ASTM E1968-19

Standard Practice for Microcrystal Testing in Forensic Analysis for Cocaine

SIGNIFICANCE AND USE
5.1 This technique involves a chemical-precipitation reaction between cocaine and the precipitating reagent. The habit and the aggregation of the crystals formed could be used to distinguish cocaine from other drugs (6).  
5.2 This technique can be utilized on cocaine present in either the salt or free base form.  
5.3 This technique does not distinguish between the salt and free base forms.
SCOPE
1.1 This practice describes procedures applicable to the analysis of cocaine using multiple microcrystal tests (1-6).2  
1.2 These procedures are applicable to cocaine, which is present in solid form or an injectable liquid form. They are not typically applicable to the analysis of cocaine in biological samples.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 These procedures could generate observations indicating a positive test for cocaine or its enantiomers which could be incorporated into the analytical scheme as defined by the laboratory.  
1.5 This standard cannot replace knowledge, skills, or abilities acquired through appropriate education, training, and experience (see Practice E2326) and is to be used in conjunction with professional judgment by individuals with such discipline-specific knowledge, skills, and abilities.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 14-Nov-2019
• ICS: 07.100.10 - Medical microbiology
• Technical Committee: E30 - Forensic Sciences
• Drafting Committee: E30.01 - Criminalistics

Relations

• Refers: ASTM E1732-24 - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Feb-2024
• Refers: ASTM E1732-19 - Standard Terminology Relating to Forensic Science
• Effective Date: 15-Jan-2019
• Refers: ASTM E1732-18b - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Nov-2018
• Refers: ASTM E1732-18a - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Jun-2018
• Refers: ASTM E1732-18 - Standard Terminology Relating to Forensic Science
• Effective Date: 15-May-2018
• Refers: ASTM E1732-17 - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Sep-2017
• Refers: ASTM E2329-14 - Standard Practice for Identification of Seized Drugs
• Effective Date: 01-Dec-2014
• Refers: ASTM E1459-13 - Standard Guide for Physical Evidence Labeling and Related Documentation
• Effective Date: 15-Feb-2013
• Refers: ASTM E1732-12 - Standard Terminology Relating to Forensic Science
• Effective Date: 15-Jun-2012
• Refers: ASTM E1732-11a - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Oct-2011
• Refers: ASTM E1732-11b - Standard Terminology Relating to Forensic Science
• Effective Date: 01-Oct-2011
• Refers: ASTM E2548-11e1 - Standard Guide for Sampling Seized Drugs for Qualitative and Quantitative Analysis
• Effective Date: 01-Sep-2011
• Refers: ASTM E2548-11 - Standard Guide for Sampling Seized Drugs for Qualitative and Quantitative Analysis
• Effective Date: 01-Sep-2011
• Refers: ASTM E1492-11 - Standard Practice for Receiving, Documenting, Storing, and Retrieving Evidence in a Forensic Science Laboratory
• Effective Date: 01-Jun-2011
• Refers: ASTM E2764-11 - Standard Practice for Uncertainty Assessment in the Context of Seized-Drug Analysis (Withdrawn 2020)
• Effective Date: 01-Jun-2011

Overview

ASTM E1968-19, Standard Practice for Microcrystal Testing in Forensic Analysis for Cocaine, provides well-established guidelines for identifying cocaine in seized materials through microcrystal testing. This forensic analysis technique utilizes a chemical precipitation reaction between cocaine and selected reagents, with the resulting crystal formation observed under a microscope. The unique characteristics of crystal habit and aggregation aid forensic scientists in distinguishing cocaine from other substances. The standard applies to both the salt and free base forms of cocaine in solid or injectable liquid forms but is not intended for use on biological samples.

Key Topics

• Microcrystal Test Principle:

  • Relies on the precipitation of crystals when cocaine reacts with specific chemical reagents.
  • Observation and identification are conducted using a standard or polarized light microscope.
  • The distinctive morphology of the resulting crystals provides evidence for the presence of cocaine.

• Applicability and Limitations:

  • Suitable for cocaine found in solid dosage or injectable liquid forms.
  • Not applicable to biological specimens such as blood or urine.
  • Cannot distinguish between the salt and free base forms of cocaine.
  • The method requires the analyst to have appropriate education, training, and professional judgment.

• Sample Preparation and Equipment:

  • Utilizes standard laboratory instruments such as light microscopes, reagents including gold chloride or platinum chloride, and prepared slides.
  • Best practices include documentation through digital photography and adherence to evidence management protocols.

• Interferences:

  • Common adulterants in street drugs (e.g., lidocaine, benzocaine) may affect crystal quality or identification.
  • Sample dilution or alternative testing may be needed if adulterants obscure results.

Applications

• Forensic Drug Identification:

  • Provides a rapid, cost-effective presumptive test for cocaine in seized materials.
  • The method forms part of a broader analytical scheme, often followed by confirmatory analysis using uncorrelated techniques.

• Legal and Criminal Investigations:

  • Used by forensic laboratories to support law enforcement in drug-related offenses.
  • Results contribute to the chain of evidence in legal proceedings.

• Laboratory Practice and Quality Control:

  • Serves as a practical guide for analysts, ensuring consistent procedures and reliable results.
  • Includes instructions for calibrating microscopes, verifying reagents, and thorough documentation of analytical findings.

Related Standards

• ASTM E2329: Practice for Identification of Seized Drugs - outlines multiple technique requirements for definitive drug identification.
• ASTM E2326: Practice for Education and Training of Seized-Drug Analysts - details the necessary skills and knowledge for competent analysis.
• ASTM E1459: Guide for Physical Evidence Labeling and Related Documentation - ensures proper sample tracking.
• ASTM E1492: Practice for Handling Forensic Evidence - covers receiving, storing, and retrieving criminal case materials.
• ASTM E2548: Guide for Sampling Seized Drugs for Analysis - addresses correct sampling approaches.
• ASTM E2764: Practice for Uncertainty Assessment in Drug Analysis - supports the documentation of test limitations and uncertainty.

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By adhering to ASTM E1968-19, forensic laboratories promote standardized, reliable, and legally defensible practices for the presumptive identification of cocaine in seized substances. The standard emphasizes the technical proficiency of practitioners and the critical role of high-quality evidentiary procedures in the administration of justice.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1968 − 19 An American National Standard
Standard Practice for
Microcrystal Testing in Forensic Analysis for 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.Anumber 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 Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 This practice describes procedures applicable to the
2 Barriers to Trade (TBT) Committee.
analysis of cocaine using multiple microcrystal tests (1-6).
2. Referenced Documents
1.2 These procedures are applicable to cocaine, which is
present in solid form or an injectable liquid form.They are not
2.1 ASTM Standards:
typically applicable to the analysis of cocaine in biological
E1459Guide for Physical Evidence Labeling and Related
samples.
Documentation
E1492Practice for Receiving, Documenting, Storing, and
1.3 The values stated in SI units are to be regarded as
Retrieving Evidence in a Forensic Science Laboratory
standard. No other units of measurement are included in this
E1732Terminology Relating to Forensic Science
standard.
E2326Practice for Education and Training of Seized-Drug
1.4 These procedures could generate observations indicat-
Analysts
ing a positive test for cocaine or its enantiomers which could
E2329Practice for Identification of Seized Drugs
be incorporated into the analytical scheme as defined by the
E2548GuideforSamplingSeizedDrugsforQualitativeand
laboratory.
Quantitative Analysis
1.5 This standard cannot replace knowledge, skills, or
E2764PracticeforUncertaintyAssessmentintheContextof
abilities acquired through appropriate education, training, and
Seized-Drug Analysis (Withdrawn 2020)
experience (see Practice E2326) and is to be used in conjunc-
3. Terminology
tion with professional judgment by individuals with such
discipline-specific knowledge, skills, and abilities.
3.1 Definitions:
3.1.1 For definitions of terms used in this standard, refer to
1.6 This standard does not purport to address all of the
Terminology E1732.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3.2 Definitions of Terms Specific to This Standard:
priate safety, health, and environmental practices and deter-
3.2.1 aggregation, n—the collecting of units or parts into a
mine the applicability of regulatory limitations prior to use.
mass or whole.
1.7 This international standard was developed in accor-
3.2.2 birefringence, n—property of some crystals, those
dance with internationally recognized principles on standard-
havingmorethanonerefractiveindex;thispropertywillresult
ization established in the Decision on Principles for the
in interference colors, which are viewed through a polarized
light microscope.
This practice is under the jurisdiction of ASTM Committee E30 on Forensic
Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 15, 2019. Published January 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1998. Last previous edition approved in 2011 as E1968–11. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E1968-19. the ASTM website.
The boldface numbers in parentheses refer to a list of references at the end of The last approved version of this historical standard is referenced on
this standard. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1968 − 19
3.2.2.1 birefringent, adj—material exhibiting birefringence. 7.1.2 The best practice for documenting the crystal forma-
tionresultsistotakeadigitalphotograph.Itisadvisedthatthe
3.2.3 cocaine, n—either d- or l- cocaine; it should be noted
minimum equipment required also has the capability of digital
that l-cocaine is the naturally occurring isomer found in the
photography.
coca plant.
3.2.4 habit, n—the external morphology of the crystal.
8. Reagents and Materials
3.2.5 microdrop, n—a small drop of liquid that would fit on
8.1 10 %–20 % Solution of Acetic Acid (hereafter, dilute
the end of a standard size, flattened toothpick; the approximate
acetic acid).
volume of this drop would be 10 to 25µL.
8.2 Cocaine Standard.
3.2.6 needles (acicular), n—long, thin crystals with pointed
8.2.1 l-Cocaine Standard.
ends.
8.3 5 % Gold Chloride (HAuCl ), in reagent grade water.
4. Summary of the Technique
8.4 10 % or 0.5 N Solution of Hydrochloric Acid (hereafter,
dilute HCl).
4.1 Asmallamountoftestmaterialcontainingthesuspected
cocaine is dissolved in a dilute acid and the appropriate 8.5 Platinum Chloride (H PtCl ), in reagent grade water.
2 6
precipitating reagent is added.The crystals that are formed are
8.6 10 mg TDTA (+)-O,O’-Di-p-toluoyl-D-tartaric Acid
observed and distinguished utilizing a light microscope.
Monohydrate [CAS 32634-68-7] in 1 mL ethanol, 1 mL
glycerin, and 8 mL distilled water (8).
5. Significance and Use
8.7 10 mg TLTA (-)-O,O’-Di-p-toluoyl-L-tartaric Acid
5.1 This technique involves a chemical-precipitation reac-
Monohydrate [CAS 32634-66-5] in 1 mL ethanol, 1 mL
tion between cocaine and the precipitating reagent. The habit
glycerin, and 8 mL distilled water (8).
and the aggregation of the crystals formed could be used to
8.8 Methanol or Diethyl Ether.
distinguish cocaine from other drugs (6).
5.2 This technique can be utilized on cocaine present in
9. Sampling, Test Specimens, and Test Units
either the salt or free base form.
9.1 The general handling and tracking of samples should
5.3 Thistechniquedoesnotdistinguishbetweenthesaltand
meetorexceedtherequirementsofPracticeE1492andGuides
free base forms.
E1459 and E2548.
6. Interferences 10. Performance Verification
6.1 Diluents/Adulterants—Diluents/adulterants, such as li- 10.1 Prior to casework, the reagents used for these microc-
rystal tests shall be tested for reliability using a cocaine
docaine or benzocaine, present in combination with cocaine in
the sample to be tested could inhibit crystal formation or could standard and negative controls following the prescribed proce-
generate crystals that are distorted or otherwise rendered dure. Only when it is determined that the reagents are produc-
unidentifiable (7). Diluting the sample could reduce the inter- ing the expected response could the reagents be used in the
ference. The higher the concentration of the adulterant, the testing procedure.
moredifficultitwillbetoobservecharacteristiccrystals.There
10.2 The microscope should be inspected, adjusted, and
could be cases where diluting the sample would not work. In
aligned to ensure it is in proper working order. This can be
these instances, it will be necessary to separate the cocaine
confirmed during the testing of the cocaine standard. Perform
from the diluents/adulterants or to use other testing methods to
theanalysisofunknownsamplesandstandardsunderthesame
analyze for cocaine.
microscope operating procedures (for example, use of cross
polarizers).
7. Apparatus
11. Procedure
7.1 Standard Light Microscope, capable of varying magni-
fications including 100× is needed for viewing the crystals.
11.1 Gold Chloride or Platinum Chloride Tests:
This is the minim
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E1968 − 11 E1968 − 19
Standard GuidePractice for
Microcrystal Testing in Forensic Analysis offor 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
1.1 This guidepractice describes some standard procedures applicable to the analysis of cocaine using multiple microcrystal
tests (1-56).
1.2 These procedures are applicable to cocaine, which is present in solid dosage form or an injectable liquid form. They are not
typically applicable to the analysis of cocaine in biological samples.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 These procedures could generate observations indicating a positive test for cocaine or its enantiomers which could be
incorporated into the analytical scheme as defined by the laboratory.
1.5 This standard cannot replace knowledge, skill,skills, or abilityabilities acquired through appropriate education, training,
and experience (see Practice E2326) and should is to be used in conjunction with sound professional judgment.professional
judgment by individuals with such discipline-specific knowledge, skills, and abilities.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E1459 Guide for Physical Evidence Labeling and Related Documentation
E1492 Practice for Receiving, Documenting, Storing, and Retrieving Evidence in a Forensic Science Laboratory
E1732 Terminology Relating to Forensic Science
E2326 Practice for Education and Training of Seized-Drug Analysts
E2329 Practice for Identification of Seized Drugs
This guidepractice is under the jurisdiction of ASTM Committee E30 on Forensic Sciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.
Current edition approved March 1, 2011Nov. 15, 2019. Published April 2011January 2020. Originally approved in 1998. Last previous edition approved in 20032011 as
E1968 – 98 (2003).E1968 – 11. DOI: 10.1520/E1968-11.10.1520/E1968-19.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1968 − 19
E2548 Guide for Sampling Seized Drugs for Qualitative and Quantitative Analysis
E2764 Practice for Uncertainty Assessment in the Context of Seized-Drug Analysis
3. Terminology
3.1 For definitions of terms used in this standard, refer to Terminology E1732.Definitions:
3.1.1 For definitions of terms used in this standard, refer to Terminology E1732.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 aggregation, n—the collecting of units or parts into a mass or whole.
3.2.2 birefringence, n—property of some crystals, those having more than one refractive index; this property will result in
interference colors, which are viewed through a polarized light microscope.
3.2.2.1 birefringent, adj—material exhibiting birefringence.
3.2.3 cocaine, n—either d- or l- cocaine; it should be noted that l-cocaine is the naturally occurring isomer found in the coca
plant.
3.2.4 dendritic, adj—multibrachiate or branching crystals, growing in a tree-like manner; each branch of the crystal is
contiguous structurally.
3.2.4 habit, n—the external morphology of the crystal.
3.2.5 microdrop, n—a small drop of liquid that would fit on the end of a standard size, flattened toothpick; the approximate
volume of this drop would be 10 to 25 μL.
3.2.6 needles (acicular), n—long, thin crystals with pointed ends.
4. Summary of the Technique
4.1 A small sampleamount of thetest material containing the suspected cocaine is dissolved in a dilute acid and the appropriate
precipitating reagent is added. The crystals that are formed are observed and distinguished utilizing a light microscope.
5. Significance and Use
5.1 This technique producesinvolves a chemical-precipitation reaction between cocaine and the precipitating reagent. The habit
and the aggregation of the crystals formed maycould be used to distinguish cocaine from other drugs (6).
5.2 This technique can be utilized on cocaine present in either the salt or free base form.
5.3 This technique does not distinguish between the salt and free base forms.
6. Interferences
6.1 Diluents/Adulterants—Diluents/adulterants, such as lidocaine or benzocaine, present in combination with cocaine in the
sample to be tested maycould inhibit crystal formation or may result in could generate crystals that are distorted or otherwise
rendered unidentifiable.unidentifiable (7). Diluting the sample could reduce the interference. The higher the concentration of the
adulterant, the more difficult it will be to observe characteristic crystals. There could be cases where diluting the sample would
not work. In these instances, it will be necessary to separate the cocaine from the diluents/adulterants or to use other testing
methods to analyze for cocaine.
7. Apparatus
7.1 Standard Light Microscope, capable of varying magnifications including 100× is needed for viewing the crystals. This is
the minimum equipment required. A polarized light attachment is not essential, but is desirable, because the heavy metal crystals
of cocaine are birefringent.
7.1.1 Polarized Light Microscope (PLM), capable of varying magnifications from 40× to 400×. The following are typical
accessories on a PLM and could be useful, but are not required, to conduct microcrystalline testing: specialized rotating stage
(360°) and compensator (retardation plate). Cross-polarizers are verified by observing a black background when the polarizer and
analyzer are in the optical path at 90 degrees to one another (for example, polarizer is in the east-west direction and the analyzer
is in the north-south direction).
7.1.2 The best practice for documenting the crystal formation results is to take a digital photograph. It is advised that the
minimum equipment required also has the capability of digital photography.
8. Reagents and Materials
8.1 10 %–20 % Solution of Acetic Acid 10 % Solution of Acetic Acid.(hereafter, dilute acetic acid).
8.2 Cocaine Standard.
8.2.1 l-Cocaine Standard.
8.3 5 % Solution of 5 % Gold Chloride (HAuCl ), in reagent grade water.
E1968 − 19
8.4 10 % or 0.5 N Solution of Hydrochloric Acid 10 % Solution of Hydrochloric Acid.(hereafter, dilute HCl).
8.5 5 % Solution of Platinum Chloride (H PtCl ), in reagent grade water.
2 6
8.6 10 mg TDTA (+)-O,O’-Di-p-toluoyl-D-tartaric Acid Monohydrate [CAS 32634-68-7] in 1 mL ethanol, 1 mL glycerin, and
8 mL distilled water (8).
8.7 10 mg TLTA (-)-O,O’-Di-p-toluoyl-L-tartaric Acid Monohydrate [CAS 32634-66-5] in 1 mL ethanol, 1 mL glycerin, and 8
mL distilled water (8).
8.8 Methanol or Diethyl Ether.
9. Sampling, Test Specimens, and Test Units
9.1 The general handling and tracking of samples should meet or exceed the requirements of Practice E1492 and Guides E1459
and E2548.
10. Calibration and StandardizationPerformance Verification
10.1 The reagents utilizedPrior to casework, the reagents used for these microcrystal tests are to shall be tested for reliability
using a cocaine standard. standard and negative controls following the prescribed procedure. Only when it is determined that the
reagents are producing the expected response, mayresponse could the reagents be used in this the testing procedure.
10.2 The microscope should be inspected, adjusted, and aligned to ensure it is in proper working order. This can be confirmed
during the testing of the cocaine standard. Perform the analysis of unknown sa
...