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Analysis of Cannabis Using Tenax-GC
0Forensic Science Society 1985
ORIGINAL PAPERS
Analysis of Cannabis Using Tenax-GC A OSMAN* and B CADDY? Forensic Science Unit, University of Strathclyde, 204 George Street, Glasgow, United Kingdom G I I X W Abstract Headspace volatiles of cannabis resin have been examined by gas chromatography using a capillary column. A new approach for the analysis of cannabis has been developed which involves the use of Tenax-GC for adsorbing a wide range of the volatile constituents. The simplicity and reproducibility of this procedure make it attractive for both forensic applications and chemotaxonomical studies of cannabis plants. Additionally, the method has proved applicable for the detection of cannabis in the presence of different types of tobacco. Key words: Capillary column; Headspace analysis; Tenax-GC; Cannabis. Journal of the Forensic Science Society 1985; 25: 377-384 Received 22 June 1984 Introduction Gas chromatography was introduced for the analysis of cannabis resin in the early 1960s [I] and it is now known that cannabis resins are very complex mixtures containing many hundreds of components [2]. Several papers have been published indicating that a correlation may exist between the chemical composition of resins and their geographical origins [3,4]. However, the problem is complicated by many factors which may influence the chemical composition of the cannabis resin, such as plant genetics, the soil, climate, the state of maturity at the time of harvest, as well as the storage time and the storage conditions [5]. Investigations have been carried out which indicate that the genetic properties are the dominating factor [6,7]. Recently, some workers have used isothermal headspace analysis in conjunction with packed columns and flame ionisation detection [8] for the analysis of a variety of compounds other than the cannabinoids present in Cannabis sativa L. Alternative headspace analysis procedures have been used by other workers; for example, Caddy and others [9] employed capillary columns, while headspace-mass spectrometry has been used by * Present address: Department of Forensic Medicine and Toxicology, Faculty of Medicine, University of Mansoura, Mansoura, Egypt. t To whom correspondence should be addressed. 377
Urich and fellow workers [lo] and gas chromatography-mass spectrometry by Balkon and Leary [ I l l . Headspace analysis avoids tedious sample preparation and is a most useful auxiliary technique because of its simplicity and speed of execution. Its non-destructive character ensures that neither the sample composition nor the structure of the substances under examination are altered. This latter is most important where samples to be investigated, such as the "reefer" cigarette, are normally destroyed in order to gain access to the analyte. Recently much attention has been given to a modified headspace technique by which organic niolecules in ambient air are analysed by adsorption onto porous polymers from which they may subsequently be thermally desorbed into a gas chromatograph [12]. A common adsorbant for this purpose is the porous polymer Tenax-GC whose structure is based upon 2,6-diphenyl-paraphenylene oxide [13]. It possesses a high stability temperature (375 "C limit) and will allow the collection and desorption of high molecular weight hydrocarbons. This material has been successfully used for trace analysis of volatiles in air pollution studies [14-161, for monitoring the cabin atmosphere in Skylab 4 [17], in a number of biological studies [18,19], and in the analysis of volatile hydrocarbons in fire debris [20]. White [21] compared normal headspace analysis in which millilitres of vapour were taken from above specimens of fire debris impregnated with hydrocarbon accelerant with a method employing a Tenax-GC concentration trap. He concluded that conccntrating the accelerant vapours before gas chromatographic analysis gave significantly enhanced sensitivity over headspace analysis. The chemical composition of the essential oil of marijuana has been thoroughly investigated [22] and some data is available on the volatiles which give rise to the emitted aroma [23]. The composition of any headspace, as it contributes directly to the odour, may be more significant than that of cannabis oil for the characterisation of marijuana aroma. The essential oil of cannabis resin has long been known to contain terpenes and sesquiterpenes which boil at temperatures much lower than the physiologically-active cannabinoids especially the isomeric tetrahydrocannabinds. Publications by Stromberg [24-261 indicate that the minor constituents of cannabis could be an important factor in determining the geographical origin of cannabis samples and in answering the question as to whether cannabis samples seized at different geographical sites can be assigned to the same source, thereby tracing back the lines of distribution. The purpose of the present work, therefore, was to develop a method for the analysis of volatiles of Cannabis sativa L employing an adsorption1 desorption system. Additionally, it was hoped that while the method of analysis might be useful for characterising the geographical origins of 378
cannabis, its primary function was to ascertain if cannabis mixed with "rolling" and burnt tobacco contained within personally-prepared as well as commercially-available cigarettes could be characterised without the need to destroy the original physical structure of the evidence.
Experimental Apparatus and conditions of analysis A Carlo Erba Strumentazione Fractovap Model 2350 gas chromatograph was employed for all analysis and was fitted with a 24 m quartz capillary column coated with methyl silicone and operated at a flow rate of 2 mllmin of nitrogen and a temperature of 40°C for 5 min. programmed from 40°C to 180°C at 5"CImin; injection and detector temperature was 275°C and detection was by flame ionisation. The splitless mode of injection was adopted. Sample used for analysis Various samples of cannabis resin of at least 10 years of age and a selection of common tobaccos and cigarcttcs (Rothman, Marlboro, Benson and Hedges, Club and Silkcut; two types of rolling tobacco, Golden Virginia and Old Holborn) were used. Analytical procedure Samples of cannabis resin (100 mg) were heated for one hour at 100°C in a closed vial of 10 ml capacity. Samples of vapour (2 ml) were injected onto the chromatograph under the conditions described above. The concentration and analysis of the volatiles of cannabis resin using Tenax-GC ( 6 W 0 mesh, Phase Separations Ltd., Queensferry, Clwyd, U.K.) employed a method described in an earlier report by Russell [20] for hydrocarbons. While vapour volumes of 2 ml were necessary for these old resin samples, more recent preparations would probably require a much smaller volume. Several vials of the same capacity (10 ml) containing different amounts of the resin in the range 3 mg-100 mg were tested by the same two procedures detailed immediately above, in order to establish the optimum operating conditions. This same procedure was again repeated using different types and amounts (200 mg) of tobacco, burnt tobacco and rolling tobacco. Kovats Indices for the monoterpenes, myrcene, limonene, linalool, terpineol and /karyophyllene were determined using standard alkanes under the conditions of the temperature programme run.
Results and discussion A typical chromatogram for headspace analysis of a lOOmg sample of cannabis resin is shown in Figure l a . This shows two sets of peaks. The first group eluting up to 14 min. and covering the temperature range 40 to 80" 379
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FIGURE 1 (a) Headspace cannabis analysis (2 ml of vapour). (b) Chromatogram of the same cannabis resin after concentration on Tenax-GC. Analytical conditions: 24 m quartz capillary column coated with methyl silicone operated at a flow rate of 2 ml/min of nitrogen and a temperature of 40" for 5 min, programmed for 40" to 155" at S0/min. Injection and detector temperatures were maintained at 275"; FID detector; splitless mode.
represents compounds having greatest volatility and of molecular weight less than 100. Examination of this fraction by other workers indicates that these principally consist of low-molecular-weight oxygenated compounds [23,27]. The second group of peaks, eluting between 16 min. and 24 min. over a temperature range of 100" to 140" consist of monoterpene hydrocarbons and oxygenated compounds of molecular weights ranging from 100 to 200. The greater degree of resolution for the latter part of the chromatogram demonstrates the advantage of quartz capillary columns over conventional packed columns. This profile is highly reproducible both qualitatively and quantitatively. For identification purposes, retention indices of these peaks have been recorded and compared with values obtained for some standard monoterpenes (1010, 1041, 1155, 1283 and 1384 for myrcene, limonene, linalool, terpineol and P-caryophyllene respectively). The main peak in this profile was found to be consistent with the retention data for Pcaryophyllene (I = 1383). Tenax-GC was selected as the adsorbent to trap and concentrate cannabis vapours because volatile components common to cannabis are effectively
retained by Tenax-GC, as demonstrated by their high "breakthrough" volumes. Breakthrough can be defined as the volume of gas that must be passed through an adsorbent before the compound of interest begins to be eluted from the adsorbent. High breakthrough volumes reflect the high retentive power of an adsorbent towards a particular substance [28]. Additionally, Tenax is insensitive to the presence of water vapour, for which it has an extremely low affinity. These results clearly confirmed earlier studies [29] that water had no effect on the adsorption properties of Tenax-GC. Also, the thermal desorption of Tenax-GC is rapid and complete at temperatures above 190°C [20]. This means that the adsorption tube can be re-used over and over again without any danger of carryover of sample from one headspace to the next. Figure l b shows a chromatogram of the same cannabis resin after concentration of its vapours on Tenax-GC. As might be expected, the chromatographic pattern formed by conventional headspace sampling does,
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FIGURE 2. (a) Headspace tobacco (Golden Virginia) analysis. (b) Headspace burnt tobacco (Golden Virginia) analysis. Analytical conditions: 24 m quartz capillary column coated with methyl silicone operated at a flow rate of 2mllrnin of nitrogen and a temperature of 40" for 5 min, programmed for 40" to 155' at SO/rnin. Injection and detector temperatures were maintained at 275'; FID detector; splitless mode.
in some instances, differ from those formed after concentration on Tenax-GC. These differences can be attributed to the varied trapping and desorption efficiencies of Tenax-GC toward hydrocarbons. Interestingly, the chromatogram does not differ either qualitatively or quantitatively in that region of the elution profile between 16 min. and 24 min. and consequently no difficulties were encountered in matching and comparing the G C patterns in this section.
A major reason for implementing a concentration step for cannabis analysis is its enhanced sensitivity over a normal headspace analysis. This expectation proved justified. Relative sensitivities between the two procedures were established by sealing the same quantities of the same cannabis resin in similar vessels and testing them by both the headspace and Tenax-GC procedure. Our findings indicate that thc lower limit of identification of cannabis resin by headspace is 10 mg, while the lower limit in the case of concentrating over Tenax-GC was 3 mg, an approximate 3-fold increase in sensitivity. Tests were carried out on a number of common tobaccos, in their natural state and also when burned, for possible interferencc in the G C pattern. Both direct headspace and Tenax-GC concentration showed that none of the samples tested could conceivably cause any interference with the cannabis profile as illustrated by Figures 2 and 3.
Temp. ("C) Time (min.)
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FIGURE 3. Chromatogram of cigarette (Marlboro) after concentration on Tenax-GC. Analytical conditions: 24 m quartz capillary column coated with methyl silicone operated at a flow rate of 2 ml/min of nitrogen and a temperature of 40" for 5 min, programmed for 40" to 180' at 5"Imin. Injection and detector temperatures were maintained at 275"; FID detector; splitless mode.
Conclusion The adsorption/desorption system developed in this work has sufficient simplicity and reproducibility to be used for applications of forensic interest. The use of Tenax-GC has been shown to be a valuable additional method for identifying cannabis resin. Finally, the method was successfully applied to the analysis of cannabis mixed with cigarettes, rolling and burnt tobacco.
References 1. Farmilo CG and Davis TWM. Paper and gas chromatographic analysis of cannabis. Journal of Pharmacy and Pharmacology 1961; 13: 767-768. 2. Novotny M, Merli F, Wiesler D, Fencl M and Saeed T. Fractionation and capillary gas chromatographic-mass spectrometric characterization of the neutral compouents of marijuana and tobacco smoke condensates. Journal of Chromatography 1982; 238: 141-150. 3. Turner CE, Hadley KW and Fetterman PS. Constituents of Cannabis sativa. VI. Propyl homologs in samples of known geographical origin. Journal of Pharmaceutical Sciences 1973; 62: 1739-1741. 4. Turner C E and Hadley KW. Chemical analysis of Cannabis sativa of distinct origin. Archives of Investigative Medicine 1974; 5: 141-150. 5. Turner CE, Hadley KW, Fetterman PS, Doorenbos NJ, Quimby MW and Waller C. Constituents of Cannabis sativa. IV. Stability of cannabinoids in stored plant material. Journal of Pharmaceutical Sciences 1973; 62: 1601-1605. 6. Fetterman PS, Keith ES, Waller CW, Guerrero 0, Doorenbos NJ and Quimby MW. Mississippi-grown cannabis sativa. Chemical definition of phenotype and variations in tetrahydrocannibinol content versus age, sex and plant part. Journal of Pharmaceutical Sciences 1971; 60: 12461249. 7. Ohlsson A, Abou-Chaar CI, Agurell S, Nilsson IM, Olofsson K and Sandberg, F. Metabolism of cannabis V cannabinoid constituents of male and female Cannabis sativa. Bulletin of Narcotics 1971; 23: 29-32. 8. Hood LVS and Barry GT. Headspace volatiles of marijuana and hashish: gas chromatographic analysis of samples of different geographic origin. Journal of Chromatography 1978; 166: 499-506. 9. Caddy B, Kidd CBM and Leung SC. Identification of drugs using capillary gas liquid chromatography. Journal of the Forensic Science Society 1982; 22: 3-31. 10. Urich RW, Bowerman DL, Wittenberg PH, Pierce AF, Schisler DK, Levisky JA and Pflug JL. Headspace mass spectrometric analysis for volatiles in biological specimens. Journal of Analytical Toxicology 1977; 1: 195-199. 11. Balkon J and Leary JA. An initial report on a comprehensive, quantitative, screening procedure for volatile compounds of forensic and environmental interest in human biofluids by GCIMS. Journal of Analytical Toxicology 1979; 3: 213-215. 12. Mieure JP and Dietrich MW. Determination of trace organics in air and water. Journal of Chromatographic Science 1973; 11: 559-570. 13. Van Wijk R. Use of poly (2,6-diphenyl-p-phenylene oxide) as a porous polymer in gas chromatography. Journal of Chromatographic Science 1970; 8: 418-420. 14. Pellizari ED, Carpenter BH, Bunch J E and Sawicki E. Collection and analysis of trace organic vapor pollutants in ambient atmospheres. Thermal desorption of organic vapors from sorbent media. Environmental Science and Technology 1975; 9: 556560. 15. Holzer G, Shanfield H , Zlatkis A, Bertsch W, Juarez P, Mayfield H and Liebich HM. Collection and analysis of trace organic emissions from natural sources. Journal of Chromatography 1977; 142: 755-764. 16. Brown RH and Purnell CJ. Collection and analysis of trace organic vapor pollutants in ambient atmospheres. The performance of a Tenax-GC adsorbent tube. Journal of Chromatography 1979; 178: 79-90.
Bertsch W, Zlatkis A , Liebich HM and Schneider HJ. Concentration and analysis of organic volatiles in Skylab 4. Journal of Chromatography 1974: 99: 673487. Zlatkis A, Lichtenstein HA, Tishbee A. Bertsch W. Shunbo F and Liebich HM. Concentration and analysis of volatile urinary metabolites. Journal of Chromatographic Science 1973; 11: 299-302. May WE, Chesler SN, Cram SP, Gump BH, Hertz HS, Enagonio D P and Dyszel SM. Chromatographic analysis of hydrocarbons in marine sediments and seawater. Journal of Chromatographic Science 1975; 13: 535-540. Russell LW. The concentration and analysis of volatile hydrocarbons in tire debris using Tenax-GC. Journal of the Forensic Science Society 1981; 21: 317-326. White SE. Arson analysis newsletter Dec. 1978; 2: 1-15. Martin L. Smith DM and Farmilo CG. Essential oil from fresh Cannabis sativa and its use in identification. Nature 1961; 191: 774776. Hood LVS, Dames ME and Barry GT. Headspace volatiles of marijuana. Nature 1973; 242: 402-403. Stromberg LE. Minor components of cannabis resin. 111. Comparative gas chromatographic analysis of hashish. Journal of Chromatography 1972; 68: 253-258. Stromberg LE. Minor components of cannabis resin. Separation by gas chromatography, mass spectra and molecular weights of some components with shorter retention times than cannabidiol. Journal of Chromatography 1972; 68: 24S252. Stromberg LE. Minor components of cannabis resin. Their separation by gas chromatography, thermal stability, and protolytic properties. Journal of Chromatography 1971; 63: 391-396. Novotny M, Lee ML, Low C and Raymond A. Analysis of marijuana samples from different origins by high-resolution gas-liquid chromatography for forensic application. Analytical Chemistry 1976: 48: 24-29. Saferstein R and Park SA. Application of dynamic headspace analysis to laboratory and field arson investigations. Journal of Forensic Sciences 1982; 27: 484494. Janak J, Ruzickova J and Novak J. Effect of water vapour in the quantitation of trace components concentrated by frontal gas chromatography on Tenax-GC. Journal of Chromatography 1974; 99: 689-696.
ORIGINAL PAPERS
Analysis of Cannabis Using Tenax-GC A OSMAN* and B CADDY? Forensic Science Unit, University of Strathclyde, 204 George Street, Glasgow, United Kingdom G I I X W Abstract Headspace volatiles of cannabis resin have been examined by gas chromatography using a capillary column. A new approach for the analysis of cannabis has been developed which involves the use of Tenax-GC for adsorbing a wide range of the volatile constituents. The simplicity and reproducibility of this procedure make it attractive for both forensic applications and chemotaxonomical studies of cannabis plants. Additionally, the method has proved applicable for the detection of cannabis in the presence of different types of tobacco. Key words: Capillary column; Headspace analysis; Tenax-GC; Cannabis. Journal of the Forensic Science Society 1985; 25: 377-384 Received 22 June 1984 Introduction Gas chromatography was introduced for the analysis of cannabis resin in the early 1960s [I] and it is now known that cannabis resins are very complex mixtures containing many hundreds of components [2]. Several papers have been published indicating that a correlation may exist between the chemical composition of resins and their geographical origins [3,4]. However, the problem is complicated by many factors which may influence the chemical composition of the cannabis resin, such as plant genetics, the soil, climate, the state of maturity at the time of harvest, as well as the storage time and the storage conditions [5]. Investigations have been carried out which indicate that the genetic properties are the dominating factor [6,7]. Recently, some workers have used isothermal headspace analysis in conjunction with packed columns and flame ionisation detection [8] for the analysis of a variety of compounds other than the cannabinoids present in Cannabis sativa L. Alternative headspace analysis procedures have been used by other workers; for example, Caddy and others [9] employed capillary columns, while headspace-mass spectrometry has been used by * Present address: Department of Forensic Medicine and Toxicology, Faculty of Medicine, University of Mansoura, Mansoura, Egypt. t To whom correspondence should be addressed. 377
Urich and fellow workers [lo] and gas chromatography-mass spectrometry by Balkon and Leary [ I l l . Headspace analysis avoids tedious sample preparation and is a most useful auxiliary technique because of its simplicity and speed of execution. Its non-destructive character ensures that neither the sample composition nor the structure of the substances under examination are altered. This latter is most important where samples to be investigated, such as the "reefer" cigarette, are normally destroyed in order to gain access to the analyte. Recently much attention has been given to a modified headspace technique by which organic niolecules in ambient air are analysed by adsorption onto porous polymers from which they may subsequently be thermally desorbed into a gas chromatograph [12]. A common adsorbant for this purpose is the porous polymer Tenax-GC whose structure is based upon 2,6-diphenyl-paraphenylene oxide [13]. It possesses a high stability temperature (375 "C limit) and will allow the collection and desorption of high molecular weight hydrocarbons. This material has been successfully used for trace analysis of volatiles in air pollution studies [14-161, for monitoring the cabin atmosphere in Skylab 4 [17], in a number of biological studies [18,19], and in the analysis of volatile hydrocarbons in fire debris [20]. White [21] compared normal headspace analysis in which millilitres of vapour were taken from above specimens of fire debris impregnated with hydrocarbon accelerant with a method employing a Tenax-GC concentration trap. He concluded that conccntrating the accelerant vapours before gas chromatographic analysis gave significantly enhanced sensitivity over headspace analysis. The chemical composition of the essential oil of marijuana has been thoroughly investigated [22] and some data is available on the volatiles which give rise to the emitted aroma [23]. The composition of any headspace, as it contributes directly to the odour, may be more significant than that of cannabis oil for the characterisation of marijuana aroma. The essential oil of cannabis resin has long been known to contain terpenes and sesquiterpenes which boil at temperatures much lower than the physiologically-active cannabinoids especially the isomeric tetrahydrocannabinds. Publications by Stromberg [24-261 indicate that the minor constituents of cannabis could be an important factor in determining the geographical origin of cannabis samples and in answering the question as to whether cannabis samples seized at different geographical sites can be assigned to the same source, thereby tracing back the lines of distribution. The purpose of the present work, therefore, was to develop a method for the analysis of volatiles of Cannabis sativa L employing an adsorption1 desorption system. Additionally, it was hoped that while the method of analysis might be useful for characterising the geographical origins of 378
cannabis, its primary function was to ascertain if cannabis mixed with "rolling" and burnt tobacco contained within personally-prepared as well as commercially-available cigarettes could be characterised without the need to destroy the original physical structure of the evidence.
Experimental Apparatus and conditions of analysis A Carlo Erba Strumentazione Fractovap Model 2350 gas chromatograph was employed for all analysis and was fitted with a 24 m quartz capillary column coated with methyl silicone and operated at a flow rate of 2 mllmin of nitrogen and a temperature of 40°C for 5 min. programmed from 40°C to 180°C at 5"CImin; injection and detector temperature was 275°C and detection was by flame ionisation. The splitless mode of injection was adopted. Sample used for analysis Various samples of cannabis resin of at least 10 years of age and a selection of common tobaccos and cigarcttcs (Rothman, Marlboro, Benson and Hedges, Club and Silkcut; two types of rolling tobacco, Golden Virginia and Old Holborn) were used. Analytical procedure Samples of cannabis resin (100 mg) were heated for one hour at 100°C in a closed vial of 10 ml capacity. Samples of vapour (2 ml) were injected onto the chromatograph under the conditions described above. The concentration and analysis of the volatiles of cannabis resin using Tenax-GC ( 6 W 0 mesh, Phase Separations Ltd., Queensferry, Clwyd, U.K.) employed a method described in an earlier report by Russell [20] for hydrocarbons. While vapour volumes of 2 ml were necessary for these old resin samples, more recent preparations would probably require a much smaller volume. Several vials of the same capacity (10 ml) containing different amounts of the resin in the range 3 mg-100 mg were tested by the same two procedures detailed immediately above, in order to establish the optimum operating conditions. This same procedure was again repeated using different types and amounts (200 mg) of tobacco, burnt tobacco and rolling tobacco. Kovats Indices for the monoterpenes, myrcene, limonene, linalool, terpineol and /karyophyllene were determined using standard alkanes under the conditions of the temperature programme run.
Results and discussion A typical chromatogram for headspace analysis of a lOOmg sample of cannabis resin is shown in Figure l a . This shows two sets of peaks. The first group eluting up to 14 min. and covering the temperature range 40 to 80" 379
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FIGURE 1 (a) Headspace cannabis analysis (2 ml of vapour). (b) Chromatogram of the same cannabis resin after concentration on Tenax-GC. Analytical conditions: 24 m quartz capillary column coated with methyl silicone operated at a flow rate of 2 ml/min of nitrogen and a temperature of 40" for 5 min, programmed for 40" to 155" at S0/min. Injection and detector temperatures were maintained at 275"; FID detector; splitless mode.
represents compounds having greatest volatility and of molecular weight less than 100. Examination of this fraction by other workers indicates that these principally consist of low-molecular-weight oxygenated compounds [23,27]. The second group of peaks, eluting between 16 min. and 24 min. over a temperature range of 100" to 140" consist of monoterpene hydrocarbons and oxygenated compounds of molecular weights ranging from 100 to 200. The greater degree of resolution for the latter part of the chromatogram demonstrates the advantage of quartz capillary columns over conventional packed columns. This profile is highly reproducible both qualitatively and quantitatively. For identification purposes, retention indices of these peaks have been recorded and compared with values obtained for some standard monoterpenes (1010, 1041, 1155, 1283 and 1384 for myrcene, limonene, linalool, terpineol and P-caryophyllene respectively). The main peak in this profile was found to be consistent with the retention data for Pcaryophyllene (I = 1383). Tenax-GC was selected as the adsorbent to trap and concentrate cannabis vapours because volatile components common to cannabis are effectively
retained by Tenax-GC, as demonstrated by their high "breakthrough" volumes. Breakthrough can be defined as the volume of gas that must be passed through an adsorbent before the compound of interest begins to be eluted from the adsorbent. High breakthrough volumes reflect the high retentive power of an adsorbent towards a particular substance [28]. Additionally, Tenax is insensitive to the presence of water vapour, for which it has an extremely low affinity. These results clearly confirmed earlier studies [29] that water had no effect on the adsorption properties of Tenax-GC. Also, the thermal desorption of Tenax-GC is rapid and complete at temperatures above 190°C [20]. This means that the adsorption tube can be re-used over and over again without any danger of carryover of sample from one headspace to the next. Figure l b shows a chromatogram of the same cannabis resin after concentration of its vapours on Tenax-GC. As might be expected, the chromatographic pattern formed by conventional headspace sampling does,
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FIGURE 2. (a) Headspace tobacco (Golden Virginia) analysis. (b) Headspace burnt tobacco (Golden Virginia) analysis. Analytical conditions: 24 m quartz capillary column coated with methyl silicone operated at a flow rate of 2mllrnin of nitrogen and a temperature of 40" for 5 min, programmed for 40" to 155' at SO/rnin. Injection and detector temperatures were maintained at 275'; FID detector; splitless mode.
in some instances, differ from those formed after concentration on Tenax-GC. These differences can be attributed to the varied trapping and desorption efficiencies of Tenax-GC toward hydrocarbons. Interestingly, the chromatogram does not differ either qualitatively or quantitatively in that region of the elution profile between 16 min. and 24 min. and consequently no difficulties were encountered in matching and comparing the G C patterns in this section.
A major reason for implementing a concentration step for cannabis analysis is its enhanced sensitivity over a normal headspace analysis. This expectation proved justified. Relative sensitivities between the two procedures were established by sealing the same quantities of the same cannabis resin in similar vessels and testing them by both the headspace and Tenax-GC procedure. Our findings indicate that thc lower limit of identification of cannabis resin by headspace is 10 mg, while the lower limit in the case of concentrating over Tenax-GC was 3 mg, an approximate 3-fold increase in sensitivity. Tests were carried out on a number of common tobaccos, in their natural state and also when burned, for possible interferencc in the G C pattern. Both direct headspace and Tenax-GC concentration showed that none of the samples tested could conceivably cause any interference with the cannabis profile as illustrated by Figures 2 and 3.
Temp. ("C) Time (min.)
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FIGURE 3. Chromatogram of cigarette (Marlboro) after concentration on Tenax-GC. Analytical conditions: 24 m quartz capillary column coated with methyl silicone operated at a flow rate of 2 ml/min of nitrogen and a temperature of 40" for 5 min, programmed for 40" to 180' at 5"Imin. Injection and detector temperatures were maintained at 275"; FID detector; splitless mode.
Conclusion The adsorption/desorption system developed in this work has sufficient simplicity and reproducibility to be used for applications of forensic interest. The use of Tenax-GC has been shown to be a valuable additional method for identifying cannabis resin. Finally, the method was successfully applied to the analysis of cannabis mixed with cigarettes, rolling and burnt tobacco.
References 1. Farmilo CG and Davis TWM. Paper and gas chromatographic analysis of cannabis. Journal of Pharmacy and Pharmacology 1961; 13: 767-768. 2. Novotny M, Merli F, Wiesler D, Fencl M and Saeed T. Fractionation and capillary gas chromatographic-mass spectrometric characterization of the neutral compouents of marijuana and tobacco smoke condensates. Journal of Chromatography 1982; 238: 141-150. 3. Turner CE, Hadley KW and Fetterman PS. Constituents of Cannabis sativa. VI. Propyl homologs in samples of known geographical origin. Journal of Pharmaceutical Sciences 1973; 62: 1739-1741. 4. Turner C E and Hadley KW. Chemical analysis of Cannabis sativa of distinct origin. Archives of Investigative Medicine 1974; 5: 141-150. 5. Turner CE, Hadley KW, Fetterman PS, Doorenbos NJ, Quimby MW and Waller C. Constituents of Cannabis sativa. IV. Stability of cannabinoids in stored plant material. Journal of Pharmaceutical Sciences 1973; 62: 1601-1605. 6. Fetterman PS, Keith ES, Waller CW, Guerrero 0, Doorenbos NJ and Quimby MW. Mississippi-grown cannabis sativa. Chemical definition of phenotype and variations in tetrahydrocannibinol content versus age, sex and plant part. Journal of Pharmaceutical Sciences 1971; 60: 12461249. 7. Ohlsson A, Abou-Chaar CI, Agurell S, Nilsson IM, Olofsson K and Sandberg, F. Metabolism of cannabis V cannabinoid constituents of male and female Cannabis sativa. Bulletin of Narcotics 1971; 23: 29-32. 8. Hood LVS and Barry GT. Headspace volatiles of marijuana and hashish: gas chromatographic analysis of samples of different geographic origin. Journal of Chromatography 1978; 166: 499-506. 9. Caddy B, Kidd CBM and Leung SC. Identification of drugs using capillary gas liquid chromatography. Journal of the Forensic Science Society 1982; 22: 3-31. 10. Urich RW, Bowerman DL, Wittenberg PH, Pierce AF, Schisler DK, Levisky JA and Pflug JL. Headspace mass spectrometric analysis for volatiles in biological specimens. Journal of Analytical Toxicology 1977; 1: 195-199. 11. Balkon J and Leary JA. An initial report on a comprehensive, quantitative, screening procedure for volatile compounds of forensic and environmental interest in human biofluids by GCIMS. Journal of Analytical Toxicology 1979; 3: 213-215. 12. Mieure JP and Dietrich MW. Determination of trace organics in air and water. Journal of Chromatographic Science 1973; 11: 559-570. 13. Van Wijk R. Use of poly (2,6-diphenyl-p-phenylene oxide) as a porous polymer in gas chromatography. Journal of Chromatographic Science 1970; 8: 418-420. 14. Pellizari ED, Carpenter BH, Bunch J E and Sawicki E. Collection and analysis of trace organic vapor pollutants in ambient atmospheres. Thermal desorption of organic vapors from sorbent media. Environmental Science and Technology 1975; 9: 556560. 15. Holzer G, Shanfield H , Zlatkis A, Bertsch W, Juarez P, Mayfield H and Liebich HM. Collection and analysis of trace organic emissions from natural sources. Journal of Chromatography 1977; 142: 755-764. 16. Brown RH and Purnell CJ. Collection and analysis of trace organic vapor pollutants in ambient atmospheres. The performance of a Tenax-GC adsorbent tube. Journal of Chromatography 1979; 178: 79-90.
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