FIELD SAMPLING AND DETECTION USING A NOVEL PORTABLE GAS CHROMATOGRAPH-MASS SPECTROMETER
Jacolin A. Murray, Jesse A. Contreras,1 Samuel E. Tolley,2 Joseph L. Oliphant,2 H. Dennis Tolley,1 Stephen A. Lammert,2 Edgar D. Lee,2 Jeffrey, L. Jones,2 Randall W. Waite,2 Douglas W. Later,2 and Milton L. Lee1
1 Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT
2 Torion Technologies, American Fork, UT
The ability to rapidly detect and identify hazardous analytes in the field has become increasingly important. One of the most important analytical detection methods in the field is gas chromatography-mass spectrometry (GC-MS). A portable GC-MS based on a miniature toroidal ion trap mass analyzer and a low thermal mass GC is described. The system has an effective mass/charge (m/z) range of 50-442 with mass resolution at full-width half-maximum (FWHM) of 0.55 at m/z 91 and 0.80 at m/z 222.This portable GC-MS system weighs <13 kg (28 lb), including batteries and helium carrier gas cartridge, and is totally self-contained within the dimensions of 47 x 36 x 18 cm (18.5 x 14 x 7 in.). System start-up takes about 3 min and sample analysis with library matching typically takes about 4 min, including time for column cool-down. Peak power consumption during sample analysis is about 80 W. Battery power and helium supply cartridges allow 50 and 100 consecutive analyses, respectively. The GC-MS can detect 200 pg of methyl salicylate on-column.
Sample introduction into the system is achieved through solid phase microextraction (SPME). This technique is a convenient approach for sampling gaseous and liquid samples, concentrating the analytes, and transferring them to the GC-MS. To simplify sampling with SPME, a new sampling syringe was developed that can be easily operated with one hand. A high flow air sampling trap is being developed for the portable GC-MS system using short open capillaries containing specialized coatings. By using these open tubular traps, many problems that are associated with traditional packed air sampling traps can be avoided such as high pressure drops, contamination from adsorbents, water retention, and long desorption times. However, the main disadvantage of these traps is low sample capacity, which can be increased by increasing the surface area of the polymer coating. Bundling a number of capillaries in parallel allows sampling of large volumes of air in relatively short periods of times.