High Performance Liquid Chromatography. is an analytical-chemistry-based tool for analyzing mixtures of chemical compounds. It is used to determine the amount of a chemical compound within a mixture of other chemicals, for example the exact amount of active pharmaceutical ingredient in a drug. The sample is dissolved in a solvent (like water or alcohol) and a detector measures response changes between the solvent itself, and the solvent and sample when passing through it. The electrical response is digitized and sent to a data system. Click here for more information.