Abstract: A method for assaying compounds belonging to the group biogenic amines and including catecholamines, indoleamines, their metabolites and derivatives, and other small molecular weight compounds using a boric acid extraction method followed by high pressure liquid chromatographic separation in conjunction with electrochemical detection. The method utilizes high purity chemical and liquid components, a microparticulate-silica bonded phenyl stationary phase in the chromatography column and special cleaning and maintenance measures for the various components of the assaying apparatus which result in reduced baseline noise and allow the electrochemical cell to be operated at a sensitivity of one nanoamp or less full scale deflection on a continuous basis.