[Accuracy of acidity changes in the gastrointestinal tract as determined by pH-tubes with the internal and external comparison electrodes].

It was for the first time that the presence of diffusive potentials on the borders between segments of the gastrointestinal tract (GIT) with differing compositions and pH values were detected in the practice of pH-metry. The diffusive potentials were found to be a cause for a considerably worsening accuracy of pH measurements by the second measuring electrode of the two-electrode pH-tube with the internal comparison electrode. On the contrary, when pH-tube with the external cutaneous comparison electrode is in use, the measuring accuracy does not deteriorate virtually for all electrodes in the latter case.