How to Choose the Right Electrode for Your pH Measurements
Because sampling conditions can vary dramatically between applications, there are different electrode requirements for different applications. These variances explain why no single pH electrode is recommended for use in every sampling application. Membrane shape, electrode body, and the type and number of reference junctions are some features that generally vary. The reference system and the form of reference electrolyte are also features that generally vary between different electrodes. Before selecting an electrode, it is important to consider the application in which it will be used as well as its features. The best option for one application may not be the best option for the next.
What to consider when choosing an electrode for your pH measurements:
Some things to consider before choosing include the electrode body material and reference electrolyte. Electrodes with glass bodies may have a wider temperature range, but they can break easier than those with epoxy bodies. Similarly, electrodes with refillable liquid reference electrolytes have longer lives. They also have less risk of reference contamination, and faster response time than electrodes with gel electrolytes. Gel electrolytes however, require much less maintenance and tend to be a more economical choice. Furthermore, while a spear tip is ideal for piercing a semi-solid sample, it’s not the best choice for measuring surfaces of solid or gel samples. A flat surface tip is the better choice for measuring surfaces of solid or gel samples.
It is also important to consider the difference between a single-junction and double-junction electrode. Single junction electrodes are economical and ideal for general-purpose and cleaner water applications. They’re not usually recommended for use with samples containing proteins, organics, heavy metals, sulfides, Tris buffers, or any other biological media. These samples will react with the trace amount of silver that is present in the electrodes. Double-junction electrodes have an extra barrier which prevents this reaction. Double-junction electrodes also tend to last longer for a variety of applications because of the extra barrier.
Keeping all this in mind, it can be concluded that choosing the right pH electrode is not always a simple task. Therefore, it’s a good idea to weigh your options and talk to your supplier about the best electrodes for your applications.
Learn more about what pH electrodes are available for your lab by clicking here.