Urinary phenylacetic acid determination by HPLC

Summary A high-performance liquid chromatographic method for urinary total phenylacetic acid (PAA) determination is reported for clinical diagnostic purpose in depressed patients.The urine samples are hydrolized in 6N HCl at 100°C. The hydrolized samples are then adsorbed on a C₈ reversed-phase extraction cartridge and eluted with 0.05 N NaOH. This solution is extracted on an anionexchange extraction cartridge and eluted with 0.1 M phosforic acid; the eluate is injected into HPLC and separated by reversed-phase liquid chromatography with ultraviolet detection at 225 nm. The extraction recovery is 93±2.8%, the retention time is 3.7 min and the PAA minimum detectable level is 4 mg/l.The normal value determined on 10 healthy subjects was 151.3±19.1 mg/day. Ten depressed subjects were investigated, and no difference in PAA excretion between normal and depressed subjects was observed. Also, the expected PAA enhancement in depressed subjects after treatment did not occur.