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Working Group 3.13


Industry, research, analytical laboratories and even the private sector use electrochemical measurement methods in a variety of ways. Conductivity measurements are, for instance, conducted in the production of semiconductors to monitor the purity of water; the pH value is measured equally in medical laboratories and in aquariums in private households; ion-selective electrodes are used to determine important electrolytes in blood serum; the state of Li ion battery cells is measured by means of electrochemical impedance spectroscopy; and the oxygen concentration, the salinity or the acidity of seawater – all important observation parameters in the fields of oceanography and climate research – are also determined by electrochemical measurements. In contrast to many chemical analysis methods, electrochemical sensors are relatively cost-effective, easy to handle and they deliver quick, though sometimes less precise, results. They are therefore often used in process and quality control, especially when automated, simple measurement results in large amounts must be achieved at a minimum of time and cost. The measurement results must nonetheless be reliable within the limits of feasible precision, especially when they are to serve as evidence that legal or normative requirements are complied with, e.g. in medical engineering.

As a result, PTB Working Group "Electrochemistry" has developed national standards for the electrochemical measurands of electrolytic conductivity, pH value and ion activity and offers calibration services for these measurands. To ensure the reliability and international comparability of the calibration results, we regularly participate in international comparison measurements within the scope of Opens external link in new windowCIPM-MRA.

Our research activities extend to various fields and are aimed at improving the existing standards, extending their range of application, and developing new measurement procedures for electrochemical measurands. Research is usually done on a national and international level cooperating with metrological institutes, accredited laboratories, university institutes, and industry. Our current research work is focused on the traceability of the measurement results of the salinity and pH value of seawater to appropriate standards and to the measurement of the state of health of Li ion battery cells of electric vehicles. If you browse through our websites, you will find out more about our services and research tasks.

We strive to extend our range of services and to respond to new needs. In doing so, we also accept unusual challenges. Whenever you need a new reference measurement procedure for an electrochemical measurand, please contact us. We would be pleased to help you.

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Electrolytic conductivity of primary reference solutions

Electrolytic conductivity is a measure of a solution's ability to transport ionic charge. It depends on the species and concentration of the ions in the solution and is well suited to measure minimal changes in the ionic concentration of a solution without having to carry out complex sampling and sample analyses. Moreover, conductivity meters are relatively inexpensive and easy to operate. Therefore, conductivity is frequently measured to monitor the ion concentration of liquids in process control, for instance in the field of medical engineering, in power plants, in waste water treatment and in the food industry. In aqueous solutions, the measurements are made in a range between 0.055 µS∙cm-1 (ultra-pure water) and some 10 S∙m-1 (process water). In practice, conductivity measuring instruments are usually calibrated with reference solutions whose conductivity is known. As a calibration service, we offer measuring the conductivity of reference solutions traceably to the International System of Units (SI) by means of a primary measurement procedure.

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Calibration of conductivity sensors for applications in pure and ultra-pure water

Conductivity measuring cells for pure and ultra-pure water applications are often used in environments where a simple, cost-effective and fast method is necessary to monitor pure water continuously for ionic impurities, for instance water for infusions, water for steam turbines in power plants and water for cleaning semiconductors. In most cases, flow-through cells are used because they have to be installed in closed circuits.

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pH value of primary reference buffer solutions

The pH value is a measure of the content of hydrogen ions in a solution. It has a significant impact on the speed of chemical reactions and/or on the structure of molecules. Therefore, the pH value is vital for all life and there is hardly any substitute for it in process control in the chemical industry.

The pH value is defined as the negative, decadic logarithm of hydrogen ion activity. Since the activity of hydrogen ions cannot be measured directly, the pH value is realized through an internationally recognized convention that permits a sound approximation to the definition of the pH value and a high reproducibility.

In practice, the pH value is frequently measured with commercial instruments that have to be calibrated with reference buffer solutions. Frequently, glass electrodes are used which change their electrical potential as a function of the hydrogen ion activity. The electrical potential is measured against a reference electrode.

As a calibration service, our Working Group offers measue the pH value of reference buffer solutions by means of a primary measurement procedure.

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At present, no current information is available.

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