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Chemical Measurands and Material Properties

Olaf Schnelle-Werner

The Technical Committee “Chemical Measurands and Material Properties“ was established in October 2012, thus being the youngest Technical Committee of the DKD. It represents approximately 15 calibration laboratories which have been accredited by the DAkkS according to DIN EN ISO/IEC 17025:2005.

These laboratories cover the following analytical measurands: pH, electrolytic conductivity, density, viscosity and volume. The Technical Committee primarily develops calibration guidelines, in order to complement existing standards. The aim is to harmonize the calibration processes in the accredited calibration laboratories for chemical measurands at the national and international level by implementing the developed calibration guidelines. For this purpose, the Technical Committee supports the work of the DKD in the translation of guidelines and expert reports as well as their international communication. The current objective of the Technical Committee “Chemical Measurands and Material Properties“ is the development of guidelines for pH and electrolytic conductivity. Viscometers of various kinds are calibrated for the measurand viscosity, e.g. Ubbelohde capillary viscometers for the use in laboratories as well as flow cups. Reference materials and reference liquids are equally important. They provide the metrological basis for the traceability of the above-mentioned measuring instruments. These include, for example, Newtonian  standard specimen of viscosity, density reference liquids, pH reference buffer solutions and materials as well as reference solutions for electrolytic conductivity. Stability and homogeneity have a significant impact on the quality of reference materials. These requirements are laid down in the ISO Guide 34:2009 and are increasingly being required by the customers. In the future, the expansion according to  DIN EN ISO/IEC 17025:2005 / ISO Guide 34:2009 will also influence the guideline activities of the Technical Committee.

The technical subcommittee “Volume/Density”, as part of the Technical Committee, is already active in the field of the measurand volume. As a result of this work, and through the direct involvement of the manufacturers, the guideline DKD-R 8-1 “Calibration of piston-operated pipettes with air cushion” as well as several expert reports have been developed. These guideline activities will be continued and extended to include positive displacement pipettes, dispensers and piston burettes. Extensive interlaboratory comparisons according to DIN EN ISO/IEC 17043:2010 have been performed in order to metrologically confirm the results, including measurement uncertainties. 

Due to the worldwide response, the guideline DKD-R 8-1 was also published in English, French and Russian. It is already being used by several NMIs and accredited calibration laboratories.