A pH probe is an analytical instrument that measures hydrogen-ion activity in solutions and provides the acidity or alkalinity as a pH value. They are designed to deliver precise performance across various industries, such as pharmaceutical, chemical, food and beverage, water, and wastewater treatment. METTLER TOLEDO is a global manufacturer of pH probes, offering a highly reliable and diverse range suitable for use in laboratory and industrial processes.
There must be a high degree of accuracy, reproducibility, and speed in probe readings. Our pH probes are optimized for your application based on a combination of high-quality materials and trusted technologies.
We use high-quality materials and technologies to ensure that our pH probes have a long lifespan, even under extreme conditions. We use a special shaft material that strengthens the design for long-lasting, reliable performance.
Our pH probes come with Intelligent Sensor Management® (ISM) technology, which allows them to store their own data, recognize when they are installed, and deliver advanced diagnostics that inform you when the sensor requires maintenance.
METTLER TOLEDO has acquired extensive knowledge in supplying high-quality solutions for laboratory and field use since 1948. Dr. Ingold's combination glass pH electrode was the first METTLER TOLEDO success. To this day, his ingenious design simplifies the way the world measures pH.
Using digital technology, METTLER TOLEDO builds pH probes and other analytical instruments while preserving the tradition of Swiss craftsmanship. Watch this video to learn how we manufacture our Intelligent Sensor Management® (ISM) pH probes in Urdorf, Switzerland.
On a logarithmic scale, pH (potential of hydrogen) represents the acidity or alkalinity of a water-based solution. On this scale, 7 represents neutrality, lower values indicate acidity, and higher values indicate alkalinity.
A pH probe allows a user to determine the alkalinity or acidity of a solution. pH probes work by measuring a solution's hydrogen-ion activity, which is detected by a sensitive glass membrane at the end of the probe.
When exposed to an aqueous solution, the exterior surface of the glass membrane develops a gel layer. Because the probe is filled with an aqueous electrolyte solution, a similar gel layer forms on the inner side of the glass membrane. Depending on the pH value, the H+ ions in and around the gel layer can diffuse into or out of this layer. As a result, the solution's H+ ion concentration is determined.
If the solution is alkaline, H+ ions diffuse out of the layer and a negative charge forms on the membrane's outer surface. If the solution is acidic, H+ ions diffuse into the layer and a positive charge forms on the membrane's outer surface. Because the probe contains an internal buffer with a constant pH, the potential on the inner surface of the membrane remains constant throughout the measurement. As a result, the pH probe potential is the difference between the inner and outer charges of the membrane.
To learn more about the theory of pH Measurement, we recommend watching our webinar What is pH?
 |
A pH probe is made up of several components with the primary ones being:
 |
A reference electrode is needed while measuring pH with a pH probe to provide a defined stable reference potential against which the pH probe potential will be measured. To do this, the reference electrode needs to be made of glass, which is not sensitive to the H+ ions in the solution. It must also be open to the sample environment into which it is dipped. To achieve this, an opening or junction is made in the shaft of the reference electrode, allowing the inner solution or reference electrolyte to flow into the sample environment. The reference electrode and pH probe (half-cell) must be in the same solution for correct measurements.
 |
pH probes should be cleaned before calibration and after each measurement. To clean your pH probe, rinse it thoroughly with distilled water and dab it dry with a clean tissue.
In order to prolong the lifetime of your pH probe and to achieve the most accurate results, it is important to clean and maintain it properly. Probes that are not cleaned after use or are neglected for a long time lose their accuracy, lowering the measurement precision of the whole system. To learn more, refer to our pH Essentials guide.
