Solid-phase extraction (SPE) traditionally uses gravity or vacuum to move the liquid through the sorbent bed. This is simple and generally works well. However, some environments are potential sources of contamination. Ye Jinglei of the Xiamen Ocean Vocational College in Xiamen, China, described an apparatus that moves the liquids (sample, wash, displace) under positive pressure (A novel ship-borne positive pressure solid phase extraction device to enrich organo chlorinated and pyrethroid pesticides in sea water. Chin. J. Chromatogr. 2017, 35[9], 907–11). This greatly reduces the risk of sample contamination.
The apparatus uses a nut and bolt to hold the SPE cartridge in place against the seal. Pressure is applied to the plastic sample collection bottle from a small air pump. With a pressure of 0.1–0.3 MPa, a flow of 4–6 mL/min is produced.
Preconditioned SPE cartridges should be loaded within four weeks of use. Loaded SPE cartridges show 90% recovery after seven days and 80% after six-week hold times. Limits of quantitation are 0.8–6 ng/L, depending upon the analyte.
Operation of SPE extractions with small positive pressure offers improved convenience and speed for sample processing in sites remote from the laboratory. Perhaps some commercial firm will use this design to provide a viable product.
Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected]
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