Question

2. Paper chromatography was used to separate a mixture. Five chromatograms were prepared and each was eluted with a different mobile phase. The five mobile phases used were mixtures with different percentages of water and isopropanol. The following Re values were obtained. Rr Values 25% Isopropanol Isopropanol Isopropanol Isopropanol 50% 75% 100% Component Water 1.00 0.99 0.98 0.97 Blue Red Green Orange 0.96 0.91 0.61 0.32 0.91 0.72 0.41 0.16 0.85 0.52 0.41 0.10 0.7 0.31 0.42 0.01 Prepare a graph of Rf value versus percentage of isopropanol in the eluting mixture. Assign a different symbol to each component of the mixture. Determine if each set of data represents a linear or curved trend and the construct an appropriate trend line for each set.

Answer 1

PAPER CHROMATOGRAPHY :

• Paper chromatography is an analytical tool used to separate different components in a given mixture.
• The chromatography consists of a stationary phase and a mobile phase. Stationary phase is the water held between the cellulose of the paper and the mobile phase is the eluting solvent used by us.
• Components get separated based on their affinity to the stationary or mobile phase.
• On running a paper chromatography, we obtain the different Rf values for the components of a mixture.

Rf value :

Distance travelled by the center of the sopt ( Component) / Distance travelled by the solvent phase.

• These Rf values can be compared to the reference Rf values of different chemical compounds to identify the different components in a mixture.
• Best separation occurs when none of the Rf values of the mixture coincide on the paper, and there is proper separation between the spots.