Welcome to UK420

Register now to gain access to all of our features. Once registered and logged in, you will be able to contribute to this site by submitting your own content or replying to existing content. You'll be able to customize your profile, receive reputation points as a reward for submitting content, while also communicating with other members via your own private inbox, plus much more!

This message will be removed once you have signed in.


Sign in to follow this  
Followers 0
namkha

Illicitly imported Cannabis products in the 1970s

you can find the original papers on the UNODC website

Illicitly imported Cannabis products: some physical and chemical features indicative of their origin


Author: P. B. BAKER, T. A. GOUGH, B. J. TAYLOR
Pages: 31 to 40
Creation Date: 1980/01/01


P. B. BAKER Laboratory of the Government Chemist, Cornwall House, London, United Kingdom of Great Britain and Northern Ireland
T. A. GOUGH Laboratory of the Government Chemist, Cornwall House, London, United Kingdom of Great Britain and Northern Ireland
B. J. TAYLOR Laboratory of the Government Chemist, Cornwall House, London, United Kingdom of Great Britain and Northern Ireland

ABSTRACT

Samples taken from seizures of illicitly imported cannabis and cannabis resin of known geographical origin have been examined by thin-layer chromatography. The chromatographic characteristics were considered in conjunction with the gross physical appearance of the materials and it was found possible to discriminate between samples of different origin. Thus by carrying out thin-layer chromatography and a visual inspection on a sample of unknown provenance, an opinion as to its geographical origin can be offered. Extensive use is made of a reference collection of samples.


Introduction

Although Cannabis 1 is grown in many parts of the world, there is only a relatively small number of countries from which supplies of the illicit products (cannabis, cannabis resin and liquid cannabis) reach the United Kingdom. A means of identifying the geographical origin of samples of any of these materials would be extremely useful in the ensuing criminal investigations and in aiding international control [ 1] [ 2] [ 3] [ 4] .

1 The term Cannabis in this paper refers to Cannabis sativa L.; cannabis to marijuana; and cannabis resin to hashish.


Discussion

It is well known that there are wide variations in the relative amounts of cannabinoids in Cannabis and that furthermore some plants contain additional cannabinoids [ 5] . Many factors have been considered in attempts to explain these variations. These include the genetic characteristics of the seedstock, the environment in which the plant is grown, the maturity, sex and part of the harvested plant and the time which has elapsed between harvesting and chemical analysis, as well as the conditions of storage of the plant. The mode of preparation will additionally affect the cannabinoid content, particularly in the case of liquid cannabis.

Several groups of workers are of the opinion that the major factor governing the amounts of cannabinoids in a plant is genetic [ 1] [ 6] [ 7] [ 8] [ 9] [ 10] . Bearing this in mind and assuming that seeds are freely transferred from one country to another, Ohlsson [ 9] concludes that there is little valid basis for attempts to correlate the cannabinoid content with country of origin. In addition, the majority of seizures of illicit cannabis received in the Laboratory of the Government Chemist contain fertile seeds, thus indicating little need for inter-country transfer of seeds. The effect of the environment upon the cannabinoid content of the products from Cannabis is widely considered to be small [ 11] [ 12] , but although the ratios between the cannabinoids may remain unchanged, the absolute quantities may vary [ 13] .

There is no conclusive evidence to show that changes in environment do not affect the cannabinoid content of successive generations of seeds of common stock. However, there are other authors who consider that the environment plays a major part in the determination of the cannabinoid content of Cannabis products [ 14] [ 15] [ 16] .

Until recently the male Cannabis plant was thought to be less pharmacologically active than the female. The main active constituent is Δ-9-tetrahydrocannabinol (THC), but this compound and several other cannabinoids are found in similar amounts in both sexes of plants grown under the same conditions [ 9] [ 12] [ 17] . In contrast, the cannabinoid ratios vary within a plant at different stages of its growth [ 11] [ 18] [ 19] [ 20] . Neither of these latter two factors is of great concern in examining cannabis imported into this country since the vast. majority of such seizures are of fully mature female plant material bearing fertile seeds.

On storage of samples of Cannabis products, the THC content gradually decreases as a result of oxidation to cannabinol (CBN) [ 21] . Similarly, the 3-propyl homologue, tetrahydrocannabivarin (THV), gives rise to cannabivarin (CBV) [ 22] . The two products CBN and CBV are absent in fresh cannabis or cannabis resin [ 9] and are not therefore relevant to the geographical origin of the sample. Although the presence of CBV may indicate that the sample originally contained THV, it cannot be regarded as conclusive as there may be other precursors. The formation of CBN from THC is not quantitative [ 23] [ 24] , neither is it useful for determining origin since all Cannabis products will originally have contained THC.

Cannabis has been broadly classified into fibre-type or drug-type [ 7] [ 25] [ 26] . The former is characterized by a high cannabidiol (CBD) to THC ratio (usually > 5) and the latter by a much lower ratio (usually < 0.2). Small and co-workers have introduced further classification, one type with a CBD:THC ratio close to unity [ 27] and a second in which cannabigerol methyl ether (CBGM) is present [ 13] , following discovery of this compound by Yamauchi and others [ 28] . Although Fairbairn has suggested that the causes of the differences between fibre and drug plants may be geographic [ 29] , the existence of varieties intermediate between these extremes makes this simple classification of little value in the determination of the origin of a given sample. Marshman and others found considerable variation in the quality of Jamaican cannabis [ 19] . Further, some plants are found to contain no detectable amounts of CBD [ 30] [ 31] [ 32] ]. The cannabivarins have been found in samples from different parts of the world and although Turner reports different amounts for different geographical origins, he does not believe these compounds alone to be reliable indications of origin [ 33] . A summary of published data on the presence or absence of CBD and THV [table 1, references [ 34] [ 35] [ 36] [ 37] [ 38] confirms that these compounds alone are not sufficiently diagnostic to establish origin. However, de Faubert Maunder, as a result of thin-layer chromatographic (TLC) studies, is of the opinion that the presence or absence of CBD and its ratio to THC is a useful criterion for indicating the country of origin provided that the gross appearance of the sample is taken into account [ 30] .

Table 1
Summary of published data on certain cannabinoids in Cannabis products

1970s Cannabis data


aC= cannabis; CR = cannabis resin.

bCBD was present in all samples of CR, whatever the country of origin.

Jenkins and Patterson [ 3] and Davis and others [ 39] , using gas-liquid chromatography (GLC), measured the amounts of THC, CBD and CBN in samples of cannabis and cannabis resin of various origins. The former authors use a 3 co-ordinate graphical plot of the proportion of each cannabinoid present in the total cannabinoid content, the latter a graph of CBD vs THC + CBN. The loss of information due to the on-column decarboxylation of the cannabinoid acids is a disadvantage and neither of these studies takes into account the occurrence and variations of the cannabivarins. The picture is further confused by the many studies, including some of those discussed above, using plant material which, although derived from seed of known geographical origin, has been grown in a second entirely different environment.

Components of Cannabis other than the cannabinoids might be useful indicators of origin. Hood and Barry studied the headspace volatiles of cannabis and cannabis resin of different origins by GLC but found no correlation between volatile constituents and geographical origin [ 40] . This study used cultivated cannabis and reservations on the use of this material have already been noted by de Faubert Maunder [ 4] . Stromberg [ 41] [ 42] [ 43] and de Zeeuw and others [ 44] consider that the minor non-cannabinoid components of cannabis products could be an important factor in determining geographical origin of cannabis and cannabis resin, but neither has studied large numbers of samples of known origin.

In view of all these considerations it is not surprising that the relationship between cannabinoid content and geographical origin has remained unclear. From the point of view of such a study the Laboratory of the Government Chemist is in the fortunate position of having available an extensive and continually expanding collection of Cannabis products. These are all derived from seizures of illicit imports, whose country of origin is known in most cases. This has provided the opportunity to study a large number of samples and this report is an updated and extended review based on these findings [ 4] [ 45] .


Experimental

Each sample was analysed as received and TLC was carried out within one month of importation. The most probable country of origin was assigned by taking into account information from the carrier, from Officers of Her Majesty's Customs and Excise and from the route of importation. In addition, some samples were received wrapped in paper or plastic bearing indications of their country of origin and others had identifying marks indicating their purported country of origin. Some of the latter were known to be spurious, particularly on cannabis resin and presumably were designed either to confuse law enforcement agencies or to indicate a higher quality product to the buyer.

TLC was the method of choice for this study as it provides a means of rapidly and visually analysing a number of samples simultaneously. Unlike the comparison of two samples in order to assess whether they are the same (or different), when quantitative analysis is essential, assessment of origin is qualitative, since the sample under study and the reference samples are, in fact, different. There is thus little point in using more powerful techniques such as high-performance liquid chromatography as the quantitative information provided is likely to confuse the picture. The TLC system was designed to give information on the cannabivarins in addition to the more commonly studied cannabinoids. The principal cannabinoids observed using this system are given in table 2. Sample preparation and detection were as previously described [ 47] [ 48] . The solvent system used was a mixture of chloroform (ethanol-free) and l,l-dichloroethane (15:10) with simple ascending TLC on 10 x 20 cm silica gel pre-coated plates with a layer thickness of 0.25 mm (E. Merck, Darmstadt, G.F.R., Art. No. 5729) [ 46] . Each extract was analysed within one hour of preparation. Twenty different samples of herbal cannabis and cannabis resin from several different countries were subjected to hot-solvent extraction to simulate the illicit preparation of liquid cannabis. The resulting chromatograms were compared with those of the starting material.


Table 2
Principal cannabinoids observed by TLC

1970s Cannabis data



Results and discussion

The visual features of cannabis and cannabis resin from the countries supplying the major proportion of these materials to the United Kingdom are listed in table 3. Although a preliminary opinion as to the geographical origin of a Sample can often be given simply from the physical appearance of a single isolated sample, this may be considerably reinforced by visual comparison with reference samples of established origin. Similarly, comparison of the TLC patterns (described in table 4) with the TLC characteristics of material of known origin is valuable supporting evidence.

Visual characteristics are based on more than 1,600 samples received in the period 1974-1979. TLC characteristics are based on 600 samples in the period 1978-1979. The survey by de Faubert Maunder [ 4] is mainly based on samples received prior to mid-1972 and, although it covers a wider range of countries than this report, it lacks the detail available from the improved TLC system. Despite the limited number of countries now covered, these supply over 95 per cent of the Cannabis products intercepted by Officers of HM Customs and Excise over the period of this study. Although some countries show similar appearances and TLC patterns consistent with those found in the previous survey, there is increasing evidence that more than one type of a given product can originate from a single country, the types being both visually and chemically distinguishable. This is particularly true of cannabis from southern Africa, where one variety contains significantly higher amounts of THV than the other (with little indication of an intermediate variety). Samples from Angola, Swaziland and Zimbabwe, although infrequently encountered, show a tendency to higher amounts of THV (one Zimbabwean sample had more THV than THC). It may be that THV is less stable than THC and that some part of the preparation procedure of the low-THV variety selectively decomposes THV. This seems unlikely, as elevated values of cannabivarin (CBV) are not found in this variety (oxidation to CBV being the most likely reaction). It is possible that the high THV is the result of early harvesting, although this too is unlikely in view of its remarkable consistency. The difference could also be the result of a distinct chemical race which gives rise to high concentrations of the cannabivarins.


Table 3
Common visual features of Cannabis and cannabis resin imported into the United Kingdom

1970s Cannabis data



Table 4
Some TLC characteristics of Cannabis and cannabis resin

1970s Cannabis data

Key to abbreviations is in table 2.

The many different products from India show wide variations and may reflect either the different environmental conditions in a very large country or the existence of several chemical races of plants. There is evidence from this Laboratory's reference collection that cannabis from Bangladesh and southern India does not contain CBD and considerable evidence that most cannabis resin from India comes from the north and north-west of the country.

The characteristic appearance of "Thai Sticks" is of particular importance as this is a recent feature of cannabis from South-East Asia. When first encountered these were of consistently high quality, but this has fallen of late. Although there have been many significant qualitative changes in some cannabis products, it is of equal forensic importance that many retain the same physical characteristics over many years.

The TLC pattern of liquid cannabis was found to be closely related to that of the parent herbal material or resin. The heating process, as used in the clandestine preparation, decarboxylates the cannabinoid acids, but the basic TLC pattern remains the same, provided no further process has been performed on the sample. Liquid cannabis not containing CBD must have been prepared from herbal material, as all resin contains at least some CBD (table 4). The converse is, however, not true (table 4).


Conclusions

On the basis of physical appearance and thin-layer chromatographic characteristics it is possible to assign the most probable country of origin to the majority of Cannabis products illicitly entering the United Kingdom. TLC examination is a valuable indicator of the country of origin where there are no characteristic physical features, for instance, in the analysis of small amounts of material or in the case of liquid cannabis.

Edited by namkha
8 people like this

Share this post


Link to post
Variation in the THC content in illicitly imported Cannabis products

Author: P. B. BAKER, K. R. BAGON, T. A. GOUGH

Creation Date: 1980/01/01

P. B. BAKER Laboratory of the Government Chemist, London, United Kingdom of Great Britain and Northern Ireland

K. R. BAGON Laboratory of the Government Chemist, London, United Kingdom of Great Britain and Northern Ireland

T. A. GOUGH Laboratory of the Government Chemist, London, United Kingdom of Great Britain and Northern Ireland

ABSTRACT

The tetrahydrocannabinol (THC) content of 304 seizures of illicit Cannabis products was determined using gas chromatography. This procedure results in the conversion of THC acid to THC itself and thus gives the total THC content of the material, which reflects its potency as experienced by the smoker. The study was carried out over three years, thus enabling comparisons to be made between THC levels from a given country of origin over this time span in addition to any variations between the countries. In the early part of the study, herbal cannabis from South East Asia was consistently the best quality and that from the Caribbean the poorest quality. In the third year of the study, the material from South East Asia was in general no richer in THC than material from other areas of the world. Cannabis resins normally had higher THC contents than most herbal material, but the highest levels were found in "hash oil" from the Middle East and the Indian subcontinent.

Introduction

The price of Cannabis products on the illicit market is governed inter alia by their quality as perceived by the user. It has been established for some years that the major psychoactive constituent in Cannabis is Δ 9-tetrahydrocannabinol (THC) and the level of this compound in Cannabis products can therefore be used as a guide to quality.

* Cannabis = Cannabis sativa L.; cannabis = marijuana; cannabis resin = hashish; cannabis oil = liquid cannabis or "hash oil".

The major cannabinoids (THC, cannabinol and cannabidiol) can be separated by thin-layer chromatography. Quantitative information can be obtained by making absorption measurements after reacting the separated constituents with azo dyes. Using this method Nielsen [ 1] examined cannabis grown in Denmark and found that the THC content of the dried mature plant varied between 0.04 and 1.7 per cent. The majority of reports describe the use of gas chromatography to separate the cannabinoids, and quantitative information is based on measurements using the flame-ionization detector. Quantitation has been carried out using either internal or external standards with coefficients of variation ranging from 1 to 3 per cent, which is adequate for the present work [ 2] - [ 6] . Reviews of gas chromatographic procedures have been published [ 7] , [ 8] in which various stationary phases and operating conditions have been compared. Satisfactory separation of cannabinoids, after extraction, may be obtained using a variety of silicone gum phases. It has, however, been noted that loss of THC by absorption on stationary phases can occur at low THC levels [ 9] .

A method has also been described in which the direct injection of solid cannabis is made [ 10] . However, there is ample evidence to show that the cannabinoid content varies within a plant [ 11] . This method has therefore no advantage over extraction procedures as in order to obtain representative and homogeneous samples a large amount must be prepared from which an aliquot is taken. Ohlsson et al. [ 12] have shown that there is no significant difference between the THC levels (and between other cannabinoid levels) in male and female plants grown under the same conditions. We have, however, noticed that the majority of herbal sample seizures submitted to us do not contain a significant proportion of male plants.

The cannabinoid acids are thermally labile and the use of gas chromatography results in their decarboxylation to the corresponding cannabinoids. Quantitative measurement of the THC content by gas chromatography therefore gives the total amount of THC and its acid (THCA), the latter being quantitatively converted to THC on injection [ 12] , [ 13] . For the present study this is an advantage because the acids also decarboxylate during the process of smoking. It is possible to determine the THC and THCA content separately by gas chromatography using derivatization [ 14] , [ 15] or selective extraction [ 16] , although recent developments enable this to be done more readily using high-performance liquid chromatography [ 15] , [ 17] , [ 18] . There have been reports of the conversion of cannabidiol (CBD) to THC, or a compound of the same gas chromatographic retention time, and this could give rise to erroneous THC levels using gas chromatography [ 19] . Under the conditions used in the present work this conversion was not observed. Changes in the THC content during the growth of the plant have been studied and seasonal variations in THC content have been noted [ 3] , [ 20] . The THC content of harvested material decreases on storage and there have been several studies in which plant material from a single plant has been stored under different conditions to determine the effects of temperature, light and air on changes in cannabinoid levels [ 11] , [ 21] . Even after solvent extraction, cannabinoid concentrations will still change and analysis should be carried out as soon as possible after preparation of the extract [ 22] , [ 23] .

There are several reports in the literature on the THC content of cannabis and these are summarized in table 1. In the present context the origin refers to the country in which the plant was grown and not the country of origin of the seeds. It should be noted that, although all the THC levels quoted are expressed as a percentage of dry weight of cannabis, it is not clear in all cases whether any selection of plant material had taken place. In all but one study, values were obtained by gas chromatography and therefore include THCA. As far as can be ascertained, samples were extracted and analysed within a short space of time so that the effects of sample or extract storage on the THC levels was minimal [ 24] . Most of the data in table 1 are derived from cannabis legitimately grown and processed as part of scientific studies on cannabinoids. In contrast, the present work is concerned with the THC content of illicit supplies of Cannabis products and all samples have been taken from seizures by law enforcement agencies in the United Kingdom. Jenkins and Patterson [ 25] have extensively studied illicit Cannabis products, but the data are expressed in terms of the relative proportions of THC, CBD and cannabinol (CBN) rather than their concentrations in the plant. The valuable study by Marshman et al. [ 20] is restricted to Jamaican cannabis. The origins of the samples analysed by Eskes et al. [ 26] , all of which were seizures, are not quoted.

Table 1

Summary of published data on THC content of mature cannabis

1970s Cannabis data

We now report the findings of a study of the THC content of cannabis, resin and oil as received in the United Kingdom from a number of different countries over three one-year periods. The most probable country of origin was assigned by taking into account information from the carrier, visual appearance [ 27] , and the thin-layer and high-performance liquid chromatographic characteristics [18, 28]. For completeness, the data for 1975 for cannabis and resin which have been published in the Report of the Government Chemist 1976 [ 29] have been included.

Experimental

Sample selection

Only samples which to the best of our knowledge were fresh (i.e. less than three months old) on arrival in the United Kingdom were included in the study. This represents approximately 15 per cent of all illicit Cannabis samples submitted to the laboratory over the same period of time. Most samples were analysed within one month of seizure, during which time they were stored in sealed plastic bags at room temperature. Each seizure was analysed as received, except that in the case of herbal material intact stems were first removed. Resin (5 g) or herbal material (2.5 g) was subjected to Soxhlet extraction using 100 ml of ethanol (PBS grade) and the optimum extraction time was found to lie between 60 and 90 minutes. Excessive time resulted in loss of THC by thermal degradation and too short a time in incomplete extraction. It was necessary to grind the resin prior to extraction in order to recover all the THC. For example, two samples of the same resin, one untreated and the other ground, gave THC values of 2.4 and 4.6 per cent, respectively, when extracted for the same time. Examination of the final extract was made on all samples to ensure that extraction was complete, and in no case was any THC found.

Reproducibility of extraction was measured using nine samples of herbal material from a single seizure and results were sensibly constant. It is known from other studies [ 18] that in resin, at least from Pakistan and Lebanon, the cannabinoids are uniformly distributed within a block.

Liquid cannabis ("hash oil"), which varied in viscosity from a freely flowing liquid to almost solid, was warmed and diluted with ethanol to give a 1 mg/ml solution.

Analysis of extract

Each extract, which was analysed on the same day that it was prepared, was made up to 200 ml in ethanol, a 1-ml aliquot was diluted to 10 ml and 5μl of this solution analysed by gas chromatography. A Pye-Unicam model 104 instrument was fitted with a 1.5 m x 4 mm internal diameter glass column containing 3 per cent OV17 stationary phase on 100-120 mesh Gaschrom Q support. The carrier-gas flow rate was 30 ml/min and the column temperature was 250°C. Detection was by flame ionization and the detector was calibrated for THC response using a primary standard of 0.01 per cent THC in ethanol.

Results

The THC content of plant material, resin and hash oil seizures are given in tables 2-4. For some countries there were very few samples, but it is apparent that the range of THC content varies widely even from a given country of origin. This is to be expected, since even plants grown under carefully controlled conditions show wide variations in THC content (see table 1). However, the quality of cannabis from some areas is consistently better than others. During 1975 and 1976, Ghana yielded cannabis low in THC compared with other African countries, but the samples seen in 1978 were of better quality. Jamaican cannabis was consistently poor in 1975 and 1976 and no material high in THC, such as obtained by other workers from dealers in Jamaica [ 20] , was found in the United Kingdom. By contrast, there was a noticeable improvement in the Jamaican material in the third year of the study. Mean values for all samples in the present study were, however, little different from published mean values [ 20] , [ 30] .

Table 2

Total THC content of seized cannabis

1970s Cannabis data

Table 3

Total THC content of seized cannabis resin

1970s Cannabis data

Table 4

Total THC content of seized "hash oil"

1970s Cannabis data

In the same two years, by far the highest quality cannabis originated in South East Asia (exclusively in the form of "Thai sticks") and this was reflected in its street price, at least in the United Kingdom, over the same period. However, the 1978 seizures which originated in Thailand, while still prepared in the form of sticks, showed a dramatic decrease in THC level compared with previous years. A careful study of the physical appearance of seizures of Thai origin for the three years revealed an increasing seed content in the cannabis. It is not possible to examine the data for any correlation of THC content with season because our procedure for estimating age will not discriminate between differences of less than three months and because there were, in most cases, insufficient samples upon which to base any such conclusion.

The cannabis resins generally had a higher THC content than most of the herbal material with the exception of the best Indian, Rhodesian and Thai material. For any given country there was a wide range of THC values. Not surprisingly, the highest levels of THC were encountered in the hash oil seizures, with values as high as 40 per cent. A comparison of the mean amounts of THC in cannabis resin and hash oil from the same countries (tables 3 and 4) shows that for India, Lebanon and Pakistan, the oil contains approximately three times the amount present in the resin. By contrast, Moroccan oil, which is the least viscous encountered, has no more THC than resin from the same country.

Edited by namkha
2 people like this

Share this post


Link to post

just to add, for comparison: I saw at icmag that some traditional Kerala got grown and tested in California and had 15% THC - the South Indian strains in these LGC reports were showing more like mid single figures to low double figures... whereas good Thaistick was around 17%THC

Share this post


Link to post

Eesh I'll wait for the abstract

Share this post


Link to post

It's all abstract considering they only used tlc to test in the 1st place. lol

All aside to the fact it's nonsense anyhow, lol nothing more than guessing when comparing to other samples that could easily have 0 relation what so ever.

Just seems to be giving themselves credit for something they've not even really accomplished as dna would be the only way to actually match anything up n even that has questionable results in the end.

Pretending really, for a self pat on the back, n the pay for the "study" I'm sure was funded by the gov. lol

cheers,............................................gps

1 person likes this

Share this post


Link to post

It's all abstract considering they only used tlc to test in the 1st place. lol

All aside to the fact it's nonsense anyhow, lol nothing more than guessing when comparing to other samples that could easily have 0 relation what so ever.

Just seems to be giving themselves credit for something they've not even really accomplished as dna would be the only way to actually match anything up n even that has questionable results in the end.

Pretending really, for a self pat on the back, n the pay for the "study" I'm sure was funded by the gov. lol

cheers,............................................gps

you're not wrong that TLC is a crap way to test compared to gas chromatography

but I don't follow what you're saying here:

All aside to the fact it's nonsense anyhow, lol nothing more than guessing when comparing to other samples that could easily have 0 relation what so ever.

Just seems to be giving themselves credit for something they've not even really accomplished as dna would be the only way to actually match anything up

are you saying they didn't know where the stuff came from really - and only DNA tests would have told them the country of origin? These are samples from seizures busted by the cops, so there are pretty obvious ways the country of origins would have been known.

Share this post


Link to post
Sign in to follow this  
Followers 0