Abstract: A new type of PVC membrane ISE of pyridine as well as of N, N-dimethylaniline was prepared by using chromium trioxide-pyridine complex as active material. The potential Nernst responses for pyridinium and N, N-dimathylanilinium ions ranged in 1?10^-1-1?10^-5M and 1?10^-1-6.3?10^-6M respectively. Pyridinium chlorochromate C₅H₅NHCrO₃Cl can also be used as active material and its potential Nernst response range was found to be the same as chromium trioxide-pyridine complex.