Investigation of the odour profile of Cannabis sativa,

in relation to the training of drug detection dogs

Clare Shave

Supervisor: Dr Gillian Taylor

TEESSIDE UNIVERSITY

School of Science and Engineering

2016

Keywords: Cannabis, Gas Chromatography, Headspace, Drug Detection, Pseudo Scent

Author Biography

I am currently undertaking a bachelor honours degree in Forensic Science at Teesside University and hope to go on to study Forensic Science at Master’s degree

level.

Acknowledgments

I would like to thank Dr Gillian Taylor for the help and support she has given me.

Without her dedication and hard work, I do not believe this work would have been

possible.

ContentsAcknowledgments...............................................................................................................................2

Document Information........................................................................................................................2

Abstract................................................................................................................................................3

Introduction..........................................................................................................................................4

Experimental........................................................................................................................................9

Reagents and materials.....................................................................................................................9

Preparation of laboratory cannabis oil..............................................................................................9

Preparation of standards for analysis................................................................................................9

HS-GC-MS analysis.............................................................................................................................9

Testing of Laboratory Cannabis Oil with Drug Detection Dogs........................................................10

Results...............................................................................................................................................10

Discussion..........................................................................................................................................14

Conclusion.........................................................................................................................................17

References........................................................................................................................................19

Appendices........................................................................................................................................23

Document Information

Total Word Count: 4500

Number of Pages: 37

Number of References: 39

Page 2 of 37

Abstract

Cannabis sativa L. is often detected using drug detection canines (Canis lupus var.

familiaris) due to the highly sensitive olfactory system of the animal. Training drug

detection canines is usually performed using aged cannabis samples and pseudo

scents produced by Sigma Aldrich®, known as Narcotic Scent Marijuana

Formulation. A lack of information regarding these pseudo scents has caused

speculation into the effectiveness of these compounds as training aids.

This research was conducted to determine if the pseudo scent is an effective training

aid for canines, the pseudo scent was tested in comparison to odour profiles of

cannabis, scented oils and soaps and cannabis oil produced within the laboratory.

Gas chromatography – mass spectrometry coupled with headspace (Head Space -

GC/MS) was utilised to analyse limonene, myrcene, frankincense, cannabis burning

oil, soap, candle and laboratory produced cannabis oil. The samples were placed

directly into headspace vials ready for analysis.

The analysis of the pseudo scent headspace profile showed that it contained two

terpenes, in comparison to the sixteen found in the cannabis profile. Alternatively,

the odour profile of cannabis oil produced results comparable to that of cannabis.

Preliminary testing using a canine trained in cannabis detection provided by

Cleveland Police, proved that drug detection canines respond positively to the oil

when used as a training aid.

Page 3 of 37

Introduction

Cannabis sativa L., is a dioecious plant which originates from Eastern and Central

Asia, but is actively grown worldwide (Jagadish, Robertson and Gibbs, 1996; de

Cassia Mariotti et al., 2015). Tropical climates allow the plant to be cultivated outside

naturally, however, temperate climates such as those exhibited in the UK require

indoor cultivation – allowing for year round production (de Cassia Mariotti et al.,

2015; Negrusz and Cooper, 2013). The spread of cannabis from Eastern and Central

Asia is thought to have taken place over the last 10000 years (Jagadish, Robertson

and Gibbs, 1996). Throughout this time there has been many different uses for a

multitude of different civilisations, these include: medicinal, intoxicant, ritual

purposes, sources of fibre, food and oil (de Cassia Mariotti et al., 2015). The use of

cannabis for the recreational purposes is what it is most infamous for in modern

times, the effects of which vary from person to person and the reaction time is

determined by the method of administration (Baggio et al., 2014). Inhalation of

cannabis allows for rapid speeds of absorption allowing the first effects to be felt

within seconds and the full effect within minutes; oral ingestion, however, delays the

affects as absorption is slower within the gut (Vale, 2012).

Cannabis is the most commonly used illicit drug worldwide (Baggio et al., 2014) with

the World Drug Report (2015) stating that the current number of cannabis users,

globally, was approximately 181.8 million, in 2013. The European Drug Report

(2015) also showed an increase in the worldwide seizure of both herbal and

cannabis resin, finding cannabis to be the most commonly seized drug accounting

for eight out of ten seizures. It is suggested that the cause for this fluctuation was an

increase in law enforcement activities, or a possible overall increase in the

production and trafficking of cannabis, with two-thirds of all European seizures being

reported by the United Kingdom and Spain (World Drug Report, 2015; European

Drug Report, 2015). There is also growing evidence to support the opinion that

cannabis is becoming more potent with rising levels of THC within newer varieties,

with current studies showing cannabis with THC levels of up to 30% - triple the levels

from the 1980s (Handwerk, 2015). The detection of cannabis can be performed with

the use of an electronic “sniffer” which uses a portable mass spectrometer to detect

Page 4 of 37

volatile vapours, such as those exhibited in Table 1, emitted from the drug (Hood,

Dames and Barry, 1973). However, drug detection canines are the most recognised,

fast, flexible, mobile and durable form of detecting illicit substances such as cannabis

(Jezierski et al., 2014). Detection dogs are selected upon several factors including;

gender, instinct to hunt, sense of smell, ability to be trained and general stamina

(Ensminger, 2012). They are used for a variety of tasks such as drug detection and

in the detection of human remains, due to their exceptionally sensitive olfactory

senses (Sorg, Rebmann and David, 2000). In comparison to the average sense of

smell within humans (approximately five million receptor cells), the dog’s sense of

smell is highly superior with breeds such as the Bloodhound displaying 100 million

receptor cells (Sorg, Rebmann and David, 2000).

The olfactory system of a dog works through the passing of air molecules over the

olfactory neurons within the nose, receptors residing upon the neurons bond to

molecules within the air. The air pathway within a canine is distinctly different from

when a dog is breathing to when it is sniffing; sniffing allows for a larger amount of

air to pass over the olfactory mucosa. This larger amount of air provides a larger

amount of molecules available to bond with the olfactory receptors which send

signals to the brain (Jensen, 2007). Certain properties of the molecules are thought

to affect what causes the neurons to fire once the molecules have bound to the

receptors; the suggestion is that physical properties including solubility and volatility

are key factors, but it is not fully understood (Sorg, Rebmann and David, 2000).

Page 5 of 37

Step 1:The dog is

introduced to the scent and is taught

to develop a committment to

locating the source of the scent

Step 2: The dog is taught to

give an easily identifiable signal to

its handler that it has identified the

source

Step 3:The scent is hidden

from the dog, causing the dog to learn to search for

the scent

Step 4:The dog is

introduced to realistic scenarios

and taught to search under

differing conditions

Figure 1. The training process for drug detection dogs, adapted from Sorg, Rebmann

and David (2000)

A study by Jezierski et al. (2014) found that the German shepherd is the best breed

in terms of giving a correct indication, whilst Terriers give poor all round detection

performance. However, the study also shows a large variation in the effectiveness of

dogs within breeds with the German shepherd having a correct indication time of 61

seconds +/- 74 seconds. This variation between and within breeds shows the need

for efficient and effective training in dog detection in order to produce dogs which are

able to consistently detect drugs. Despite this research, Correa (2011) describes the

use of breeds including: German shepherds, Labradors and Golden retrievers, within

customs and border controls. The use of detection dogs has recently been extended

to use in medical diagnostics, a study by Gordon et al. (2008) states that the strong

olfactory sense of the dog can be used to detect human cancers. This is thought to

be possible due to the volatile organic compounds emitted by cancer patients within

their breath or urine (Gordon et al., 2008).

The analysis of cannabis has determined more than 525 different chemical

compounds which are categorised into: monoterpenes, sesquiterpenes, sugars,

hydrocarbons, steroids, flavonoids, nitrogenous compounds and amino acids

(ElSohly and Slade, 2005). A further category of molecules found within cannabis

are cannabinoids, there are believed to be more than 90 of these found within the

plant; the most prominent of which is Tetrahydrocannabinol (THC) (Fischedick et al.,

2010). Cannabinoids are psychoactive substances which act upon the CB1

receptors in the brain responsible for functions such as: motor activity; emotion,

sensory perception and automatic / endocrine functions (Leonard, 2003). It is also

thought that the interaction of the cannabinoids with the CB1 receptors can strongly

reduce pain responses within the spinal cord, brain and sensory neurons (Leonard,

2003). The relevant class within this study is terpenes, volatile organic compounds

(VOCs) which are synthesised and stored within herbaceous plants (Borge et al.,

2016). VOCs are defined as being carbon based chemicals which easily evaporate,

an example of a group of VOCs is terpenes (Minnesota Department of Health, 2016).

Terpenes are classed as mono- or sesqui- terpenes according to the number of

isoprene (C5H8) groups there are within the molecule, for example monoterpenes

and sesquiterpenes are commonly C10H16 and C15H24, respectively (Encyclopaedia

Page 6 of 37

Britannica Inc., 2016). Borge et al. (2016) explains that the diversity of terpenes

varies between plants, depending upon factors such as; maturity of the plant,

environmental conditions, and the general composition of the plant itself.

Table 1. Commonly found terpenes within the headspace of Cannabis sativa,

adapted from Casano et al. (2011).

CompoundChemical

FormulaType of Terpene

Percentage found in

cannabis headspace

(average)

β-Myrcene C10H16 Monoterpene 46.1 +/- 2.6

α-Pinene C10H16 Monoterpene 7.3 +/- 1.3

α-Terpinolene C10H16 Monoterpene 10.2 +/- 1.8

Limonene C10H16 Monoterpene 7.3 +/- 1.3

β-Ocimene C10H16 Monoterpene 6.6 +/- 0.7

β-Pinene C10H16 Monoterpene 6.1 +/- 0.4

α-Terpinene C10H16 Monoterpene 3.6 +/- 1.0

β-

CaryophylleneC15H24 Sesquiterpene 1.2 +/- 0.2

α-

PhellandreneC10H16 Monoterpene 0.7 +/- 0.1

Δ-3-Carene C10H16 Monoterpene 0.6 +/- 0.1

Many investigations into the odour profiles of cannabis, such as those conducted by

Rice and Koziel (2015), Marchini et al. (2014) and Da Porto, Decorti and Natolino

(2014), use Solid Phase Microextraction (SPME) as a method of extracting the

volatile compounds such as those seen in Table 1. This is the use of a fused silica

fibre coated with a layer of a silica such as Polydimethylsiloxane. The fibre coating is

extremely important in the effectiveness of the SPME method, and therefore the fibre

coating is designed specifically for the desired analytes (Bicchi, Drigo and Rubiolo,

2000). This fibre is exposed to the vaporous headspace for a predetermined time

and temperature allowing compounds within the headspace to absorb into the silica

layer. Once equilibrium has been reached between the sample and the fibre coating,

the fibre is injected into the manual injection port of the gas-chromatographer – mass

spectrometer (GC-MS) (Pawlinszyn, 1997). Exposure of the fibre to a high

Page 7 of 37

temperature causes the compounds to desorb allowing for identification (Sporkert

and Pragst, 2000). Within this investigation, static headspace analysis coupled with

GC-MS was utilised, this was due to it being a much faster, simpler, more efficient

and environmentally friendly method of sampling (Cai et al., 2016). This involves the

sampling of the gas phase whilst in equilibrium with either a solid or liquid phase,

once equilibrium is achieved a sample of the headspace / gas phase is extracted for

analysis (Restek, 2000). Another method used in the extraction of headspace

compounds is Thermal Desorption, this is similar to SPME and static headspace in

that it is a simple and rapid method (Kuwayama et al., 2007). There are three

different methods used in thermal desorption, these are: indirect heat; indirect fired

and direct fired – these are different methods of heating the sample to volatilise the

VOCs (VertaseFLI, 2016).

Sigma Pseudo Marijuana Formulation is a trademarked product of Sigma-Aldrich Co.

LLC, and is used as a substitute for controlled substances within the training of drug

detection dogs. It is stated that the formulation is designed to mimic the odour of

cannabis. Sigma Aldrich has provided no evidence as to the odour profile of the

formulation, however Rice and Koziel (2015) states that the composition is listed as:

Pyrogenic Collodial Silica (1%), Cellulose (98.5%), Butane-2,3-diol (0.4%), and p-

mentha-1,4-diene (0.1%). They go on to claim that all of their “Sigma Pseudo Canine

Training Aids” are being used by dozens of agencies in the training of detection

dogs, however, no data pertaining to the odour of the formulation is given.

The aim of the investigation was to identify odour compounds within Sigma Pseudo

Marijuana Scent and to compare it to the odour profile of the Cannabis plant. The

odour profiles of both the pseudo formulation and that of the cannabis plant were

used to determine if the pseudo cannabis scent is the most effective training aid for

drug detection dogs, and to establish whether a more efficient alternative is

conceivable.

Page 8 of 37

Experimental

Reagents and materials

The following reagents were procured from Sigma Aldrich®: limonene standard, β-

myrcene standard, Δ-3-carene standard, frankincense standard, cannabis burn oil

standard, cannabis scented soap oil standard, cannabis scented candle oil.

Laboratory cannabis oil was prepared within the laboratory using cannabis plant

material provided by Cleveland Police.

Preparation of laboratory cannabis oil

A single cannabis leaf was removed from the plant provided by the Cleveland Police,

placed into a headspace vial filled with sunflower oil and sealed. The cannabis leaf /

oil combination was left for several months to allow the essential oils within the

cannabis matrix to transfer into the oil.

Preparation of standards for analysis

Laboratory cannabis oil was prepared by extracting 100μl of the oil from the vial

using a Gilson pipette, the sample was placed into a fresh headspace vial, capped

and sealed. Limonene, β-myrcene, frankincense, cannabis burning oil, cannabis

scented soap oil and cannabis scented candle oil were all prepared by extracting 1μl

of the sample using a Gilson pipette and placing it into individual, fresh headspace

vials. The headspace vials were all capped and sealed.

HS-GC-MS analysis

The GC-MS analysis was performed using Perkin Elmer Clarus 500 GC system

linked to a Perkin Elmer TurboMatrix 40 Trap Headspace sampler. The detector

used was a Perkin Elmer Clarus 500 mass spectrometer with a Zebron ZB-5MS

capillary column (30m x 0.25mm x 0.25μm). The carrier gas was 99.999% Helium.

The analyses were performed using Total Ion Count (TIC) mode. Sample volume of

1μl was injected into split mode (20:1). Injector temperature was set to 320°C. Initial

carrier flow was 1ml/min, initial oven temperature was set to 60°C held for 5 min,

ramped to 250°C at 10°C/min and held for 11 min.

Page 9 of 37

Testing of Laboratory Cannabis Oil with Drug Detection Dogs

The laboratory cannabis oil was tested using a trained law enforcement drug

detection dog supplied by the canine unit of Cleveland Police, using standard

training methods known to the dog.

Results

Dried cannabis leaf was analysed using HS-GC-MS in order to create a comparison

against the pseudo scent produced by Sigma Aldrich. The percentage of different

compounds found within the headspace of the dried cannabis leaf was calculated

using peak area in order to determine the overall composition. Frankincense

standards, cannabis burning oil standards, cannabis scented soap oil standards and

cannabis scented candle oil standards were all analysed using HS-GC-MS in order

to compare against the true cannabis leaf and against the pseudo scent. The

analysis of all but frankincense produced two peaks in common with dried cannabis

leaf and one peak in common with the pseudo scent, these peaks were identified as

α-pinene, β-pinene and γ-cymene, respectively. Frankincense produced a profile

with five peaks in common with dried cannabis leaf which were identified as; α-

pinene, β-pinene, β-myrcene, limonene and β-caryophyllene. Two peaks were also

identified to correspond to peaks found within the profile of the pseudo scent, which

was identified as γ-cymene and γ-terpinene. The laboratory prepared cannabis oil

originally produced a chromatogram similar to that of the dried cannabis leaf,

however further analysis was not able to reproduce the initial results.

The laboratory cannabis oil was tested using trained law enforcement drug detection

dogs. The dog responded positively to the cannabis oil, signalling to its handler that it

detected the cannabis scent.

Page 10 of 37

Figure 2. Gas Chromatogram of Dried Cannabis Leaf

Table 2. Total percentage of compounds within the headspace of Dried Cannabis Leaf

Peak Retention Time (Mins) Peak Area Total Percentage

(%) Identification

7.19 2502738 19.83% α-Pinene7.65 436276 3.46% Camphene8.33 1265399 10.02% β-Pinene8.53 1331218 10.55% β-Myrcene9.50 2533314 20.07% Limonene9.79 331889 2.63% β-Ocimene

10.87 654371 5.18% Linalool11.35 918579 7.28% Fenchol11.50 231983 1.84% Trans-2-pinanol12.32 101420 0.80% Borneol12.67 168043 1.33% α-Terpineol15.99 691196 5.48% β-Caryophyllene

16.04 105919 0.84% Trans-α-Bergamotene

16.49 195067 1.55% α-Humulene17.54 172193 1.36% δ-Cadinene17.59 282870 2.24% γ-Cadinene

*Unidentified compounds accounted for 5.55% of the total headspace

Analysis of the dried cannabis leaf provided a profile which displayed good

chromatography, shown in Figure 2. Using the chromatogram, percentages of each

Page 11 of 37

1.50 3.50 5.50 7.50 9.50 11.50 13.50 15.50 17.50 19.50 21.50 23.50 25.50 27.50 29.50 31.50 33.50Time0

100

%

0

100

%

pseudo b Scan EI+ TIC

3.14e7Area

10.09;93;829591

9.41119

302105

1.4684

1161363.65207

13776

7.97281

6003

5.7976

4110

33.9797

13806

22.0897

7180

19.1797

6056

14.0589

5305

10.28146

8763

15.6497

3506

16.73106

8223

27.9392

2076

26.9073

3085

25.80102

3768

31.96150

5235

29.52125

4988

30.26102

8303

34.9573

3143

Dried plant b Scan EI+ TIC

9.50e7Area

9.48;93;2483137

7.1893

2488809

1.4891

591665 6.3584

32805

3.63207

30854

11.3681

90714416.00133

65965911.5093

21534515.67

9128504

17.58161

254912 32.5573

170426

26.4991

20540

33.9491

96277

Peak Area (Mv)

Time (Minutes)

compound were calculated using peak areas to create an odour profile of sixteen

compounds which can be seen in Table 2. It was found that the highest percentage

compound found within the headspace was Limonene, composing 20.07% of the

total headspace. The lowest identifiable compound was calculated to be Borneol,

composing 0.80% of the total headspace. Each of the peaks were identified using

Restek (2016) and NIST Webbook (2016).

Figure 3. Gas chromatogram of Sigma Aldrich® marijuana scent formulation

Analysis of the Sigma Aldrich® marijuana scent formulation produced a

chromatogram which displayed good chromatography, shown in Figure 3. Using the

chromatogram, percentages were calculated using peak areas, an odour profile was

created for the pseudo scent which can be seen in Table 3. Only two identifiable

compounds were found within the pseudo scent profile, the more prominent of the

two was found to be γ-terpinene which accounted for 71.25% of the overall

Page 12 of 37

1.50 3.50 5.50 7.50 9.50 11.50 13.50 15.50 17.50 19.50 21.50 23.50 25.50 27.50 29.50 31.50 33.50Time0

100

%

0

100

%

pseudo b Scan EI+ TIC

3.14e7Area

10.09;93;829591

9.41119

302105

1.4684

1161363.65207

13776

7.97281

6003

5.7976

4110

33.9797

13806

22.0897

7180

19.1797

6056

14.0589

5305

10.28146

8763

15.6497

3506

16.73106

8223

27.9392

2076

26.9073

3085

25.80102

3768

31.96150

5235

29.52125

4988

30.26102

8303

34.9573

3143

Dried plant b Scan EI+ TIC

9.50e7Area

9.48;93;2483137

7.1893

2488809

1.4891

591665 6.3584

32805

3.63207

30854

11.3681

90714416.00133

65965911.5093

21534515.67

9128504

17.58161

254912 32.5573

170426

26.4991

20540

33.9491

96277

Peak Area (Mv)

Time (Minutes)

Peak Retention Time (mins) Peak Area Total Percentage (%) Identification

9.41 302105 25.95% ρ-Cymene10.09 829591 71.25% γ-Terpinene

*Unidentified compounds accounted for 2.80% of the total headspace

headspace. The second of the compounds identified within the headspace was

determined to be ρ-cymene, making up 25.95% of the overall profile. Each of the

peaks were identified using Restek (2016) and NIST Webbook (2016).

Table 3. Total percentage of compounds within the headspace of Sigma Aldrich Marijuana Scent Formulation

1.50 3.50 5.50 7.50 9.50 11.50 13.50 15.50 17.50 19.50 21.50 23.50 25.50 27.50 29.50 31.50 33.50Time0

100

%

0

100

%

pseudo b Scan EI+ TIC

3.14e7Area

10.09;93;829591

9.41119

302105

1.4684

1161363.65207

13776

7.97281

6003

5.7976

4110

33.9797

13806

22.0897

7180

19.1797

6056

14.0589

5305

10.28146

8763

15.6497

3506

16.73106

8223

27.9392

2076

26.9073

3085

25.80102

3768

31.96150

5235

29.52125

4988

30.26102

8303

34.9573

3143

Dried plant b Scan EI+ TIC

9.50e7Area

9.48;93;2483137

7.1893

2488809

1.4891

591665 6.3584

32805

3.63207

30854

11.3681

90714416.00133

65965911.5093

21534515.67

9128504

17.58161

254912 32.5573

170426

26.4991

20540

33.9491

96277

Figure 4. Gas chromatogram comparison of dried cannabis leaf and Sigma Aldrich®

marijuana scent formulation

Further examination into the odour profiles of both the dried cannabis leaf, and the

Sigma Aldrich® marijuana scent formulation showed no comparison between the

identifiable peaks of both profiles, this can be seen in Figure 4.

Page 13 of 37

Dried Cannabis Leaf

Sigma Aldrich® Marijuana Scent FormulationPeak Area (Mv)

Peak Area (Mv)

Time (Minutes)

Time (Minutes)

Discussion

The study found sixteen identifiable VOCs within the headspace of dried cannabis

leaf, this is a small number compared to literature from Marchini et al. (2014) who

reported a total number of 186 constituents within their samples and Rice (2015)

who reported 233. However, the studies by Marchini et al. (2014) and Rice and

Koziel (2015) used an SPME method in conjunction with HS-GC-MS. A study by

Pfannkoch and Whitecavage (2016) showed that SPME can prove to be ten to fifty

times more sensitive than headspace analysis, this is, however, dependent upon the

fibre coating being used. This loss of sensitivity from using the headspace method

could explain the inability to detect further VOCs. HS-GC-MS analysis of dried

cannabis leaf also found limonene to be the most dominant VOC within the sample

(20.07%). The study by Marchini et al. (2014) analysed different strains of cannabis

herbs which found varying levels of limonene between the samples from 0.83% -

8.26%. In comparison, a study by Hood, Dames and Barry (1973) showed the

headspace as being 5.4% limonene, and the largest percentage of the headspace

was α-pinene at 55.5%, in comparison to this study which showed α-pinene as

composing 19.83% of the headspace. A further study by Rothschild, Bergstrom and

Wangberg (2005) also showed a varying limonene percentage within the headspace

of different plants (0%-18.6%). The obvious differences between the percentages of

each of the cannabis samples used within each of these studies shows an obvious

difference in headspace composition between strains of cannabis. This difference

shows how complex a synthetic training aid would have to be in order to ensure the

detection of the many different varieties of cannabis which are currently available.

This study compared the headspace of dried cannabis leaf (the most likely form to

be found in the search for illicit cannabis), to the Sigma Aldrich® marijuana

formulation which is designed to be used in the training of drug detection dogs. The

analysis showed no evidence to suggest the pseudo cannabis scent would be an

effective training aid for dogs, due to the complete lack of corresponding peaks

between the chromatograms produced for both substances. The pseudo scent

produced two identifiable peaks at 9.41 and 10.09 mins which were identified as ρ-

cymene and γ-terpinene, respectively. These two terpenes were not found within the

cannabis sample this study analysed, however, studies by Hillig (2004), Hood,

Page 14 of 37

Dames and Barry (1973), and Ross and ElSohly (1996) identified γ-terpinene but not

ρ-cymene. Restek (2016) provides an elution order and chromatogram of terpenes

within cannabis which shows both ρ-cymene and γ-terpinene as compounds found

within the headspace of cannabis. This is supported by a study by Marchini et al.

(2014) which also shows the two compounds as having been found within the

headspace. As previously stated, there is an obvious difference in terpene

composition between strains and even individual plants, this could be the reason as

to why this study did not find the two peaks present in the pseudo scent, within the

cannabis (Hillig, 2004). Again, this also could be down to the method in which the

headspace was extracted, it could be possible that the compounds are within this

particular plant, but are undetectable due to the restrains of static headspace

analysis. However, with such a variety of studies which either do or do not find ρ-

cymene and/or γ-terpinene, it can be said that it is impractical to use these particular

VOCs within a training aid used specifically to train dogs to locate cannabis.

Especially compounds which despite being found within the plants, are not of high

concentrations. For example, the study by Marchini et al. (2014) found the

concentration of ρ-cymene within the headspace to range from trace amounts to

0.33%, an insignificant amount in comparison to other VOCs.

As previously stated, the odour profile of the pseudo scent varies greatly from the

odour profile of the dried cannabis leaf. A study by Macias, Harper and Furton (2008)

showed the use of the pseudo scent in field experiments with certified law

enforcement drug detection dogs. The results of the investigation determined that

the pseudo scent was not reliably detected. This was confirmed within a study by

Rice and Koziel (2015) which also stated that 1g of Sigma Pseudo Marijuana scent

is not a representative odour mimic for the illicit samples of marijuana that were

tested during their investigation. The study by Macias, Harper and Furton (2008)

states that this may be due to the training aid not producing the same volatile odour

as the illicit cannabis product. Should any drug detection canines be trained upon the

pseudo scent, it is highly likely that they are not efficiently detecting hidden stores of

cannabis. This possibility has repercussions in law enforcement wherever these

dogs are being utilised, as a larger amount of illicit cannabis could possibly be

transported without detection, contributing to the already high usage of cannabis

worldwide. The study also goes on to describe a lack of response to a mixture of the

Page 15 of 37

most prominent terpenes found within the headspace of cannabis (mixtures were

composed of α-pinene, β-pinene, myrcene, limonene and β-caryophyllene). The

study suggests that the lack of response is due to a short amount of time in which

the headspace is detectable by the dogs and that the longer the retention time of the

compound, the slower the rate of dissipation is. It is necessary to further study the

drug detection dogs themselves, to determine what it is the dog is honing in on when

it detects cannabis. This could be done by testing the dogs upon individual

components of the headspace to identify the exact substance(s) that the dog is

smelling. Using this information in relation to the two compounds (ρ-cymene and γ-

terpinene) found within the pseudo scent which have relatively short retention times;

they are still not a sufficient choice to have as a training aid for the detection of

cannabis.

To create a suitable synthetic training aid for dogs in the detection of cannabis,

several components are important; it should first be determined whether or not dogs

are honing in on a particular compound or upon the cannabis odour profile as a

whole. Secondly, a large variety of cannabis strains would need to be analysed in

order to create an average percentage of each compound found within the plant,

from this a “general” odour profile for cannabis could be determined. A general

profile for cannabis could, in theory, be used in order to manufacture a synthetic

cannabis training aid which is more specific to the cannabis plant. Another method

that was explored in the search for an alternative training aid was a laboratory

produced cannabis oil. Preliminary testing upon the cannabis oil produced a profile

comparable to that of the cannabis leaf, however further testing failed to reproduce

these results. An explanation for the lack of reproducibility is currently not fully

understood, however it is thought to be caused by the VOCs being trapped within the

oil and is not being efficiently separated. As the oil was also tested using headspace

analysis, it may be an issue with the method which could be solved by using a more

sensitive method such as SPME or thermal desorption. A study by Lerch and

Hasselbach (2014) describes the use of thermal desorption in conjunction with slitted

microvials. This technique allows for the important volatile compounds within the oil

to be transferred to the GC-MS whilst leaving the non-volatile oil matrix behind,

preventing contamination of the sample. Using this technique it may be possible to

truly analyse the profile of the laboratory produced cannabis oil, and allow further

Page 16 of 37

study into the possible use of it as a new training aid for drug detection dogs. Also,

despite the failure to produce good chromatography results, the oil tested positive

during preliminary field tests with a law enforcement drug detection dog. This

suggests that the oil may be a better choice than the pseudo scent as the study by

Macias, Harper and Furton (2008) reported that no dogs responded to the pseudo

scent. However, there is a large variation in concentrations of terpenes within

different strains of cannabis plants (Hillig, 2004). This is suggestive that different

strains of cannabis would need to be used in order for the drug detection dogs to be

able to detect them, as the study by Macias, Harper and Furton (2008) proved that

dogs do not respond to the main constituents of cannabis when they are in the

wrong concentrations.

This study was based upon the odour emitted directly from the cannabis leaf, which

in real-life scenarios is not often the case. The cannabis is commonly found

packaged in plastic, Johnson (2016) states that “plastic is a huge part of the

packaging dynamic in the cannabis industry and it’s only getting bigger”. Rice and

Koziel (2015) used three different forms of packaging to test the effect of packaging

upon the odour profile (a US military style duffel bag, a sample of dried cannabis with

no packaging and a plastic zip top sandwich bag). 134 volatiles were detected

through all three of the packaging, however over time key components such as β-

caryophyllene were no longer detected and after 68 hours only 51 compounds were

detected through the packaging. This effect of time on the odour profile of cannabis

certainly suggests further study into the degradation of any surrogate scents, also it

suggests that different formulas need to be created to allow for this difference in

compounds at different stages of degradation.

ConclusionFrom this investigation it can be stated that, in agreement with previous studies, the

cannabis leaf has a complex mixture of mono and sesquiterpenes, which makes the

synthesis of a substitute compound a difficult task to undertake. Considering this, the

lack of a corresponding odour profile produced by the pseudo scent in comparison to

the odour profile of the dried cannabis leaf, with the consideration that different

cannabis strains do not always have the terpenes seen within the pseudo scent,

Page 17 of 37

suggests that the Sigma Aldrich marijuana formulation is an unsuitable tool in the

training of drug detection dogs and that a suitable alternative is necessary.

This study determined that the synthesis of a cannabis pseudo scent, other than the

formulation produced by Sigma Aldrich® is possible. However, it is complex in the

different variables that will need to be considered such as; the percentages of

terpenes, the variation in the number of compounds found in the headspace over

time, as well as the number of compounds released through packaging. As the odour

profile of cannabis is thought to change over time, this could be suggestive that a

range of training aids need to be produced in order to account for this change in the

profile, to ensure that the dogs are sensing the cannabis whether it has been stored

for a short or long period of time.

The laboratory prepared cannabis oil is a definite possibility as a replacement for the

pseudo scent. However, greater investigation needs to be conducted upon the

substance, a detailed and reproducible odour profile is required to determine its

similarity to the cannabis leaf. Further investigation is also required into the

degradation of the sample, to determine whether or not the number of compounds

released in the headspace does not reduce over time, and if they do, is this

mimicked by the cannabis leaf.

Despite the strong results produced using the headspace technique, when these

results are compared to those of studies which used an SPME method, it is clear to

see that SPME is the stronger and more sensitive method. In order to create a more

detailed odour profile of both the dried cannabis and possibly the pseudo scent, it

would be important for future studies to implement the use of SPME. The level of

detail gained from the use of SPME greatly outweighs the simplicity and efficiency of

the headspace method.

This study also determined that most commercially bought scents which proclaim

that they are cannabis scented are, in terms of odour, fall short of matching the smell

produced by the true cannabis leaf. The odour profiles of the scents produced very

few compounds in common with cannabis, and as previously mentioned, it is the

complexity of cannabis which produces its distinctive odour.

Page 18 of 37

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Page 22 of 37

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Appendices

Page 23 of 37

Gas Chromatogram for Headspace Analysis of Dried Plant

Page 24 of 37

Time (Minutes)

Peak Area (Mv)

Gas Chromatogram for Headspace Analysis of Myrcene Standard

Page 25 of 37

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

drie

d pl

ant a

Scan

EI+

TI

C4.

77e7

9.49

;93

7.17 93

1.48 91

0.01 91

3.65

207

8.52 93

7.64 93

11.3

581

10.8

871

9.80 93

16.0

091

11.4

981

12.6

893

17.5

916

1

17.5

491

34.7

773

26.9

073

25.0

497

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

myr

cene

aS

can

EI+

T

IC6.

92e9

8.59

;93 8.94 93

Time (Minutes)

Gas Chromatogram for Headspace Analysis of Laboratory Cannabis Oil

Page 26 of 37

Peak Area (Mv)

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

oil a

Sca

n E

I+

TIC

8.55

e61.

48;9

1

0.06 91

8.53 93

3.66

207

1.76 91

4.41 91

7.17 91

5.61 91

33.6

997

32.8

591

28.9

820

79.

57 9119

.17

9711

.45

9115

.36

9112

.70

91

16.0

291

17.4

691

25.4

191

20.1

491

30.1

091

Peak Area (Mv)

Time (Minutes)

Gas Chromatogram of Headspace Analysis of Laboratory Cannabis Oil

Page 27 of 37

Time (Minutes)

Gas Chromatogram of Headspace Analysis of Limonene Standard

Page 28 of 37

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

lim a

Sca

n EI

+ T

IC9.

90e9

9.54

;93

Time (Minutes)

Gas Chromatogram of Headspace Analysis of Frankincense Standard

Page 29 of 37

Peak Area (Mv)

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

fran

aSc

an E

I+

TIC

6.62

e97.

21;9

3

6.97 93

9.49 93

9.42

119

8.19 93

16.0

093

Peak Area (Mv)

Time (Minutes)

Gas Chromatogram of Headspace Analysis of “Cannabis” Burning Oil Standard

Page 30 of 37

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

burn

ing

aSc

an E

I+

TIC

3.75

e815

.20;

82

14.7

082

7.19 93

6.96 93

8.34 93

9.42

119

18.1

014

9

16.1

310

517

.03

107

Peak Area (Mv)

Time (Minutes)

Gas Chromatogram of Headspace Analysis of “Cannabis” Soap Oil Standard

Page 31 of 37

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

soap

Sca

n E

I+

TIC

9.56

e87.

19;9

3

6.96 93

15.1

982

14.6

982

8.34 93

9.41

119

18.0

914

916

.12

105

Peak Area (Mv)

Time (Minutes)

Gas Chromatogram of Headspace Analysis of “Cannabis” Candle Oil Standard

Page 32 of 37

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

cand

leSc

an E

I+

TIC

1.35

e97.

19;9

3

6.96 93

15.2

082

14.7

082

8.34 93

9.42

119

18.1

014

916

.13

105

Time (Minutes)

Gas Chromatogram of Headspace Analysis of Caryophyllene Oxide Standard

Page 33 of 37

Peak Area (Mv)

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

cary

o ox

idSc

an E

I+

TIC

6.60

e818

.16;

79

Time (Minutes)

Gas Chromatogram of Headspace Analysis of Δ-3-Carene Standard

Page 34 of 37

Peak Area (Mv)

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

care

ne a

Sca

n E

I+

TIC

1.95

e10

9.08

;79

Peak Area (Mv)

Time (Minutes)

Gas Chromatogram of Headspace Analysis of Cannabis Leaf Removed from Laboratory Cannabis Oil

Page 35 of 37

1.50

3.50

5.50

7.50

9.50

11.5

013

.50

15.5

017

.50

19.5

021

.50

23.5

025

.50

27.5

029

.50

31.5

033

.50

Tim

e0

100 %

wet

pla

nt a

Sca

n E

I+

TIC

2.75

e715

.99;

93

1.46 84

9.59 81

8.54 93

15.8

894

16.0

593

17.5

816

1

17.5

316

1

Peak Area (Mv)

Time (Minutes)

Complete Table of Compounds and their Percentages Pertaining to the Headspace of the Dried Cannabis Leaf

Peak Retention Time (Mins)

Peak Area

Total Percentage

(%)Identification

3.64 35489 0.28% Unknown (91, 105, 207 mz)6.35 38790 0.31% Unknown (72, 82, 84, 91, 105 mz)6.94 13460 0.11% Unknown (77, 91, 105 mz)7.19 2502738 19.83% α-Pinene7.41 11753 0.09% Unknown (91, 105 mz)7.65 436276 3.46% Camphene7.98 15228 0.12% Unknown (83, 91, 105, 281 mz)8.33 1265399 10.02% β-Pinene8.53 1331218 10.55% β-Myrcene8.98 15629 0.12% Unknown (77, 91, 93, 105 mz)9.20 14215 0.11% Unknown (77, 91, 93, 105, 121,207 mz)9.50 2533314 20.07% Limonene9.79 331889 2.63% β-Ocimene10.08 14054 0.11% Unknown (91, 93, 105, 119 mz)10.34 55822 0.44% Unknown (81, 91, 94, 111, 217 mz)10.62 26588 0.21% Unknown (77, 91, 93, 105, 121, 136 mz)10.79 86577 0.69% Unknown (81, 91, 152 mz)10.87 654371 5.18% Linalool11.35 918579 7.28% Fenchol11.50 231983 1.84% Trans-2-pinanol12.06 20021 0.16% Unknown (91, 96, 105, 111, 115 mz)12.32 101420 0.80% Borneol12.67 168043 1.33% α-Terpineol15.24 26652 0.21% Unknown (91, 105, 119, 120, 161, 207 mz)15.67 33388 0.26% Unknown (91, 105, 108, 133 mz)15.79 24354 0.19% Unknown (91, 93, 105, 119 mz)15.88 16671 0.13% Unknown (91, 94, 105 mz)15.99 691196 5.48% β-Caryophyllene16.04 105919 0.84% Trans-α-Bergamotene16.22 53050 0.42% Unknown (79, 91, 93, 105, 120, 133 mz)16.49 195067 1.55% α-Humulene16.84 13985 0.11% Unknown (91, 105, 119, 133 mz)16.94 43785 0.35% Unknown (79, 91, 105,161 mz)17.02 43785 0.35% Unknown (79, 91, 93, 105 mz)17.21 33702 0.27% Unknown (79, 91, 105, 121 mz)17.31 37189 0.29% Unknown (79, 91, 105, 119, 161, 204 mz)17.42 25813 0.20% Unknown (91, 105, 119 mz)17.54 172193 1.36% δ-Cadinene17.59 282870 2.24% γ-Cadinene

Page 36 of 37

Page 37 of 37