Capillary Liquid Chromatography at Ultrahigh Pressures

Ultrahigh-pressure liquid chromatography (UHPLC) is a method of liquid chromatography utilizing sub-2-μm particles packed into capillary columns 25 to 100 cm long. Columns of this length packed with particles this fine require operation with pressures from 1,000 to 7,000 bar (15,000 to 100,000 psi). The advantages of this technique are high separation powers (theoretical plate counts from 100,000 to 300,000) and run times from a few minutes (isocratic) to a few hours (long gradients). This review discusses the background and theoretical basis of UHPLC, practical aspects of UHPLC hardware, examples of separations, future areas for research in UHPLC, and techniques that are both competitive with and complementary to UHPLC.