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2.2.3 Interpreting Chromatograms - Coggle Diagram
2.2.3 Interpreting Chromatograms
Identifying Mixture
If the substance is a mixture, it will separate on the paper to show all the different components as separate spots
An impure substance therefore will produce a chromatogram with more than one spot
If two or more substances are the same, they will produce identical chromatograms
(look at comments)
Pure substances will produce only one spot on the chromatogram
Rf Values
The Rf value of a particular compound is always the same but it is dependent, however, on the solvent used
If the solvent is changed then the value changes
Rf stands for retention factor
Calculating the Rf value allows chemists to identify unknown substances because it can be compared with Rf values of known substances under the same conditions
These values are used to identify the components of mixtures
These values are known as reference values
Calculating Rf
The Rf value will always lie between 0 and 1; the closer it is to 1, the more soluble is that component in the solvent
The Rf value is a ratio and therefore has no units
Rf = distance travelled by substance ÷ distance travelled by solvent
(look at comments)
The Retention factor is found using the following calculation: