Abstract: An ion sensor has a flow path through which a sample flows. An ion-exchange membrane is in contact with the sample in the sample flow path. An internal solution is provided on one side of the ion-exchange membrane. An internal electrode is provided so as to come in contact with the internal solution. The surface of the ion-exchange membrane that does not come in contact with the sample is coated with a two-liquid-mixed epoxy resin.

Abstract: An ion-exchange membrane has a mesh structure with microscopic pores in which water can infiltrate. When the ion-exchange membrane is incorporated in the sensor body, the one side of the membrane comes in contact with the sample solution and the other side thereof comes in contact with the internal solution. The water in the internal solution gradually migrates to the side of the sample flow path permeating through the membrane. When the sensor is used for extended periods of time, therefore, the sensor performance often decreases due to a decrease in the electric conductivity between the internal electrode and the ion-exchange membrane.