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Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: wtolf2 on April 23, 2013, 05:36:32 AM

Title: A simple question about cation-exchange chromatography
Post by: wtolf2 on April 23, 2013, 05:36:32 AM
Which will come out first through the column? Aliphatic or Aromatic amino acid?
They are uncharged!!
Title: Re: A simple question about cation-exchange chromatography
Post by: Babcock_Hall on April 23, 2013, 08:56:16 AM
Is this a homework problem?
Title: Re: A simple question about cation-exchange chromatography
Post by: wtolf2 on April 23, 2013, 10:22:48 AM
Yes it is. Any idea?
Title: Re: A simple question about cation-exchange chromatography
Post by: Arkcon on April 23, 2013, 10:40:00 AM
What can you pull together for an answer given their structures.  You seem to know that there's no obvious charge to cause binding, but can you come up with other effects that would slow one or the other?
Title: Re: A simple question about cation-exchange chromatography
Post by: wtolf2 on April 23, 2013, 11:45:09 AM
Yeah there is no other effect affects the order of amino acids coming out. It seems there is no answer...
Title: Re: A simple question about cation-exchange chromatography
Post by: Babcock_Hall on April 23, 2013, 01:10:02 PM
One, you need to show your attempt first before we can help with homework (Forum rules).  Two, you have not provided any information about pH or what matrix is employed, which would be helpful.  Three, there are other effects besides pure ion-exchange that sometimes come into play.  In my experience it depends on the matrix, however.
Title: Re: A simple question about cation-exchange chromatography
Post by: Arkcon on April 23, 2013, 01:29:35 PM
Well, for practical applications, you'll have to consider the matrix supporting the cation-exchange group, and the size of the pores vs the size of the molecules.  But for a homework question, looking for some sort of transient phenomena would be what's needed to answer the problem
Title: Re: A simple question about cation-exchange chromatography
Post by: Babcock_Hall on April 23, 2013, 04:28:48 PM
@OP, At low pH values, the amino acids will not be uncharged.  What charge will they have?