In 1906, Mikhail Tswett separated plant pigments on a chalk column. Alluding to the separated colors, he termed his technique chromatography.1 Nearly a century later, chromatography hasn't changed all that much; it still relies on the differential affinities of analyte components for the mobile and stationary phases of the separation. Yet in high-performance liquid chromatography (HPLC), the technique assumes a decidedly high-tech air, with gleaming stainless steel components, computer control, and advanced detectors.
The stationary phase is typically packed into a small column through which the mobile phase migrates. An injector valve introduces the analyte into the mobile phase, and one or more detectors scan the column output. This general setup describes most medium-pressure and low-pressure systems, as well. Lou Bellafiore, president of TechniKrom in Evanston, Ill., points out that the basic distinction "is really the backpressure generated by the [stationary phase] particle size .... Ultimately the particle size dictates ...
