Abstract— An improved method for the measurement of catecholamines in brain parts has been developed, based on reverse‐phase ion‐pair chromatography. The new method offers the advantages of high efficiency microparticulate liquid chromatography packings and the flexibility of ion‐pair chromatography. By this approach norepinephrine and dopamine (DA) have been measured in the hypothalamus and corpus striatum of the rat brain during various stages of development (15, 21, 30 days). Data are reported on the basis of the whole part and per weight of tissue. For the adult animals, the following concentrations (ng/g wet tissue) were observed for the hypothalamus: NE = 2261 ± 274, DA = 440 ± 103, and for the corpus striatum: DA = 11,888 ± 1840. The overall precision of the method was ±5.6% relative s.d. The absolute recovery was 60 ± 5% relative s.d. and was constant over the range of 1 ng to 1 μg of dopamine or norepinephrine per tissue sample. The relative retention behavior of 18 neurologically important catechol derivatives is reported for reverse‐phase chromatography with octyl sulfate as the stationary phase modifier.

We describe an improved reversed-phase liquid-chromatographic method for concurrent measurement of tryptophan and eight of its metabolites in serum. These were separated by gradient elution and detected both by ultraviolet absorption at 254 nm and amperometrically at an oxidation potential of +0.700 V vs Ag/Cl. Detection limits for the electrochemically-detected compounds were between 100 pg and 1.0 ng, and approximately 1-5 ng for the ultraviolet-absorbing compounds. Analytical recovery of the compounds after deproteinization (by ultrafiltration) varied between 65 and 95%. As little as 500 microL of serum is required. No interference(s) from other naturally occurring serum constituents were encountered. This highly sensitive method is relatively fast and offers a useful tool for diagnosis and treatment of diseases involving derangement in tryptophan metabolism.