1、Designation: E1968 11Standard Guide forMicrocrystal Testing in Forensic Analysis of Cocaine1This standard is issued under the fixed designation E1968; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A num
2、ber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONMicrocrystal tests are primarily chemical-precipitation tests in which a light microscope is used toobserve and distinguish the different
3、types of crystals formed. These tests require skill and expertiseon the part of the analyst that can be gained adequately only through appropriate training andexperience in their use. These tests should not be attempted by those who are unfamiliar with themfor use in the analysis of cocaine.1. Scope
4、1.1 This guide describes some standard procedures appli-cable to the analysis of cocaine using multiple microcrystaltests (1-5).21.2 These procedures are applicable to cocaine, which ispresent in solid dosage form or an injectable liquid form. Theyare not typically applicable to the analysis of coca
5、ine inbiological samples.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard cannot replace knowledge, skill, or abilityacquired through appropriate education, training, and experi-ence and should be used in co
6、njunction with sound profes-sional judgment.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulat
7、ory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E1459 Guide for Physical Evidence Labeling and RelatedDocumentationE1492 Practice for Receiving, Documenting, Storing, andRetrieving Evidence in a Forensic Science LaboratoryE1732 Terminology Relating to Forensic ScienceE2329 Pr
8、actice for Identification of Seized DrugsE2548 Guide for Sampling Seized Drugs for Qualitativeand Quantitative Analysis3. Terminology3.1 For definitions of terms used in this standard, refer toTerminology E1732.3.2 Definitions of Terms Specific to This Standard:3.2.1 aggregation, nthe collecting of
9、units or parts into amass or whole.3.2.2 birefringence, nproperty of some crystals, havingmore than one refractive index; this property will result ininterference colors, which are viewed through a polarized lightmicroscope.3.2.3 cocaine, neither d- or l- cocaine; it should be notedthat l-cocaine is
10、 the naturally occurring isomer found in thecoca plant.3.2.4 dendritic, adjmultibrachiate or branching crystals,growing in a tree-like manner; each branch of the crystal iscontiguous structurally.3.2.5 habit, nthe external morphology of the crystal.3.2.6 microdrop, na small drop of liquid that would
11、 fit onthe end of a standard size, flattened toothpick; the approximatevolume of this drop would be 10 to 25 L.3.2.7 needles (acicular), nlong, thin crystals with pointedends.4. Summary of the Technique4.1 A small sample of the material containing the suspectedcocaine is dissolved in a dilute acid a
12、nd the appropriateprecipitating reagent is added. The crystals that are formed areobserved and distinguished utilizing a light microscope.1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.01 on Criminalistics.Current
13、edition approved March 1, 2011. Published April 2011. Originallyapproved in 1998. Last previous edition approved in 2003 as E1968 98 (2003).DOI: 10.1520/E1968-11.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the AS
14、TM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Unit
15、ed States.5. Significance and Use5.1 This technique produces a chemical-precipitation reac-tion between cocaine and the precipitating reagent. The habitand the aggregation of the crystals formed may be used todistinguish cocaine from other drugs (6).5.2 This technique can be utilized on cocaine pres
16、ent ineither the salt or free base form.5.3 This technique does not distinguish between the salt andfree base forms.6. Interferences6.1 Diluents/AdulterantsDiluents/adulterants, such as li-docaine or benzocaine, present in combination with cocaine inthe sample to be tested may inhibit crystal format
17、ion or mayresult in crystals that are distorted or otherwise renderedunidentifiable. In these instances, it will be necessary toseparate the cocaine from the diluents/adulterants or to useother testing methods to analyze for cocaine.7. Apparatus7.1 Standard Light Microscope, capable of varying magni
18、-fications including 1003 is needed for viewing the crystals. Apolarized light attachment is not essential, but is desirable,because the heavy metal crystals of cocaine are birefringent.8. Reagents and Materials8.1 10 % Solution of Acetic Acid.8.2 Cocaine Standard.8.3 5 % Solution of Gold Chloride (
19、HAuCl4), in reagentgrade water.8.4 10 % Solution of Hydrochloric Acid.8.5 5 % Solution of Platinum Chloride (H2PtCl6), in reagentgrade water.9. Sampling, Test Specimens, and Test Units9.1 The general handling and tracking of samples shouldmeet or exceed the requirements of Practice E1492 and GuidesE
20、1459 and E2548.10. Calibration and Standardization10.1 The reagents utilized for these microcrystal tests are tobe tested for reliability using a cocaine standard. Only when itis determined that the reagents are producing the expectedresponse, may the reagents be used in this procedure.11. Procedure
21、11.1 Gold Chloride:11.1.1 Place a small sample, a few particles of powder, lessthan 1 mg of the suspected cocaine on a microscope slide.11.1.2 Dissolve the sample in a few microdrops of 10 %hydrochloric acid or 10 % acetic acid.11.1.3 Add a few microdrops of 5 % gold chloride to theedge of the acid
22、solution on the microscope slide.11.1.4 Observe the formation of the crystals using a prop-erly aligned and adjusted light microscope. This observationcan be done between crossed polars if desired. If crossed polarsare to be used, orient the polarizer in the east-west directionand the analyzer in th
23、e north-south direction, verified by ablack background.11.1.5 Formation of crystals in a habit corresponding tothose obtained with standards is indicative of the presence ofcocaine. The shape of these crystals may vary slightly depend-ing on the concentration of the cocaine in the acid solution.11.1
24、.6 If a dense cloud of precipitate is formed upon theaddition of the precipitating agent, the crystals may not bereadily visible. It may be necessary to repeat the test reducingthe concentration of suspected cocaine in the acid solution.This reduction is done by either decreasing the sample size ori
25、ncreasing the volume of solvent.11.2 Platinum Chloride:11.2.1 Place a small sample, a few particles of powder, lessthan 1 mg of the suspected cocaine on a microscope slide.11.2.2 Dissolve the sample in a few microdrops of 10 %hydrochloric acid or 10 % acetic acid.11.2.3 Add a few microdrops of 5 % p
26、latinum chloride tothe edge of the acid solution on the microscope slide.11.2.4 Observe the formation of the crystals using a prop-erly aligned and adjusted light microscope. This observationcan be done between crossed polars if desired. If crossed polarsare to be used, orient the polarizer in the e
27、ast-west directionand the analyzer in the north-south direction, verified by ablack background.11.2.5 Formation of crystals in a habit corresponding tothose obtained with standards is indicative of the presence ofcocaine. The shape of these crystals may vary slightly depend-ing on the concentration
28、of the cocaine in the acid solution.11.2.6 If a dense cloud of precipitate is formed upon theaddition of the precipitating agent, the crystals may not bereadily visible. It may be necessary to repeat the test reducingthe concentration of suspected cocaine in the acid solution.This reduction is done
29、by either decreasing the sample size orincreasing the volume of solvent.12. Interpretation of Results (7)12.1 Gold chloride is capable of distinguishing cocainefrom its diastereoisomers (8).12.2 If crystals structurally similar to those formed by acocaine standard are formed by both precipitating re
30、agents, thesample may be considered positive by this technique for thepresence of cocaine.12.3 All observed crystalline precipitates must be docu-mented and included in the analysts notes for each itemanalyzed.12.4 The forensic identification of cocaine requires the useof multiple uncorrelated techn
31、iques, see Practice E2329.13. Precision and Bias13.1 No information is presented about either the precisionor bias of this technique.14. Keywords14.1 analysis; cocaine; microcrystalline testingE1968 112REFERENCES(1) Fulton, C., “Modern Microcrystal Tests for Drugs,” Wiley-Interscience, New York, NY,
32、 1969.(2) Clarke, E.G.C., “Isolation and Identification of Drugs,” Pharmaceu-tical Press, London, England, 1971, pp. 139141.(3) Cunniff, P., (ed.) A.O.A.C. Offcial Methods of Analysis, 16th edition,1995, Chapter 18, p. 45.(4) Chamot, E. and Mason, C., Handbook of Chemical Microscopy: VolI, John Wile
33、y, New York, NY, 1930.(5) Chamot, E. and Mason, C., Handbook of Chemical Microscopy: VolII, John Wiley, New York, NY, 1931.(6) Wood, M.R., Brettell, T.A., and Lalancette, R.A., “The gold (III)tetrachloride salt of L-cocaine,” Acta Crystallographica Section C,Vol 63, Part 2, February 2007, p. m33m35.
34、(7) Nichols, R., “Drug Proficiency Test False Positives: A Lack of CriticalThought,” Science and Justice, Vol 37, No. 3, pp. 191196, 1997.(8) Allen,A. C., Copper, D.A., Kiser, W. O., Cottrell, R. C., “The CocaineDiastereoisomers,” Journal of Forensic Sciences, Vol 26, No. 1, Jan.1981, pp. 1226.ASTM
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38、 Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).E1968 113
