Portable Gas Chromatography

Portable gas chromatography (GC) instruments are those that are used outside the laboratory, and both transportable and person-portable types exist within the larger class. A transportable instrument requires external power and a vehicle for movement, while a person-portable instrument may be operated on battery power with a self-supplied carrier gas . Additionally, an arbitrary weight limit of 50 pounds (23 kg) has been used in the past to define a person-portable GC instrument that allows for movement by a single individual. Historically, the capabilities of transportable GC instruments have reflected those of contemporary laboratory gear, while power constraints imposed by battery operation have caused the performance of person-portable GC instruments to suffer. However, recent advances in column heating technology have improved the capabilities of portable GC instruments in both categories, and analysis completed outside of the laboratory is increasingly relied on to answer questions related to industrial processes, material composition, military and homeland defense against terrorism, and workplace and environmental health and safety. The developments that led to the widespread adoption of open tubular fused silica columns in the 1980s, primarily for chromatographic performance, coincidentally made this important GC component strong and lightweight. Also, the low thermal mass of an open tubular GC column allows temperature program analysis using relatively little power if heating may be limited mostly to the column itself, and within the past 10 years the idea of resistive column heating to complete rapid temperature program analysis has led to the commercial availability of very small column assemblies based on this heating approach. Using such a column assembly , aggressive temperature ramp rates are possible even when an instrument is operated using battery power, and the resulting rapid analysis speeds improve the ability to quickly complete GC analyses in the field. With the advent of commercially available resistive column heating, temperature ramping is now routine for newer person-portable instruments and the performance of transportable instruments can in many ways exceed that of traditional laboratory gear. In addition to the developments in portable GC that have resulted from the incorporation of open tubular columns in resistively heated modules, GC components based on microelectromechanical systems (MEMS), particularly the use of micromachining of silicon, has led to new types of components in the field of “micro GC” (µGC). Historical context and some implications of the possibility to create low-cost batch produced µGC components are discussed for this developing field. Discussion is also provided regarding available solventless sample introduction methods to support analysis by portable GC, including sorbent sampling for thermal desorption, solid-phase microextraction, and the use of needle trap sampling devices. Keywords: portable gas chromatography; resistive column heating; thermal desorption; solid-phase microextraction; needle trap sampling