Further Studies on Spot Tests and Microcrystal Tests for Identification of Cocaine

• NCJ Number: 200464
• Journal: Journal of Forensic Sciences Volume: 8 Issue: 3 Dated: May 2003 Pages: 581-585
• Author(s): Jamie Swiatko B.S.; Peter R. De Forest; Morris S. Zedeck Ph.D.
• Date Published: May 2003
• Length: 5 pages
• Publication Format: Article
• Publication Type: Report (Study/Research)
• Language: English
• Country: United States of America

Annotation

This study tested 17 chemical species by using 3 different spot tests (Wagner, Marquis, and cobalt thiocyanate followed by stannous chloride reactions) and 2 microcrystal tests (gold chloride and platinic chloride) to determine whether the results could be differentiated from the results of these tests on cocaine.

Abstract

Crime laboratories that analyze large numbers of seized drug samples, such as those in the New York City Police Department and in the Drug Enforcement Administration (DEA), have traditionally used a selected sequence of a limited number of spot tests as a practical means for rapidly screening samples for the presence of cocaine or opioids. A sequences of spot tests used by the New York City Police Department for at least the past 10 years consists of Wagner, Marquis, and cobalt thiocyanate reagents. Individual scientists at the DEA laboratory in New York have used the sequence of Marquis and cobalt thiocyanate spot tests for at least the past 10 years. This study found that by using just the three specified spot tests, including the use of stannous chloride reagent, cocaine could not be differentiated from nine other compounds; thus, the spot tests may lead to false positive identifications of cocaine. The addition of microcrystal tests, however, did differentiate cocaine from the nine other compounds. None of the compounds except cocaine produced distinct crystals with platinic chloride; however, reaching an accurate conclusion using microcrystal tests will depend on the level of experience of the analyst, the proper use of standards and controls, the presence of adulterant and/or diluent in the seized samples, the reaction pH, the temperature and humidity, and the concentration of the reagent and the chemical. This study demonstrates the value of the combined use of spot and microcrystal tests to differentiate cocaine from other chemical species. 8 figures and 18 references