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Comparison of R for two columns
Posted: Thu Mar 29, 2012 2:54 pm
by LCFan
Hello,
I have column A (150 x 4.6 mm) and column B (75 x 3.0 mm), particle size for both is 3 µm.
For a given mobile phase, column A and column B give the same resolution of 1.5 for a critical peak pair.
I intend to normalize the resolution on the same column dimensions, e.g. 150 x 4.6 mm.
How do I calculate this?
Thank you very much
Florian
Re: Comparison of R for two columns
Posted: Thu Mar 29, 2012 8:06 pm
by tom jupille
I'm not quite sure about the question. You know the resolution on each column. What do you mean by "normalize" the resolution to the column dimensions?
Re: Comparison of R for two columns
Posted: Fri Mar 30, 2012 7:30 am
by LCFan
Dear Tom,
I scanned several columns I found in my column cupboard. Two of them gave me the same resolution for a critical peak pair, but the first of these columns has a length of 150 mm and the second one of 75 mm only. Thus, in my kind of thinking, the second column is more selective due to the fact that the same resolution is obtained as with a column with double the length.
Therefore, I thought about normalizing the R value to one single set of dimensions in order to have a substantial basis for selectivity comparison based on the normalized R value.
Regards
Florian
Re: Comparison of R for two columns
Posted: Fri Mar 30, 2012 10:25 pm
by tom jupille
OK, I see what you're trying to do, but the problem is that two columns may not have the same efficiency (plates/meter) -- particularly if they have been lying in a drawer for a while
.
If I wanted to compare the selectivity of different columns for your compounds, I would just use the alpha values (the ratio of the k's for the two peaks).