Dr. Ross J. Harper Profile

Dr. Ross J. Harper

at FLIR Systems Inc

SPIE Involvement:

Author

Publications (5)

Proceedings Article | 5 May 2010 Paper

Intricacies of comparative testing of explosives detectors at the ultra-trace level

Ross Harper, Mark Fisher

Proceedings Volume 7665, 76650R (2010) https://doi.org/10.1117/12.850373

KEYWORDS: Explosives, Sensors, Palladium, Statistical analysis, Contamination, Chemical analysis, Explosives detection, Failure analysis, Glasses, Standards development

Read Abstract +

This paper shall demonstrate the reduced lifetime of ultra-trace explosive residues when subjected to standard laboratory conditions, citing examples of flawed experimental design. The traditional view of "trace" level residue may lie within the detection limit capabilities of bench-top instrumentation. Gas chromatography / mass spectrometry, often the main stay of many trace evidence analysis laboratories can readily deliver nanogram and now potentially upper picogram detection limits. Today, emerging technologies continue to push the limits of detection, and sub-nanogram restrictions give way to picogram and femtogram opportunities. As instrument technologies become more sensitive, the need to work at continually lower detection levels is expressed. Generation of reliable, reproducible ultra-trace samples for the testing, analysis and evaluation of those technologies is challenged by the chemical properties of the very samples under investigation. Unlike testing against bulk quantities of explosives, at the picogram level unforeseen sublimation and sorption phenomena may potentially disrupt an otherwise well-planned test. While it may be valid to assume that the properties of bulk samples of most explosives are relatively constant with respect to time, it may not be safe to assume the same is true of ultra-trace level deposits of explosive residue. The vapor pressures of many common military explosives are low, but they are not zero. This fact cannot be ignored when working with trace levels of explosive residue. Failure of an inexperienced technician to consider these factors when conducting an evaluation may unnecessarily introduce bias into the data, and may result in the misrepresentation of a sensor's capabilities. The analyst is now faced with the complication of working with amounts of explosive so potentially low, that loss of a few picograms of material due to evaporation, air currents, poor laboratory technique or some other diluting factor represents a significant percentage of the total sample mass. Added to the complication are sample and substrate matrix, carry-over, and potential cross contamination effects that may now pose a significant effect rather than a slight background nuisance.

Proceedings Article | 20 April 2010 Paper

Combined pre-concentration and real-time in-situ chemical detection of explosives in the marine environment

Matthew Dock, Ross Harper, Ed Knobbe

Proceedings Volume 7678, 76780U (2010) https://doi.org/10.1117/12.850727

KEYWORDS: Explosives, Sensors, Water, Chemical analysis, Environmental sensing, Molecules, Polymers, Oceanography, Ocean optics, Target detection

Read Abstract +

Proceedings Article | 4 May 2007 Paper

Underwater olfaction for real-time detection of submerged unexploded ordnance

Ross Harper, Matthew Dock

Proceedings Volume 6540, 65400V (2007) https://doi.org/10.1117/12.719742

KEYWORDS: Explosives, Sensors, Oceanography, Water, Environmental sensing, Polymers, Explosives detection, Ocean optics, Biological and chemical sensing, Chemical fiber sensors

Read Abstract +

Proceedings Article | 20 May 2005 Paper

Discrimination of smokeless powders by headspace SPME-GC-MS and SPME-GC-ECD, and the potential implications upon training canine detection of explosives

Ross Harper, Jose Almirall, Kenneth Furton

Proceedings Volume 5778, (2005) https://doi.org/10.1117/12.603928

KEYWORDS: Explosives, Explosives detection, Chemical analysis, Manufacturing, Sensors, Chromatography, Additive manufacturing, Forensic science, Analytical research, Solids

Read Abstract +

Proceedings Article | 22 September 2003 Paper

Optimization of biological and instrumental detection of explosives and ignitable liquid residues including canines, SPME/ITMS and GC/MSⁿ

Kenneth Furton, Ross Harper, Jeannette Perr, Jose Almirall

Proceedings Volume 5071, (2003) https://doi.org/10.1117/12.498122

KEYWORDS: Explosives, Liquids, Sensors, Ions, Spectroscopy, Chemical analysis, Interfaces, Silica, Explosives detection, Forensic science

Read Abstract +

A comprehensive study and comparison is underway using biological detectors and instrumental methods for the rapid detection of ignitable liquid residues (ILR) and high explosives. Headspace solid phase microextraction (SPME) has been demonstrated to be an effective sampling method helping to identify active odor signature chemicals used by detector dogs to locate forensic specimens as well as a rapid pre-concentration technique prior to instrumental detection. Common ignitable liquids and common military and industrial explosives have been studied including trinitrotoluene, tetryl, RDX, HMX, EGDN, PETN and nitroglycerine. This study focuses on identifying volatile odor signature chemicals present, which can be used to enhance the level and reliability of detection of ILR and explosives by canines and instrumental methods. While most instrumental methods currently in use focus on particles and on parent organic compounds, which are often involatile, characteristic volatile organics are generally also present and can be exploited to enhance detection particularly for well-concealed devices. Specific examples include the volatile odor chemicals 2-ethyl-1-hexanol and cyclohexanone, which are readily available in the headspace of the high explosive composition C-4; whereas, the active chemical cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) is not. The analysis and identification of these headspace 'fingerprint' organics is followed by double-blind dog trials of the individual components using certified teams in an attempt to isolate and understand the target compounds to which dogs are sensitive. Studies to compare commonly used training aids with the actual target explosive have also been undertaken to determine their suitability and effectiveness. The optimization of solid phase microextraction (SPME) combined with ion trap mobility spectrometry (ITMS) and gas chromatography/mass spectrometry/mass spectrometry (GC/MSⁿ) is detailed including interface development and comparisons of limits of detection. These instrumental methods are being optimized in order to detect the same target odor chemicals used by detector dogs to reliably locate explosives and ignitable liquids.

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years