You perform column chromatography on a mixture of reaction products which shows

Question

You perform column chromatography on a mixture of reaction products which shows two spots on TLC. However, under coulumn conditions you chose those two compounds do not seperate.

One can alter a number of factors in order to improve the resolution of components by column chromatography. For each of the factors listed in the following table, seperation can be improved by either increasing (+) or decreasing (-) the factor. For each describe how changes in sample size or interactions between components and chromatography medium are altetred by (+) or (-) the factor so that resoultion will be improved.

Column Diameter:

Column Length:

Sample voulume:

Sample concentration:

Loading time:

Flow rate:

Explanation / Answer

The parameters that increase the difference in retention time between two components are to be increased to increase resolution.

Column diameter - Increasing column diameter allows the mobile phase to diffuse laterally and in contact with stationary phase for longer duration, hence a higher resolution can be expected.

Column Length - similar effect to column diameter can be achieved, however it increases the peak width of the chromotagram, which decreases the resolution. Therefore, it should be at optimal level.

Sample volume - increasing or decreasing sample volume will have little or no effect on the resolution, as it will only lead to a saturation level of absorption by the absorbent, stationary phase.

Sample concentration - decreasing sample concentration leads to an increase in difference between retention time of components as the sample tend to move faster through the column when it is diluted.

Loading time - decreasing loading time allows the dispersion of mobile phase through the column faster and hence results in a better resolution

Flow rate - an increase in flow rate enhances the difference in retention time as the time in contact with stationary phase is decreased and hence a better resolution is expected.

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.