Uses for a pH Meter in a Laboratory

About pH Meters

• A pH meter is an electronic instrument which is capable of reading and displaying the pH of a solution almost instantly. It is made up of a main body which houses the electronics, a digital display, an internal reference electrode and an external electrode probe. The external probe ends in a thin membrane made of a specially selected material which is sensitive to the presence of H+. This electrode changes its potential in response to different concentrations of H+ and the on board electronics change this potential into a display of pH. Dip the electrode probe in the solution you are testing to use the pH meter.

Acid/Base Titrations

• Labs performing chemical analysis sometimes use titrations to find the strength of an unknown acid or base. In this procedure, a standard solution of known concentration is added to the sample until the pH becomes neutral. Since this means the acid and base components of the sample are now balanced, the lab can calculate the strength of the unknown. Labs often use a pH meter to track the pH of the solution during the titration.

Direct Measurement of Acidity

• There are many occasions where a lab or test facility may want to know the exact pH of a solution, in which case they can directly measure the solution with a pH meter. This is important, for example, in the quality control or regulatory analysis of foods. Many foods, such as pickled products, have to be maintained at a certain pH range to prevent spoilage. In some cases, as with pickle brines, the lab will directly test the food by inserting the meter electrode, while in other instances the lab may have to prepare or homogenize it prior to testing.

Testing Buffers

• A buffer solution is a mixture of various solids dissolved in a liquid, typically water. A buffer is carefully designed so that it resists changes in pH, even if an acidic or basic chemical is added to it. These solutions are used often in biological science, since some biologically active chemical substances, such as proteins, must be kept within a specific pH range. Once a lab makes up a stock of buffer solution, they will use a pH meter to double check that the buffer is at the correct pH value.