Name: controlled odor mimic permeation systems for olfactory training and field testing
Uploaded: 2021-01-28T12:30:00
Description: Watch this Scientific Journal Video about Controlled Odor Mimic Permeation Systems for Olfactory Training and Field Testing at JoVE.com

This work was funded in part by the Office of Naval Research and the National Institute of Justice (2006-DN-BX-K027). The authors wish to thank the many &#8220;Furton Group&#8221; students that have participated in this project, as well as collaborators from the U.S. Naval Research Laboratory and the Naval Surface Warfare Center (Indian Head EOD Technology Division). Finally, the authors thank Peter Nunez of U.S. K-9 Academy, Tony Guzman of Metro-Dade K9 Services, and Miami-Dade area law enforcement canine teams.

1. Assembly of COMPS (Figure 1)
<ol>
	<li>For neat (liquid) compound on a substrate (Figure 1A)
	<ol>
		<li>To impregnate the substrate with odorant, use a calibrated pipette to add 5 &#181;L of neat compound to a 2 x 2 inch cotton gauze pad or other substrate of choice (see Table of Materials).</li>
		<li>Fold the gauze pad in half and place this (or an alternative substrate material) into a 2 x 3 inch low-density polyethylene permeable bag. ...

<ol>
	<li>Buck, L., Axel, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+multigene+family+may+encode+odorant+receptors:+A+molecular+basis+for+odor+recognition.">A novel multigene family may encode odorant receptors: A molecular basis for odor recognition.</a> Cell. 65, 175-187 (1991).</li><li>Furton, K. G., Myers, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scientific+foundation+and+efficacy+of+the+use+of+canines+as+chemical+detectors+for+explosives.">Scientific foundation and efficacy of the use of canines as chemical detectors for explosives.</a> Talanta. 54, 487-500 (2001).</li><li>Leitch, O., Anderson, A., Kirkbride, K., Lennard, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biological+organisms+as+volatile+compound+detectors:+A+review.">Biological organisms as volatile compound detectors: A review.</a> Forensic Science International. 232, 92-103 (2013).</li><li>Simon, A. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+for+controlled+odor+delivery+in+canine+olfactory+testing.">Method for controlled odor delivery in canine olfactory testing.</a> Chemical Senses. 44 (6), 399-408 (2019).</li><li>Hallowell, L. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+hidden+explosives:+New+challenges+and+progress+(1998-2009).">Detection of hidden explosives: New challenges and progress (1998-2009).</a> Forensic Investigation of Explosives. 2nd Ed. , 53-77 (2012).</li><li>Papet, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Narcotic+and+explosive+odors:+Volatile+organic+compounds+as+training+aids+for+olfactory+detection.">Narcotic and explosive odors: Volatile organic compounds as training aids for olfactory detection.</a> Canine Olfaction Science and Law. , 265-278 (2016).</li><li>Furton, K., Harper, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+Odor+Mimic+Permeation+System.">Controlled Odor Mimic Permeation System.</a> US Patent. , (2017).</li><li>Macias, M. S., Guerra-Diaz, P., Almirall, J. R., Furton, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+piperonal+emitted+from+polymer+controlled+odor+mimic+permeation+systems+utilizing+canis+familiaris+and+solid+phase+microextract-ion+mobility+spectrometry.">Detection of piperonal emitted from polymer controlled odor mimic permeation systems utilizing canis familiaris and solid phase microextract-ion mobility spectrometry.</a> Forensic Science International. 195, 132-138 (2010).</li><li>Harper, R., Almirall, J., Furton, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+dominant+odor+chemicals+emanating+from+explosives+for+use+in+developing+optimal+training+aid+combinations+and+mimics+for+canine+detection.">Identification of dominant odor chemicals emanating from explosives for use in developing optimal training aid combinations and mimics for canine detection.</a> Talanta. 67, 313-327 (2005).</li><li>Francis, V. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+identification+of+volatile+organic+compounds+from+synthetic+cathinone+derivatives+for+the+development+of+odor+mimic+training+aids.">The identification of volatile organic compounds from synthetic cathinone derivatives for the development of odor mimic training aids.</a> Florida International University. , (2017).</li><li>Huertas-Rivera, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+the+active+odors+from+illicit+substances+for+the+development+of+optimal+canine+training+aids.">Identification of the active odors from illicit substances for the development of optimal canine training aids.</a> Florida International University. , (2016).</li><li>DeGreeff, L. E., Furton, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collection+and+identification+of+human+remains+volatiles+by+non-contact,+dynamic+airflow+sampling+and+SPME-GC/MS+using+various+sorbent+materials.">Collection and identification of human remains volatiles by non-contact, dynamic airflow sampling and SPME-GC/MS using various sorbent materials.</a> Analytical and Bioanalytical Chemistry. 401, 1295-1307 (2011).</li><li>DeGreeff, L. E., Curran, A. M., Furton, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+selected+sorbent+materials+for+the+collection+of+volatile+organic+compounds+related+to+human+scent+using+non-contact+sampling+mode.">Evaluation of selected sorbent materials for the collection of volatile organic compounds related to human scent using non-contact sampling mode.</a> Forensic Science International. 209 (1-3), 133-142 (2011).</li><li>Simon, A. G., Mills, D. K., Furton, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+and+canine+analysis+as+complimentary+techniques+for+the+identification+of+active+odors+of+the+invasive+fungs,+Raffaelea+lauicola.">Chemical and canine analysis as complimentary techniques for the identification of active odors of the invasive fungs, Raffaelea lauicola.</a> Talanta. 168, 320-328 (2017).</li><li>Penton, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+development+with+solid+phase+microextraction.">Method development with solid phase microextraction.</a> Solid Phase Microextraction: A Practical Guide. , 27-58 (1999).</li><li>Robards, K., Haddad, P. R., Jackson, P. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Principles and Practice of Modern Chromatographic Methods. , (2004).</li><li>MacCrehan, W., Moore, S., Schantz, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+headspace+component+vapor-time+profiles+by+solid-phase+microextraction+with+external+sampling+of+an+internal+standard.">Evaluating headspace component vapor-time profiles by solid-phase microextraction with external sampling of an internal standard.</a> Analytical Chemistry. 83, 8560-8565 (2011).</li><li>Macias, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Development of an Optimized System of Narcotic and Explosive Contraband Mimics for Calibration and Training of Biological Detectors. , (2009).</li><li>Simon, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Detection of an Invasive Pathogen through Chemical and Biological Means for the Protection of Commercial Crops. , (2017).</li></ol>

Controlled Odor Mimic Permeation Systems (COMPS) are easily created by sealing an odorant of interest into a permeable bag. This may be done by pipetting a neat liquid compound onto an absorbent material and then placing the absorbent material into the bag; by placing a pure, solid compound directly into the bag4, as was done in the case of piperonal8; or by placing the target material containing multiple or unknown odorants into a permeable bag, as was done with fungus-inf...

Olfaction is a crucial, yet often overlooked, sensing mechanism used by most animals. For many it is the main mechanism for locating food, finding a mate, or sensing danger1. Furthermore, the olfactory capabilities some animals, most notably canines, are regularly exploited by humans for the detection of contraband (e.g., narcotics or explosives), or other objects of interest, such as missing persons, invasive species, or diseases2,3. For canine detection research or other olfaction research topics, investigators often study the process of olfaction and the strengths and limitations of the olfactory system. As such, it is generally desirable to control the release of an odorant vapor into the environment to reproducibly deliver known quantities of odorant during testing. Failure to account for variations in odor availability due to factors such as vapor pressure or environmental effects often complicates data interpretation and applicability4. It is similarly desirable to provide an established quantity of odor during training scenarios for detection canines. For example, studies by Hallowell et al.5 and by Papet6 have indicated the importance of odor intensity in odor perception, and that altering the intensity of an odorant can affect how it is perceived alone or in a mixture.
In laboratory settings, the use of analytical equipment such as permeation tubes with controllable ovens, vapor generators, or olfactometers may be used to control odor delivery. However, this type of equipment is impractical for use during field testing and training scenarios4. The Controlled Odor Mimic Permeation System (COMPS) was developed as a simple, low-cost, and disposable method for controlled odor delivery requiring no external power. Therefore, they can easily be incorporated into a variety of different testing and training scenarios7. COMPS units are simply composed of an odorant of interest on an absorbent material sealed inside of a permeable polymer bag, stored in a secondary containment system. The utilization of COMPS reduces variability between tests and improves consistency during training exercises8.
Odor delivery or availability from COMPS is measured in terms of permeation rate, as determined by gravimetric analysis in terms of mass of vapor released over time. Permeation rates can be controlled by a number of factors, including the thickness of the polymer bag, its available surface area, the type of absorbent material (substrate) used, and the amount of the odorant. Permeation rate is constant for a given period of time (hours or days) depending on the odorant being used. This allows for minimal variability in odor delivery during testing or training. During storage, COMPS come to equilibrium within the impermeable outer container, resulting in an instant source of odorant vapor at a known permeation rate.
COMPS were initially designed to contain odorants associated with explosive materials and to be used as odor mimics7. As defined by Macias et al., an odor mimic simulates a material of interest, such as an explosive, by providing the dominant volatile compounds, or odorants, found in the headspace of that material without the presence of the parent material itself8. To create an odor mimic, the active odorants of the parent material must be determined. An active odorant, in this scenario, is described as a volatile compound that a trained explosive-detection canine detects, believing that there is an actual explosive material present. Having identified dominant volatile compounds in the headspace of several explosive materials, COMPS were prepared to release these individual odorants at a controlled rate for the duration of canine olfactory detection field trials and determine the active odorant associated with several explosive materials. COMPS were successfully used for this purpose7,9 and have since been used as odor mimics for further explosive detection training.
Macias et al. utilized COMPS containing piperonal, a pure chemical solid at room temperature that, in the vapor phase, has been shown to be the active odorant for MDMA (3,4-methylenedioxymethamphetamine), the psychoactive drug known as ecstasy. The researchers used varying thicknesses and surface areas of low-density polyethylene bags to adjust the permeation rate of piperonal vapor. This series of COMPS was then used to estimate piperonal detection threshold for trained narcotics-detection canines8. Conversely, in a separate study, COMPS bag thicknesses were adjusted to minimize the deviation of permeation rates between each compound in a homologous series though they possessed drastically varying vapor pressures. If a single bag thickness had been used in this study, those compounds with higher vapor pressures would have yielded much higher permeation rates. By increasing the bag thickness for the higher volatility compounds, the permeations rates were adjusted so that they were similar for all compounds4. Both studies demonstrate the utility and adaptability of the COMPS to control vapor release. Similar studies optimizing polymer bag thickness as well as absorbent material have been carried out in the creation of odor mimics for synthetic cathinones (i.e., bath salts)10, other narcotics (including heroin and marijuana11), and human odor compounds12,13. In a final example, Simon et al. investigated the active odorants associated with an invasive fungus species14. Whole pieces of infected tree bark, instead of the extracted odorants, were placed directly into the polymer bag to control release during canine olfaction testing14. COMPS can be utilized for a variety of scenarios, and the protocols discussed herein were chosen to demonstrate the diversity of this tool.

<table>
	<tbody>
		<tr>
			<td>16 oz economy jars (70-450 finish)</td>
			<td>Fillmore container</td>
			<td>A16-08C-Case 12</td>
			<td></td>
		</tr>
		<tr>
			<td>7890A gas chromatograph / 5975 mass selective detector</td>
			<td>Agilent</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Analytical balance</td>
			<td>Mettler Toledo</td>
			<td>01-911-005</td>
			<td></td>
		</tr>
		<tr>
			<td>Ball regualr bands and dome lids</td>
			<td>Fillmore container</td>
			<td>J30000</td>
			<td></td>
		</tr>
		<tr>
			<td>Cotton gauze (2&#34; x 2&#34;)</td>
			<td>Dukal</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable weighing boats</td>
			<td>VWR</td>
			<td>10803-148</td>
			<td></td>
		</tr>
		<tr>
			<td>Epoxy-lined sample containers, 1 gallon</td>
			<td>TriTech Forensics</td>
			<td>CANG-E</td>
			<td></td>
		</tr>
		<tr>
			<td>Epoxy-lined sample containers, 1 pint</td>
			<td>TriTech Forensics</td>
			<td>CANPT-E</td>
			<td></td>
		</tr>
		<tr>
			<td>Low density polyetheylene bag</td>
			<td>Uline</td>
			<td>S-5373</td>
			<td></td>
		</tr>
		<tr>
			<td>Rtx-Volatiles (30 m x 0.32 mmID) column</td>
			<td>Restek</td>
			<td>10901</td>
			<td></td>
		</tr>
		<tr>
			<td>Silver metalized mylar barrier bag (3.5&#34; x 4.5&#34;)</td>
			<td>ESP Packaging</td>
			<td>95509993779</td>
			<td></td>
		</tr>
		<tr>
			<td>Silver metalized mylar barrier bag (5&#34; x 8.5&#34; x 3&#34;)</td>
			<td>ESP Packaging</td>
			<td>95509993793</td>
			<td></td>
		</tr>
		<tr>
			<td>Solid phase microextration fiber assembly (PDMS/DVB/CAR)</td>
			<td>Sigma-Aldrich</td>
			<td>57328-U</td>
			<td></td>
		</tr>
		<tr>
			<td>Solid phase microextration holder</td>
			<td>Sigma-Aldrich</td>
			<td>57330-U</td>
			<td></td>
		</tr>
		<tr>
			<td>Tabletop Impulse Sealer</td>
			<td>Uline</td>
			<td>H-190</td>
			<td>Heat sealer</td>
		</tr>
	</tbody>
</table>

controlled odor mimic permeation systems for olfactory training and field testing

The Controlled Odor Mimic Permeation System (COMPS) was developed to provide a convenient field testing method of odor delivery at controlled and reproducible rates. COMPS are composed of an odorant of interest on an absorbent material sealed inside of a permeable polymer bag. The permeable layer allows for a constant release of the odorant over a given amount of time. The permeable bag is further stored in a secondary, impermeable bag. The double-containment procedure allows for equilibration of the odorant from the permeable bag but within the impermeable outer layer, resulting in an instant and reproducible source of odorant vapor upon removal from the outer packaging. COMPS are used in both olfactory testing for experimental scenarios and for olfactory detection training, such as with detection canines. COMPS can be used to contain a wide range of odorants (e.g., narcotics powders) and provide a controlled release of the associated odorants. Odor availability from COMPS is expressed in terms of permeation rate (i.e., the rate of the odorant vapor released from a COMPS per unit time) and is typically measured by gravimetric means. The permeation rate for a given mass or volume of odorant can be adjusted as needed by varying the bag thickness, surface area, and/or polymer type. The available odor concentration from a COMPS can also be measured by headspace analysis techniques such as solid phase microextraction with gas chromatography/mass spectrometry (SPME-GC/MS).

The primary objective of using COMPS in olfactory testing/training is to control the release of the chosen odorants and deliver a controlled amount of the odorant over the duration of the test or training session. Odorant release is measured by gravimetric analysis in terms of mass loss per unit time. Figure 2 gives an example of gravimetric results from the permeation of three identical COMPS prepared from 5 &#181;L of pentanoic acid on cotton gauze through a 3 MIL LDPE bag. A line of regre...

Watch this Scientific Journal Video about Controlled Odor Mimic Permeation Systems for Olfactory Training and Field Testing at JoVE.com

Controlled Odor Mimic Permeation Systems for Olfactory Training and Field Testing

The Controlled Odor Mimic Permeation System is a simple, field-portable, low-cost method of odor delivery for olfactory testing and training. It is constructed of an odorant retained on an adsorbent material and contained inside of a permeable polymer bag allowing controlled release of the odorant vapor over time.

The Controlled Odor Mimic Permeation System (COMPS) was developed to provide a convenient field testing method of odor delivery at controlled and ...

Olfactory research is limited by the lack of methodology for delivering known and reproducible odors during operational testing or training. COMPS provides a convenient fieldable method for controlled odor delivery. COMPS can contain a wide range of odorants and the delivery rates can be varied by adjusting either the bag thickness, the surface area, and/or the polymer type.To impregnate a substrate with odorant, use a calibrated pipette to add five microliters of neat compound onto a two by two inch cotton gauze pad and fold the pad in half. Then place the gauze into a two by three inch low density polyethylene permeable bag and immediately seal the bag with a heat sealer. To determine the permeation rate of the odorants through the permeable bag, place a newly made COMPS in a weight boat inside a fume hood and use a second clean weight boat to zero an analytical balance.Transfer the COMPS from the fume hood onto the balance and to record the mass before quickly returning the COMPS to the fume hood. Then calculate the permeation rate from the COMPS by plotting mass versus time and finding the slope of the line. To analyze the headspace by SPME with gas chromatography mass spectrometry, allow the COMPS to equilibrate in the open weight boat in the fume hood for 30 minutes, transferring the COMPS to a non-reactive container, such as a glass jar or an epoxy lined metal container.For sampling after equilibration, place a lid with a one centimeter hole in the lid onto the one gallon container and insert inappropriate SPME fiber into the hole to extract the analyte of interest. At the end of the extraction period, transfer the fiber into the heated inlet of a gas chromatography mass spectrometer for thermal desorption and analysis. For storage, place a single COMPS in a metalized 3.5 by 4.5 inch barrier bag and heat seal to close, removing as much air as possible from the bag prior to sealing.If multiple odorants or odorants'delivery rates are being tested in a single experiment, placed the bag and secondary containment to eliminate any possible cross-contamination during transportation and storage. Place replicate multiple barrier bags containing individual COMPS of the same analyte and permeation rate in an outer larger container for storage and transport. Then store the bag in cool ambient or refrigerated conditions.To set up a basic canine olfactory test, layout multiple lines of at least five identical containers and set up the trials so that each line contains one container with a target COMPS and four with blank COMPS. Positive control lines prepared in the same manner, but with a known target odor, may be used as appropriate for the experiment, training, or testing scenario. An additional negative control or blank line should contain five blank COMPS and no targets.Next, transfer the permeable bag for each COMPS from the secondary and outer containers into the appropriate trial containers. After 30 minutes of equilibration, start the test. Here, an example of gravimetric results from the permeation of three identical COMPS prepared from five microliters of pentanoic acid on cotton gauze through a three mil low density polyethylene bag are shown.The addition of regression to the graph reveals that the permeation rate is 37 micrograms per minute for this set of COMPS. The amount of odorant released for a given test can be adjusted by modifying the amount of material in the bag, the surface area of the permeable bag material, or the bag thickness. Here, the variation in vapor pressures across the groups of analytes are compared to the variation in permeation rate after adjusting the bag thickness to the control permeation rates of each analyte, making the rates as similar as possible.Conversely, adjusting the bag thickness for a single analyte allows the permeation rates to vary by three orders of magnitude. Headspace measurements can be used to better measure the amount of odorant available during a given testing or training scenario. For example, in this representative chromatograph, the piperonal peak areas can be observed to increase with the increasing permeation rate.Using these three sets of piperonal COMPS in canine trials, a measurement of the limit of detection of the canines for piperonal was estimated. In this analysis, the permeation rate and thus the odor availability, increased as well as the number of canines alerting to the appropriate COMPS. Since COMPS were first developed, we've used them to establish active odor signatures for a variety of detection targets, estimate limits of detection, and test canine discrimination capabilities.

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