Controlled Odor Mimic Permeation Systems for Olfactory Training and Field Testing

Summary

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.

Abstract

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).

Introduction

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 diseases^2,3. For canine detection research or other olfaction research topics, investigators often study the process of olfaction and the strengths and limitations of ....

Protocol

1. Assembly of COMPS (Figure 1)

1. For neat (liquid) compound on a substrate (Figure 1A)
   1. To impregnate the substrate with odorant, use a calibrated pipette to add 5 µL of neat compound to a 2 x 2 inch cotton gauze pad or other substrate of choice (see Table of Materials).
   2. 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. The suggested bag thicknesses are between 1 MIL, for the fastest permeation rate, to 8 MIL, for a slower permeation rate.
      NOTE: Variations in ....

Results

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 µL of pentanoic acid on cotton gauze through a 3 MIL LDPE bag. A line of regression.......

Discussion

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.......

Materials

List of materials used in this article

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