SIMULTANEOUS MEASUREMENT OF PLASMA SEROTONIN, CATECHOLAMINES, AND THEIR METABOLITES BY AN IN-VITRO MICRODIALYSIS-MICROBORE HPLC AND A DUAL AMPEROMETRIC DETECTOR

Many advantages of a method for the simultaneous measurement of plasma norepinephrine (NE), epinephrine (E), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin, and 5-hydroxyindole-3-acetic acid by the in vitro microdialysis-microbore high-performance liquid chromatography-electrochemical detection (MD-MHPLC-ED) technique have been described in our previous article. The present experiment uses a dual electrode electrochemical detector (DUED) in the MD-MHPLC system, providing an additional reliable measurement or assignment of peaks by identifying the peaks based on their redox ratios at the oxidation/reduction cycle. Thus, the important early eluting front and interfering peaks were eliminated on the cathodic chromatogram. Within 15 minutes, an isocratic separation of these analytes is achieved by using microbore column. Hence, theoretically, over 90 analyses can be performed in a single working day. The detection limit (S/N = 3) of this method was about 0.2 to 0.5 pg per injection. The required volume of plasma samples is less than 200 mu L. Thus, blood loss is minimal with repeated blood sampling, especially in experiments using small animals. This simple, efficient, and sensitive method can, therefore, be used as a basic research tool in the investigation of blood biogenic amines and their metabolites.