A Modern Compendium of Microcrystal Tests for Illicit Drugs and Diverted Pharmaceuticals
Kelly M. Brinsko, M.S.; Dean Golemis, B.A.; Meggan B. King, B.S.; Gary J. Laughlin, Ph.D.*; and Sebastian B. Sparenga, M.S.
McCrone Research Institute, Chicago, IL, USA
*Corresponding author: Gary J. Laughlin, Ph.D., firstname.lastname@example.org
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Citation: McCrone Research Institute. A Modern Compendium of Microcrystal Tests for Illicit Drugs and Diverted Pharmaceuticals: https://www.mccroneinstitute.org/uploads/A_Modern_Compendium_of_Microcrystal_Tests.pdf
Published: November 25, 2015
1st revision: February 5, 2016
2nd revision: November 2, 2016
3rd revision: January 2, 2018
4th revision: September 13, 2021
Copyright © 2015 – 2021 McCrone Research Institute. All rights reserved.
This document presents A Modern Compendium of Microcrystal Tests for Illicit Drugs and Diverted Pharmaceuticals for use by forensic scientists in the crime laboratory and researchers in the analytical chemistry laboratory.
A Modern Compendium of Microcrystal Tests for Illicit Drugs and Diverted Pharmaceuticals contains 19 drugs for which microcrystal tests using various reagents have been previously developed. It describes in detail the microcrystals formed from each test and includes photomicrographs, morphology illustrations, optical properties, notes and infrared (IR) spectra of the microcrystals.
The 19 drugs chosen for inclusion in the compendium were selected from annual reports compiled by the National Forensic Laboratory Information System (NFLIS). The reports issued by NFLIS describe in detail the controlled substances that are identified by federal, state and local forensic laboratories across the United States. The NFLIS reports also include the national estimates for the 25 most frequently reported drugs, along with observed trends. Of these 25 drugs, 18 already have known, published microcrystal tests. The 19th drug, ephedrine, was added to this compendium because of its prevalence as a precursor in clandestine methamphetamine laboratories.
Information about known microcrystal tests and reference material from numerous sources spanning past decades were located and evaluated, including textbooks, journal articles and standard operating procedures. Many of these are out of print and not easily accessible. Such references often contain few photomicrographs of microcrystals, and their reagent formulations and procedures may be difficult to interpret. There is also a lack of information regarding potential interferences from other drugs that may be present in combination with pharmaceuticals or from adulterants in street drug samples.
A survey of crime laboratories was conducted to determine which reagents and microcrystal tests are currently in use. Because the literature contains numerous microcrystal tests that could be used to identify a single compound, it is most efficient to compile only the most commonly used protocols within the compendium. This approach has several advantages: Presumably, the popularity of a test is indicative of its expediency. After decades of use, less expedient microcrystal tests have been eradicated or modified in favor of more reliable and/or more sensitive ones. Compiling and ranking this data is an efficient way to evaluate the use and reputation of certain microcrystal tests. By including the most commonly used microcrystal tests utilized by many forensic laboratories makes it less complicated for individual laboratories to amend their current procedures. It also ensures that the reagents used in the tests are accessible and available.
Most drugs in this compendium include two or three reagents that may be used for their identification; in a few cases, only one reagent is provided. These drugs may have had only one previously published reagent, or may have had additional reagents that were found to be unreliable, inaccessible or impractical
Techniques have also been developed for drugs with non-traditional delivery mechanisms, including gels and transdermal patches. All procedures were vetted and evaluated by McCrone Research Institute research microscopists, together with practicing forensic scientists in other collaborative laboratories. The compendium includes recommended protocols, reagents, morphology of crystals (with numerous photomicrographs), IR spectra of microcrystals, and potential interferences. In addition, the compendium includes optical and crystallographic properties of the microcrystals. Optical properties are not included in many references, which is unfortunate because microcrystals are unique when they are presented together with morphology. By including the optical data in the compendium, the application of many microcrystal tests is refined, which potentially strengthens their use within the criminal justice system.
The following topics are included for each drug: reagents; test methods; sensitivity of the test and limit of detection; time required for crystal formation; crystal morphology; evaluation of the tests in the presence of common excipients, diluents and adulterants (for street drug samples) or combination drugs (for pharmaceutical preparations); and evaluation of the tests for drugs from selected pharmaceutical delivery devices, e.g. tablets, capsules, gels, transdermal patches and oral solutions.
An ideal microanalytical method for forensic drug analysis would be inexpensive, fast, automated and suitable for all known drugs; however, no such tool currently exists. Traditional light microscopy and microcrystal tests have been used together for more than 100 years, and are proven useful when automated instrumental analysis is unavailable or not appropriate, if mixtures of one or more drugs, excipients, diluents or adulterants are present, or when the drug is held in alternative delivery devices such as gels or transdermal patches. Furthermore, while some crime laboratories may lack certain automated instrumental capabilities, most have light microscopes and properly trained microscopists. Microcrystal tests, using polarized light microscopy (PLM), can identify most illicit drugs specifically and quickly (usually within a few minutes), and they are inexpensive compared to other methods. In addition, proper use of the light microscope and microcrystal tests can check and confirm the results obtained by alternative methods. It is envisaged that this compendium will fulfill a critical need for reliable analytical methods and assist forensic scientists and other researchers in their work.
A Modern Compendium of Microcrystal Tests for Illicit Drugs and Diverted Pharmaceuticals is presented in a PDF file and comprises 19 drugs. It includes reagents, microcrystal test methods, optical properties and IR spectra. This compendium will remain a work-in-progress and be updated with additional drugs, reagents and microcrystal tests once such data become available.
Sebastian Sparenga, Meggan King, and Kelly Brinsko performed and evaluated the microcrystal tests, documented the optical properties, and assisted in the format, layout, and design of the compendium. Sparenga performed the infrared microspectroscopy. Dean Golemis designed the layout, created the pages and edited the content. Gary Laughlin provided the editorial and technical review and overall project management. All authors read and approved the final document.
The authors would like to thank James Dunlop (Kalamazoo County Sheriff’s Office), Hiram Evans (San Bernardino County Sheriff’s Department, Retired) and Skip Palenik (Microtrace, LLC) for their advice and assistance throughout this project.
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This project was supported by Award No. 2011-DN-BX-K528, awarded by the National Institute of Justice, Office of Justice Programs, U.S. Department of Justice. The opinions, findings, and conclusions or recommendations expressed in this publication/program/exhibition are those of the author(s) and do not necessarily reflect those of the Department of Justice.