Supported Liquid Extraction (SLE), also known as solid-supported Liquid-Liquid Extraction (LLE), is a sample preparation technique that utilizes an aqueous phase and an immiscible organic phase, along with a chemically inert solid support, commonly modified diatomaceous earth, which acts as a stationary-phase sorbent. In the SLE process, an aqueous sample is loaded onto the sorbent, which serves as a stationary vehicle by retaining the solvents. Target analytes are then eluted by applying a water-immiscible solvent and collected.

SLE does not require a dedicated system, and generally utilizes cartridges or 96-well plates with an automated liquid handling robot. SLE uses the same principles as its traditional LLE counterpart, but the sample’s immobilization and extraction take place on an inert solid support. Although diatomaceous earth is used most commonly as a bulk sorbent for the inert support, newer synthetic SLE sorbents, which can be manufactured in labs, provide an attractive alternative to traditional SLE sorbents by ensuring a more consistent cleanup and recovery of phospholipids.

SLE offers a range of advantages over traditional LLE techniques, including higher throughput, ease of automation, better reproducibility and faster sample preparation time. SLE also eliminates the need for manual steps of washing, conditioning and vigorous shaking, thereby reducing glassware and labor requirements as well as preventing the formation of emulsions.

SLE is used for multiple applications, including the extraction of drugs, hormones and metabolites from biological fluids such as whole blood and plasma. Hence, SLE is used predominantly in the biotechnology, pharmaceutical, CROs, hospital and clinical industries. However, its applications in the agriculture/food industry, such as for multi-residue pesticide screening and the extraction of chemical compounds used in preservatives, are growing increasingly popular.

SLE is a consumables-only market. Global demand was estimated to be over $40 million in 2016. The market is growing fast, with a forecasted annual growth rate over 6% in 2017, as an increasing number of LLE techniques are being replaced by the faster and more efficient SLE. This market growth can be attributed primarily to the automation-driven nature of SLE techniques, which favor high-throughput applications in the biotech and pharmaceutical industries.

Agilent leads the SLE market, owing to its range of consumable products, including ChemElut cartridges, CombiElut 96-well plates and Hydromatrix bulk sorbent. Biotage has the next largest market share through its ISOLUTE series of aftermarket offerings and its multi-application Extrahera Automation System, which can be utilized as a platform for multiple sample-extraction techniques, including SLE. Thermo Fisher Scientific ranks third, thanks to its HyperSep SLE cartridges and 96-well plates that utilize a specially treated diatomite sorbent. Phenomenex is another vendor in the SLE market and manufactures the synthetic Novum SLE plates.

SLE At a Glance:

Leading Vendors:

• Agilent Technologies
• Biotage
• Thermo Fisher Scientific

Largest Markets:

• Pharmaceuticals
• Biotechnology
• Hospital and Clinical

Cost per Plate:

• $1.00­–$2.50