Emerging chemical threats to homeland security challenge the specificity of sensor-based chemical detectors. As the
number of chemicals to detect increases, the false alarm rates of these sensor-based systems tend to increase and the
usefulness of the detector in real world situations declines. The infrared (IR) absorption spectrum of a material is a
physical constant and highly specific for the molecule of interest. For many years, IR spectra have been used by chemists
to identify unknowns based on comparison with spectra of known materials and to determine the presence of chemical
functional groups through spectral interpretation. IR spectroscopy is well suited for the identification of broad-based
chemical threats. This discussion shall concern the conceptual development of a hand held IR spectroscopy system for
the identification of chemical vapor threats. The discussion shall focus on design tradeoffs where miniaturization is of
paramount importance. Quantitative IR absorption spectra of threat compounds were used to model absorption line
strengths at moderate spectral resolutions. IDLH detection limits targets, acquisition time, etendué, and signal-to-noise
parameters guided the concept design and pathlength of a long path gas cell used in conjunction with a hand held FT-IR
spectrometer.
IR spectroscopy is a broadly applicable technique for the identification of covalent materials. Recent advances in instrumentation have made Fourier Transform infrared (FT-IR) spectroscopy available for field characterization of suspect materials. Presently, this instrumentation is broadly deployed and used for the identification of potential chemical hazards. This discussion concerns work towards expanding the analytical utility of field-based FT-IR spectrometry in the characterization of biological threats. Two classes of materials were studied: biologically produced chemical toxins which were non-peptide in nature and peptide toxin. The IR spectroscopic identification of aflatoxin-B1, trichothecene T2 mycotoxin, and strychnine was evaluated using the approach of spectral searching against large libraries of materials. For pure components, the IR method discriminated the above toxins at better than the 99% confidence level. The ability to identify non-peptide toxins in mixtures was also evaluated using a "spectral stripping" search approach. For the mixtures evaluated, this method was able to identify the mixture components from ca. 32K spectral library entries. Castor bean extract containing ricin was used as a representative peptide toxin. Due to similarity in protein spectra, a SIMCA pattern recognition methodology was evaluated for classifying peptide toxins. In addition to castor bean extract the method was validated using bovine serum albumin and myoglobin as simulants. The SIMCA approach was successful in correctly classifying these samples at the 95% confidence level.
A new point sensor for identifying chemical weapons of mass destruction and other hazardous materials based on Fourier transform infrared (FT-IR) spectroscopy is presented. The sensor is a portable, fully functional FT-IR system that features a miniaturized Michelson interferometer, an integrated diamond attenuated total reflection (ATR) sample interface, and an embedded on-board computer. Samples are identified by an automated search algorithm that compares their infrared spectra to digitized databases that include reference spectra of nerve and blister agents, toxic industrial chemicals, and other hazardous materials. The hardware and software are designed for use by technicians with no background in infrared spectroscopy. The unit, which is fully self-contained, can be hand-carried and used in a hot zone by personnel in Level A protective gear, and subsequently decontaminated by spraying or immersion. Wireless control by a remote computer is also possible. Details of the system design and performance, including results of field validation tests, are discussed.
The feasibility of using IR mapping microspectroscopy to locate and identify a neuroanatomical probe in brain tissue has been demonstrated. Frequency specific IR maps were generated from a latex nanosphere injection site in brain tissue. The 2240 cm-1 vCN absorption band, attributable to the latex, was used as an analytical band.
Conference Committee Involvement (10)
Next-Generation Spectroscopic Technologies XI
16 April 2018 | Orlando, FL, United States
Next-Generation Spectroscopic Technologies X
10 April 2017 | Anaheim, CA, United States
Next-Generation Spectroscopic Technologies IX
18 April 2016 | Baltimore, MD, United States
Next-Generation Spectroscopic Technologies VIII
20 April 2015 | Baltimore, MD, United States
Next-Generation Spectroscopic Technologies VII
5 May 2014 | Baltimore, MD, United States
Next-Generation Spectroscopic Technologies VI
29 April 2013 | Baltimore, Maryland, United States
Next-Generation Spectroscopic Technologies V
23 April 2012 | Baltimore, Maryland, United States
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