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8. Chemical Measurands and Material Properties

Olaf Schnelle-Werner

The Technical Committee ʺChemical Measurands and Material Propertiesʺ was established in October 2012. It is the youngest of the DKD Committees and represents approximately 15 calibration laboratories accredited by DAkkS according to DIN EN ISO/IEC 17025:2005. These laboratories cover the following analytical measurands: pH, electrolytic conductivity, density, viscosity and volume. The Committee's activities are focused on developing calibration guidelines as complement to existing standards. By implementing these calibration guidelines, it is intended to harmonize the calibration processes in the accredited calibration laboratories for chemical measurands, both nationally and internationally.

The Technical Committee supports the work of the DKD regarding the translation of guidelines and expert reports as well as their international dissemination. Currently, the Technical Committee ʺChemical Measurands and Material Propertiesʺ is working on guidelines dealing with pH and electrolytic conductivity. In the field of viscosity, viscosimeters of various types are calibrated - ranging, for example, from the Ubbelohde capillary viscometer for use in laboratories to 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 are, for example, Newtonian viscosity standards, density reference liquids, pH reference buffer solutions and materials, and 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 extended requirements according to DIN EN ISO/IEC 17025:2005 / ISO Guide 34:2009 will also influence the guideline activities of the Technical Committee.

The Subcommittee ʺVolume/Densityʺ, as part of the Technical Committee, is already active in the field of the measurand volume. As a result of these activities - and by directly involving the manufacturers - the guideline DKD-R 8-1 “Calibration of piston-operated pipettes with air cushion” as well as several other expert reports have already 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. As a result of the worldwide feedback, the guideline DKD-R 8-1 has also been published in English, French and Russian. It is already being used by several NMIs and accredited calibration laboratories.