One of the most important and most frequently measured quantities in analytical chemistry is the pH value. It is possible to determine pH in several ways – the easiest being a simple test strip. For more accurate and precise measurements, pH meters are the best option. When using such a device, the pH value can easily be measured, read directly, and then immediately archived in accordance with GLP. In order to verify the accuracy of the results, the points described in this article should always be considered before taking a pH measurement.