Gas chromatographic analysis of endogenous catecholamines, phenolic amines and derived isoquinolines using short...

A gas chromatographic method is described for the concomitant separation and analysis of catecholamines, catecholamine or 3,4-dihydroxyphenylethylamine condensation products (tetrahydroisoquinolines), and their isomeric mono-O-methyl (phenolic) metabolites which may be present in neuronal tissues, utilizing short glass capillary columns and electron-capture detection. Isomeric phenolic amines that were not generally separable with conventional-packed gas chromatographic columns were rapidly resolved on the capillary system, and with their catecholamine or catechol isoquinoline precursors, quantitated with high sensitivity (0.25-7.0 pg) and reproducibility. Key steps in the approach with tissues include initial amine isolation with a weak cation-exchange resin (BioRex-70), fluoracyl derivative formation, and brief washing of the derivatives with ammonium phosphate buffer (pH 5.8) just prior to capillary analysis; overall recoveries of amines or alkaloids added to rat brain homogenates ranged from 79% to 89%. Application of the method is demonstrated in an assay of endogenous dopamine in rat corpus striatum and hypothalamus. This new procedure should complement and in some instances may be preferred over liquid chromatographic assays for catecholic and phenolic amines and isoquinolines, and ought to be applicable to mass spectrometric detectors as well.