Technology Forum: GC–MS

With the heparin, melamine, and lead paint scares hitting the media news cycles in rapid succession over the last few years, it is clear that the need for advanced GC–MS techniques and instrumentation is greater now than ever before. While the field of analytical chemistry continues to grapple with these crises, practitioners of GC–MS also continue to prepare for the next challenge on the horizon.

Joining us for this discussion are Julie Kowalski of Restek Corporation; Adam Patkin and Bill Goodman of PerkinElmer Inc.; and Mark Taylor of Shimadzu Scientific Instruments Inc.

What trends do you see emerging in GC–MS?

Kowalski:With the emergence and booming growth of LC–MS-MS, I believe GC–MS-MS will soon follow. There are signs of this already. The benefits of tandem mass spectrometry have excited people and now a kind of retrofitting to GC is occurring. Instrument manufacturers are using the accomplishments of LC–MS-MS instrumentation and coupling traditionally LC–MS-MS mass spectrometers to gas chromatographs. Instrument manufacturers are launching new GC–MS-MS instrumentation, one only two months ago.

Specificity and sensitivity as well as accurate identification are hallmarks of tandem mass spectrometry. The promises of reduced sample preparation and alleviation of isobaric matrix interferences are very enticing to analysts.

Patkin and Goodman: There is continuous technological development improving scan speed, detection limits, reliability, ease-of-use, and post-run software processing. New analyzer technology continues to develop, especially portable, triple quadrupole, GCxGC-MS and time-of-flight. Simpler and more robust microchannel front-end technologies for column flow switching continue to develop, enhancing the separation power of the GC while simplifying the plumbing and maintenance.

Analysts continue to accelerate their demands for more information from their analyses. Applications that used to be GC-only, such as blood alcohol using static headspace/GC/FID are with increasing frequency splitting the effluent to an MS for unambiguous target identification and tentative identification of unknown peaks. Similar trends are apparent in FAMES and many other analyses.

Much of the growth in GC–MS sales comes from regions whose native language is not English. As this trend continues over the next several years, more data systems will support more local languages.

The increasing cost of helium in many parts of the world will cause more users to switch to hydrogen and sometimes nitrogen for carrier gas.

What is the future of GC–MS?

Kowalski:Let us out of the 70eV box!

GC–MS is considered a mature technique thought to have little new or exciting to offer. The future of GC–MS already exists in untapped approaches to using the method. Gas chromatography and mass spectrometry especially, undergo constant development. The forgotten piece is the ionization step. Scientists experiment very little with ionization mainly because this has been the historical culture of early adopters and instrument manufacturers.

Most users considered ionization a set parameter and assume that it is not a parameter that can and should be changed. This limits the way GC–MS can be used (often only for identification based on library matching). Reliance on commercial libraries and therefore set ionization parameters is easily addressed by increased software capabilities, allowing in-house user libraries to be easily built. We are trapped in a 70eV box!

Ionization is variable for different compounds based on chemical structure. GC–MS utility is lost when ionization is not optimized. By optimizing the degree of ionization as well as ionization efficiency, traditional compound identification experiments could benefit from better detection limits and the possible reduction of isobaric interferences. Control over the ionization process could trigger an emergence of fundamental investigations of chemical structure and gas phase chemistries.

Patkin and Goodman:The future is very strong as evidenced by increasing demand. The market is demanding more sensitive instruments that are faster, less expensive, and easier to use. The analysts are less experienced in GC–MS and have increasing levels of responsibility for other analyses. GC–MS needs to be “smarter.” Several years ago, the concept of “chemist in a box” was popular – an analytical instrument with software smart enough to tell the user when the data meets required QA/QC criteria, coupled with self diagnostics sophisticated enough to work with the customer to resolve most instrumental and method-related problems without having to call in an expert. While not yet implemented, this is still required.

Taylor:GC–MS is a well known, well developed analytical tool that provides chemists a relatively inexpensive means of characterizing their organic samples. As such, we believe it will have a place in the lab for many years to come.

What is the GS–MS application area that you see growing the fastest?

Kowalski:GC–MS is ideal for trace analysis and when compound identity is critical, especially those applications that can have legal ramifications. In general, food safety as an industry is growing because of recent contamination issues in the news, i.e. melamine and Bisphenol A, resulting in a severe decrease in consumer confidence. GC–MS fits a segment of this market well and has benefitted from the crossover with the environmental industry, like pesticide analysis.

LC–MS-MS is growing rapidly in this market as well but some analyses remain more amenable to GC–MS, for example brominated flame retardants and polycyclic aromatic hydrocarbons. Also, GC–MS instrumentation is much more prevalent in the market and this includes the number of skilled users. Food contaminants knowledge is growing rapidly not only due to our ability to use technology to investigate, but also because industrial society has introduced many problems. These pollutants or contaminants straddle the food safety and environmental arenas and require governments and scientists to investigate potential problems and vigilantly monitor problems that already exist. GC–MS will play an important role is this effort.

Patkin and Goodman:The application area growing fastest for GC–MS is quality testing of consumer products on a broad scale. This testing includes children’s products, food, and nutraceuticals, among others. This type of testing includes many different types of samples with a wide variety of potential contaminants or adulterants. GC–MS is uniquely suited for this type of application as a result of its ability to identify unknowns with the aid of large, trusted mass spectral data libraries.

The dynamic nature of quality problems in these sectors requires a complete analytical solution focused on a specific application, rapid response times, ease of use, and reliability. These solutions will allow users of GC–MS to minimize ramp-up time and begin verifying product quality.

Taylor:One of the hot research areas now is in biofuels. Researchers are working on the fermentation process to optimize the conversion of cellulosic materials into usable fuel. There is a lot of interest in this area for obvious reasons and GC–MS provides these researchers a tool to help characterize their fermentation results.

What obstacles stand in the way of GC–MS development?

Kowalski:Two main obstacles block the development of GC–MS. One is the 70eV box that has developed for historical reasons and not scientific reasons. Early in GC–MS development, ionization was standardized because mainly one industry adopted the technique quickly. The environmental industry set the standard for ionization parameters based on the compounds of interest at that time. Spectral libraries were built based on 70eV and that appears to be the end of the story. New user-friendly software packages have helped to free us by making it easy to build in-house spectral libraries. This fits hand-in-hand with the idea of using a tunable ion source to optimize ionization.

The second barrier to GC–MS development and popularity lies with the GC inlet. Having spent hours on technical service with customers, I can estimate that, conservatively, 80 percent of problems can be linked to the GC inlet. Most of the time, cleanliness of the liner and seals are the culprits. As a user, I am much more reluctant to perform regular maintenance and troubleshooting when I have to vent the mass spectrometer. A new inlet that allowed for easier column installation and changing inlet parts without venting the mass spectrometer would be incredible. The gas chromatograph and mass spectrometer would benefit from proper care and the technique would become more time and cost efficient. I know it would have saved me some frustration and tears when I first started.

Patkin and Goodman:The major technological obstacle to GC–MS is noise. There have been significant advancements over the last few years in eliminating background noise through ion optics, electronics, and software. Improving signal-to-noise without a significant cost increase continues to be an area of active research.

Most quadrupole GC–MS systems can now scan over 10,000 µ/s and 50 scans/s for compatibility with “fast GC.” The ongoing challenge is to maintain good mass peak shape and resolution, since the MS is scanning so fast that the ions may not have enough RF cycles in the rods to be well-filtered.

What was the biggest accomplishment or news in 2008 for GC–MS? Were there any changes or developments since 2007?

Kowalski:Traditionally, GC–MS is configured with a single quadrupole mass spectrometer. In the past few years, there has been recognition of GC–MS instruments with alternative mass analyzers, like ion traps and time-of-flights. When I teach seminars, more and more individuals raise their hands when I ask who is using ion traps and time-of-flight mass (TOF) spectrometers. These analyzers expand the capabilities of the technique, providing accurate mass, sensitivity, and MS-MS ability. Instrument manufacturers are providing diverse platforms and labs are actually adopting and using these instruments. As chemists welcome and implement less common mass analyzers, this can lead to a bright future for more sophisticated techniques like 2D GC-TOFMS.

Patkin and Goodman:2008 saw a continued expansion of GC–MS into new market areas as a result of product recalls and quality problems. This began in 2007 with recalls of pet food as a result of melamine, and of toys due to an erroneous chemical coating.

GC–MS is a critical technology in the investigation and ongoing quality control behind the scenes of many high-profile recalls and regulations. The new regulations dictate GC–MS as a preferred technology to verify product quality. In response to additional regulations, many new laboratories and scientists are exposed to and are now using GC–MS to preserve the quality of consumer products.

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