Article written by Jamie Hoban, Organics QC Technician, Analytical Products Group, Inc.
Complete article from Edition 28 APG eNewsletter
"Well, I manage spurts of activity on occasion, but I really spend most of the time just sitting around."
This description is unlikely to receive high regard when given by any employee or coworker. Why then is it the standard practice in many analytical methods? Since introduction roughly forty-five years ago, the use of highly efficient capillary columns in gas chromatographic (GC) methods has neared universal application. The full capabilities of capillary techniques, however, are infrequently the subject of current research and largely underestimated in the typical laboratory. Useable data, in the form of analyte peaks, is often a relatively small portion of the GC chromatogram, with the balance of analysis time wasted in unproductive baseline.
The stalled progress of GC methods has a defendable history. At the beginning of the capillary revolution, early researchers believed that improvements in sample introduction and data recording could mark another great step in GC technique. Though these inspiring visions were many years before their time, the necessary technologies are available today. And though the defense of impossibility has aided a long-standing complacency in GC methods, research and applications scientists alike would benefit from a new call for revolution.
Fast GC techniques are capable of reducing analysis times fifty to seventy-five percent, or more. These decreased run times translate into lower costs, higher productivity, and faster turnarounds; a winning combination in most imaginable situations. As instrument and column manufacturers have slowly increased availability of the required materials and technology, possibilities for fast, accurate GC analysis have greatly improved during the past five to ten years. Increased offerings in educational seminars are evident more recently as well and provide analysts the opportunity to shift into a higher gear.
The advances in technology required for widespread use of Fast GC include sample introduction, gas control, column designs, and data handling. A completely inclusive system is optimal, as any individual lacking of these requirements becomes a hindrance to efficient application. This initial installment will review the importance of each described technology, while next month’s newsletter will focus on tips and techniques for Fast GC method development and application.
Fast GC "begins at the beginning," with sample introduction becoming a critical step in each analysis. The increased pace of all aspects of the Fast GC run makes quick, repeatable injections a necessity for consistency in peak response and retention time. The prevalence of robotic autosamplers has made days spent performing manual injections a wistful memory for some and an inconceivable notion for those with less time in the field. While GC injectors commonly allow sample introduction in the microliter range to accommodate the capacities of narrow-bore capillary columns, the continued push to decrease the size of these injections to nanoliter amounts simplifies Fast GC applications.
Electronic pneumatic control systems capable of pressures exceeding one hundred pounds per square inch are another advance towards reliable Fast GC. The importance of maintaining a steady flow of carrier gas and limiting retention fluctuations is amplified when the total length of each analysis is reduced and the amount of unproductive baseline is minimized. Electronic controls also allow automatic measures, such as stopping instrument operation when a malfunction is indicated, thereby reducing the safety concerns often raised when considering hydrogen as a carrier gas.
Although all aspects of an analysis are important, column selection is arguably the most important factor in reducing GC run time while maintaining quality results. Advances in manufacturing processes have continually reduced capillary column dimensions while preserving or even improving separation efficiency. A small number of pioneers now offer GC columns only ten meters long with diameters of one hundred micrometers and phase coatings of a mere hundred nanometers. The next installment will contain special attention to column designs and phases.
This final section of Part 1 deals somewhat with advances in GC instrumentation, but also with the general progress of technology. All of the available improvements discussed so far are muted without the capability to collect and record the swift and compact data that Fast GC techniques produce. Data recording and analysis today requires that commonly found assistant to any GC instrument: the computer. Data acquisition rates now make it possible to detect peaks only milliseconds in width that would have gone unnoticed as few as ten years ago. This advancement coupled with the use of high-speed instrument-computer networks and large data storage capacities brings data acquisition inline with current needs, but may again become a limiting factor in the future.
While the information in this first installment may not prove thrilling, the important highlight is that each of the components discussed is necessary and available. Next month's complimentary installment, Techniques and Tradeoffs, will be devoted to specific examples and considerations for applying the time saving methods of Fast GC analysis.
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