Abstract
Abstract— The isomeric phenolic acids, homovanillic acid (4‐hydroxy,3‐methoxyphenylacetic acid) and homo‐iso‐vanillic acid (3‐hydroxy,4‐methoxyphenylacetic acid), were separated and identified by means of paper chromatography of their azo‐derivatives with diazotized para‐nitroaniline. Using this chromatographic procedure, homo‐iso‐vaniliic acid was identified in several samples of human cerebrospinal fluid, an observation which suggests that dopamine may be partly metabolized in brain, with the production of 4‐methoxy derivatives.