Separation of the catecholamine metabolites 4-hydroxy-3-methoxy- and 3-hydroxy-4-methoxymandelic acid by reversed-phase high performance liquid chromatography.

The catecholamine metabolites 4-hydroxy-3-methoxy- and 3-hydroxy-4-methoxymandelic acid can be completely separated by reversed-phase high performance liquid chromatography with chemically bonded octadecylsilane as stationary phase and a citrate/ammonium phosphate buffer (pH 4.5) containing 8% methanol as mobile phase. The two isomers can be electrochemically detected and produce different hydrodynamic voltammograms.