What You Need to Know About SPE

Often called SPE, Solid Phase Extraction is a Laboratory technique used widely nowadays. The function of the technique is to clean and, or concentrate samples before chromatography. Solid Phase Extraction (SPE) is a widely used sample preparation technique in analytical chemistry, particularly in chromatographic methods such as high-performance liquid chromatography (HPLC) and gas chromatography (GC). SPE is employed to selectively concentrate, purify, and/or extract specific analytes from a complex sample matrix, making them more amenable to subsequent analysis. Here’s what you need to know about SPE:

To optimize the extraction, there are three main parameters that should be known: the choice of column sorbent, wash solvent, and eluting solvent. And the choice of solvents depends on what kind of stationary phase you need. When finding the point that balances three parameters, you will achieve a reliable and sturdy method.

  1. Principle: SPE is based on the principle of selective adsorption and desorption. A solid phase, often packed into a cartridge or disk, interacts with the sample, retaining the analytes of interest while allowing unwanted matrix components to pass through. The analytes are then eluted from the solid phase using an appropriate solvent, resulting in a concentrated and purified sample.

5 steps can be concluded to describe how SPE works as follows. The first step is sample pretreatment, such as pH adjustment, protein precipitation, and filtration. And the second step is Column conditioning, which is to make sure the column is ready for loading the sample. After we load the Sample onto the cartridge as the third step, the last two are column wash and sample elution. With interferences being washed from the column, the sample will be eluted by solvent and collected, as interference left behind on the cartridge.

  1. Applications: SPE is used in a wide range of applications, including environmental analysis (e.g., water and soil samples), pharmaceutical analysis, food and beverage testing, clinical research, and more. It’s particularly valuable when dealing with complex sample matrices that may contain interfering compounds.
  2. Sample Cleanup: One of the primary purposes of SPE is sample cleanup. By removing interfering substances from the sample matrix, such as proteins, lipids, salts, and other contaminants, SPE improves the selectivity and sensitivity of subsequent analytical techniques.
  3. Types of SPE: There are different types of SPE based on the characteristics of the solid phase used:
    • Reversed-Phase SPE: Similar to reversed-phase chromatography, this method uses a nonpolar solid phase for the extraction of hydrophobic analytes. Such as Reversed Phase C18 SPE Cartridge
    • Normal-Phase SPE: Utilizes a polar solid phase for the extraction of polar compounds. Such as Normal Phase Cyanopropyl (CN) SPE Cartridge
    • Ion-Exchange SPE: Used for selectively retaining and releasing ions based on charge interactions. Such as Ion-Exchange PRS SPE Cartridge
    • Mixed-Mode SPE: Combines multiple retention mechanisms, providing increased selectivity for complex samples. Such as Mixed Mode Octyl(C8)/SAX SPE Cartridge
    • Affinity SPE: Specific for target analytes that can interact with the affinity ligands on the solid phase.
  4. Procedure: A typical SPE procedure involves several steps, including sample loading onto the SPE cartridge, washing to remove unwanted matrix components and elution of the analytes of interest. The eluate can then be concentrated if necessary before analysis.
  5. Column Conditioning: Prior to use, SPE columns need to be conditioned with appropriate solvents to ensure consistent and reproducible results. The choice of conditioning solvents depends on the type of solid phase and the analytes being extracted.
  6. Quality Control: Proper quality control measures should be taken during SPE, including using appropriate blanks and standards to monitor potential contamination and ensure accurate quantification.
  7. SPE Variations: There are automated SPE systems available, which improve reproducibility and throughput. Miniaturized SPE techniques, such as micro-SPE and pipette-tip SPE, are also popular for smaller sample volumes.
  8. Environmental Considerations: Proper disposal of used SPE cartridges is important, especially if the analytes are hazardous or if the matrix contains chemicals that could impact the environment.

SPE is a powerful tool in the analytical chemist’s toolkit, enabling efficient and effective sample preparation for a wide range of analytical methods. The choice of the appropriate SPE protocol depends on the sample matrix, the analytes of interest, and the analytical method to be used.