In honor of LCGC's celebration of 30 years covering the latest developments in separation science, we asked a panel of experts to assess the current state of the art of gas chromatography (GC) column technology, and to try to predict how the technology will develop in the future. This article is part of a special group of five articles covering the state of the art in sample preparation, GC column technology, GC instrumentation, liquid chromatography (LC) columns, and LC instrumentation.
For Paola Dugo, Luigi Mondello, and Peter Tranchida of the University of Messina, ionic compounds were high on the list of valuable developments. "Ionic liquids are characterized by interesting properties, such as high thermal stability and a dual-type selectivity," they commented. "Specifically, the same ionic liquid can show a high selectivity toward both apolar and polar compounds."
Philip Marriott of Monash University, in turn, feels the most significant recent improvement is the enhanced selectivity achieved with coupled-column technology, largely based on microfluidic methods. "Smart coupled-column technologies should be able to provide both improved separation and an increased sensitivity if properly implemented, and these address the goals that have been searched for since GC was invented," he said.
John Seeley of Oakland University, however, was most impressed by another technology development: direct column heating strategies. "Several studies have shown how these modules allow high-resolution multidimensional separations to be produced with far greater ease than if conventional column ovens were used," he said. "I think these low thermal mass heating modules will have a large impact on the coupled-column separations developed of the future."
The Biggest Problems, and How to Overcome Them
In spite of recent advances, however, challenges remain. John Hinshaw, of BPL Global and the editor of LCGC's "GC Connections" column, believes that the areas of greatest advance are also on the list of ongoing improvements still needed: deactivation and thermal stability. Other key issues cited by panelists included improving column ruggedness and stability over its lifetime, better low-bleed columns, and the limited chromatographic background of many end users.
"The continual development of low-bleed stationary phases for gas chromatography–mass spectrometry (GC–MS) will mark important advances in column technology," notes Jared Anderson of the University of Toledo.
Another area with room for improvement is thin-film coatings, particularly for high-speed and GC×GC separations. "Problems can be encountered with thin stationary phase films, namely in relation to a non-uniform coating across the column length," note the group from the University of Messina. Marriott seconded that idea. "Making reproducible, uniform, thermally stable, very thin film phases in narrow-bore format with adequate deactivation of the support (capillary wall) will be of interest to technologists," he notes.
Another important challenge is the need for users to have available, and understand, the use of multiple stationary phases. "As interest in multidimensional GC moves from academic laboratories to industry, classification and utilization of orthogonal stationary phases will be important," noted Anderson. "Therefore, new stationary phases will continue to be developed for application-specific separations."
Seeley agrees. "I think it is important that theoretical tools are developed that allow users to accurately predict the retention of analytes on a wide range of stationary-phase combinations," he said.
Dorman sees user understanding of columns to be important generally, even for one-dimensional GC, particularly given that today's end users of GC often do not have a high degree of specialized training. "Users are less interested and able to optimize separations, and often try to separate everything using the same GC column," he notes. "In many cases, simple installation can be a major source of poor analytical performance." He wonders whether these challenges can be overcome by changing the format of the GC column to allow for easier installation, or alternatively, if hardware improvements could reduce the potential for incorrect installation.