I'm studying the new technology of separation based on HILIC columns, but I don't understand the difference between normal phase chromatography and HILIC. It seems to me to be the same separation mechanism. Can anyone please explain the main difference between the two techniques?
I actually consider HILIC to be a normal phase technique. It behaves as normal phase- increase the polar solvent (water) and the solvent strength increases causing compounds to elute faster, certainly normal phase behavior.
Please note Figure 1 in the reference link- as the percentage of water increases (% acetonitrile decreases), the k (retention) decreases (ref: http://www.chromatographyonline.com/lcgc/article/articleDetail.jsp?id=714661 ). This is normal phase behavior.
For some columns used as HILIC, depending on the eluting compounds and the column, the column may exhibit a changeover from normal phase to reverse phase. This occurs with bonded phase columns such as diol. For an example, see: http://www.isco.com/WebProductFiles/Applications/101/Application_Notes/AN86_Chimeric_Diol_Column_Behavior.pdf
Ok. I think I understand...more or less. But I think is not clear the separation mechanism.
Carlos- there are probably several theories on the separation mechanism, and the mechanism may even be different for different stationary phases.
Here's the publication about HILIC that you can read if you cannot sleep at nite.
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