So what i have to make sure of is my preparation and not to make a fairly concwntrated buffer. But how concwntrated are we takling about and where can i find the practical pka values?
Obviously I agree with Borek that one should in general make the buffer using a calibrated pH meter. when I calculate how much acid or base to add, I usually think of that calculation as an estimate, anyway. Others may have different points of view.
The ability of the buffer to resist changes in pH is greatest at a pH that is identical its the pKa
. Assuming that I have the freedom to choose any buffer that I want, I typically look for buffers with pKa
values close to the pH of my experiment. However, when one is trying to duplicate someone else's experiment, this may not be an option.
I may have brought about unnecessary confusion when I mentioned ionic strength. One usually choose the concentration of the buffer according to the needs of the experiment and then accepts the ionic strength for what it is. For sorbate buffers the effect will probably be small anyway.