Liquid Chromatography

[Narendra]

Can we used Sodium Phosphate buffer in place of Pottasium Phosphate buffer or vice versa ? Why majority time of Sodium and pottasium phosphate buffer used in RP Chromatography ? How this buffer exactly function in RP Chromatography ? Is there any book which explain all this ?

[sonal]

I don't think that using a sodium or potassium salt should make any difference. After all you just need phosphate ions. A buffer is a mixture of a strong and a weak acid and baseand whichever salt you use will give you phosphate ions. But it is definitely mentioned at many places that potassium salts are preferred, the reason to which I don't know myself.

Phosphate buffers are preferred with a UV detector because of their transparency in the entire UV range. Acetate buffers are used with MS.

The function of a buffer is to maintain the pH of the mobile phase. If your compound is ionic it will ionize in the solution/ mobile phase giving you ionized as well as non ionized part which will eventually lead to broadening of your band because both the ionic and non-ionic moeities will be retained to different degrees by the stationary phase. it is preferrable to maintain your drug in the non-ionic state in RP chromatography unless you have a too long retention time when ionized species will be better to elute your compound faster.

You can type buffers for hplc in google and you will get all the required information.

[tom jupille]

Also, a series of three excellent articles by Bill Tindall (a frequent contributor to the Forum, by the way) appeared in LC-GC (North America) magazine, November 2002 - January 2003. You can download pdf versions from their web site (the link is in the "sponsored by" section at the top of the page).

[diya]

Narender...Well Na ions tends to preciptate in ACN so we prefer using potassium phosphate.

Regards

Diya

[tom_mizukami]

Here is another relavent article:
http://www.lcgcmag.com/lcgc/article/art ... p?id=97119
good luck.