Hi, I have a solution containing acetic acid and NaCl. The solution is adjusted to a particular pH value by adding NaOH. For the calculation of the undissociated acetic acid concentration, I use the correction suggested by Sortwell 2001 (J. Food Prot. 63(2): 222-230 (2000)), which says that I have to account for the ionic strength in order to calculate pKa properly. But my question is: how do I calculate this ionic strength? Do I only take NaCl into account? Or do I also account for the presence of NaOH? Thanks!