Cocaine

Cocaine is a naturally occurring alkaloid and powerful nervous system stimulant derived from the coca plant (Erythroxylum coca). Indigenous to South America, the coca leaf itself is commonly chewed (often mixed with an alkaline substance) to suppress appetite and fatigue. However of more relevance to forensic investigations is the product that can be formed from the coca leaves – they are commonly used in the illicit production of cocaine.

The process of deriving cocaine from this plant is somewhat long, but relatively simple with the appropriate equipment and knowledge. The coca leaves are harvested and sun-dried before being macerated with an inorganic base such as lime or carbonate salt, dampened with water and placed in a maceration pit. The inorganic base ensures the cocaine is in its free base form. Kerosene or a similar water-immiscible solvent is added to the slurry and mixed for several hours, extracting the cocaine free base into the solvent. The solvent is then removed and filtered if necessary. The large volume of organic solvent is extracted into a smaller volume of sulphuric acid, converting to cocaine to cocaine sulphate, which dissolves in the aqueous layer. An excess of lime or carbonate is added to the mixture, converting the cocaine back to the free base once again, which precipitates out of solution as a yellowish solid known as coca paste. The coca paste is filtered, dried and packaged. Alternatively an acid extraction technique can be used to achieve similar results as this process. If desired, the base form of cocaine is typically produced by neutralisation of cocaine hydrochloride with a solution of sodium bicarbonate and water. It is also possible to synthesis cocaine using methyl ecgonine hydrochloride as the starting material.

Cocaine is most commonly insufflated (snorted) or inhaled, though it can also be taken orally by rubbing the powder on the gums or swallowing. The drug inhibits the uptake of dopamine, serotonin and norepinephrine, leading to an increase in the concentration of these chemicals in the brain. Effects include increased alertness, feelings of happiness or agitation, fast heart rate, sweating, dilated pupils and numbing effects. It is an addictive drug that can lead to dependence after just a short period of use. The effects of cocaine typically last for 15 minutes to an hour, depending on the amount of drug taken and the route of administration used.

Types of Cocaine
Cocaine is often encountered in a variety of forms, depending on whether the drug is in its water-soluble salt or water-insoluble base form. Cocaine will frequently contain a number of adulterants, with the most common chemicals being levamisole, phenacetin, lidocaine, caffeine, diltiazem, hydroxyzine, procaine, benzocaine and sugars. These are used to ‘bulk out’ the drug, allowing dealers to make more money from the starting product. Adulterants are typically similar in appearance to cocaine and may even bring about some of the same effects, such as analgesia.

Cocaine Salt

Cocaine is commonly encountered in its salt form, appearing as a white powder. The name of the salt form of cocaine will depend on the acid used to produce the drug. Cocaine hydrochloride is the most commonly encountered, however sulphate and nitrate forms of cocaine may also be seen.

Cocaine Base Cocaine may also be encountered as the base form, typically administered by smoking. Crack cocaine is a lower purity form of free-base cocaine, produced by neutralisation of cocaine hydrochloride. It is a hard and brittle off-white/brown substance, with the name ‘crack’ originating from the crackling sound produced when the material is heated.

Analysis

Presumptive Tests

Scott’s test is used as a presumptive test for the presence of cocaine, a pale pink reagent which is composed of cobalt thiocyanate in water and hydrochloric acid. Upon contact with cocaine (both the hydrochloride and base form), a blue colouring will form. However presumptive tests cannot definitively confirm the presence of a drug, as other substances may cause false positives.

Gas Chromatography-Mass Spectrometry (GC-MS)
GC-MS is an analytical technique used to separate the components of a mixture and subsequently identify them. Following MS analysis, a unique spectrum will be produced for each particular compound, which can be compared to spectra of known compounds to determine the identity of components in the mixture. Not only can this technique be used to confirm the presence of cocaine, but it can also identify the cutting agents mixed with the cocaine, such as paracetamol or caffeine.

Fourier Transform Infrared Spectroscopy (FTIR)
Although GC-MS can confirm that a suspected sample is cocaine, the technique cannot distinguish between cocaine hydrochloride and cocaine base, as the mass spectra produced are not sufficiently different. In order to confirm whether the cocaine is in its hydrochloride or base form, FTIR can be used. The spectra of the two forms of cocaine, although similar, will be distinguishable from one another.

High Performance Liquid Chromatography (HPLC)
HPLC may be used to determine the purity of a cocaine sample. More can be read about this technique on the chromatography page.

United Nations Office on Drugs and Crime. Recommended methods for the identification and analysis of cocaine in seized materials. [online] Available: https://www.unodc.org/documents/scientific/Cocaine_Manual_Rev_1.pdf