Method of measuring ion concentration and apparatus therefor

摘要

An ion concentration measuring apparatus for measuring the concentration of a measuring ion in a sample solution containing the measuring ion and an interfering ion having the same ionic charge number as that of the measuring ion. This apparatus comprises a first ion-selective electrode for generating a potential in response to the measuring ion, and a second ion-selective electrode in response to the interfering ion. The first ion-selective electrode is brought about in contact with a first, second and third standard solutions, each containing known concentrations of ions. A selectivity coefficient of the ion-selective electrode is calculated on the basis of the output potential of the first ion-selective electrode. The first and second ion-selective electrodes are brought about in contact with the sample solution. The concentration of the measuring ion in the sample solution is calculated on the basis of the output potential of the first and second ion-selective electrodes which have been obtained through the contact thereof with the sample solution and the selectivity coefficient. A ratio between the concentration of the measuring ion and the interfering ion in the first standard solution being identical to a ratio between the concentration of the measuring ion and the interfering ion in the second standard solution, and not identical to a ratio between the concentration of the measuring ion and the interfering ion in the third standard solution.