<Tr> <Th_colspan="2"> Other techniques </Th> </Tr> <Tr> <Th> Related </Th> <Td> Thin layer chromatography </Td> </Tr> <P> Paper chromatography is an analytical method used to separate colored chemicals or substances . It is primarily used as a teaching tool, having been replaced by other chromatography methods, such as thin - layer chromatography . A paper chromatography variant, 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 . The setup has three components . The mobile phase is a solution that travels up the stationary phase, due to capillary action . The mobile phase is generally an alcohol solvent mixture, while the stationary phase is a strip of chromatography paper, also called a chromatogram . A chromatographic method is called adsorption chromatography if the stationary phase is solid . </P> <P> The retardation factor (R) may be defined as the ratio of the distance traveled by the solute to the distance traveled by the solvent . R values are usually expressed as a fraction of two decimal places . If R value of a solution is zero, the solute remains in the stationary phase and thus it is immobile . If R value = 1 then the solute has no affinity for the stationary phase and travels with the solvent front . To calculate the R 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 value = 0.779 or 0.78 . R value depends on temperature and the solvent used in experiment, so several solvents offer several R values for the same mixture of compound . A solvent in chromatography is the liquid the paper is placed in, and the solute is the ink which is being separated . </P>

When do we carry out a dimensional paper chromatography