A pH Meter is a device used for potentiometrically measuring the pH, which is either the concentration or the activity of hydrogen ions, of an aqueous solution. It usually has a glass electrode plus a calomel reference electrode (meter), or a combination electrode.The pH (always written little p, big H) of a substance is an indication of how many hydrogen ions it forms in a certain volume of water. There’s no absolute agreement on what “pH” actually stands for, but most people define it as something like “power of hydrogen” or “potential of hydrogen.” For pH meters to be accurate, they have to be properly calibrated, so they usually need testing and adjusting before you start to use them. You calibrate a pH meter by dipping it into buffers (see photo below) and adjust the meter accordingly. The standard buffers are a pH of 4, 7, and 10. Another important consideration is that pH measurements made this way depend on temperature. Some meters have built-in thermometers and automatically correct their own pH measurements as the temperature changes. Our pH meters have the thermometers built in. Calibrations should be performed daily, or before each use if not used daily. All sterile CSPs (compounded sterile products) are pH-ed when made.
The pH is one of the most important factors affecting the stability of a preparation. Pharmacists use published pH and stability profiles to determine the pH that will ensure maximum stability. The pH is important in drug formulations, both in sterile and non-sterile compounding and also for pet and human medications. The reason is because it affects drug solubility, activity, absorption, stability, and patient comfort. A slight increase or decrease in pH can cause some drugs to precipitate from a solution. Conversely, a slight adjustment of pH can aid in solubilizing some drugs. Higher and lower pH can cause discomfort and/or burns on the skin or mouth, so patient comfort should always be a priority.