Joseph T. Vanderslice

Laminar dispersion in flow-injection analysis.

Simple expressions are given for the dispersion and the travel times of samples in simple flow-injection analysis systems. The sum of these two quantities is the total residence time of the sample in the system. The expressions are based on numerical solutions of the diffusion-convection equation. Preliminary experiments are in agreement with the derived simple expressions, as are peak curve shapes. Diffusion coefficients can be obtained in a straightforward manner.

Vitamin C content of foods: sample variability

A recent survey of foods that constitute the major sources of vitamin C in the American diet yielded information on the total content of this vitamin as well as the amount of its two forms, ascorbic acid and dehydroascorbic acid (DHAA) in these foods. Samples of individual foods showed a surprising large range of vitamin content even for foods collected from the same regions of the country and from the same source. The amount of DHAA in the different foods varied from approximately 10% to 20% of the total vitamin content. The large range of values for the vitamin content in a given food suggests further that in human-diet studies, when the major sources of vitamin C are from a few foods, daily analyses are required for the necessary precision.

Extraction and Quantitation of B-6 Vitamers from Animal Tissues and Human Plasma: A Preliminary Study

Reports from recent conferences on vitamin B-6 metabolism indicate that it would be most useful to identify and quantitate all forms of vitamin B-6 in animal tissue and physiological fluids (1,2). Enzyme or microbiological assays by themselves do not yield information on the individual species, but chemical assays, particularly those involving high performance liquid chromatography (HPLC), do have this potential (3,4). The problem with chemical assays is that a suitable extraction procedure must be found which quantitatively extracts the compound(s) of interest from complex samples, prevents decomposition or metabolism during the extraction, and is compatible with the analytical HPLC systems.