I use 1% ammonium Acetaate with Acetonitrile with for several anlyses. Please let me if it is a buffer??? If it is at what pH it buffers. How should I determine the right pH for analysis??

thanks

Dear Anonymous,

Ammonium acetate IS a buffer...if you make it right. You can purchase ammonium acetate from Sigma chemicals or make it from acetic acid and sodium acetate, or you can make it from acetic acid and a strong base. The pH range for this buffer is 3.8 to 5.8. Your buffer pH should be within this range BEFORE you add your ACN, preferrably. Measuring the pH of your mobile phase AFTER the organic is adding may not be as reproducible from batch to batch.

You determine the "right pH" for your analysis based on the form (charged, neutral) you want your analyte(s) to be in. In this case, you typically need to know the pKa of the functional groups on your analytes.

For EXCELLENT, indepth knowlege on all of the above, and much more, see: Practical HPLC Method Development, 2nd Ed., Synder, et al. (I have no affiliation with the book or authors, I just like the book).

Good luck.

See this website for buffer preparation:
http://www.bi.umist.ac.uk/users/mjfrbn/buffers/makebuf.asp

oops, ...disregard my blunder regarding aa and Na acetate... sorry.