Molecules of a protein or carbohydrate are moderately polar

Molecules of a protein or carbohydrate are moderately polar. Would the retention time of such a molecule increase or decrease if the mobile phase becomes less polar (for example, the percentage of methanol is increased in the methanol/water mobile phase) in reversed phase liquid chromatography (RPLC)? Please explain your answer briefly.

Solution

In reversed-phase liquid chromatography (RPLC), polar compounds like protein and carbohydrates elute first than the non-polar compounds. Hence for polar compounds, the retention time (time required for the elution) is less when compared with the nonpolar compounds.

If the mobile phase made less polar as stated in the question, the retention time for polar compounds will increase as it takes more time to elute the polar compounds like protein or carbohydrates.