How to Choose a Potentiostat
Posted on Fri, Aug 28, 2020 by Chris Bracher
Choosing a potentiostat can be complicated, in part because the term describes a wide range of devices which differ significantly from one another in terms of both functionality and price. Broadly speaking, a potentiostat is any piece of equipment which controls the potential across a cell in response to changes in current. Potentiostats interface with a three electrode cell which contains a working electrode, reference electrode, and counter electrode. They control the potential between the working and reference electrodes and measure the changing current between the working and counter electrodes. Put simply, potentiostats are electronic devices which use feedback circuitry to control the potential across an electrochemical cell.
The main distinguishing factor between the different types of potentiostat is their intended application. It may sound obvious, but when choosing a potentiostat, the main thing to consider is what you plan to use it for. Most potentiostats on the market have been designed for use in the lab for the electrochemical analysis of materials, but the umbrella-term can also refer to portable devices designed for environmental testing or for health applications like blood testing.
Most potentiostats feature a single channel. This is sufficient for most types of electrochemical analysis, but some methods require one or more additional channels and hence need to be performed with a multi-channel potentiostat, more properly as bipotentiostats or polypoteniostats. It is also worth noting that potentiostats are also sometimes confused with other similar pieces of electrochemistry equipment, such as galvanostats. Galvanostats are less closely related to potentiostats than bipotentiostats or polypoteniostats but share some common working principles (more on this below).
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Equipment designed for voltammetric methods like cyclic voltammetry control and measure a three electrode cell using a single working electrode and channel. For some less common methods such as rotating ring-disc electrode (RRDE), a cell with more than one working electrode (and hence multiple channels) is required. Potentiostats that control two working electrodes are known as bipotentiostats and those that can control more than two electrodes are known as polypoteniostats. In both cases, aside from the additional channels, the basic operating principles remain the same.
Multichannel potentiostats typically cost much more than ‘normal’ potentiostats and most people will never need the extra functionality. Choose a bipotentiostat or polypoteniostat if you intend to perform experiments that require multiple channels, but otherwise, opt for a single channel potentiostat.
Potentiostats vs. Galvanostats
Galvanostats (also known as amperostats) are similar to potentiostats in a lot of ways, and the two are often confused for one another. Chiefly, both galvanostats and potentiostats control and measure electrochemical cells by using the basic relationship between potential, current, and resistance described by Ohm’s law.
However, whereas potentiostats maintain a constant potential across a cell with a varying resistance by supplying more or less current, galvanostats maintain a constant current by varying their output potential. The two types of device have different feedback circuitry and are therefore not interchangeable.
In terms of applications in research environments, while potentiostats are used for voltammetric methods such as cyclic voltammetry, galvanostats are most commonly used for a technique called galvanostatic cycling. You are most likely to come across a galvanostat outside of the lab in the form of an everyday battery charger.
Portable and Handheld Potentiostats
Portable potentiostats are small, handheld, battery powered devices. Compared to desktop models, they are typically less powerful and are more likely to be limited to a specific function. Handheld potentiostats are most useful for testing in the field, particularly for environmental measurements where a quick quantitative result is more important than a full electrochemical analysis.
Many portable devices are designed to detect the presence and quantity of a single material in a sample. For example, they might be able to measure the amount of lead in drinking water or the amount of iron in a sample of blood. The ability to get an instant result without needing to bring the sample to the lab is clearly desirable in these situations. For commercial or academic research and education and for performing cyclic voltammetry, a compact desktop device like the Ossila Potentiostat is much more suitable.
USB / Desktop Potentiostats
USB potentiostats are the opposite of handheld potentiostats. While the latter might use an inbuilt screen or a smartphone app to display the results of a scan, USB potentiostats interface with a computer. Also known as desktop potentiostats, these are the devices that you are most likely to find in an electrochemistry lab where they are routinely used for the electrochemical analysis of materials. The pairing of a potentiostat with dedicated PC software as opposed to inbuilt firmware gives the user more control over the experiment and means that the results can be analysed in more depth. The Ossila Electrochemistry software, shown below, allows you to quickly and easily set up your experiment, save scan profiles so that you can easily repeat experiments, and export the results as a comma-separated value (.csv) file for use with nearly any analytical tool.
The Ossila Potentiostat
The Ossila Potentiostat is a low cost, USB potentiostat which has been designed and built specifically for performing cyclic voltammetry. By focusing on the most common use case of a laboratory potentiostat, we have been able to create a cost effective way for researchers and teachers to equip their labs without sacrificing ease-of-use, accuracy, or build quality. When bought as a package deal with an electrochemical cell, working electrode, reference electrode, and counter electrode (all available separately), the potentiostat comes with everything you need to start taking measurements in just a few minutes.
The Ossila Potentiostat is available from just £1,300 as a standalone unit. If you are unsure if the Ossila Potentiostat is right for you, please refer to the product details or contact us for more information.
Author: Chris Bracher
Chris joined Ossila in 2016 after completing a PhD in polymer and perovskite solar cells at the University of Sheffield. During his PhD, he gained expertise in photovoltaic device fabrication and characterisation, thin-film solution processing, and the construction of automated testing systems. Formerly part of the OFET and 2D materials teams at Ossila, he now focuses on the development of new test and measurement systems, with an emphasis on software.