Thin Layer Chromatographic Methods for Detecting Illegal Drugs

Deborah Shalev, Pharmaceutical Engineering, Azrieli College of Engineering Jerusalem, Jerusalem, Israel (debbie@jce.ac.il)
Moshe Burshtein, Division of Identification and Forensic Science, Israel Police, Jerusalem, Israel
Shira Vaknin, Pharmaceutical Engineering, Azrieli College of Engineering Jerusalem, Jerusalem, Israel
Hanna Elkouby, Pharmaceutical Engineering, Azrieli College of Engineering Jerusalem, Jerusalem, Israel

There is a continual need for simple, efficient tests to identify drugs by police officers in the field. This precludes the use of expensive and complex instrumentation in the initial screening stage and requires simple, robust, but sensitive and selective methods to determine whether a sample is suspect and must be transferred back to the main laboratory for more extensive testing.

The rise in cannabis-derived products is driving the need for a simple test that will be able to differentiate between marijuana and hemp, and detect the illegal tetrahydrocannabinol (THC) among other, legal cannabinoids, such as cannabidiol (CBD). The test must be sufficiently sensitive to detect THC concentrations of at least 0.3% of the cannabinoids, which is the legal limit, and selective enough to distinguish between THC and other cannabinoids and compounds in the sample. Commonly used color tests can identify cannabinoids in general but are less accurate in selectively indicating THC within a mixture of cannabinoids.

A thin layer chromatography (TLC) test was developed in conjunction with known color tests that can selectively identify THC from among other plant compounds, CBD and another cannabinoid, cannabinol. A second color-based TLC method was developed to identify cocaine, which is illegal at any amount, from among many derivatives with similar structures.

These tests require more time to perform than simple color-based swab tests, however they can be developed for use in the field to differentiate between illegal drugs and other legal compounds that are commonly found with them. This will give a reliable and timely result and thus both reduce the testing load on the more expensive instrumentation at the Division of Identification and Forensic Science and potentially prevent false positives with their associated costs.