The success of UHPLC (ultrahigh-performance liquid chromatography) in its various forms has been a pleasant surprise. All major vendors have released, in one form or another, high-end, high-pressure systems employing columns with stationary-phase particle sizes below 2.5 microns. Not everyone agrees on the merits of ultrasmall particle technology, but the technology is definitely here to stay and is entering the mainstream.
“We have customers who are asking to transfer isocratic as well as gradient methods to UHPLC format,” observes Alessandro Baldi, Ph.D., product manager for chromatography at PerkinElmer. He calls this “an interesting development” because it means that UHPLC is no longer reserved for power-users, and is “capturing much more of the LC market than we had originally anticipated.”
Dr. Baldi refers to the three major groupings of LC column technology as tiers that include the specific instrument, column, workflow, application, and operator skills. “Classical HPLC” refers to the pressure domain up to about 6,000 psi, with particle sizes toward the upper end of the 3–5 micron range. “Near-UHPLC” consists of systems operating in the 6,000–10,000 psi range, with particle sizes between 2 and 2.5 microns. “True UHPLC” operates from about 10,000 to 15,000 psi, with particle sizes below two microns.
Porting methods from conventional HPLC to near-UHPLC takes work but is relatively straightforward. But because of radically different pressures, instrument geometries, flows, solvents, injected volumes, and buffers, switching to true UHPLC is much more difficult.
Near-UHPLC represents a compromise that nevertheless provides three- to fourfold throughput improvements. In March, Dr. Baldi presented a paper at the “Pittcon” conference in Chicago describing a near-UHPLC system with fourfold higher throughput and 50 times greater sensitivity than conventional HPLC, and which used a fraction of the organic solvent.
PerkinElmer sells instruments that fit all three tiers, according to Dr. Baldi. In March the company introduced the Flexar™ LC platform, which is controlled by the new Chromera® Chromatography Data System. Flexar uses a sub-2 micron particle column and consumes about one-fifteenth as much solvent as conventional HPLC, Dr. Baldi adds.