Thin Layer Chromatography

This procedure involves the addition of a solvent to the sample causing the drugs and their metabolites to travel up a porous strip leaving color spots behind. As each different substance travels a specific distance, the strip can then be compared with known standards. This test gives no quantitive information, it merely indicates the presence of drugs or their metabolites. Furthermore, it relies on the subjective judgment of a technician and requires considerable skill and training. It is not widely used.