Chromatography - How does flow rate affect peak width?

• CrimpJiggler
In summary, the retention time of a solute will change depending on its path length through the stationary phase." is right.
CrimpJiggler
Today in a lecture on chromatography the lecturer gave an explanation which seems pure ******** to me. The example she used was a handful of solutes, each taking a different path through the stationary phase, obviously some paths will be longer than others and thus each solute will have a different retention time. She said that altering the flow rate doesn't alter the bandwidth (the width of the peak), it just shaves an certain amount of time off the retention time for each solute. For example, it shaves 5 seconds off each analyte (regardless of how long their path is) so that the peak moves down the x-axis a bit but doesn't change in width. I'm a visual thinker and my visual image for this concept calls ********. Let's say we have solutes A, B and C and their retention times are:
A = 10s
B = 12s
C = 16s

the way I see it, if I double the flow rate then I will half the retention time for each solute. If I alter the flow rate by a certain amount, then the retention time of each solute will vary depending on their path length. This is a bad example, let's say A, B and C are different compounds with their own specific retention times instead.
If I alter the flow rate by x, my lecturer says that the retention time of each compound will change by y. I say that each compound will change by an amount specific to each compound so the retention time of A will change by ax, B by bx and C by cx, where a, b and c are constants specific to compounds A, B and C. Can anyone here shed light on this? Who is right, me or my lecturer? I kept my mouth shut during the lecture because I couldn't think of the words to convey what I see.

Last edited by a moderator:

1. How does the flow rate affect the peak width in chromatography?

The flow rate in chromatography refers to the speed at which the solvent moves through the stationary phase. When the flow rate is increased, the peaks on the chromatogram become narrower. This is because the components in the sample are being carried through the column at a faster rate, resulting in less time for them to diffuse and interact with the stationary phase. As a result, the peak widths decrease.

2. What is the relationship between flow rate and peak width in chromatography?

The relationship between flow rate and peak width in chromatography is inverse. This means that as the flow rate increases, the peak width decreases. Conversely, as the flow rate decreases, the peak width increases. This is due to the fact that the components in the sample spend less time in the column at higher flow rates, resulting in narrower peaks.

3. Can a high flow rate be used to improve the resolution in chromatography?

While a high flow rate can result in narrower peaks, it may not necessarily improve resolution in chromatography. In fact, using a flow rate that is too high can cause the peaks to merge and result in a loss of resolution. It is important to optimize the flow rate based on the specific separation being performed.

4. How does the choice of solvent affect the flow rate and peak width in chromatography?

The choice of solvent can have a significant impact on the flow rate and peak width in chromatography. Different solvents have different viscosities, which can affect the flow rate through the column. Additionally, the choice of solvent can also affect the interaction between the components in the sample and the stationary phase, thus impacting the peak widths on the chromatogram.

5. Is there an optimum flow rate for achieving the best separation in chromatography?

There is no one optimum flow rate for all separations in chromatography. The best flow rate will depend on several factors, including the sample composition, column type, and desired resolution. It is important to experiment and optimize the flow rate for each specific separation to achieve the best results.

• Mechanical Engineering
Replies
3
Views
1K
• Chemistry
Replies
2
Views
4K
• Biology and Chemistry Homework Help
Replies
4
Views
2K
• Chemistry
Replies
16
Views
2K
• Introductory Physics Homework Help
Replies
5
Views
1K
• Engineering and Comp Sci Homework Help
Replies
1
Views
1K
• Other Physics Topics
Replies
7
Views
2K
• Mechanical Engineering
Replies
2
Views
3K
• Chemistry
Replies
14
Views
2K
• Mechanical Engineering
Replies
7
Views
1K