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Paper chromatography
Paper chromatography is an analytical method that is used to separate coloured chemicals or substances, especially pigments. This can also be used in secondary or primary colours in ink experiments. This method has been largely replaced by thin layer chromatography, but is still a powerful teaching tool. Double-way paper chromatography, also called two-dimensional chromatography, involves using two solvents and rotating the paper 90° in between. This is useful for separating complex mixtures of compounds having similar polarity, for example, amino acids.
If a filter paper is used, it should be of a high quality paper. The mobile phase is developing solutions that can travel up to the stationary phase carrying the sample along with it.
== R''ƒ'' value ==
The retention factor (R''ƒ'') may be defined as the ratio of the distance traveled by the substance to the distance traveled by the solvent. R''ƒ'' values are usually expressed as a fraction of two decimal places. If R''ƒ'' value of a solution is zero, the solute remains in the stationary phase and thus it is immobile. If R''ƒ'' value = 1 then the solute has no affinity for the stationary phase and travels with the solvent front. To calculate the R''ƒ'' value, take the distance traveled by the substance divided by the distance traveled by the solvent (as mentioned earlier in terms of ratios).
For example, if a compound travels 9.9 cm and the solvent front travels 12.7 cm, (9.9/12.7) the R''ƒ'' value = 0.779 or 0.78. R''ƒ'' value depends on temperature and the solvent used in experiment, so several solvents offer several R''ƒ'' values for the same mixture of compound.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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