Powerful New Features, And a Renaissance for Old Systems
Manufacturers of high-performance liquid chromatography (HPLC) systems continue to innovate, while simultaneously providing upgrade paths for older instruments.
Modular HPLC systems provide maximum flexibility and upgradability compared with “one box” integrated chromatographs. By switching modules, users can access the latest technology while reducing downtime during repair or servicing.
On the other hand, integrated systems are more affordable. Agilent’s 1220 Infinity, which is modular, costs about 25 percent less than a comparably equipped 1260 model, yet the two use identical subcomponents. According to Dr. Michael Frank, marketing manager for analytical HPLC at Agilent (Waldbronn, Germany), integrated systems are less expensive because they use only one power supply, one set of communication electronics, and one cover.
Since HPLCs are long-lived instruments, upwards and downwards compatibility is a major concern. Compatibility also provides a relatively straightforward upgrade path, provided components are replaceable and the manufacturer has embraced open architecture. Agilent’s diode array detector, available on the company’s latest HPLC models, also works in instruments sold in the 1990s. “All users need to do is replace the detector and they obtain almost twenty times the sensitivity of their old detector,” Dr. Frank tells Lab Manager Magazine. Similarly, older instruments may access quick-change valve technology, which facilitates plumbing tasks.
Advanced valve technology plays into the need for speed, including rapid column switching and automation, which has become the name of the game in high-volume labs that run samples more or less continuously and often unattended.
Software emulation of older methods
Method transfer has been the bane of chromatographers for years, and a major roadblock in the adoption of novel HPLC technology. Many established methods, for example from the U.S. Pharmacopoeia and the Environmental Protection Agency, specify not only solvents and gradients but columns. As a result, many labs feel tied to old technology. There are other aspects to this story: Users tend to exaggerate the cost and time involved in revalidating methods (read: inertia), and that chromatographs last so long is a tribute to the craftsmanship of HPLC manufacturers.
Regardless, a solution may be on the way. Agilent’s Intelligent System Emulation Technology (ISET), available on its top-end HPLC systems, creates a software environment in which a chromatography run on, say, an Agilent 1290, can be made to emulate any older HPLC system and, according to the company, deliver “exactly the same results.” ISET is pure software and does not require hardware modifications.
In a company announcement at Pittcon, Agilent senior marketing director Stefan Schuette described ISET as “…the beginning of a new era” in which users “…will be free to develop, validate, and execute all methods on one single instrument… and to emulate those HPLC and UHPLC instruments to which a method should be transferred or on which it has been developed.”
Dr. Frank believes legal and regulatory authorities will accept these “virtual” chromatography runs. “I’ve spoken with experts in regulated industries, and they don’t think it will be an issue.”
Columns drive instrument evolution
The advent of small-particle-size columns has caused HPLC vendors to rethink system design to exploit the new columns’ resolving power, says Alessandro Baldi, Ph.D., senior business director at PerkinElmer (Waltham, MA). “We pay close attention to reducing volumes not only inside modules but between modules, and to positioning components as closely as possible to the column.”
That means positioning the injector and gradient mix almost on-column, and the detector immediately outside at the back end. Proximity reduces volumes between modules and therefore helps eliminate dispersion while improving signal to noise and resolution. Perhaps the most exciting development affecting HPLC systems over the past several years has been the introduction of superficially porous silica particles. These are discussed in greater detail in an accompanying article.
The novel particles promise performance approximating—some vendors say exceeding—that of UHPLC but at normal back pressures. This means that labs with a significant investment in older HPLC instrumentation can continue to use their equipment and achieve results normally associated with very high back pressures.
Interestingly, system manufacturers have embraced superficially porous stationary phases despite an obvious desire to sell high-pressure systems. Dr. Baldi approaches the issue philosophically: “Remember that the HPLC market is variegated. Different users have different goals.” He calls the new particles a “step in the right direction” for busy labs that want better results without changing methods and upgrading equipment. At the same time, researchers, Baldi says, will still desire the resolution, sensitivity, and solvent-sparing capabilities of UHPLC.