Oxalic acid stabilizes dopamine, serotonin, and their metabolites in automated liquid chromatography with electrochemical detection

Use of antioxidative agents is required in automated LC assay of microdialy sis samples, due to rapid degradation of the monoamine neurotransmitters an d their metabolites. Addition of oxalic acid prevented degradation of dopam ine, serotonin, 3,4-dihydroxypheaylacetic acid, homovanillic acid and 5-hyd roxyindoleacetic acid efficiently: after a 24-h incubation at room temperat ure the decreases in peak heights were less than 10%. The long-term stabili ty of the analytes, however, was still enhanced when acetic acid and L.-cys teine were included in the solution. Using this antioxidative solution, the monoamine neurotransmitters and their. metabolites could be determined wit h an automated LC assay even at room temperature. (C) 2001 Elsevier Science B.V. All rights reserved.