ASTM E1968-98(2003)

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Designation:E1968–98(Reapproved2003)
Standard Guide for
Microcrystal Testing in the Forensic Analysis of Cocaine
This standard is issued under the fixed designation E1968; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Microcrystal tests are primarily chemical-precipitation tests in which a light microscope is used to
observe and distinguish the different types of crystals formed. These tests require skill and expertise
on the part of the analyst that can be gained adequately only through appropriate training and
experience in their use. These tests should not be attempted by those who are unfamiliar with them
for use in the analysis of cocaine.
1. Scope 2.1.6 microdrop, n—a small drop of liquid that would fit on
theendofastandardsize,flattenedtoothpick.Theapproximate
1.1 This guide describes some standard procedures appli-
volume of this drop would be 10 to 25 µL.
cable to the analysis of cocaine using multiple microcrystal
2.1.7 needles (acicular), n—long, thin crystals with pointed
tests.
ends.
1.2 These procedures are applicable to cocaine, which is
present in solid dosage form or an injectable liquid form. They
3. Summary of the Technique
are not typically applicable to the analysis of cocaine in
3.1 Asmall sample of the material containing the suspected
biological samples.
cocaine is dissolved in a dilute acid and the appropriate
2. Terminology precipitating reagent is added. The crystals that are formed are
observed and distinguished utilizing a light microscope.
2.1 Definitions of Terms Specific to This Standard:
2.1.1 aggregation, n—the collecting of units or parts into a
4. Significance and Use
mass or whole.
4.1 This technique produces a chemical-precipitation reac-
2.1.2 birefringence, n—property of some crystals, having
tion between cocaine and the precipitating reagent. The habit
more than one refractive index. This property will result in
and the aggregation of the crystals formed may be used to
interference colors, which are viewed through a polarized light
distinguish cocaine from other drugs.
microscope.
4.2 This technique can be utilized on cocaine present in
2.1.3 cocaine, n—either d- or l- cocaine. It should be noted
either the salt or free base form.
that l-cocaine is the naturally occurring isomer found in the
4.3 This technique does not distinguish between the salt and
coca plant.
free base forms.
2.1.4 dendritic, adj—multibrachiate or branching crystals,
growing in a tree-like manner. Each branch of the crystal is
5. Interferences
contiguous structurally.
5.1 Diluents/Adulterants—Diluents/adulterants, such as li-
2.1.5 habit, n—the external morphology of the crystal.
docaine or benzocaine, present in combination with cocaine in
the sample to be tested may inhibit crystal formation or may
This guide is under the jurisdiction of ASTM Committee E30 on Forensic
result in crystals that are distorted or otherwise rendered
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
unidentifiable. In these instances, it will be necessary to
Current edition approved Nov. 1, 2003. Published December 2003. Originally
separate the cocaine from the diluents/adulterants or to use
approved in 1998. Last previous edition approved in 1998 as E1968 – 98. DOI:
10.1520/E1968-98R03. other testing methods to analyze for cocaine.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1968–98 (2003)
6. Apparatus the concentration of suspected cocaine in the acid solution.
This reduction is done by either decreasing the sample size or
6.1 Standard Light Microscope, capable of varying magni-
increasing the volume of solvent.
fications including 1003 is needed for viewing the crystals. A
9.2 Platinum Chloride:
polarized light attachment is not essential, but is desirable,
9.2.1 Place a small sample, a few particles of powder, less
because the heavy metal crystals of cocaine are birefringent.
than 1 mg of the suspected cocaine on a microscope slide.
9.2.2 Dissolve the sample in a few microdrops of 10 %
7. Reagents and Materials
hydrochloric acid or 10 % acetic acid.
7.1 10 % Solution of Acetic Acid.
9.2.3 Add a few microdrops of 5 % platinum chloride to the
7.2 Authenticated Cocaine Standard.
edge of the acid solution on the microscope slide.
7.3 5 % Solution of Gold Chloride (HAuCl ), in reagent
9.2.4 Observe the formation of the crystals using a properly
grade water.
aligned and adjusted light microscope. This observation can be
7.4 10 % Solution of Hydrochloric Acid.
done between crossed polars if desired. If crossed polars are to
7.5 5 % Solution of Platinum Chloride (H PtCl ),
...