Screening tests (also called color tests) are used to tentatively identify possible components of mixtures. They are similar to screening tests performed by police officers in the field. These tests provide the chemist with an idea of which other tests need to be performed to conclusively identify the substance.
Thin Layer Chromatography
Thin Layer Chromatography (TLC) is a technique used to separate components of a mixture of organic molecules. These components are then compared to a known standard. This presumptive test provides a reasonably reliable basis for identification of a compound.