Chromatography is used to separate substances from crime scene samples to pinpoint information about materials. This information can then assist investigators with finding what was used by criminals.
Chromatography is particularly useful in analyzing materials used in bombs and explosives. High-pressure liquid chromatography (HPLC) involves placing samples in a tube and extracting the materials using downward pressure. A machine is used to detect the speed at which the particles leave the tube. The measurements are used to identify the materials because they leave the tube at different speeds.
Chromatography is also useful to identify perpetrators of bank robberies. Money bundled in banks routinely contains a small dye bomb that projects bright red dye when triggered. Each dye has a unique chemical composition, and chromatography can be used to determine if there is the specific red dye on a suspect's clothing.