Question

1. For your column to work properly, it is very important that you do not put any water in your column. Why might this be the case?

2. Which of the following changes would work to improve chromatographic separations? Explain briefly why each option would or would not help.

a. Decreasing the length of the column.

b. Increasing the diameter of the column.

c. Increasing the length of the column.

d. Decreasing the diameter of the column.

Answer 1

1)

In normal phase chromatography, silica gel is used in stationary phase. This is highly polar. If we use water, instead of making column compact, the silica gel starts to dissolve in water , that disturbs the amount of silica gel and reduces work efficiency.

Also, in nprmal phase column chromatography, never we want to have some polar solvent in column. That is why, we should not use water.

2)

Decreasing the length of column and diameter of column does never increase the chromatographic separation. The increase in column diameter also have very little effect.

The prominant effect is seen, when we increase the length of column . This increases the number of theoretical plates, and thus increases the separation extend. Option C is the best answer to choose.