Solid-supported liquid extraction (SLE) is an efficient sample preparation method that eliminates the need for conditioning, equilibration and washing. Compared to other sample preparation techniques, such as liquid-liquid extraction (LLE), SLE has lower solvent requirements, a greater degree of reproducibility and can be fully automated. Analogous to LLE, SLE uses the same aqueous sample-solvent system to remove insoluble proteins and phospholipids. SLE differs by immobilizing the sample on an inert support, with the organic phase free to flow through the support, preventing emulsion formation, as experienced with LLE.

The removal of phospholipids is paramount to organic sample preparation due to phospholipids’ ability to cause issues in end-point analysis, especially with MS. If phospholipids are not fully removed from the sample, they can often be eluted along with the sample and induce ion suppression, which erroneously decreases the peaks in MS readouts. SLE is able to remove phospholipid presence while providing a simpler protocol and full automation. SLE products are sold as cartridges and well-plates that are able to be integrated into high-throughput workflows due to their not needing sample pre-conditioning.

Biotage offers the ISOLUTE SLE+ line of SLE plates and columns. The ISOLUTE SLE+ line offers sample-volume tubes from 400 µL to 10 mL, as well as extraction plates up to 48-well plates suitable for high-throughput extractions of 1 mL sample volumes.

Thermo Fisher Scientific supplies the HyperSep SLE product line. These extraction columns utilize a specially treated diatomite sorbent and are used with biological matrices for the removal of phospholipids. Thermo offers several versions of the HyperSep SLE extraction columns, differing in size and amount per pack. The HyperSep SLE extraction columns are available at either neutral (pH = 7) or slightly basic (pH = 9) pH.

Agilent Technologies offers a range of cartridges and a 96-well plate, the VersaPlate, as part of its SLE product offerings. The company utilizes a diatomaceous-earth sorbent to suit broader, general sample preparation applications. It is available as Hydromatrix bulk material. Agilent’s SLE cartridges come as pH buffered at 4.5 or unbuffered in packs from 15 to 100, and contain 200 mg of Hydromatrix sorbent. The VersaPlate is available as a tubes-only set of 96 or as a fully assembled setup.

Applications for SLE are varied, but nest predominately in the biopharmaceutical industry. SLE extraction is suitable for therapeutic drugs, hormones, metabolites for drugs of abuse and more.

The total market for SLE is estimated to be about $25–$30 million, with growth forecast in the high single digits. This growth is being driven by the high demand from the biopharmaceutical markets and a shifting trend to SLE from analogous techniques, such as LLE.

SLE at a Glance:

Leading Suppliers

• Agilent Technologies

• Biotage

• Thermo Fisher Scientific

Largest Markets

• Pharmaceutical

• Biotechnology

• CROs

Instrument Cost

• $0.50–$1.00