What are the differences with resolution: monolithic C18 vs traditional C18? Resolution of the separated compounds by Monolithic C18 (100 mm x 4.6) is comparable with traditional C18 column with the length? Comments, opinions and observations with the use of Monolithic columns are welcome, especially about improving separation between analysed compounds. Thank you!
Hi Paul,
Thank you for the answer and the provided information.
I have and I am using Kinetex columns, but I was hoping that the monolithic columns can help to obtain better resolution between peaks. With Kinetex in some case is problem with clogging or high back pressure. Kinetex particles 5 um helping, but the separation is still not enought good in many cases.
I was thinking that maybe coupled monolithic columns till 250 mm can give better resolution between peaks then Kinetex C18 250 mm particle 5 um. Am I right or not?
And another thing, I have idea to coupled the monolithic column with the particle column. Can be done this procedure to improve the effect of resolution between peaks?
Thing is, that I believe, that can obtain better results using the coupling the monolithic column (length 100 mm) with the particle column (length 150 mm) compared to particle column (length 250 mm). Am I right or not?
Thank you for help and support.
Pawel
Hi Pawel, to my best knowledge the Onyx is indeed identical to Chromolith but an OEM product. Monolithic columns were a "hot topic" ca. 10 years ago as they provided excellent resolution and - at least for Chromolith, not the same for the Dionex ones - had very low back-pressure, so you could go to pretty high flow rates even on regular HPLCs. I think with the advent of UHPLC that can cope with small particle columns or core shell, this advantage is mostly gone.
re: you coupling project - surely unconventional and not following regular "Chromatography Lore", so I guess you will have to just give it a try, and try to rationalize your findings post-fact - a good time-honoured way of doing things!
Hi Christof,
Thank you very much for your information and opinion.
I completely agree with you, I need just give it a try, especially that not always the theory confirms the practice :).
One more time thank you.
Regards,
Pawel
Hi Paul,
Thank you very much for provided information.
Especially for information about number of theoretical plates, however, the Merck company showed that using Chromolith HR can be obtain similar effects as in case of Kinetex 2.6 um, additionaly 3-4 times lower back-presure, compared to Kinetex.
The theory is not always coinciding with the practice.
The Kinetex column was get clogged by coffee extract (extracted by 9:1, v/v n-hexane:ethyl acetate), however, the Luna column (Phenomenex) after injection of this same extracts, did not show such an effect (working great after over 1000 injections!).
Yes, I am using filters before injections and pre-columns.
Can you explain me different between Onyx Monolithic C18 and Onyx Monolithic HD-C18?
And what it means: Monolithic HD-C18 Phase Information "50 % higher performance than traditional Onyx C18"?
http://phenomenex.com/Products/HPLCDetail/Onyx/Monolithic%20C18?returnURL=/Search&phaseTab=True
"Traditional" mean particle column or monolithic?
And could be also great to get to know the difference with the back-pressure between the Monolithic HD-C18 and Monolithic C18.
Thank you.
Regards,
Pawel
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