Question

In chromatography, resolution is governed by (a) the number of plates, (b) relative retention, and (c) retention factor. Construct a set of graphs to show the dependence of resolution on each of these three parameters. Comment on the nature of the dependence of resolution on each of these three parameters.

Short answer

The solution is

a) the separation time does not vary.

b) We can observe from the graph that as relative retention increases, the peaks

shift apart and the resolution improves.

c) lowering lowers resolution.

Step-by-step solution

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We will create a set of graphs that indicate the relationship between resolution and (a) the number of plates, (b) relative retention, and (c) retention factor in this task.

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First consider the Purnell equation for resolution

$\mathrm{Resolution}=\frac{\sqrt{\mathrm{N}}}{4}\frac{\left(\mathrm{\alpha }-1\right)}{\mathrm{\alpha }}\left[\frac{{\mathrm{k}}_2}{1+{\mathrm{k}}_2}\right]$

- We may deduce from this equation that each of the values is both proportional and inversely proportional to resolution, with the exception of the number of plates, which is directly proportional.

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- Because no values are supplied in the task, we'll utilize the chromatograms from page 620 of the book.

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Take a look at the first chromatogram on page 620 of the book:

- On the chromatogram, there are two peaks that are closely spaced, the first of which is larger than the second.

- This chromatogram will be compared to the other three on the same page.

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The retention factor vs. the resolution factor (k)

When you have k , Increasing k usually enhances the resolution, although it isn't required.

- On the other hand, lowering k lowers resolution.

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Relative retention vs. resolution$\mathbf{(}\mathbf{}\mathrm{\alpha }\mathbf{}\mathbf{)}$.

- We can observe from the graph that as relative retention increases, the peaks shift apart and the resolution improves.

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Number of plates versus. resolution ( N ).

- As can be seen from the graph, as the number of plates increases, the peaks become smaller than on the original chromatogram, and therefore the resolution improves.

- the separation time does not vary.