Liquid-chromatographic determination of urinary 5-hydroxy-3-indoleacetic acid, with fluorescence detection

We describe and evaluate a procedure for measuring urinary 5-hydroxy-3-indoleacetic acid by "high-performance" liquid chromatography. After a simple organic extraction, the analyte and internal standard are chromatographed on a reversed-phase column and are detected by native fluorescence. The detection limit (3 ng per injection), between-day precision (CV 5.2%), absolute recovery (70%), analytical recovery (99%), and working linear range (up to 15 mg/L) have been determined. Compared with colorimetric results with nitrosonaphthol, values obtained with the chromatographic method are significantly lower. Reference values and clinical experience with the method are reported. The method is simple, free from interferences, and suitable for use in routine analysis in the clinical laboratory.