usually a problem of low recovery. A packed bed that is too large can result in incomplete elution, while a packed bed that is too small can result in incomplete retention, both of which are lower than expected.
4. Choose the appropriate adjustment, rinse and elution solvent: you must pay attention to the elution intensity of various solvents relative to the filler (see the figure below). The sample conditioning solvent should be a “weak solvent” without elution. It must be used. Buffering also controls the degree of ionization of potentially charged compounds. The rinsing solvent should elute the weakly retained interferent, but the elution intensity should not be too strong to cause the analyte to elute. The strength of the elution solvent should be sufficient to allow the analyte to elute completely under a small volume (1-2 ml). The solubility of a compound in a solvent is an important parameter.