The thermodynamic properties of the quaternary (CaCl2 + Ca(NO3)(2) + L-glutamine + H2O) system, determined using the potentiometric method, were reported. The potentiometric measurements were performed in aqueous solution containing 2.5% mass fraction of L-glutamine, over total ionic strengths from 0.0100 mol.kg(-1) to 4.0000 mol.kg(-1) at T = (293.2, 303.2 and 313.2) K and P = 0.1 MPa. Different series of the salt molal ratios r (r = m(CaCl2)/m(Ca)(NO3)(2) = 1, 2.5, 5.0, 7.5, 10.0) and single salt CaCl2 and Ca(NO3)(2) solution in aqueous solution containing 2.5% mass fraction of L-glutamine were used for the potentiometric measurements. The Ca-ISE was prepared in our laboratory using the ionophore treated by carbon nanotubes. The Pitzer ion interaction model was used to correlate the experimental data. The mixed ionic interaction parameters (theta(CINO3) and psi(CaCINO3)) were evaluated according to Pitzer graphical method. The mixing parameters obtained were used to calculate the values of the mean activity coefficients of Ca(NO3)(2), the osmotic coefficients, the solvent activity, the excess Gibbs free energies, the excess enthalpy, excess heat capacity, and the excess entropy for the whole series of the studied mixed electrolyte system. There is a good consistency between the experimental results and Pitzer model.