Category:SPE

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Revision as of 14:13, 6 May 2009

Solid phase extraction, or SPE, is a technique designed for rapid, selective sample preparation and purification prior to chromatographic analysis. SPE provides the sample clean-up, recovery, and concentration for quantitative analysis.

Solid-phase extraction (SPE) is a separation process that is used to remove solid or semi-solid compounds from a mixture of impurities based on their physical and chemical properties. Analytical laboratories use solid phase extraction to concentrate and purify samples for analysis. Solid phase extraction can be used to isolate analytes of interest from a wide variety of matrices, including urine, blood, water samples, beverages, soil, animal tissue, and consumer products.

SPE uses the affinity of solutes dissolved or suspended in a liquid (known as the mobile phase) for a solid through which the sample is passed (known as the stationary phase) to separate a mixture into desired and undesired components. The result is that either the desired analytes of interest or undesired impurities in the sample are retained on the stationary phase. The portion that passes through the stationary phase is collected or discarded, depending on whether it contains the desired analytes or undesired impurities. If the portion retained on the stationary phase includes the desired analytes, they can then be removed from the stationary phase for collection in an additional step, in which the stationary phase is rinsed with an appropriate eluent.

The stationary phase comes in the form of a packed syringe-shaped cartridge or a 96 well plate The analytes are collected in sample tubes inside or below the manifold after they pass through the stationary phase.

Solid phase extraction cartridges are available with a variety of stationary phases, each of which can separate analytes according to different chemical properties. Most stationary phases are based on silica that has been bonded to a specific functional group. Some of these functional groups include hydrocarbon chains of variable length (for reversed phase SPE), quaternary ammonium or amino groups (for anion exchange), and sulfonic acid or carboxyl groups (for cation exchange).

A sample preparation technique that uses a solid phase packing contained in a small plastic cartridge. The solid stationary phases are the same as HPLC packings but the principle is different from HPLC. It is sometimes referred to as digital chromatography. This processs, as it is most often practiced, requires four steps: conditioning the sorbent, adding the sample, washing away the impurities, and eluting the sample in as small a volume as possible with a strong solvent.

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