A simple analytical method involving the use of a monolithic silica disk-packed spin column and HPLC-ECD for determination of l-DOPA in plasma of patients with Parkinson's disease

Abstract

l-DOPA (l-3,4-dihydroxyphenylalanine) is commonly used in the treatment of Parkinson's disease. Monitoring the concentration of l-DOPA in human plasma will enable dose optimization, but is rarely performed because current quantification methods are tedious and time-consuming. In this study, a simple method for the determination of l-DOPA in the plasma of patients with Parkinson's disease was developed. A monolithic silica disk-packed spin column with a phenylboronate moiety, which forms stable anionic complexes with the cis-hydroxyl groups of l-DOPA, was used to extract l-DOPA from plasma with extraction recoveries exceeding 90%. The extracted l-DOPA was then separated on a reversed-phase column and detected electrochemically with a boron-doped diamond electrode. The method, which has a limit of detection of 10 fmol, was then successfully applied for the determination of l-DOPA in the plasma of healthy volunteers and patients with Parkinson's disease. © 2013 The Royal Society of Chemistry.