Illustration of pH Meters and color spectrum for article on pH Measurement
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Published On: July 25th, 2023Categories: Articles, pH Meter
One of the more fundamental tools in every laboratory, a pH meter is an absolute necessity. Decades ago, researchers would have used a pH indicator kit, but in the interest of time and faster processing, a meter (whether benchtop or handheld) is a staple in a modern lab. The “p” stands for potential, while the H is the element symbol for hydrogen. The meters measure the hydrogen-ion concentration in solutions, particularly water or those with a water base. The hydrogen-ion level is best expressed in terms of alkalinity or acidity. The pH range runs from 0 to 14, with 14 being the most alkaline and 0 being the most acidic. Something with extremely high acidity would be bleach at 13.0, while something extremely acidic may be stomach acid at 1.0. Neutral is 7.0, so anything below 7.0 is more acidic, while anything above 7.0 is more alkaline.

The basic construction and principles of pH meters consist of a pH-responsive electrode and an unvarying reference electrode attached to a voltmeter. There are many applications within the laboratory for pH meters, and pH measurement and monitoring is vital to every lab. Read on to learn more about pH, when a meter should be calibrated, and the many applications within the laboratory.

How Does a pH Meter Work?

The standard design is the same whether the meter is benchtop or handheld. The meter works by measuring the voltage (electrical potential) produced by the solution that is being tested. For example, an acidic solution will have more positive hydrogen ions.

Generally, there are three components to a meter: the meter itself, a reference electrode, and the probe, which is inserted into the solution. Inside the probe are two electrodes a reference electrode, and a glass (measuring) electrode. The measuring electrode contains a reference electrolyte that has a pH of 7.0 (neutral). When the probe is inserted into a solution, it measures the differences in voltages of the ions produced in both the solution and electrode. The difference is the pH measurement.

How to Correctly Use a pH Meter

Electrodes will wear out over time, and typically last for 12 to 18 months. It’s imperative to ensure that you always keep your probe in solution when not in use, as a dried-our probe nay not function properly. A worn probe may have cracked glass or other wear and tear. To tell a probe’s age, look at the lot code. pH meter calibration also essential. Occasionally calibration is okay in a setting such as a teaching environment or when a meter isn’t being used often. However, for pinpoint accuracy, pH meters should ideally be calibrated daily before each use by placing the probe in a pH buffer solution (7.0). Beyond calibration, meters are incredibly easy to use:

  • After calibration, place the electrode in the solution.
  • Press the “measure” button on the meter.
  • Leave the electrode in the solution for up to 2 minutes for an accurate reading.
  • After the reading stabilizes, set the pH level.
  • Measure again for the pH level of the solution.
  • Remove the electrode, and clean and dry it for the next use.

Selecting a pH Meter

There are two types of meters: handheld and benchtop. Some laboratories employ both, depending on the applications. Benchtop meters provide the most accuracy. However, there could be a better choice for fieldwork. Handheld meters are also very accurate and portable and are the best choice for working in the field. Finding an accurate meter depends largely on how often you calibrate it. If your lab needs meters for several applications, you may want to consider those not made for single-specific applications. Also, meters with more functionality and more features may be a better fit. However, in many cases, a standard benchtop or handheld meter is adequate and accurate for laboratory measurements.

pH Meter Applications

There are many pH meter applications, but the most common uses you’d find in a laboratory include measuring the pH of

  • Biological fluids (e.g., saliva, blood, urine)
  • Soil
  • Solutions in pharmaceutical manufacturing
  • Drinking water
  • Food and beverage products
  • Cells in biotechnology

pH meters are also used in microbiology laboratories to prepare chemical reagents and ensure microbial growth.

To learn more about pH meters and measurements and which may be the best fit for your laboratory, contact Hudson Robotics today to speak with a representative to receive a quote.