Description, Principle and Use of SPE Cartridge

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:
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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.

C18A Reversed Phase SPE Cartridges

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 of SPE Cartridge

The principle of SPE involves the adsorption and desorption of analytes onto and from a solid-phase material. The basic steps in the SPE process include:

  1. Adsorption:
    • The sample is loaded onto the SPE cartridge, where analytes selectively interact with the solid-phase material.
    • Analytes are adsorbed onto the surface of the solid phase through various interactions such as hydrophobic interactions, ion exchange, or specific chemical interactions.
  2. Washing:
    • Unwanted matrix components and impurities are removed by washing the cartridge with a solvent or a series of solvents.
    • The washing step helps eliminate interference and ensures the retention of only the target analytes.
  3. Elution:
    • The analytes of interest are then eluted from the solid phase using an elution solvent.
    • Elution disrupts the interactions between the analytes and the solid phase, allowing for their release.
  4. Collection:
    • The eluate containing the purified analytes is collected for further analysis or processing.

Use of SPE Cartridge

SPE cartridges find widespread application in various fields, including environmental analysis, pharmaceuticals, clinical research, food and beverage testing, and forensic analysis. Common uses of SPE cartridges include:

  1. Sample Preparation:
    • SPE is widely used for the pre-concentration and cleanup of samples before analysis by techniques such as chromatography or mass spectrometry.
    • It helps remove interfering substances and concentrates analytes, enhancing detection sensitivity.
  2. Purification:
    • SPE is employed for the purification of compounds from complex matrices, ensuring that only the target analytes are present in the final eluate.
  3. Matrix Removal:
    • Matrix components such as salts, proteins, and other impurities can be effectively removed, reducing interference in analytical methods.
  4. Fractionation:
    • SPE can be used for the fractionation of complex mixtures, separating compounds based on their affinity for the solid phase.
  5. Isolation of Specific Compounds:
    • Specific compounds or classes of compounds can be isolated and concentrated using SPE, allowing for selective extraction.
  6. Concentration of Dilute Samples:
    • SPE enables the concentration of analytes from large sample volumes, making it particularly useful when dealing with dilute samples.
  7. Removal of Interfering Matrix:
    • It helps in the removal of interfering matrix components, facilitating accurate and reliable analysis.
  8. Extraction of Polar and Non-Polar Compounds:
    • SPE cartridges are versatile and can be packed with different types of sorbents to extract both polar and non-polar compounds.
  9. Sample Cleanup in HPLC and LC-MS:
    • SPE is commonly used as a sample cleanup step in liquid chromatography (LC) and liquid chromatography-mass spectrometry (LC-MS) analyses.
  10. Drug Metabolite Analysis:
    • SPE is employed in pharmaceutical research for the extraction and purification of drug metabolites from biological samples.
  11. Environmental Monitoring:
    • SPE is used for the extraction of pollutants and contaminants from environmental samples, facilitating monitoring and analysis.
  12. Forensic Analysis:
    • In forensic science, SPE is used for the extraction of drugs, toxins, and other substances from biological samples.
  13. Clinical and Biochemical Analysis:
    • SPE is applied in clinical and biochemical research for the extraction and purification of biomolecules from biological fluids.
  14. Food and Beverage Analysis:
    • SPE is utilized in the analysis of food and beverages to extract and concentrate analytes of interest while removing unwanted components.

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.