How to Choose a pH Electrode for the Laboratory
The last several pHridays have been focused on the anatomy of a pH electrode and the role of each electrode structure. A review of the structure and design of a pH electrode can be found in figure 1. Here we point out how to choose a pH electrode for your application.
Figure 1: pH electrode anatomy overview
Can My pH Electrode Be Used in Every Application?
Sampling conditions can vary dramatically between applications, so there are different electrode requirements for different applications. This explains why no single pH electrode exists that is recommended for use in every sampling application.
As an example, a specialized spear tip membrane is needed for the measurement of semi-solids such as fruit and cheese. The YSI TruLine 21 features a spear tip membrane.
In contrast to the spear tip, measurements made on solid surfaces require another specialized membrane, the flat membrane. This membrane shape is required to ensure optimal moistening during pH measurement. The YSI TruLine 27 features a flat membrane.
Figure 2: YSI TruLine 21 (top) and 27 (bottom) pH electrodes
In addition to membrane shape, the electrode body, type and number of reference junctions, the reference system, and the form of reference electrolyte (i.e. liquid or gel) are all features that commonly vary between electrodes.
How to Select an Electrode
When selecting an electrode, the most important consideration is the application in which it will be used. To assist in electrode selection, check out the YSI Laboratory pH Electrode Application Guide.
There are additional considerations besides application when selecting an electrode for your lab. If possible, it is most convenient to have an integrated temperature sensor in your electrode to ensure pH measurements are accurately compensated for temperature.
Some additional considerations besides a built-in temperature sensor include the electrode body and reference electrolyte. Glass body electrodes have a wider temperature range but can break easier than plastic body electrodes. Electrodes with refillable liquid reference electrolyte will have a longer life, less risk of reference contamination, and faster response time than electrodes with gel electrolyte. However, electrodes with gel electrolyte are easier to maintain.
YSI offers many different pH electrodes for the lab. Therefore, in addition to the application guide, YSI also has a Laboratory pH Electrode Comparison Guide to help you understand the differences between each electrode we offer. The guide also provides an overview of each electrode family and the instrument each electrode is compatible with.
Figure 3: YSI laboratory pH electrode application and comparison guides
YSI offers a variety of platforms for the measurement of pH. Whether for the lab (MultiLab, TruLab), environmental sampling (Pro Plus, ProDSS, Pro10), or for long-term monitoring (EXO1, EXO2), YSI has what you need!
Additional Blog Posts of Interest:
Anatomy of a pH Electrode | Glass pH Probes, Part 1 of 4
pH Meter Calibration Problems? Check Out These 12 Tips!
Why Is the pH Scale Logarithmic?
Extend the Life of Your pH Electrode in 3 Practical Steps