Simple and rapid determination of 5-hydroxyindole-3-acetic acid in urine by direct injection on a liquid chromatographic column.

5-Hydroxyindole-3-acetic acid has been determined at normal and increased levels in urine. The urine samples were filtered or centrifuged and then injected into a liquid chromatograph containing a reversed phase column with tributyl phosphate as stationary liquid phase and an aqueous buffer + methanol as eluent. 5-Hydroxyindole-3-acetic acid is detected in the eluate by a fluorometric detector coupled to the outlet of the separation column and the quantitation is performed by measurement of the peak heights of the sample and external standards. The percentage recovery was 97 and the precision 0.01 (sr). The method is suitable for the determination of increased levels of 5-hydroxyindole-3-acetic acid in urine from patients suffering from carcinoid tumours. Indole-3-acetic acid can be determined simultaneously.