Proof of the consumption of cannabis


Chromatogram showing the presence of cannabis constituents in dental deposits from one subject


Pages: 65 to 67
Creation Date: 1978/01/01

Proof of the consumption of cannabis

A. NOIRFALISE Laboratory of Clinical and Forensic Toxicology, University of Liège 151 Boulevard de la Constitution, B-4020 Liège
J. LAMBERT Forensic Pathologist, B-4800- Verviers

Distinguishing between a trafficker and a consumer is still a matter of major concern for all who are professionally interested in the problem of cannabis and its derivatives. Although, as has already been pointed out (1, 3, 4), cannabis has now been thoroughly studied in its physicochemical, pharmacological, sociological and other aspects, the same is not yet entirely true of its metabolic properties, on which the possibility of demonstrating its presence and quantity in biological media depends. Except under well-defined conditions of time and place, demonstration of the absorption of any quantity of cannabis resin by laboratory examination of biological media is generally illusory.

Following on the work of Stone and Stevens [ 7] , Robinson [ 6] showed that it was possible to detect the presence of cannabis resin on the hands at autopsy; this contribution made the task much easier when a rapid examination had to be made. Robinson's publication, which was followed by those of Repetto and Menendez [ 5] and that of de Faubert Maunder [ 2] , was not entirely beyond criticism, however, and in any case did not make it possible to distinguish between traffickers and consumers.

Stone and Stevens [ 7] , however, had initially proposed, in addition to examination of the fingers (traffickers) an examination of a "mouthwash" which might catch possible consumers. The somewhat impractical nature of the operation probably accounts for the limited success finally achieved by this proposal.

We therefore considered the examination of dental deposits, which are easy to obtain using a sharp toothpick covered with a small swab of cotton wool soaked in a few drops of petroleum ether or chloroform. After the organic solvent had been allowed to evaporate, the swab is mechanically shaken for 30 minutes in the presence of 5 to 10 ml of benzene; in urgent cases, however, shaking for one minute in a "super mixer" may be sufficient.

The benzene extracts thus obtained is then cleaned by chromatography on a microcolumn of Florisil of 100-200 US mesh (B.D.H. 15,026) and the eluate, after concentration, is examined chromatographically on a thin layer of silicagel (Merck 5715) impregnated with dimethyl formamide (B.D.H. 28,425), cyclohexane (Merck 9,666) being used as migratory solvent (4). The spots are located and differentiated by spraying with a solution of Fast Blue B (Merck 3,191) (0.5 per cent in a 50:50 water-acetone mixture).

In the case of a young woman of 16 years of age who had been taking cannabis for three years, we were able to demonstrate the presence in dental deposits of the main constituents of cannabis resin, as shown in the figure, although an examination of the fingers of the right hand proved entirely negative.

In view of the ease with which the samples can be taken and the analysis performed, we believe that the examination of dental deposits can be recommended both for criminology and for clinical toxicology.

Chromatogram showing the presence of cannabis constituents in dental deposits from one subject

Full size image: 13 kB
Purple/Brick red
Δ 8-Tetrahydrocannabinol (UNC).
Deposit from teeth of subject.
Cannabichromene (UNC)
Cannabinol (KORTE).
Δ 8-Tetrahydrocannabinol (UNC).
Cannabidiol (UNC).
Cannabinol (UNC).
Cannabidiol (KORTE).
Deposit from fingers of subject.
Cannabigerol (UNC).


It is thanks to the kindness and generosity of Professor Korte of Bonn (1965), Professor de Schultz of Kiel (1965) and Dr. O.J. Braenden of the United Nations Office at Geneva (1978) that the authors were able to obtain the reference materials * needed for the present work.

They express their gratitude to all three.

*Note by the Secretariat: The National Institute of Drug Abuse of the United States of America kindly supplied the United Nations Narcotics Laboratory with some of the samples mentioned in this paper.



1. AS. Curry, Advances in forensic and clinical toyicology, C.R.C Press, pp. 29-40. 1972


2. M.J. de Faubert Maunder, "An improved procedure for the field testing of cannabis", Bulletin on Narcotics. XXVI: 4, 19-26, 1974


A. Noirfalise, "Considérations sur le cannabis sativa", Arch. Belges Méd. Soc., Hyg., Méd. Trav., Méd. Leg., 23, (6), pp. 373-386, 1965.


"Problèmes toxicologiques posés par l'emploi abusif des drogues". Arch. Belges Méd. Soc., Hyg., Méd. Trav., 29 (5), pp. 281-302, 1971.


M. J. Repetto and M. Menendez, "Identification de produits cannabiques au niveau des doigts et dans le sang des fumeurs", J.E.T., 4 (6), pp. 501-504, 1971.


A.E. Robinson, "Recovery of cannabis constituents from the hands at autopsy", Bulletin on Narcotics, XXIII: 3, 37-40


H.M. Stone and H.M. Stevens, "The detection of cannabis constituents in the mouth and on the fingers of smokers", J. For. Sci. Soc., 9, p. 31, 1969.