Thin Layer Chromatography (TLC)

Thin layer chromatography (TLC) costs less than the two most popular testing methods: EMIT and RIA. A single test can find up to 40 drugs in one urine sample. Unlike other tests, the results are not measured by a machine. Instead, trained lab people decide what the TLC results mean. So results from a urine sample may vary from lab to lab.

In TLC, a glass plate is covered with a thin layer of gel. A small dot of urine is placed near one edge of the gel. The glass plate is then placed upright in a container. After a period of time, the original spot is gone and a series of spots appears all over the gel. Each spot is a different drug that separated from the urine.