Zuverlässige Kalibrierung von pH-MesseinrichtungenTraceable Calibration of pH Measurement Devices

Abstract

Zusammenfassung DerpH-WertisteinewichtigeMessgröße zur Charakterisierung von wässrigen Lösungen und damit auch von biologischen Systemen. Von wenigen Ausnahmen der spektroskopischen Bestimmung abgesehen, wird der pH-Wert einer Lösung potenziometrisch, durch Messen der Kettenspannung einer pH-Messkette mit Glaselektrode mit Hilfe einer geeigneten pH-Messeinrichtung bestimmt. Eine Aussage darüber, ob der gemessene pH-Wert den Ansprüchen an die jeweilige Anwendung genügt, ist nur möglich, wenn die Zuverlässigkeit des Messergebnisses durch die Angabe einer Messunsicherheit belegt werden kann. In dem Beitrag wird die Rückführungs-kette für die Messgröße pH-Wert beschrieben sowie einzelne Unsicherheitsbeiträge betrachtet, die der Anwender bei der Einführung und bei der Bestimmung der pH-Werte berücksichtigen sollte. Das schließt auch die technischen Parameter, die an das Produkt gestellt werden, ein.Summary The pH value is an important quantity used to characterize aqueous solutions including biological media. There are only few fields of application for spectroscopic pH measurements. pH is usually measured electrochemically by potentiometry. The cell voltage of a pH measuring chain with glass electrode is measured by means of an appropriate pH measuring device. To be able to assess whether the result of a pH measurement meets all requirements a statement of the measurement uncertainty is mandatory. In the following the metrological traceability chain for pH is described. The paper will focus on important uncertainty contributions to be taken into account by the user. This especially includes technical product parameters.Schlagwörter pH, Kalibrierung, Rückführung

Early dark energy constraints on growing neutrino quintessence cosmologies

“…III, since κ is effectively a constant that controls the size of the kinetic function k 2 1 (ϕ) as can be seen in Eq. (21). We find that our numerical results for the evolution of dark energy are well approximated by the early dark energy parametrisation of Doran & Robbers [41], in which the dark energy density fraction is parametrised as follows:…”

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