a chromatographic technology used to separate and quantitate mixtures of substances in solution. A sample is injected into a moving stream of solvent that flows through a column and detector. Separation during passage through the column occurs by absorption, partition, ion exchange, or size exclusion. The technique is commonly used in laboratories to measure organic compounds including steroid hormones, pesticides and poisons, toxic and carcinogenic compounds, and drugs. SYN: high-pressure liquid chromatography.