What would be the effect of decrease the carrier gas flow rate, raise the column temp, have on the retention time?

Question

What would be the effect of decrease the carrier gas flow rate, raise the column temp, have on the retention time?

What would be the effect of raise the column temp and decrease the
carrier gas flow rate on the ability to resolve two closely spaced peaks?

For the first question:

I know that decreasing the rate will increase retention and increasing the temperature column will cause the retention to decrease.

For the second question:

I am not quite sure how to explain this part and I am not sure if my first answers were correct. Any help would be appreciated

Answer 1

Pg 201 of techniques under the subtitle "Poor Separation of a Mixture" should answer #2 for you.

Answer 2

For the first question, when you decrease the carrier gas flow rate, it will increase the retention time. This is because the slower flow rate allows the sample components to spend more time interacting with the stationary phase of the column, leading to increased retention. On the other hand, raising the column temperature will cause the retention time to decrease. Higher temperature increases the kinetic energy of the analyte molecules, making them move more quickly through the column and reducing their interaction with the stationary phase, thus decreasing the retention time.

For the second question, raising the column temperature and decreasing the carrier gas flow rate can improve the ability to resolve two closely spaced peaks. A higher temperature results in increased diffusion of the analytes, which helps to spread out the peaks and reduce their overlap. This can enhance the overall resolution, making it easier to distinguish and quantify the two peaks. Similarly, reducing the carrier gas flow rate can promote better separation by allowing sufficient time for the analytes to interact with the stationary phase and avoid elution overlap.

It is important to note that the effects mentioned above are general trends, but the impact of these changes may vary depending on the specific chromatographic parameters, the analytes being separated, and the type of column being used.