In a canonical simulation, one does not have a direct access to the chemical potential of hydronium ions necessary to determine pH of the system. This makes canonical titration simulations complicated , since pH must be determined separately after equilibrium has been established. Furthermore, a very small number of free hydronium ions present inside the cell makes the usual methods to obtain chemical potential, necessary to calculate pH, very inaccurate. To remedy these problems, we use the recently developed method for canonical titration simulations introduced in the Ref. [93]. Although in the present paper we only consider a PC model with one colloidal particle, the simulation method is completely general and can be applied to a system with an arbitrary number of nanoparticles inside the simulation cell with periodic boundary condition.