Recommended Methods for the Identification and Analysis of Cocaine in Seized Materials 23
Results:
Cocaine forms V-shaped long, thin needles with branching.
Figure 3. Cocaine and platinic chloride, 100x
Source: Reprinted, with permission, from Journal of Forensic Sciences, vol. 48, Issue 3, copyright ASTM
International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
Gold chloride test
Reagent: Dissolve 1 g of gold chloride in 20 ml of distilled water.
Method:
Place 2 drops of sample solution (approximately 2-3 mg of the sample/5 drops of
10% hydrochloric acid) on a clean microscope slide. Then place 2 drops of the
reagent near the drops of the sample and use a glass rod to create a tiny channel
connecting the solutions. Observe the reaction and resulting crystals without a cover
slip at 100-200 magnification using a polarized microscope.
Results:
Cocaine forms radiating clusters of fine needles with perpendicular branches.
Figure 4. Cocaine and gold chloride, 200x
Source: Reprinted, with permission, from Journal of Forensic Sciences, vol. 48, Issue 3, copyright ASTM
International, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
20
Method:
Thoroughly moisten dried test material with the reagent. After allowing excess
alcohol to evaporate, compare the odour characteristic of the sample with that of
standard cocaine material.
5.3.1.3 Microcrystal tests [12]
Microcrystal tests are quick, simple and extremely sensitive test for the identification
of substances. They involve the formation of crystals from the reaction of the target
compound with a chemical reagent, followed by the analysis of the resulting crystals
by means of a polarizing microscope and comparison with reference material.
Platinic Chloride Test
Reagent: Dissolve 1 g of platinic chloride in 20 mL of distilled water.
Method:
Place two drops of sample solution (approximately 2-3 mg of the sample/5 drops of
10% hydrochloric acid) on a clean microscope slide. Then place 2 drops of the
reagent near the drops of the sample and use a glass rod to create a tiny channel
connecting the solutions. Observe the reaction and resulting crystals without a cover
slip at 100-200 magnification using a polarized microscope.
Results:
Cocaine forms V-shaped long, thin needles with branching.
Figure 3: Cocaine and platinic chloride, 100 (Reprinted, with permission, from
Journal of Forensic Sciences, Vol. 48, Issue 3, copyright ASTM International, 100
Barr Harbor Drive, West Conshohocken, PA 19428.)
Analytical notes
Over one hundred drugs were tested for positive interference and only piperocaine (also a
benzoate ester) gave a positive result. Certain amines such as amphetamines will produce
a “weak, fishy odour”.
The sensitivity is greater than that of existing field tests, e.g. the Scott’s Test.
The sample and reagent must be kept free of water which interferes with the reaction.
Ideally the test should be performed concomitantly with a test on standard cocaine
material and the odours compared.
21
Gold Chloride Test
Reagent: Dissolve 1 g of gold chloride in 20 mL of distilled water.
Method:
Place two drops of sample solution (approximately 2-3 mg of the sample/5 drops of
10% hydrochloric acid) on a clean microscope slide. Then place 2 drops of the
reagent near the drops of the sample and use a glass rod to create a tiny channel
connecting the solutions. Observe the reaction and resulting crystals without a cover
slip at 100-200 magnification using a polarized microscope.
Results:
Cocaine forms radiating clusters of fine needles with perpendicular branches.
Figure 4: Cocaine and gold chloride, 200 (Reprinted, with permission, from Journal
of Forensic Sciences, Vol. 48, Issue 3, copyright ASTM International, 100 Barr
Harbor Drive, West Conshohocken, PA 19428.)
5.3.1.4 Solubility Tests
If it is suspected that the material has cutting agents added to it, then a solubility test
is typically carried out. The solubility of a small amount of the material in water and
in ethanol may give an indication of the form in which the drug is present. Cocaine
hydrochloride is soluble in water and ethanol. Whereas, cocaine base is soluble in
ethanol and almost insoluble in water as are many adulterants. The presence and
amount of insoluble material may give some indication of the likely purity, as sugar
diluents are largely insoluble in ethanol. The insoluble material may be filtered, dried
and subjected to further testing by, for example IR spectroscopy.
Analytical notes
Standard cocaine should be analysed concomitantly.
The dilution of the test material or the hydrochloric acid may be varied to give the
optimum results.