By Staci on Wednesday, August 18, 2004 - 11:51 pm:

I heard that pH is one of the factor that can affect the elution time of an analyte peak. How does this work? How do we find out if the chemical properties of the analyte is hydrophobic or hydrophilic as well as its polarity in nature? Is there any website that provide this sort of information?

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By Pat Kyle on Thursday, August 19, 2004 - 09:44 am:

The pH of the mobile phase alters the polarity of your analyte and consequently its interaction with the analytical column.

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By Uwe Neue on Thursday, August 19, 2004 - 03:11 pm:

Staci,

pH will only have an effect if your analyte(s) are ionizable and change their ionization at the pH at which you are working. Compounds with such properties are for example carboxylic acids, sulfonamides, amines, phenols etc.

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By Staci on Thursday, August 19, 2004 - 10:12 pm:

Hi Uwe Neue,

Pardon me for my poor chemistry knowledge, how do you know if the analyte(s) are considered as ionizable? Is it by looking at the periodic table? or do we look at the chemical structure?

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By Anonymous on Friday, August 20, 2004 - 01:26 am:

Maybe you can look at:
http://www.molnar-institut.com/

see the peaks in the middle of your screen

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By Uwe Neue on Friday, August 20, 2004 - 03:02 pm:

Well, I think you need to get a chemistry textbook and learn some basic chemistry. It is not possible to explain such basic questions in a few e-mails.

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By Staci on Saturday, August 21, 2004 - 08:24 am:

Thanks for the website, Anonymous. It had been very helpful cos' the animation indeed clearly demonstrated how pH affect the peak elution.