Experimental implementation of a measuring electrode for determining the hydrogen index in strongly acidic environments

The work is aimed at finding ways to solve the issue of metrological support for measurements of the hydrogen index pH in a highly acidic environment, which requires the presence of corrosion-resistant measuring electrodes with a stable potential, and for use in medical purposes – with an additional requirement – the absence of toxic substances on the working surface of the electrodes. Non-toxic and relatively corrosion-resistant metallic bismuth with the addition of modified graphite was chosen as the material for the electrode production. Optimal ratios of the main substance of the electrode (bismuth) and the modifying additive (graphite) have been selected, a binding solution has been proposed to increase the degree of homogeneity of the working surface of the electrode, and a method for manufacturing measuring electrodes has been described. An experimental setup has been developed to measure the potential of the manufactured electrodes relative to the potential of a normal hydrogen electrode. The setup includes a set of technical means, including a hydrogen generator, a hydrogen electrode used under standard conditions, acting as an anode, and a measuring electrode acting as a cathode, which was made up of various electrodes manufactured within the framework of this work. Electrode functions have been constructed for antimony and bismuth electrodes of different modifications. The results of measuring the potential of the manufactured bismuth and antimony electrodes, which are used as pH probes in medical equipment, have been compared. The results of studies of the influence of carbon additive on the electrode potential of measuring electrodes and their corrosion resistance are presented. Ways of further studies are proposed to optimize the composition of the working surface of electrodes for use in a strongly acidic environment.

1. Yakovlev G. A. Fundamentals of probe pH-metry in gastroenterology. Medicinа, Moscow (2009). (In Russ.)

2. Lukushkina E. F., Larionova E. E., Kuzmichev Yu. G., Belentsova L. A. Evaluation of the secretory function of the stomach in children with immunopathological conditions. Doctor.Ru, 3(81), 45–47 (2015). (In Russ.)

3. Raport S. I., Lakshin A. A., Rakitin B. V., Trifonov M. M. pH-metry of the esophagus and stomach in diseases of the upper gastrointestinal tract. Medpraktika, Moscow (2005). (In Russ.)

4. Leya Yu. Ya. pH-metry of the stomach. Leningrad, Medicinа, Leningrad (1987). (In Russ.)

5. Yakovlev G. A. pH-probe: patent RU 2115444 C1. Bull. Izobret., no. 19 (1998).

6. Pantirev Yu. M., Chernyakevich S. A., Babkova I. V. pH-metry of the upper digestive tract in a surgical clinic. Manual for doctors. Russian State Medical University, Moscow (1999). (In Russ.)

7. Isakova D., Narmaeva G. Z., Aronbaev S. D., Aronbaev D. M. Electrode materials to modern electroanalysis. Universum: chemistry and biology, (8(62)) (2019). (In Russ.) https://7universum.com/ru/nature/archive/item/7659

8. Manjakkala L., Szwagierczakb D., Dahiya R. Metal oxides based electrochemical pH sensors: Current progress and future perspectives. Progress in Materials Science, 109, 100635 (2020). https://doi.org/10.1016/j.pmatsci.2019.100635

9. M. Pourbaicks. Atlas of Electrochemical Equilibria in Aqueous Solutions. NACE International Cebelcor (1974).

10. Bykov A. N., Lokshtanova O. G. Use of ruthenium electroplating in the production of reed switches. Features of the technology. Collection of papers of the fi rst international scientifi c and practical conference “Magnetically controlled contacts (reed switches) and products based on them”, Ryazan, Russia, October 11–14, 2005. (In Russ.)

11. Shishkina L. V., Lokshtanova O. G., Karabanov S. M. Electrolytic coatings used in magnetically controlled contacts (reed switches). Collection of papers of the fi rst international scientifi c and practical conference “Magnetically controlled contacts (reed switches) and products based on them”, Ryazan, Russia, October 11–14, 2005. (In Russ.)

12. Prokunin S. V., Vengina D. A., Dobrovolsky V. I., Shchipunov A. N. Ways to reduce the total standard uncertainty of pH measurements on the state primary standard. Al'manac of modern metrology, (2(38)), 78–88 (2024). (In Russ.) https://elibrary.ru/iywpnm