Open-Source Low-Cost Wireless Potentiometric Instrument for pH Determination Experiments

Abstract

pH determination is an essential experiment in many chemistry laboratories. It requires a potentiometric instrument with extremely low input bias current to accurately measure the voltage between a pH sensing electrode and a reference electrode. In this technology report, we propose an open-source potentiometric instrument for pH determination experiments with Bluetooth wireless connectivity. The hardware is built on a solderless breadboard and mainly composed of an Arduino Nano microcontroller, a 16-bit analog-to-digital converter, two electronic buffer amplifiers, a temperature sensor, and a Bluetooth module with a total cost around $50 (US dollars, including a portable power supply ∼$10). The software is written in Arduino Sketch and the cross-platform Python language, both of which the students can access and modify freely. The instrument was demonstrated with a traditional glass electrode and a custom palladium/palladium oxide pH sensing electrode, and compared with a commercial pH meter. Results sho...