dwell volume

[gerapas]

In our lab we mostly use methods from EP. And there are some difficult gradient analysis that i think i should know the dwell volume that they had in their systems, to try to do the best i can. But i don't. Is there a rule of thumb or empirically i have to see what works for me?

[mattmullaney]

Hi gerapas,

Lost my original post...try the following sources for guidance:

High-Performance Gradient Elution: The Practical Application of the Linear-Solvent-Strength Model by Synder and Dolan, ISBN 978-0-471-70646-5

and

http://www.chromatographyonline.com/lcg ... &sk=&date=

for the LC-GC article on the same topic. It may take some work on your own to estimate the dwell volume of the HPLC system the EP used with your own hardware, but it may be possible to do so using the info from these two sources--the article cuts to the chase a bit more quickly than the book, but it's a really great book to have.

Best Wishes!

[HPLCaddict]

I've seen it only in very few instances that the dwell volume of the original system used has been stated in an EP monograph. That said, it's of course very hard to adjust the gradient to an unknown dwell volume difference .
Fortunately (and wisely) absolute retention times are very seldom part of the system suitability test so, in my opinion, as long as you pass the system suitability and the separation works, no adjustment is necessary. I'd start to care about gradient adjustment only if problems actually arise. Then, if you don't know the original dwell volume, retention times stated in the monograph or an example chromatogram from the knowledge database (if available) may give you a clue in which direction you have to adjust the gradient. The rest is trial and error, ahem, I meant empirically-based development.