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Image of pH color range for article on pH testing.
Published On: August 24th, 2021

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For over 100 years, pH has been an invaluable tool for measuring the acidity of solutions. Based on a logarithmic scale from 0 – 14, the pH scale made what was once a difficult calculation, an easy to understand measure of free hydrogen protons (H+) in a solution.

This simple scale is crucial to stability testing of pharmaceutical products. Without the pH scale, the development of new drugs would take dramatically longer and be less safe.

In drug development, stability testing of pharmaceutical products remains critical in testing new formulations. Stability testing determines which formulations will prevent a pharmacologically active compound from degrading or changing structurally from light, heat, or time. It is vital to the development of a novel medication. Using pH to measure stability testing of pharmaceutical products is one of the required tests and is simple, fast and inexpensive.

What Is a pH Meter Used For?

A pH meter is used to determine the amount of free hydrogen (H+) in a solution. This is converted into a useful number (the pH of the solution) where 0 represents the maximum amount of free hydrogen in the solution (maximal acidity), 14 represents no free hydrogen (maximal alkalinity), and 7 is a neutral solution with equal amounts of free hydrogen and hydroxide (OH-) ions. When stability testing of pharmaceutical products, the pH scale is indispensable.

What Do You Use to Measure pH?

There are many different ways to measure pH for stability testing of pharmaceutical products. But they can all be condensed into two main categories: colorimetric measurements, where a test indicator (e.g., Litmus paper or certain indicator chemicals) change color depending on the pH of a solution, and electrical measurements where two electrodes are placed into the solution. The presence of hydrogen ions acts as a battery whose voltage can be measured with the electrodes. When more hydrogen ions are present, the solution is more acidic, and the pH is lower.

While colorimetric indicators are often significantly less expensive, they are much less accurate. Electrical measurements are more expensive, time-consuming, and require significantly more training and expertise than colorimetric methods. ​​Still, they are the only reliable way to perform stability testing of pharmaceutical products. They are much more accurate and less prone to measurement errors caused by certain electrochemical components that may not be present in the finished product.

Why Is It Necessary To Calibrate the pH Meter?

Calibration of a pH meter is necessary, not just for stability testing of pharmaceutical products, but as with every piece of equipment in a life science laboratory, it must be calibrated regularly. Before measuring the pH of samples, calibration will provide a precise and accurate reading within the scale desired.

Similarly, a pH meter that is not calibrated properly will not provide accurate pH readings. This can lead to wholly unnecessary and major changes in the chemical composition of a new drug or the erroneous conclusion that a novel compound lacks needed constancy if the stability testing of pharmaceutical products is not done with high levels of accuracy.

What may look like an unstable compound because when exposed to light or heat it appears to change pH — thereby changing the amount of free hydrogen ions and its composition — may result from a poorly calibrated pH meter. It is no more useful than a bathroom scale that produces random weights every time someone steps on it.

pH Meter Automation: The Solution

Automation is the ideal solution to the inherent problems in accurately measuring pH (expense, time, and training/expertise).

Rapid pH stability testing of pharmaceutical products will give a competitive edge to any lab compared with one using older methods of pH measurement.

Some of the many benefits of an automated pH meter include:

  • No need for extensive training for manual pH measurement.
  • Time saved performing pH measurements, cleaning, and calibration of the meter.
  • Measurement errors are minimized or eliminated.
  • Expenses are reduced from the costs of chemical reagents, fewer errors, significantly increase reliability, accuracy, and reproducibility.
  • Technicians and scientists are free to perform more important tasks, and
  • Modern pH meters are simple and easy to use with no advanced programming knowledge needed.

When the rapid stability testing of pharmaceutical products is vital to the success of a lab, as it is for any life science and pharmaceutical laboratory, pH meter automation will take your laboratory to the next level.

Hudson Robotics is the leader in life science and pharmaceutical laboratory automation. With nearly 40 years of experience, they are your best source to learn more about stability testing of pharmaceutical products and every aspect of laboratory automation. To ensure you maintain that competitive edge, contact Hudson Robotics today.