The pH of a sample is an indication of its acidity or alkalinity and pH determination is one of the most commonly conducted laboratory measurements. The term pH is defined as the negative logarithm (base 10) of the Hydrogen ion concentration (or, more accurately, Activity) expressed in molarity. The measurement of pH is often done using a pH meter, paper or indicators. For most routine pH measurements, a two-point standardization of a pH meter should be used; pH 4 and 7 buffers can be used for pH measurement of samples of pH 7 or below, while pH 7 and 10 buffers can be used for pH measurement of samples of pH 7 or higher. The pH buffers themselves, can be used for the standardization of pH meters or to check color development of pH indicators. The weakest link in a pH measurement is usually the pH and/or reference electrodes. Electrodes should always be handled carefully. The more commonly used pH buffers have values of 4, 7 and 10 and are available as either clear solutions or as color-coded solutions that permit easy identification of these buffers whether in or out of the container. Buffers of pH values much less than 1 or greater than 13 are not available due to instability and other limitations of actual pH meter and its measurement.
Application: For Professional, Scientific and Technical Activities, other Professional, Scientific and Technical Activities