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It isn’t easy and long-lasting to extract solid phase substances. We’ve compiled 10 tips to help you make it easier. From cleaning to drying, these suggestions can help you maximize the benefits of the extraction process. What are you waiting for? Start extracting solid phase materials today!

1. The latest standards are the best

Some analytes can become unstable when stored for long durations and could cause precipitation out of solution. This can affect the calibration standards and recovery values of a test and the procedure must start with new standards.

2. Optimise loading pH

The pH of the solution can have a profound impact on any SPE technique , and it can be used to increase the retention of compounds on the SPE product. The reversed-phase method can be utilized to alter the pH of the solution and neutralize any charge in an analytical.

This increases the interaction with the resin, making it more hydrophobic. For the most basic compounds, you can adjust 2 pH ABOVE pKa and for acidic compounds, set 2 pH units LOWER than pKa.

3. Be aware of your compound

The properties of the substances that are being examined will have an enormous impact on which type of SPE can be performed. The pKa and log P of the analytes of interest are two of the most vital parameters. pKa is the point at which the analyte is half ionized and half un-ionized Log P is the measurement of hydrophobicity of a compound.

4. Loose-packed in contrast to. composited

The loose-packed material could cause many problems for the sorbent bed such as channeling, compression as well as voiding, and inconsistent bed weight-to-bed height ratios because of lack of compression of the frit’s top layer after loose filling.

All of these factors could have an impact on the reproducibility and recovery of results from tests. Think about composited products, such as the Microlute CP range, which were designed to address these problems and improve accuracy and reproducibility of SPE methods.

5. Sorbent conditioning

Once the pKa of a absorbent is established then the sorbent bed will be activated and ready to bind analytes via conditioning. Silica is bonded to a functional moiety, which is typically found flat on the surface of the majority of silica-based SPEsorbents.

The conditioning process, which uses organic solvents that are water-soluble (e.g. MeOH), gives them the most area of surface for the analytes to connect to and bind because it causes the bonded functionalities to stand up’ over the top.

This procedure is not required if the sorbent is water-wettable, but it can increase cleanliness of extracts by performing an aqueous wash of the bed.

6. Elution strength and refine wash

You can alter the strength of elution and wash to obtain the most effective extracts when you use mixed mode or reversed phase SPE products. Log P is a great property that can be utilized to select these settings.

Low Log P Diminish the organic strength of the solvent used for elution to prevent hydrophobic interferences while still eluting the analyte of the choice.

High Log P – Use stronger organic strengths during the washing steps.

7. Know your sorbent

In order to adjust pH of solutions in load and wash steps without deionizing compounds and resins (weak Ionic resins are the only ones) The pKa of the sorbent being utilized must be determined and utilized in conjunction with the analytes’ pKa.

8. Go with the flow (rates)

It is essential to have high flow rates in order to achieve a reversed-phase SPE workflow. The retention mechanism is heavily dependent upon Van der Waals forces of interaction between analytes of interest and sorbent.

When performing an SPE technique high flow rates hamper the ability of the substance of interest to adhere to the sorbent medium properly and can lead to a breakthrough on load and wash procedures of an SPE. Slow and steady flow is the best. It is recommended to flow at a rate of 1 drop per second (1 milliliter/minute).

9. Dry the SPE resin prior it is used for elution.

When dry, silica is very susceptible to stationary phase collapse. Avoid allowing silica-based resins to become dry during the final step of the SPE process. This is crucial in the load phase.

Recovery can be decreased by limiting the interactions between analytes, bonded phase and other compounds. These tips apply to silica and polymeric resins.

The resin needs to be dried with vacuum or positive pressure after the washing steps have been completed. Positive pressure/ vacuum should be utilized for at minimum three minutes or until no wash solvent is visible.

Drying the resin is a great way to reduce drying times when the process requires an initial dry-down and then reconstitution. Water is a component of the majority of the wash solvents and can be harder than organic solvents in the process of evaporating.

The SPE resin being dried after washing can result in the final product being less concentrated and leading to a decrease in the sensitivity of injection.

10. Dispersive SPE down

It is important to ensure that the dry-down method is sufficiently vigorous to seeably alter the surface of the solvent but not so vigorous as to allow the solution to escape out of the wells. This can lead to significant recovery and %RSD variations. Dry down can be difficult since the levels of solvent will fluctuate as the process is dried down.