Use of a correction liquid for an ion-selective electrode

This invention relates to a correction liquid for a liquid membrane type ion-selective electrode 1 that makes it possible to measure a ratio between a sodium ion concentration and a potassium ion concentration in urine by correcting an influence from an ionic strength of the urine. The correction liquid comprises a sodium ion-sensitive part 15 that selectively reacts with the sodium ion and a potassium ion-sensitive part 16 that selectively reacts with the potassium ion and measures a ratio between a sodium ion concentration and a potassium ion concentration in urine, and the sodium ion, the potassium ion and an ionic strength modifier as being an electrolyte are contained.