Lab Analysis of Marijuana

The specificity of a marijuana analysis is still a widely discussed topic among those in the forensic and legal communities. In the course of the past 25 years, the concensus of opinion concerning the analysis of marijuana has remained fairly consistent. In those situations where plant material is encountered, the marijuana is first examined using a stereomicroscope. The presence of the bear claw cystolithic hairs and other histological features are noted using a compound microscope.

The plant material is then examined chemically using Duquenois – Levine reagent in a modified Duenois Levine testing sequence. These two tests are considered to be conclusive within the realm of existing scientific certainty in establishing the presence of marijauana.3–5. The Modified Duquenois–Levine test is conducted using Duquenois reagent, concentrated hydrochloric acid, and chloroform. The Duquenois reagent is prepared by dissolving 2g of vanillin and 0.3 ml of acetaldehyde in 100 ml of ethanol. Small amounts (25 to 60 mg is usually sufficient) of suspected marijuana leaf is placed in a test tube and approximately 2 ml of Duquenois reagent is added. After 1 min, approximately 1 ml of concentrated hydrochloric acid is added. Small bubbles rise from the leaves in the liquid. These are carbon dioxide bubbles produced by the reaction of the hydrochloric acid with the calcium carbonate at the base of the cystolithic hair of the marijuana. A blue to blue-purple color forms very quickly in the solution.

Approximately 1 ml of chloroform is then added to the Duquenois reagent/ hydrochloric acid mixture. Because chloroform is not miscible with water, and because it is heavier than water, two liquid layers are visible in the tube—the Duquenois reagent/hydrochloric acid layer is on top, and the chloroform layer is on the bottom. After mixing with a vortex stirrer and on settling, the two layers are again clearly distinguishable. However, the chloroform layer has changed from clear to the blue to blue-purple color of the Duquenois reagent/hydrochloric acid mixture.

One variation in this testing process involve pouring off the Duquenois reagent sitting in the tube with the leaves before adding the hydrochloric acid. The remainder of the test is conducted using only the liquid. Another variation involves conducting the test in a porcelain spot plate. This works, although some analysts find the color change a bit more difficult to detect. A third variation involves extracting the cannabis resin with ether or some other solvent, separating the solvent from the leaves, allowing the solvent to evaporate, and conducting the Modified Duquenois–Levine test on the extract.

Marquis reagent is prepared by mixing 1 ml of formaldehyde solution with 9 ml of sulfuric acid. The test is done by placing a small amount of sample (1 to 5 mg) into the depression of a spot plate, adding one or two drops of reagent, and observing the color produced. This color will usually be indicative of the class of compounds, and the first color is usually the most important. A weak reponse may fade, and samples containing sugar will char on standing because of the sulfuric acid. Marquis reagent produces the following results:

1. Purple with opiates (heroin, codeine).
2. Orange turning to brown with amphetamine and methamphetamine.
3. Black with a dark purple halo with 3,4-methylenedioxyamphetamine (MDA) and
3,4- methylenedioxymethamphetamine (MDMA).
4. Pink with aspirin.
5. Yellow with diphenhydramine.

A thin-layer chromatographic (TLC) analysis, which detects a systematic pattern of colored bands, can then be employed as an additional test.6,7 Though it is not required, some analysts will run a gas chromatograph/mass spectrometrometer (GC/MS) analysis to identify the cannabinoids in the sample.

The solvent insoluble residue of hashish should be examined with the compound microscope. Cystolythic hairs, resin glands, and surface debris should be present. However, if most of the residue is composed of green leaf fragments, the material is pulverized marijuana or imitation hashish.

MARIJUANA

History and Terminology of Marijuana

Marijuana is a Schedule I controlled substance. In botanical terms, “marijuana” is defined as Cannabis sativa L. Legally, marijuana is defined as all parts of the plant, Canabis sativa L. (and any of its varieties) whether growing or not, the seeds thereof, the resin extracted from any part of the plant, and every compound, manufacture, salt, derivative, mixture, or preparation of such plant; its seeds and resins. Such terms do not include the mature stalk of the plants, fibers
produced from such plants, oils or cakes made from the pressed seeds of such plants, any other compound, manufacture, salt derivative, mixture or preparation of such mature stalks (except the resin extracted therefrom), fiber, oil or cake, pressed seed, or the sterilized seed which is incapable of germination.1 Pharmaceutical preparations that contained the resinous extracts of cannabis were available on the commercial market from the 1900s to 1937. These products were prescribed for their analgesic and sedative effects. In 1937 the Food and Drug Administration declared these products to be of little medical utility and they were removed from the market in 1937. Cannabis, in the forms of the plant material, hashish, and hashish oil, is the most abused illicit drug in the world.

Cannabis is cultivated in many areas of the world. Commerical Cannabis sativa L. is
referred to as “hemp”. The plant is cultivated for cloth and rope from its fiber. A valuable drying oil used in art and a substitute for linseed oil is available from the seeds. Bird seed mixtures are also found to contain sterilized marijuana seeds. In the early days of the U.S., hemp was grown in the New England colonies. Its cultivation spread south into Pennsylvania and Virginia. From there it spread south and west most notably into Kentucky and Missouri.

Its abundance in the early days of the country is still evident by the fact that it still grows wild in many fields and along many roadways. The plant is now indigenous to many areas, and adapts easily to most soil and moderate climatic conditions.

Marijuana is classifed as a hallucinogenic substance. The primary active constituents in the plant are cannabinol, cannabidiol, and the tetrahydrocannabinols, The tetrahydrocannabinols (THCs) are the active components responsible for the hallucinogenic properties of marijuana. The THC of most interest is the Δ9- tetrahydrocannabinol. The other THCs of interest in marijuana are the Δ 1 cis- and trans- tetrahydrocannabinols, the Δ6 cis- and trans- tetrahydrocannabinols, and the Δ 3- and Δ4- tetrahydrocannibinols. The concentrations varies dramatically from geographic area to geographic area, from field to field, and from sample to sample. This concentration range varies from less than 1% to as high as 30%. In recent hash oil exhibits, the highest official reported concentration of Δ9-THC is 43%. 2 Five other terms associated with marijuana are:

Hashish: Resinous material removed from cannabis. Hashish is usually found in the form of a brown to black cake of resinous material. The material is ingested by smoking in pipes or by consuming in food.

Hashish oil: Extract of the marijuana plant which has been heated to remove the extracting solvents. The material exists as a colorless to brown or black oil or tarlike substance.

Sinsemilla: The flowering tops of the unfertilized female cannabis plant. (There are no seeds on such a plant.) Sensemilla is usually considered a “gourmet” marijuana because of its appearance and relatively high concentrations of the THCs.

Thai sticks: Marijuana leaves tied around stems or narrow diameter bamboo splints. Thai sticks are considered a high quality product by the drug culture. The THC concentrations of the marijuana leaves on Thai sticks are higher than domestic marijuana. Unlike hashish and sinsemilla, seeds, and small pieces of stalks and stems are found in Thai sticks.

Brick or Kilo: Marijuana compressed into a brick-shaped package with leaves, stems, stalk, and seeds. The pressed marijauna is usually tightly wrapped in paper and tape. This is the form of marijuana encountered in most large scale seizures. These large scale seizure packages weigh approximately 1000 g (1 kg). This is the packaging form of choiced for clandestine operators because of the ease of handling, packaging, shipping, and distribution.