Technology Forum: GC-MS

This month, our Technology Forum will discuss the topic of gas chromatography–mass spectrometry (GC–MS). Joining us for this discussion is Monty Benefiel of Agilent Technologies, Sky Countryman, GC Product Manager at Phenomenex, and Douglas Later, President of Torion Technologies.

What trends do you see emerging in GC-MS?

Benefiel:There are two main trends in GC–MS, technology enhancements and process optimization for higher performance. Although improvements in sensitivity specifications are routinely discussed, that is only a small part of what users need. The standard sensitivity test is based on an inert compound in a clean solvent – far different than the complex samples with reactive compounds that are encountered in most laboratories. That is why recent technologies such as capillary flow technology devices to select or reject parts of a chromatogram, inert sources to preserve reactive compounds, trace ion detection to distinguish signal from chemical noise, and deconvolution software to resolve co-eluting peaks have been developed. These changes recognize that we must look at the GC–MS as a system with specific technologies that contribute to solving difficult analyses.

At the same time, we must look at laboratory process improvements, not just technology enhancements. Most users are accustomed to operating GC–MS in scan (for library searching) or selected ion monitoring modes (for ultimate sensitivity). More modern instruments offer a combination that gives both scan and SIM modes in one run. However, instrument capability is only a part of a practical solution. To set up a complex SIM and scan analyses can be a time-consuming process that requires extensive manual entry of SIM ions, scan ranges and retention times. Furthermore, once a column is clipped for maintenance, the retention times must be reset and the method updated. These setup and maintenance tasks prevented combined scan and SIM from being used routinely. Recent advances have overcome these difficulties. Software is now available to automatically create a SIM/scan method from a scan data file. Retention time locking makes retention times permanent so that the method does not have to change once a column is clipped. Advanced GC–MS technologies are made practical with software capabilities that focus on the process.

Countryman:There are several trends that will emerge in GC–MS. The biggest things Ihear people want are higher sensitivity and faster analysis. In addition,stability will also be very important because many high volume labs, such asthe environmental and toxicology labs, analyze very dirty samples that caneasily foul a sensitive instrument. These trends will result in competitionbetween system manufactures to develop a sensitive and robust system that ismore user friendly.

Later: Along with the push for better sensitivity, faster analyses times and affordability, GC–MS technology is being miniaturized for hand-portability and field measurements.  GC–MS instruments that weigh less than 25 lbs, are battery operated, have on-board carrier gas supply, and are field-ruggedized will be used more and more by first responders and soldiers to detect chemical and biological threat agents.  The operation of these types of GC–MS instruments is also being simplified so that field personnel can use them to obtain immediate answers in emergency and threat situations.  The primary advantages of GC–MS technology over other field measurement technologies is selectivity and sensitivity; less false positives and fewer false negatives.  Miniaturization of GC–MS technology will also make contributions in conventional laboratories for simpler applications, as well as in production environments for process monitoring.

What is the future of GC–MS?

Benefiel:As the previous discussion shows, GC–MS improvements can be made in terms of both technology enhancements and process improvements. Although GC and MS are both relatively mature technologies, they do have a synergistic relationship. Too often, companies and users look at the GC simply as an injection system for the MS. By looking at the system with complementary separation capabilities, greater overall capabilities can be achieved. Improvements to GC–MS are not strictly due to hardware technologies. Advanced designs take advantage of links with firmware and software. For this reason, we have been able to give new capabilities to 10-year old GC–MS’s through a combination of hardware and software upgrades. Many of the process improvements can be had by simply upgrading to the latest version of software.

Countryman: GC–MS has an established market in the environmental and toxicologicalfields. In GC, the trend is not so much in new applications areas but newsystems. As the cost in bench top GC–MS systems continue to decrease, itbecomes more attractive to buy GC–MS instead of the standard GC-FID systems.Analysts like getting more data with a GC–MS but at a similar cost to aGC-FID.

Later: Faster speeds of analysis will be required by users to provide more instantaneous data and answer time-sensitive questions immediately.  To do this, GC–MS systems will require more sophisticated deconvolution algorithms, simpler user interfaces, and automated, library-based analyte identification capabilities.

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

Benefiel: This question can be answered in a specific and a general sense. The one application area which will see the greatest rate of growth is probably metabolomics because it is currently small compared to traditional applications such as drug and environmental testing. A larger, growing application area is food safety. While there is an overlap with environmental analysis, there is a significant difference. Environmental analyses are primarily target compound analyses where a specific list of compounds is quantitated. Food safety involves target compound analyses, but also screening analyses. In this latter form, you do not necessarily know what may be found in the sample. You cannot inject standards containing all the potential targets – such as pesticides. This is where it is important to have a large database of pesticides incorporating both retention times and spectra to determine whether a specific compound may be present, even though it was not in the injected standard. For the low-levels and complex matrices involved with food analyses, the ability to deconvolute co-eluting spectra is also vital.

In a much more general sense, any GC–MS application dealing with complex samples will grow fast with the new instruments and software. Advances in chromatographic and spectrometric selectivity will be as important as enhanced sensitivity. Sensitivity improvements alone will not be the answer if your compound of interest cannot be separated from interferences. This is the reason why technologies such as capillary flow devices and deconvolution software are key developments that will enhance laboratory capabilities.

Countryman: The use of GC–MS for homeland security and other air monitoring programs isincreasing steadily and will continue to be important as miniaturizationcontinues to make smaller, more portable systems.

Later: GC–MS will be increasingly used by first responders, combat solders, police, firefighters, airport security screeners, and others involved in homeland security, emergency response and defense applications.  GC–MS will also experience growth in the area of on-site field measurements in determining environmental contamination of air, water and soil.

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

Benefiel: The major obstacle at this time is not so much in GC–MS development, but in making operation routine for users. Most laboratories are not using current instruments to their limits. For instance, most laboratories want higher productivity, but many have not changed their methods to reflect what instruments and analytical columns can do today. A common reason is that people are too busy to spend time to optimize their methods. We have made it easier by publishing application notes with downloadable methods. To get the most out of a GC–MS instrument, laboratories must take time to investigate what current instruments and software can do.

Countryman: The GC market isn't growing rapidly. The biggest challenge in GC–MS iskeeping the applications that are historically run using this technique.Many methods are being moved to LC–MS-MS because the analytes are morestable and require less pre-treatment before analysis.

Later:(1) Simplification of the otherwise complex operations of a GC–MS instrument for non-scientist users; (2) Ruggedization for reliable operation in field environments that are more harsh than the laboratory environment in terms of movement and shock, temperature stability and extremes, reliable lightweight power sources, and operating environment air quality; and (3) development of extensive instrument-specific mass spectral libraries for automated identifications.