ASTM E1968-98

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: E 1968 – 98
Standard Guide for
Microcrystal Testing in the Forensic Analysis of Cocaine
This standard is issued under the fixed designation E 1968; 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 (e) 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 cocaine is dissolved in a dilute acid and the appropriate
precipitating reagent is added. The crystals that are formed are
1.1 This guide describes some standard procedures appli-
observed and distinguished utilizing a light microscope.
cable to the analysis of cocaine using multiple microcrystal
tests.
4. Significance and Use
1.2 These procedures are applicable to cocaine, which is
4.1 This technique produces a chemical-precipitation reac-
present in solid dosage form or an injectable liquid form. They
tion between cocaine and the precipitating reagent. The habit
are not typically applicable to the analysis of cocaine in
and the aggregation of the crystals formed may be used to
biological samples.
distinguish cocaine from other drugs.
2. Terminology 4.2 This technique can be utilized on cocaine present in
either the salt or free base form.
2.1 Definitions of Terms Specific to This Standard:
4.3 This technique does not distinguish between the salt and
2.1.1 aggregation, n—the collecting of units or parts into a
free base forms.
mass or whole.
2.1.2 birefringence, n—property of some crystals, having
5. Interferences
more than one refractive index. This property will result in
5.1 Diluents/Adulterants—Diluents/adulterants, such as
interference colors, which are viewed through a polarized light
lidocaine or benzocaine, present in combination with cocaine
microscope.
in the sample to be tested may inhibit crystal formation or may
2.1.3 cocaine, n—either d- or l- cocaine. It should be noted
result in crystals that are distorted or otherwise rendered
that l-cocaine is the naturally occurring isomer found in the
unidentifiable. In these instances, it will be necessary to
coca plant.
separate the cocaine from the diluents/adulterants or to use
2.1.4 dendritic, adj—multibrachiate or branching crystals,
other testing methods to analyze for cocaine.
growing in a tree-like manner. Each branch of the crystal is
contiguous structurally.
6. Apparatus
2.1.5 habit, n—the external morphology of the crystal.
6.1 Standard Light Microscope, capable of varying magni-
2.1.6 microdrop, n—a small drop of liquid that would fit on
fications including 1003 is needed for viewing the crystals. A
the end of a standard size, flattened toothpick. The approximate
polarized light attachment is not essential, but is desirable,
volume of this drop would be 10 to 25 μL.
because the heavy metal crystals of cocaine are birefringent.
2.1.7 needles (acicular), n—long, thin crystals with pointed
ends.
7. Reagents and Materials
7.1 10 % Solution of Acetic Acid.
3. Summary of the Technique
7.2 Authenticated Cocaine Standard.
3.1 A small sample of the material containing the suspected
7.3 5 % Solution of Gold Chloride (HAuCl ), in reagent
grade water.
This guide is under the jurisdiction of ASTM Committee E-30 on Forensic 7.4 10 % Solution of Hydrochloric Acid.
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
Current edition approved Nov. 10, 1998. Published January 1999.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 1968
7.5 5 % Solution of Platinum Chloride (H PtCl ), in reagent 9.2.2 Dissolve the sample in a few microdrops of 10 %
2 6
grade water. hydrochloric acid or 10 % acetic acid.
9.2.3 Add a few microdrops of 5 % platinum chloride to the
8. Calibration and Standardization
edge of the acid solution on the microscope slide.
8.1 The reagents utilized for these microcrystal tests are to 9.2.4 Observe the formation of the crystals using a properly
be tested for reliability using an authenticated cocaine stan-
aligned and adjusted light microscope. This observation can be
dard. Only when it is determined that the reagents are produc- done between crossed polars if desired. If crossed polars are to
ing the expected response, may the reagents be used in this
be used, orient th
...