Chromatography

#science #chemistry

Chromatography is used to seperate mixtures consisting of soluble substances such as ink.

Method

![[large.png1. Mark filter paper with a pencil line. Pencil is not soluble so it can be used. Place one or more blobs of ink or plant dye onto the line equally. ]]

![[large (1).png2. Lower the paper into the solvent, the ink will slowly separate and spread up the paper.]]

![[large (2).png3. Once the paper has fully absorbed the solvent, the less soluble substances will have travelled the furthest up the paper.]]

The ink is mobile, as it moves up the paper, whilst the paper is stationary.

Processing a chromatogram

This method produces a chromatogram, it can be used to tell between mixtures and pure substances. On a chromatogram, mixtures will have two or more substances shown as spots of color whilst a pure substance will only have one substance. This can also identify unknown mixtures by comparing them to one of the same pattern of spots. These have identical Rf values.

Rf value

Rf value can be calculated with dividing the distance travelled by the substance by the distance travelled by the solvent. If the Rf value is more than one or less than zero it is not valid. $\frac{\text{distance travelled by substance}}{\text{distance travelled by solvent}} = \text{Rf}$