52 SPECTROSCOPY
the identification of certain compounds: a new instrument was introduced to collect GC effluent on a liquid-nitrogen cooled, IR transparent window, enabling direct analysis of the deposited solid material. Tis technique proved superior to the IR light pipe in sensitivity, IR spectral quality, and allowed direct comparison of the collected spectra to existing IR databases. Te research focused on the routine identification of commonly encountered drugs, designer drugs, closely related drug isomers, as well as the fundamentals of the GC and IR systems, the team reported. “Te research was undertaken to develop this technology into a viable technique for the forensic community.” Te instrument proved to be a powerful forensic tool providing complementary data to GC/MS.
Detecting explosives For the purpose of explosive detection on-site (for instance, a crime scene or security checkpoint) Kirchner concedes
that ion mobility is better suited: “It is superior in short time analysis (seconds) with no need of sample preparation.” However, his team’s method is capable of providing quantitative analysis (how much of the explosive was present). “Our method would be used for evaluation of the potentially new developed system.” In their research the team
employed fast GC with electron capture detector (GC-EDC) and fast GC with quadrupole mass spectrometry detector (QMS) to improve the detectability of tested explosives.
Tey found that the energy
of electrons for EI ionisation had no significant influence on the detectability of the searched explosives. “In the case of ECD used for detection, significant band broadening was observed in the cell of the detector and increase of auxiliary gas flow rate had no positive effect on the peak shapes.”
Although GC separation of polar explosives is affected by their adsorption in the
chromatographic system, which results in decreased response and peak tailing, the team found the application of analyte protectants lowered the degree of explosives adsorption in the system greatly. Tis resulted in improved peak shapes and linearity of response.
The future
Te use of GC and MS is a preferred method in chemical detection and analysis. GC- MS combines the features of both to identify different substances within a test sample. Applications include drug detection and explosives analysis. Furthermore, the combination of GC, MS and other technology is taking lab analysis forward, so refining scientific testing and the better isolating of target elements from background disturbance. Tese advances may not be regarded as newsworthy as the novel miniature systems deployed in the field, but the hard-nosed, in-laboratory progress is not only fundamental to in-depth analysis, but also key to all associated technology.
The Vermont Forensic Laboratory
www.scientistlive.com
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