Determination of urinary and plasma dihydroxyphenylalanine by coupled-column high-performance liquid chromatography with C8 and C18 stationary phases.

This paper describes a rapid, simple and sensitive method for measurement of L-dihydroxyphenylalanine (DOPA) in biological fluids. The method uses a two step frontal-chromatographic clean-up, followed by coupled minibore HPLC with electrochemical detection. The use of phenylboronate removes the peaks that interfere with the detection of DOPA. Inclusion of [14C]DOPA corrects for any variability in recovery.