How to Use Solid Phase Extraction Cartridge?

The following points should be considered when selecting the separation mode and adsorbent for solid phase extraction.

The solubility of the target compound is polar or non-polar solvents mainly involves the choice of the eluent. Whether the target compound is possible to ionize (the pH value can be adjusted to achieve ionization), so as to decide whether to use ion exchange solid phase extraction cartridge.

Is it possible for the target compound to form a covalent bond with the adsorbent, such as forming a covalent bond, you may encounter trouble during elution. The degree of competition between non-target compounds and target compounds on the adsorption point of the adsorbent is related to whether the target compounds and interfering compounds can be separated well.

Steps for Using a Solid Phase Extraction Cartridge

  1. Select the Appropriate Cartridge:
    • Choose an SPE cartridge with the appropriate sorbent material (e.g., silica, reversed-phase, ion-exchange) based on the characteristics of your sample and the analytes you want to extract.
  2. Condition the Cartridge:
    • Before use, condition the SPE cartridge with the appropriate solvent. This helps to wet the sorbent and remove any impurities that may be present in the cartridge. Common conditioning solvents include methanol, acetonitrile, or the solvent you plan to use for your sample.
  3. Equilibrate the Cartridge:
    • After conditioning, equilibrate the cartridge with the solvent that will be used for your sample. This ensures that the sorbent is in the correct solvent environment for efficient extraction.
  4. Load the Sample:
    • Load your liquid sample onto the SPE cartridge. This can be done by passing the sample through the cartridge under gravity or using a vacuum or positive pressure. Ensure that the sample volume does not exceed the cartridge capacity.
  5. Wash the Cartridge:
    • Wash the cartridge with a suitable solvent to remove interfering substances and impurities while retaining the analytes of interest on the sorbent. The choice of wash solvent depends on the type of analytes and the sorbent used.
  6. Dry the Cartridge (Optional):
    • In some cases, it may be necessary to dry the sorbent bed after washing to remove residual moisture. This can be done by applying a gentle stream of nitrogen or air through the cartridge.
  7. Elute the Analytes:
    • Elute the analytes from the sorbent bed using a solvent that is selective for the analytes of interest. This elution solvent is typically different from the wash solvent. Collect the eluate in a clean vial or container.
  8. Concentration (Optional):
    • If necessary, concentrate the eluate using techniques such as evaporation or nitrogen blowdown. This is particularly useful if the elution volume is large, and you want to concentrate the analytes for more sensitive detection.
  9. Analysis:
    • Analyze the concentrated eluate using the desired analytical technique (e.g., chromatography, spectroscopy) to quantify and identify the extracted analytes.
  10. Dispose of the Cartridge:
    • Properly dispose of the used SPE cartridge according to your laboratory’s waste disposal procedures.

Commonly used adsorbents (stationary phase) for solid phase extraction

Since solid phase extraction is essentially a liquid chromatography separation, in principle, all materials that can be used as liquid chromatography cartridge packing can be used for solid phase extraction cartridge.

Alumina SPE Cartridges Alumina SPE Columns Mixed Mode SPE Cartridges

However, because the cartridge pressure of liquid chromatography can be higher and the column efficiency is required to be higher, the particle size requirements of its packing are strict. In the past, 10μm particle size packing was commonly used, and now high-efficiency cartridges use 5μm packing, even 3μm packing (As the HPLC pump pressure increases, the particle size of the filler is gradually decreasing). The requirements for the particle size distribution of the filler are also very narrow. The pressure on the solid phase extraction cartridge is generally not large.

The purpose of separation is only to separate the target compound from the interfering compound and the matrix. The column efficiency requirements are generally not high.

Therefore, the fillers used as solid phase extraction adsorbents are relatively coarse. 40μm can be used, and the particle size distribution requirements are not strict, which can greatly reduce the cost of the solid phase extraction cartridge. Types and uses of adsorbents commonly used in solid phase extraction.

Solid phase extraction equipment and operating procedures

The simplest solid phase extraction device is a small cartridge with a diameter of several millimeters. The small cartridge can be glass, polypropylene, polyethylene, polytetrafluoroethylene, and other plastics, or stainless steel. There is a sintered sieve plate with a pore size of 20μm at the lower end of the small cartridge to support the adsorbent. If the self-made solid phase extraction cartridge does not have a suitable sintered sieve plate, it can also be filled with glass wool instead of the sieve plate, which can support the solid adsorbent and allow the liquid to flow through.

Fill the sieve plate with a certain amount of adsorbent (100㎎~1000㎎, depending on the need), and then add a sieve plate on the adsorbent to prevent damage to the column bed when adding samples (it is also possible if there is no sieve plate Replace with glass wool). At present, solid phase extraction cartridges of various specifications and loaded with various adsorbents have been sold, which is very convenient to use.