A high performance liquid chromatographic method for the determination of alpha-naphthylacetic acid has been established on a Hypersil C18 column(4.6 mm i.d. x 250 mm, 5 microns), with the mobile phase of methanol-water-phosphoric acid(60:40:0.35, V/V), and UV detection at 272 nm. The linear correlation was observed within the range of 16 mg/L-1,000 mg/L(r = 0.9997). The RSD was 0.8%(n = 5). The method is simple and accurate.
