Introduction of SPE for Reaction Workup

Solid phase extraction (SPE) is a flow-through technique using column or 96-well plate formats. SPE can be used to selectively retain products (catch & release SPE) or impurities (scavenging SPE) from solutions onto a solid functional medium.

Retention Mechanisms
The retention mechanism can be ionic, polar, or non-polar. Unlike ArgoResin scavengers, SPE interactions are relatively nonselective, reversible, and are not based on specific chemical reactions between compounds and functionalized sorbents. SPE columns and 96-well plates can be used in both catch & release and scavenging SPE modes.

Catch & Release SPE
In catch & release SPE, the sorbent bed “catches” the compound of interest along with some impurities. Rinsing the column or well removes impurities, leaving the compound of interest on the column for subsequent elution in an appropriate solvent or solvent mixture.

Scavenging SPE
In scavenging SPE, the sorbent bed retains impurities and allows the compound of interest to pass straight through the column or well. Compound isolation is achieved through interaction between the sorbent and the impurities, which are retained on the column.

Column Sizes
SPE columns are available in a range of sizes and formats. The traditional syringe barrel format is most convenient for processing up to 20 samples at a time. For higher throughput, a tab-less SPE column format allows column arrangement in a microplate footprint. This provides options for 24- and 48-well workup. Fixed well and modular 96-well formats are also available for high throughput applications.

SPE Column Capacity
The amount of material that can be isolated using SPE depends on the capacity of the sorbent bed. As a general guideline, non-polar and SPE columns can retain approximately 5% w/w of the total sorbent bed. For example, a 1 g sorbent mass will retain 50 mg of target compound or impurities. The capacity of ion exchange SPE columns is measured in milliequivalents (meq) per gram of sorbent. An SPE column packed with 500 mg of strong cation exchange sorbent (sulfonic acid functional group), with an exchange capacity of 0.6 meq/g, can retain up to 70 mg of a typical basic compound with a molecular weight of 250 g/mol.

SPE Column Materials
ISOLUTE SPE column reservoirs and 96-well plates are made of polypropylene. Frits are made of polyethylene. Both have a high degree of solvent resistance and are compatible with all commonly used solvents, acids, and bases.

Processing
SPE columns and plates can be processed manually using a vacuum manifold or using automated liquid handling systems for high throughput applications.
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FlashVac-10 & -20 Sample Processing Manifolds for processing columns manually
• VacMaster-96 Sample Processing Manifold for processing 24- and 96-well plates manually

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