What is pH? - A Comprehensive Theory Guide

Welcome back to the final video in our comprehensive pH electrode handling series! In this concluding segment, we'll be delving into the art of sensor troubleshooting - equipping you with the know-how to address common challenges and ensure smooth pH measurements.
Learning how to troubleshoot and resolve these problems will boost your confidence and efficiency in pH measurement.
🎬 Join us as we explore troubleshooting techniques, share practical solutions, and provide valuable insights into resolving sensor-related hurdles.
📁 In case you missed the earlier videos, you can catch up using the links below:
pH Electrode Unboxing and Quality Check Guide | How-To-Video (1/6)
• pH Electrode Unboxing ...
pH Electrode Preparation | How-To-Video (2/6)
• pH Electrode Preparati...
pH Measurement Tips and Hints | How-To-Video (3/6) • pH Measurement Tips an...
pH Electrode Cleaning | How-To-Video (4/6)
• pH Electrode Cleaning ...
pH Electrode Storage | How-To-Video (5/6)
• pH Electrode Storage |...
#pHmeasurement #WhatispH #METTLERTOLEDO

[@charleswettish8701]

Short version: Is it important to calibrate a pH meter at 25c or not?
Long version:
I have become a bit desperate as I can find no info on the subject of how to calibrate a pH meter in which they talk about temperature during calibration.
I must be misunderstanding something, because I do know that pH depends on temperature and my calibration fluids have an actual chart of the changes in pH at different temperatures, so, to me, this seems like you must calibrate at the recommended temp of 25c, and yet, in dozens of "how to calibrate" videos, this is never mentioned.
Can someone point me to a video that explains this?
I guess if the answer is "yes, you must calibrate at 25c" it would make sense with my current understanding, but if the answer is "no, you can calibrate at any temperature", I would be confused as to how this is possible.

[@METTLERTOLEDOLaboratory]

Dear Charles Wettish,
pH measurement is a simple process. But if not done carefully, it provides ample scope to introduce errors. Temperature compensation is one such important parameter that affects the accuracy of results. So, thank you for writing to us. Let me make an attempt to address your concern, and hope that I can help you understand this process.
As you correctly mentioned, pH is temperature dependent because the activity of H+ ions is temperature dependent. So, it is important to measure the temperature during the measurement. This can be understood by having a look at the Nernst equation
E(cell) = E° (cell) - 2.303 RT/nF log aH+
Substituting the constant values, we would have
E(cell) = E° (cell) - 0.198 x T x pH
Two ways in which this can change is
1. Change the response of the electrode to pH as a result of variation in temperature
2. Change the activity of the sample (or buffer), as the ions within the solution move faster with an increase in temperature.
Since every sample has a different pH behavior that varies with the temperature, the temperature should be measured. For this, the temperature probe is integrated into the pH electrode, or an external one can be used. If the electrode and the sample have different temperatures, enough time must be given to the system to equilibrate. To compare the pH of different samples (two or more), they should always be measured at the same temperature.
A general calibration process is as follows
1. Take a minimum of two pH buffers bracketing the sample pH.
2. Use a fresh aliquot of non-expired pH buffer for every calibration point.
3. Pour enough to submerge the sensor junction.
4. Stir the buffers (if required).
5. Start the calibration and take the temperature of the buffers into account (MT Meters have value tables pre-fed that allow automatic temperature compensation during calibration. Hence temperature is automatically compensated during the calibration process).
6. Rinse the electrode thoroughly with deionized water and blot dry with a tissue.
7. Repeat steps 2- 6 for the next buffer.
8. Evaluate the results.
We also have two on-demand webinars that explain the process of pH theory and sensor calibration in detail. These 60-minute sessions can be watched at your convenient time for a quick revision of pH theory. I am sharing the links for the same below
On Demand Webinar: Calibrating a pH Meter I METTLER TOLEDO (www.mt.com/global/en/home/library/on-demand-webinars/lab-analytical-instruments/How-to-calibrate-pH.html)
Webinar - What Is pH? | METTLER TOLEDO (www.mt.com/global/en/home/library/on-demand-webinars/lab-analytical-instruments/what-is-pH.html)
We also suggest you check out our quick guide called pH essentials, which helps build essential fundamentals to quickly start with pH measurements.
pH Essentials Guide | METTLER TOLEDO (www.mt.com/global/en/home/library/guides/lab-analytical-instruments/pH-measurement-guide.html)
You’d also want to check our latest interactive poster on pH electrode maintenance which walks through all the necessary steps from electrode unboxing to electrode troubleshooting. It shares some good measurement practices to improve pH electrode performance and suggests helpful troubleshooting measures you can use if the electrode shows fluctuating readings or does not pass calibration. The easy-to-understand visuals accompany maintenance suggestions, and QR codes provide access to electrode handling and troubleshooting videos for additional insights. To download our poster use the link shared below
pH Electrode Maintenance Poster | METTLER TOLEDO (www.mt.com/global/en/home/library/tips-and-tricks/lab-analytical-instruments/pH-electrode-maintenance-poster.html)
Hope this helps.
For personalized assistance on pH calibration, we recommend contacting us at [e-mail] with detailed information about your instrument, sensor, and sample pH range, and our experts can provide you with a solution to your problems.