Abstract: A new ascorbic acid (I) assay is described which is highly suitable for determination of I in brain tissue in the presence of catecholamines and metabolites. In this method, a soluble sample containing I plus other electrooxidizable substances is passed over an inactive reactor bed to generate a peak amperometric signal that is proportional to the sum of all the concentrations Then the same injection is passed through an active bed which contains ascorbate oxidase immobilized on Sepharose, and the I is selectively removed, producing a smaller signal. From precalibrations, the difference between the 2 signals is an accurate measure of I. An amperometric detector allows very low level determinations of I. The technique is adaptable to the determination of I in a variety of samples and was used to determine 2.07 µmol I/g rat brain caudate nucleus.

Abstract: A simple, versatile flow-injection anal. procedure is described for the precise and accurate determination of the diffusion coefficients of e.g. biogenic amine neurotransmitters, their metabolites, and related compounds of neurochem. interest. The procedure uses the baseline-to-baseline peak dispersion equation of J. F. Vanderslice et al. (1981), and the app. consists of a pump, autoinjector, flow-module system, recorder, and either a UV/visible spectrophotometer or a fixed-wavelength, liquid chromatography detector. The internal standards are 1-5 mM solutions of K3Fe(CN)6 and K4Fe(CN)6 in 1 or 2 M KCl. Diffusion coefficients are given for such compounds as dopamine, epinephrine, homovanillic acid, leu-enkephalin, amphetamine, and others.