SPE Cartridge Washing and Drying Parameters Selection

If the target compound is a neutral compound and a hydrophobic non-polar filler (such as C4, C8, C18, etc.) is selected, it can be washed with water or a buffer used for cartridge equilibration. If the analyte has a strong adsorption force on the solid phase extraction column, a water-soluble organic solvent may be added to the washing solution to enhance the washing effect.

If the recovery is found to be reduced, collect this component and check if the target compound is eluted at this step. If the ionizable target compound has been neutralized by adjusting the pH and adsorbed by the hydrophobic force of the SPE cartridge, care must be taken to maintain the same pH during washing to avoid the target compound in the washing step due to pH changes. loss.

If the target compound is an anion or a cation (as extracted using an ion exchange cartridge such as SAX SPE Cartridges, PSA, NH2, SCX, CBA, and PRS), it can be washed with a buffer used for cartridge equilibration. For singly charged analytes, the ionic strength of the buffer solution should not exceed 50 mmol/L. For doubly charged analytes, the ionic strength of the buffer solution should not exceed 10 mmol/L. Reversed Phase Cartridges, such as Reversed Phase C18A SPE Cartridges. Mixed Mode Cartridges, such as Mixed Mode Octyl(C8)/SCX SPE Cartridges.

Under certain circumstances, the presence of moisture can have an effect on the elution of the target compound and subsequent analysis. Therefore, the SPE cartridge must be dried before eluting the target compound.

The method of drying mostly uses positive pressure or negative pressure. The positive pressure is generally blown by the air or nitrogen at a certain pressure from the upper part of the SPE cartridge; the negative pressure is in a vacuum given below the extraction column so that the residual moisture is removed from the SPE cartridge.

Sometimes, in order to better remove residual moisture, a small amount of polar organic solvent such as 50 μL of methanol can be used. If the target compound is more volatile, care should be taken to control the time during which the positive/negative pressure is removed to prevent the target compound from being lost during the drying process.

The washing and drying parameters for SPE (Solid-Phase Extraction) cartridges depend on the specific sample matrix, target analytes, and the type of stationary phase used. Here are some considerations for selecting the washing and drying parameters:

  1. Solvent Selection: Choose a suitable washing solvent that can effectively remove unwanted matrix components while retaining the target analytes on the SPE cartridge. The solvent should have good solubility for the interfering substances and should not elute the analytes of interest.
  2. Washing Volume: Determine the appropriate volume of washing solvent based on the sample matrix and the amount of interfering substances. It should be sufficient to wash away impurities but not excessively dilute the analytes of interest.
  3. Flow Rate: Consider the flow rate at which the washing solvent is passed through the SPE cartridge. A moderate flow rate is often used to ensure efficient washing without compromising the retention of analytes.
  4. Elution Solvent Compatibility: Ensure that the washing solvent is compatible with the elution solvent that will be used to extract the target analytes from the SPE cartridge. Compatibility ensures a smooth transition from washing to elution without any adverse interactions or precipitation.
  5. Drying Method: After washing, it is important to dry the SPE cartridge to remove residual solvent before elution. Common drying methods include applying a vacuum, passing an inert gas (such as nitrogen), or using a mild temperature. The selection of the drying method depends on the solvent used, the nature of the analytes, and the type of cartridge.
  6. Drying Time: The drying time depends on factors such as the type of solvent used, the cartridge material, and the drying method. Sufficient drying time should be allowed to ensure complete evaporation of the solvent, but excessive drying time should be avoided to prevent any potential analyte degradation or losses.
  7. Validation and Optimization: It is important to validate and optimize the washing and drying parameters for each specific application. This can be achieved through method development, method validation, and performance testing using appropriate reference standards and quality control samples.

Always refer to the manufacturer’s instructions, method protocols, and established best practices specific to the SPE cartridge and analytes of interest. Optimization and validation of the washing and drying parameters are crucial for achieving reliable and accurate results in SPE.