By ali on Tuesday, July 20, 2004 - 09:33 am:

I have a one question?
why the retention time of a compound does not change over change the PH 2-6.
it C18 reverse phase HPLC
need three explanation i know 2 one is may be this compound does not have a functional group
secound at PH 6 all compound is ionized so decreasing more PH make no Effect
the last one is?????
please answer

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By tom jupille on Tuesday, July 20, 2004 - 11:10 am:

Here's a two-part hint:
1. What type of function is pH ?
2. What is the definition of pKa ?

Put those together with your second explanation and you will have a third answer.

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By ali on Thursday, July 22, 2004 - 01:39 pm:

Hi Tom
Can you please explain little more
thanks

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By tom jupille on Friday, July 23, 2004 - 08:19 am:

No, Ali, that's not the way it works! You have to go first.

Let's start here: what is the definition of pH?