Sensitive high-performance liquid chromatographic method for the determination of coumarin in plasma

A high-performance liquid chromatographic method was developed for the determination of coumarin in plasma at low concentrations. The method involves a single-step extraction of the alkalinized sample with hexane and subsequent evaporation of the organic phase in the presence of hydrochloric acid to collect and concentrate the coumarin. Analysis of the acidic phase was performed on a C8 column and coumarin was detected by measuring the UV absorbance at 275 nm. The limit of detection was 0.3 microgram l-1. The assay was used to study the evolution of concentrations of coumarin in one volunteer after oral administration of a single 10-mg dose.