pH measurement

The determination of pH values is a common procedure in daily laboratory work. It measures how acidic or basic an aqueous solution is and is calculated by using the concentration of hydrogen ions in the test substance. The pH scale ranges from 0 (extremely acidic) to 14 (very alkaline), described as follows:

• pH below 7: acidic
• pH equal to 7: neutral, e.g. pure water
• pH greater than 7: alkaline or basic

The pH value is measured for a various reasons, e.g. to manufacture products with defined properties or to optimise production processes. In addition, the determination of the pH value is essential in order to comply with legal requirements or adapt to the (environmental) quality, e.g. in rivers and lakes.

pH meters:

Different tools are used to measure pH, including pH meters, test sticks and other indicators. pH meters are mainly used in the chemical, pharmaceutical, environmental technology and food industries. These industries require very precise measurement results to maintain hygiene standards, like in the food and beverage industry and fulfilling requirements in wastewater treatments and water purification methods.

Such electrochemical measuring systems makes use of a glass electrode which detects hydronium ions and converts them into a corresponding potential to produce an electric current. It measures the voltage (electric potential) produced by the test solution. The reference electrode in the measuring device is suspended in a solution of potassium chloride which has a pH of 7 (neutral). The difference in voltage (potential difference) converts into the pH reading of the solution.

Buffer solutions:

Besides measuring devices, indicators or test sticks, buffers (test solutions of known pH) are also very important in laboratories. High-quality buffer solutions are essential to achieve best possible results in laboratory tests that require a constant pH in the test solution. The pH of a buffer solution changes very little when an acid or base is added to it, thus keeping pH at a nearly constant value. Buffer solutions are not only important in laboratories, they are often used in chemical engineering, especially in galvanizing processes, the production of dyes and in analysis.