Paper chromatography
The paper chromatography , in the default language and paper chromatography is a chromatographic separation process for small amounts of substance, in which a fine filter paper, the stationary (at rest) phase and a solvent representing the mobile (moveable) phases.
Procedure
The dissolved sample is applied to the filter paper in a small drop, next to it usually one or more drops with one or more known reference substance (s). The dried filter paper is placed or hung in a closed glass vessel so that the paper does not touch the glass wall. The starting point is so far away from the edge of the paper at the lower end that it is not immersed in the solvent . Due to the capillary action , the solvent rises and transports the substances with it, whereby the interaction ( adsorption and desorption ) of the substance with the paper, more precisely with the water contained on it due to air humidity, results in a substance-specific migration speed. This separation process is also called "ascending" paper chromatography and is more common than so-called "descending" paper chromatography.
In addition to one-dimensional paper chromatography, two-dimensional paper chromatography (two passages of the substance when the chromatogram is rotated by 90 °) is used to separate more complex mixtures, such as amino acids from proteins . After the chromatogram has dried, colorless samples are made visible with a reagent , in the case of amino acids, for example, by spraying on ninhydrin .
Paper chromatography is very well suited as a student experiment, since an important analysis process can be carried out by yourself with simple means without any risk. So z. B. the dye composition of different felt pen inks can be examined. Water is used as the solvent. In addition to the principle of chromatography, basic knowledge of subtractive color mixing is also conveyed.
Award ceremony
The Nobel Prize in Chemistry in the year 1952 was at Archer John Porter Martin and Richard Laurence Millington Synge awarded for the development of this type of chromatography.
literature
- Friedrich Cramer : Paper Chromatography. Verlag Chemie, Weinheim 1953 and new editions.
Individual evidence
- ^ A b Walter Wittenberger: Chemische Laboratoriumstechnik , Springer-Verlag, Vienna, New York, 7th edition, 1973, pp. 209-211, ISBN 3-211-81116-8 .
