A functional and accurate pH meter is integral to a microbiology laboratory. pH measurements are used for various applications, such as testing municipal water quality supplies, blood chemistry, swimming pools, soil, environmental remediation, the spirits brewing, manufacturing, and many other applications. Choosing the right pH meter for your specific needs will enhance your laboratory. However, there are some things to consider.
There are two main pH meter types: benchtop pH meters and handheld ones. Both are useful for different applications.
Benchtop pH meters work well for:
Formulations testing
Biological samples
Wine labs
Food processing
QA labs
Titrations
University laboratories
Handheld pH meters work best in industries and applications where mobility is a priority, such as in oceanography, agriculture, field studies, wastewater treatment plants, and aquaculture, among others.
Many benchtop pH meters are available on the market, and there are certain features and things to remember when purchasing one.
What Is a Benchtop pH Meter?
To understand what to look for in a pH meter, you should understand the meter itself. What does a pH meter measure? It measures the alkalinity or acidity of the substance being tested, which is a semi-solid.
A benchtop pH meter will have a measuring electrode, meter, and reference electrode. The measuring electrode measures pH as the sample surrounds the glass bulb. Many benchtop meter types have various measurement modes, including pH, mV, ion, and conductivity. This is where knowing what is needed for your application is imperative.
pH electrodes are dependent on temperature, so temperature compensation is also important. The millivolt (mV) output from the pH electrode will change in correlation to the sample’s temperature change. Variations in temperature can affect the accuracy of the result. The process may sound difficult, but how to use a pH meter is relatively simple.
What to Consider in a pH Meter
As you look at pH meters for your lab, there are things to consider—not all pH meters are created alike. The electrode is one of the most essential components of your pH meter, as it measures the concentration of hydrogen ions. Most electrodes in benchtop pH meters are glass bulbs, but glass cannot be used in some food applications. In these instances, you want to search for a non-glass pH meter. Some electrodes also have non-clog tips, which can be a plus.
Calibrating your pH meter before every use is a must, so calibration functions on your pH meter should be intuitive. Buffer solutions (most commonly 4, 7, and 10) are used to calibrate the meter. Look for a benchtop pH meter that offers a 2-point calibration. For much larger applications, there are 3- and 5-point calibrations also.
You want a pH meter to be as accurate as possible for your needs, but it’s important to know that the accuracy of meters varies. You’ll find pH meters with accuracy that ranges from ±0.1 pH to ±0.001 pH, and different applications work better with different accuracies. For instance, in a QA lab, accuracy as close to ±0.1 pH as possible is a must, but a school laboratory could easily use a pH meter with an accuracy of ±0.001 pH.
Again, the temperature is important when selecting your benchtop pH meter. pH readings are always affected by temperature, and more advanced pH meters will have temperature compensation features to avoid variances in temperature. As a tip, it’s wise to calibrate your pH meter just before monitoring product pH.
Portability is also another factor, but this is considered when choosing between a benchtop pH meter and a handheld one. If you plan to use a pH meter in the field but also need accuracy in the lab, consider investing in both a benchtop and a handheld.