The response of an ion sensor consisting of polyacrylamide (PAA) coupled to benzo-15-crown-5 (B15C5) to sodium, potassium, magnesium, calcium and barium ions in propylene carbonate (PC) were investigated. The PAA—B15C5 electrode showed a Nernstian response to sodium and calcium ions in PC. The electrode was applied to obtain the successive complex formation constants of the calcium ion in PC with such basic aprotic solvents, D, as N,N-dimethylformamide, N-methylpyrrolidinone, N,N-dimethylacetamide, dimethyl sulfoxide, and hexamethylphosphoric triamide. From the constants obtained in PC-rich solutions, the Gibbs energies of transfer of the calcium ion from PC to D and PC—D mixtures were calculated. The electrode was also used to obtain directly the Gibbs energies of transfer of the calcium ion from PC to PC—D mixtures. The successive complex formation constants of the sodium ion in PC with D and the Gibbs energies of transfer of the sodium ion from PC to D and to PC—D mixtures were also obtained to certify the developed electrode.