Liquid-chromatographic assay for urinary homovanillic acid, with fluorescent detection

We describe a procedure for measuring urinary homovanillic acid by "high-performance" liquid chromatography. The pH of urine samples is adjusted, and they are chromatographed directly on an octyl silica column. The effluent is reacted with a ferricyanide reagent, to convert homovanillic acid to a product that is fluorescent at 420 nm on excitation at 320 nm. The standard curve is linear up to a homovanillic acid concentration of 20 mg/L; the detection limit is 0.3 mg/L. The method is evaluated for precision, recovery, potential interference, and reference values, and compared (r = 0.99) with a published spectrophotometric method. The proposed method is suitable for the routine analysis for homovanillic acid in urine.