Preparing HPLC Mobile Phase Solutions Consistently

Have you ever read what seemed like simple method conditions and found yourself pondering how exactly something was done? For example, what does “0.1% ammonium acetate” mean? Is the 0.1% in terms of w/v? What about w/w or v/v percent? I always try to avoid ambiguities such as these when describing some method conditions. What may be obvious to assume for one person may not be so with another. This becomes especially crucial when you want a method that’s reproducible across different laboratories and analysts. Ideally, anyone should be able to read the method conditions and arrive at the same end result as the person who wrote it.

What about premixed mobile phases with an aqueous buffer and an organic solvent? I often have some of the same questions about these. If a 90 : 10 acetonitrile : aqueous buffer is said to be “10 mM ammonium acetate,” is that just for the buffer component or for the total solution? It would actually make a big difference in the ammonium acetate concentration depending on how it was interpreted (a factor of ten in this case).

For this reason, we thought it would be helpful to show you a simple step-by-step walkthrough on how to make a premixed 90 : 10 acetonitrile : 10 mM ammonium acetate buffer. This mobile phase solution is used quite frequently in ANP methods and LC-MS, so it would be good to have a handy resource to refer to when you need it.

See the link below for our tutorial:

http://kb.mtc-usa.com/article/AA-03145