Product Focus: Gas Chromatography Systems
Streamlining workflows while improving accessibility
According to one major vendor, gas chromatography sales closely follow the ups and downs of specific economic sectors related to energy and the environment.
From the perspective of Shimadzu Scientific Instruments (Columbia, MD), gas chromatography sales closely follow the ups and downs of specific economic sectors related to energy and the environment. According to GC product manager Mark Taylor, the uptick in sales to government and government-funded research during 2010—likely due to stimulus money trickling down—has abated. A fair portion of that demand came from biofuels R&D.
Through early 2011, sales to the petrochemical industry picked up, which Taylor attributes to the rise in energy prices. “With fuel so expensive, it became economically viable to tap into energy sources that are more costly to reach or clean up,” Taylor says.
Although demand from this sector has slowed somewhat, interest in GC from the environmental sector remains vibrant. Greenhouse gas analysis driven by government regulations and pure academic research is on the rise. For the most part, instruments sold into this sector are turnkey, black-box systems, Taylor says. “They’re all fully ‘applicated,’” as are most GC systems sold today.
Up in smoke
Now that medical marijuana is legal in about a dozen states, testing for marijuana potency is an up-and-coming application. Scott Bergeron, applications manager at Buck Scientific (Norwalk, CT), wryly observes that “for reasons you’d expect we see a lot of non-chromatographers undertaking that particular analysis.” Dispensaries are interested in the relative quantities of THC and other cannabinoid constituents in pot because their relative abundances affect the drug’s potency for relief of pain, nausea, or stress.
Buck Scientific custom-builds every GC system it sells. Bergeron describes his firm’s products as “user-friendly but not high-throughput,” and the instruments are not available directly from Buck with mass detectors.
One can construct a good argument for custom-building: Customers only pay for what they need, so prices are often lower than for off-the-shelf systems. “It’s an à la carte sort of deal,” Bergeron says. “Customers can specify detectors and whether they require split or splitless injection, purge-trap capability, or autosamplers. Some of our purchasers have added mass detectors, but we do not service or support them.”
Custom-building works well because many GC purchasers are unsure of the features they really need. Buck stocks several column oven types and system case sizes. But based on the application, any number of injectors or detectors (or combinations of detectors) might be appropriate. For example, labs analyzing fatty acid methyl esters require a split-splitless injector and a capillary column, whereas academic labs should select a conventional injector, Bergeron advises, “so students have a harder time messing them up.”
Two interesting and fairly recent trends in GC systems are “fast GC” and the use of hydrogen as the carrier gas.
Hydrogen is much less expensive than helium. It also has superior optimal linear velocity and produces a very low effective plate height, meaning more theoretical plates are available for a given column length. Because of its lower density relative to helium, hydrogen works extremely well with very narrow-bore columns. In one test run, Supelco, a subsidiary of Sigma-Aldrich (St. Louis, MO), has published data on separations with hydrogen on a 0.1 mm ID column that were impossible with a helium mobile phase due to the high backpressures.
Fast GC provides benefits of lower instrument and human resource costs, higher revenues for high-throughput testing or service labs, and more rapid method development. Perhaps best of all, these benefits accrue with no additional capital investment. Ultra-high-performance liquid chromatography, by comparison, requires purchasing an instrument capable of generating and withstanding high backpressures.
Fast GC is achieved by shortening column length, ramping up temperatures faster, and raising the carrier gas flow rate. The negative effects on resolution are countered by narrowing the column’s internal diameter, reducing the film thickness, and (a second trend) switching from helium to hydrogen carrier.
Not everyone is enamored with fast GC. According to Taylor, methods involving rapid temperature-ramping in resistively heated columns are “not mainstream.” He notes that traditional fast GC is a high-pressure, high-gas-flow technique conducted in very narrow columns with high split ratios.
Very narrow-bore columns have very low volumes, and therefore low sample capacity. Trace compound analysis may be limited due to the quantity of sample that may be injected. The other challenge is the difficulty in transferring methods from conventional GC/column formats to fast GC. Busy analytical labs must weigh the benefits of shorter analysis times vs. revalidation of methods already working perfectly with conventional GC.
Agilent Technologies (Santa Clara, CA) GC product manager Dave Johnson observes that top GC vendors have all introduced technologies for enhancing and simplifying workflows while improving productivity.
Historically, advanced features were deployed for early-adopter expert users. But the vast majority of GC users today lack the experience, and cannot devote the time, for hacking complex instrumentation. “To make these technologies more accessible to a broader user base, major vendors are offering factory-built, preconfigured ‘analyzers and solutions,’” Mr. Johnson says, and this accessibility extends to sample preparation.
Sample and standards preparation is time-consuming for any instrumental analysis, particularly for GC. Some industries, such as biofuels, require users to formulate calibration standards through complex processes that take hours.
Agilent has recently published an application note (find it at http://bit.ly/n3Mdue) describing a technique, enabled by an automated liquid handling system, for derivatizing glycerol, monoglycerides, and diglycerides, and subsequently adding an internal standard to biodiesel samples. According to Mr. Johnson, this technique has evolved from a “fairly basic” liquid-handling exercise to a fully automated technique based on an Agilent liquid handler.
“Customers are increasingly asking for help on the front end as well as with the instrument, methods, and detectors,” Johnson adds.