Portable gas chromatographs

Flammable atmospheres can be assessed using portable gas chromatographs or, for selected compounds, by colour indicator tubes. More commonly, use is made of explos-imeters fitted with Pellistors (e.g. platinum wire encased in beads of refractory material). The beads are arranged in a Wheatstone bridge circuit. The flammable gas is oxidized on the heated catalytic element, causing the electrical resistance to alter relative to the reference. Instruments are calibrated for specific compounds in terms of 0—100% of their lower flammable limit. Recalibration or application of correction factors is required for different gases. Points to consider are listed in Table 9.10. 

Field Measurement of Polychlorinated Biphenyls in Soil and Sediment Using a Portable Gas Chromatograph... 

Perras JC (1973) Portable gas chromatographic technique to measure dissolved hydrocarbons in seawater. US NTIS AD report no 786583/5GA... 

Presley LA. 1979. Evaluation of a portable gas chromatograph for arson analysis Column selection. Arson Anal Newsl 3(5) 18-34. 

Liu, X. and J. Pawliszyn. 2005. On-site environmental analysis by membrane extraction with a sorbent interface combined with a portable gas chromatograph system. Int. J. Environ. Anal. Chem. 85 1189-1200. 

Jerpe J, Davis A. 1987. Ambient capillary chromatography of volatile organics with a portable gas chromatograph. J Chromatogr Sci 25 154-157. 

Today there are several good portable gas chromatograph units on the market. Any further development of this approach for the development of a successful field method will have to consider the following criteria ... 

One of the instruments obtained by ERDA will be evaluated at ORNL to assess its potential as a monitor for hazardous by-products from alternative energy sources. Investigations to determine the desirability of a membrane inlet system for concentrating organic vapors are planned. The feasibility of using a portable gas chromatograph with the portable mass spectrometer, when a complex mixture analysis is required, is also being studied. 

Ciucanu 1 and Chiriac A. Membrane and trap system for continuous monitoring of volatile organic compounds using a portable gas chromatograph with thermal conductivity detector. J. Sep. Sci. 2002 25 447 52. 

The dramatic advance in GC instrumentation is the introduction of portable gas chromatographs, which have been developed during 1990s to provide a field-based analysis. Recently, the micro high-speed GC portable has also appeared to carry out the analysis up to 10 times faster than conventional laboratory GCs. ... 

Figure 2.19 Portable gas chromatograph. A lightweight (6.6kg), battery operated, isothermal GC. This miniature analytical engine using a capillary column and a photoionization detector is conceived for the analysis of gas and other volatile compounds (VOCs) (reproduced courtesy of Photovac). Below is an example of chromatogram obtained with such an instrument.

Microsensor Systems, Inc. (Fairfax, VA) offers SAW devices and coatings for organophosphorus compounds, aromatic hydrocarbons, water vapor, and others. A four-sensor array consisting of four 158 MHz dual-delay-line oscillators and a portable gas chromatograph with an SAW detector are also available. 

Practical aspects. The detector is especially suitable for portable gas chromatographs since no additional gases are needed for its operation. 

The PID is nondestructive, relatively inexpensive, of rugged construction and easy to operate. The linear range is approximately 10. For favorable compounds the PID is 5 to 50 times more sensitive than the FID [280,286]. In other cases it may not respond at all or respond poorly determined by the ionization potential of the compound and the photon energy and flux. On an individual compound basis relative detector response factors vary over a wide range allowing the PID to be used as a selective detector for some applications. Major applications of the PID are the analysis of volatile organic compounds from environmental samples and in field-portable gas chromatographs [292]. 

C, Gas Chromatograiphie Analysis, The use of a portable gas chromatograph located in a sheltered area near the sampling system is the best method to follow the course of the coking cycle. 

On the reactor, GC sample ports and temperatxue and pressure sensors provided monitoring of reactor inlet and outlet VOC concentrations and temperature and pressxffe drop throughout the system. A portable gas chromatograph provided on-line VOC organic anal-... 

Portable GCs GC and GC-MS remain dominant techniques for the determination of multiple volatile and semivolatile organic compounds in workplace air analysis. Portable gas chromatographs were introduced in the late 1970s and the technology has continued to evolve ever since. Most field GCs consist of an injection system with either syringe... 

Sixth-generation portable GCs, which are highspeed portable gas chromatographs, have been introduced recently. They can analyze single or multiple compounds within as little as a few seconds up to a couple of minutes. 

A variety of portable instruments commonly referred to as sniffers are used. They tend to be nonspecific detectors based on the principles of flame ionization and photoionization. More recently portable gas chromatographs and gas chromatographs coupled with mass spectrometers have become available for use at the fire scene. These provide more information about the sample than sniffers but require more training in their use and interpretation of data. 

Sekiguchi, H., Matsushita, K.,Yamashiro, S., Sano,Y., Seto, Y, Okuda, T., Sato, A. (2006) On-site determination of nerve and mustard gases using a field-portable gas chromatograph-mass spectrometer. Forensic Toxicology, 24,17-22. 

Contreras, J.A., et al. (2008) Hand-portable gas chromatograph-toroidal ion trap mass spectrometer (GC-TMS) for detection of hazardous compounds. Journal of the American Society for Mass Spectrometry, 19,1425-1434. 

C. Tedlar Gas Sampling Bags-Samples are collected by drawing a known volume of air into a Tedlar gas sampling bag. The ethylene oxide concentration is often determined on-site using a portable gas chromatograph or portable infrared spectrometer. 

EPA/600/R97/019 (SCAPS-LIF), EPA/600/R97/020 (ROST) Field portable gas chromatograph/ mass spectrometer Bruker-Franzen EM 640 (EPA/600/R-97/I49)... 

Hence, all compounds having a conductivity less than the carrier gas will be detected by the TCD, which is a universal concentration-sensitive detector. The TCD is nondestructive, and may be used for preparative separations. The detector has however low sensitivity, and the minimum detectable (M D) mass is about 10 ng even using He or H2 as carrier gas. Other detector characteristics can be found in Table 2.4. The TCD is commonly used for determination of light and permanent gases in packed or PLOT columns. The TCD is well suited for portable gas chromatographs because it is easily miniaturized and does not require extra gases. 

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