Determination of 4-hydroxy-3-methoxymandelic acid in urine using HPLC with electrochemical detection.

A method is described for the assay of 4-hydroxy-3-methoxymandelic acid (HMMA) in urine using HPLC coupled with electrochemical detection. In this method acidified urine is extracted with ethyl acetate which is then washed with the chromatography solvent to back extract HMMA. The solvent is a pH 5.0 citrate buffer. At this pH, HMMA separates clearly from all other electroactive compounds present in urine.