Marijuana is still illegal. Many states endorse it for medical use. Yet most of them remain firm on keeping pot out of the hands of every citizen. The police still have a job to do.
With hemp becoming legal on a Federal level, things have changed for law enforcement. With a completely legal product that looks and smells exactly like an illegal substance, their job has become much more difficult. Confusion is inevitable, and in order to make sure that innocent people aren’t stuck behind bars, it’s up to the crime lab to set things straight. With the importance of skilled technicians at an all-time high, let’s look at the tests they make to identify marijuana.
This is the third test in the Thorton-Nakumura protocol that is used by most labs around the U.S.
What is the test?
Thin Layer Chromatography (TLC) is a chromatographic technique. It’s a colorimetric test that is measured in terms of separation. A colorimetric test works by analyzing color in terms of a standard color, certain primary colors, or a scale of colors.
How is it done?
TLC depends on two phases. The stationary phase is usually a glass plate coated with silica that has been properly desiccated or dried. The mobile phase is a solvent mixture made of toluene and diethylamine. A sample of the plant being tested is dissolved, and a drop of it is placed on the sheet. The location of the drop is marked. The stationary plate is placed in a beaker with solvent at the bottom. The solvent moves up the silica through capillary action. As it takes components of the sample with it, the individual colors and chemicals spread out in a verifiable pattern that identifies what is in the sample.
Who is performing the test?
A crime lab analyst makes the test. They know the basics of the test but are not trained beyond that. Why the test works is probably beyond their reach, as are the reasons for specifics of the test like the ratios of the solvents.
How accurate is the test?
TLC has the potential to be verifiable. Photographs and even videos can be taken to show the results of the test to prove them later. Like other tests, this isn’t the process that labs follow. Nor do they usually verify the results with a peer.
This test can be used to identify cannabis, but it has not been specifically validated to test for THC. It is a generic test that can result in false positives from plants like coffee, tobacco, and basil.