In the RR-cpH algorithm, one specifies the pH and concentrations of ions and polyelectrolyte inside the simulation cell as the input parameters. The method then provides the degree of ionization, along with ensemble averages of observables after equilibrium has been established. It is often stated that pH in Eq. 3 corresponds to the pH inside the canonical simulation cell. This, however, is not correct. In a canonical reactive Monte Carlo simulation, the total number of protons inside the system is fixed, simulation algorithm then determines how many of these protons will remain free (in the form of hydronium ions) and how many will become associated with the polyelectrolyte surface groups. The pH of the system, which is related to the electrochemical potential of hydronium ions, does not make part of the detailed balance condition and can not appear in the acceptance probabilities of titration moves. The correct canonical reactive Monte Carlo algorithm will be presented in the following section.