This paper deals with ionic species migration based on classical mass balance equations in conjunction with a charge balance equation and the electroneutrality condition. Two new methods are proposed to apply the electroneutrality condition, avoiding the elimination of one of the conservation equations of chemical species and permitting to explicitly apply boundary conditions on all species. The first method is based on variational principles and the second on a Lagrange multiplier. It is shown that the new methods are analytically equivalent to the more standard method in which one conservation equation is eliminated without any other consideration. The variational method is more complex to implement than the Lagrange multiplier method. The new methods were applied to a multi-ionic problem together with the charge conservation equation without capacitive effects. Different kinds of boundary conditions were applied: Neumann, Dirichlet and a nonlinear case based on Butler-Volmer kinetics. All methods gave the same results for non-complex problems. In the case of complex problems including chemical equilibrium between each ionic species, it was found that more investigations are necessary even for more conventional methods.