Inexpensive and Disposable pH Electrodes

Inexpensive electrodes for the measurement of pH have been constructed using the ionophore tribenzylamine for sensing H+ concentrations. Both traditional liquid-membrane electrodes and coated-wire electrodes have been constructed and studied, and both exhibit linear, nearly Nernstian responses to changes in pH. Measurements of pH from these electrodes are accurate when compared to values obtained from simultaneous measurements using commercially available pH electrodes. The electrodes function well between pH values of 3 and 10. These electrodes are typically functional for two or more months before performance begins to degrade. Performing measurements in samples with abrasive solids, such as soils, also limits the working lifetimes of the electrodes. Students have successfully constructed these electrodes and used them in the measurement of soil pH levels.