| 摘要 |
The ion concentration of a sample is measured by introducing the sample into a measuring vessel containing three ion-selective electrodes (32a to 32c) and a reference electrode (33), measuring an electrode potential, introducing a standard solution of known ion concentration into the measuring vessel after removing the sample from it, measuring an electrode potential and taking the difference between these two electrode potentials. After a comparatively long interruption of the measurement, during which the electrodes remain immersed in the standard solution, the state of the electrodes is established by introducing the standard solution repeatedly, namely four times, into the measuring vessel and removing it from the latter, measuring four electrode potentials during these repeated steps while the electrodes are immersed in the standard solution, taking the difference between the third and fourth electrode potential, and then comparing it with a predetermined permissible differential value in order to assess the electrodes as altered and deviating from the standard if the difference is greater than the permissible differential value. <IMAGE>
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