The SPE cartridge is a sample pretreatment device developed from the chromatography cartridge for extraction, separation, and concentration. It is mainly used in sample pretreatment of target compounds in various food, agricultural and livestock products, environmental samples, and biological samples.
Reuse of SPE cartridge It is mainly used in sample pretreatment of target compounds in various food, agricultural and livestock products, environmental samples and biological samples.
Before choosing, you must first understand this knowledge:
1. Selection of cartridge pressure for solid phase extraction The cartridge pressure can be divided into a reduced pressure, pressurized, and normal pressure. The reduced pressure cartridge can reduce the amount of stationary phase silica gel used. The disadvantages are: a large amount of air passing through the silica gel will volatilize the solvent (sometimes there is condensation outside the SPE cartridge); it may cause the loss of easily decomposable substances; the use of air pumps will extend the extraction time through the cartridge and increase noise. SPE cartridge pressurization is a better way to use, especially suitable for the separation of easily decomposable samples.
The pressurization can increase the flow rate of the eluent and reduce the product collection time. The disadvantages are: reduce the number of trays in the cartridge; if the pressure is too high, the solvent flow rate is too fast and the separation effect is reduced, so cartridge pressurization is used in the separation of ordinary organic compounds. More applicable. When other conditions are the same, the atmospheric cartridge has high efficiency but time-consuming, such as the separation of natural compounds.
Size selection of SPE cartridge The ideal type of SPE cartridge should be larger in inner diameter and length. As the cartridge length increases, the corresponding number of trays is higher, the cartridge inner diameter is larger, and the origin of the sample after injection is smaller (reflected on the cartridge, the sample layer is thinner), and the resolution becomes larger. The disadvantage is that the use of an extraction cartridge with a larger inner diameter requires more silica gel and solvent, which increases the cost of the experiment.
The ratio of diameter to length of commonly used extraction cartridges is generally 1:5 to 1:10, and the amount of stationary phase silica gel is 30 to 40 times that of the sample. The shorter the extraction cartridge has a smaller inner diameter, the corresponding number of plates is lower, and the origin of the sample after injection is larger (reflected on the cartridge, the sample layer is thicker, and the sample layer is less than 0.5 cm in the SPE cartridge. It is easier to separate completely), and the degree of separation becomes smaller.
If the separation of the required components and impurities is large (the required component separation R>1), use an extraction cartridge with less silica gel and a smaller inner diameter (for example, use a 2cm×20cm cartridge for a 200 mg sample); if The required group and impurity separation are small (required component separation R<1), the inner diameter of the extraction cartridge can be enlarged, and the eluent with smaller polarity can also be used.
Principle and use The solid phase extractor uses a solid adsorbent to adsorb the target compound in the liquid sample, separate it from the sample matrix and interfering compounds, and then use the eluent for elution or heat desorption to achieve the purpose of separating and enriching the target compound. Compared with liquid-liquid extraction, solid-phase extraction has many advantages: solid-phase extraction does not require a large number of immiscible solvents, and no emulsification occurs during the treatment process.
It uses a highly selective adsorbent (stationary phase), It can significantly reduce the amount of solvent, simplify the sample processing process, and reduce the cost. Generally speaking, the time required for solid-phase extraction is 1/2 of liquid-liquid extraction, and the cost is 1/5 of liquid-liquid extraction. The disadvantage is that the recovery rate and precision of the target compound are lower than that of liquid-liquid extraction. The mode and principle of solid phase extraction. Solid phase extraction is essentially a liquid chromatography separation.
Its main separation mode is the same as that of liquid chromatography and can be divided into normal phase (the polarity of the adsorbent is greater than the polarity of the eluent), reverse phase (the polarity of the adsorbent is less than that of the eluent), ion exchange and adsorption. The adsorbent used in solid phase extraction is also the same as the stationary phase commonly used in liquid chromatography but differs in particle size. The adsorbents used in normal-phase solid phase extraction are all polar, used to extract (retain) polar substances.
How the target compound remains on the adsorbent during normal phase extraction depends on the interaction between the polar functional groups of the target compound and the polar functional groups on the surface of the adsorbent, including hydrogen bonds, π-π bond interactions, and dipoles. -Dipole interaction and dipole-induced dipole interaction and other polarity-polarity interactions. Normal phase solid phase extraction can adsorb polar compounds from non-polar solvent samples.
The adsorbents used in reversed-phase solid-phase extraction are usually non-polar or weakly polar, and the extracted target compounds are usually medium-polar to non-polar compounds. The effect between the target compound and the adsorbent is hydrophobic interaction, mainly non-polar-non-polar interaction, van der Waals force, or dispersion force. The adsorbent used in ion exchange solid phase extraction is a charged ion exchange resin, the target compound to be extracted is a charged compound, and the interaction between the target compound and the adsorbent is electrostatic attraction.