Electrochemical Potentiostat Uncertainty and Traceability

Many electrochemical measurements use a potentiostat or galvanostat to apply and measure potentials and currents. While ubiquitous, the practical limitations on the accuracy of these devices and the uncertainty they can introduce into measurements are often unappreciated. This article serves as an introduction to instrumentation uncertainty in electrochemistry with the aim of orienting electrochemists to the likely magnitude of error introduced by common commercially available instrumentation. There is currently no standardized method for determining whether instruments meet their expected specifications, so a method for traceably testing that a potentiostat meets a required level of accuracy is presented. The results of example tests on four brands of potentiostats illustrate the method and highlight the limitations of commonly used devices. Practically, it was found that at voltages ≤1.5 V, the devices studied introduced an expanded (k = 2) uncertainty of <2 mV between 0.1 μA and 100 mA and an uncertainty on current of <1 % when used within specifications.