Electro-chromatography inside filter paper : Diffusion and its effect on electrophoretic separations
✍ Scribed by Michael Lederer
- Publisher
- Elsevier Science
- Year
- 1952
- Tongue
- English
- Weight
- 402 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0003-2670
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✦ Synopsis
There are several phenomena which have been termed "diffusion" insitlc filter paper. The spreading of a spot placed on dry paper and the separation of substances to form a capillary picture have both been ascribed to diffusion. True diffusion between a solute and a pure solvent both supported on filter paper has been studied by BROOKS AND BADGERS to differentiate several nitrocellulose fractions. These authors placed one sheet of filter paper containing the solute and saturated with the solvent on top of a pad of IOO solvent-saturated filter papers, and, by permitting diffusion to go on for some time, obtained ;I three dimensional diffusion rate through the pad. The measurement of diffusion was carried out by separating the filter paper sheets and detecting the solute by spot tests.
In studies on spot size on paper chromatograms, various methods were employed to assess spot areae, and several relations for the increase of spot area with concentration3 and time of development4 were found.
Although the rates of diffusion of many substances are well known in a homogeneous mediums, no systematic study of diffusion of spots inside filter paper seems to have been recorded. It was decided to investigate this problem, as diffusion data can throw some light on the conditions under which paper chromatograms and electropherograms should be conducted, as well as providing a simple method to determine relative diffusion rates.
It was found that, for most ions and small molecules, the spots placed on moistened filter paper increased regularly with time, also that the rate of diffusion is proportional to the concentration of the substance present; thus confirming FICK'S first law. It could also be shown that the rate of diffusion of large molecules, such as proteins, is strongly influenced by the electrolyte concentration in the solvent.