Sensitive and specific method for the simultaneous determination of natural and synthetic catecholamines and 3,4-dihydroxyphenylglycol in microdialysis samples

The relatively new technique of microdialysis provides new possibilities fo r investigating in vivo the functioning of the sympathetic nervous system. The small sample volumes obtained, however, are a great challenge for analy tical chemists. We report here a HPLC method for measuring in one run both natural and synthetic catecholamines [dopamine, (nor)epinephrine, alpha-met hylnorepinephrine, isoproterenol and epinine] and the intraneuronal metabol ite 3,4-dihydroxyphenylglycol in small microdialysis samples after derivati zation with the fluorogenic agent 1,2-diphenylethylenediamine. No prior cle an-up step is necessary. N-Ethylmaleimide is necessary for preventing an in hibitory action on derivatization occurring in in vivo microdialysis sample s. The method can handle large numbers of samples, is sensitive (on-column detection limits 30 to 200 fg) and reproducible (RSD 1 to 7%). Recovery cha racteristics of the commercial microdialysis probe used (CMA/20) were exten sively investigated both in vitro and in vivo at Various perfusion rates; f or practical purposes a rate of 2 mu l/min and sampling at 10-min intervals was found to be workable and to give good and reproducible recoveries (50 to 70%). (C) 1999 Elsevier Science B.V. All rights reserved.