Subcommittee on pH


Taking into account IUPAC leadership in this field, the importance of pH measurements in general, and the historical place of electrochemical methods in the past IUPAC structure, the Analytical Chemistry Division is considered the appropriate organizational entity to host a subcommittee on pH.

!! Read about the Realisation of a Unified pH Scale, in CI Oct 2018, p. 29; !!
Aiming at developing a practical and reliable method of measuring and expressing acidity of any medium on a universal scale (pHabs), based on a solvent-in- dependent standard state, a project UnipHied (project 17FUN09), with a 1 May 2018 start date and a duration of 36 months, has been approved and funded from the EMPIR programme, from the Participating States and from the European Union’s Horizon 2020 research and innovation programme.

Terms of Reference

The Analytical Chemistry Division is the home for the designated SpH which is responsible for:
1. Fostering an understanding of both the concept of pH and its fundamental importance among the general public.
This includes,
a) Actively engaging in education and training actions aiming at all age and academic levels,
b) Production of appropriate educational tools, namely written material that supports.

2. Promoting a general understanding of the measurement of pH and the importance of its traceability to the SI among the chemical community as a whole.
This includes,
a) Participation in public events with the presentation of interesting work results from scientific research and technical development perspectives,
b) Publication of pertaining data and information in both specialised journals and the media in general.

3. Establishing and disseminating the traceability chain for pH measurement by focusing on the primary, secondary and the routine pH measurements relating each one to the respective target uncertainties.
This includes,
a) Investigation of the factors that limit the uncertainty of the measurement of the acidity function in cells without transference with which the primary measurement per se of pH is realised.
b) Collecting information on and evaluate models for single-ion activity as candidates to supersede the Bates-Guggenheim convention, the uncertainty of which currently limits the traceability of pH to the SI via the primary measurement method for pH.
c) Study of the influential parameters for pH meter calibration and pH practical measurement, in cells with diffusion, such as liquid junction potential, indicator and reference electrode (e.g, single and combination electrode assemblies) behavior, reference buffer standards and temperature,
d) Providing data that enable informed users to assign credible uncertainties in such measurements of the pH of samples encountered in real-world analyses.

4. Addressing new challenges, proposing and undertaking actions that contribute to updating the relevance of pH.
This includes,
a) Investigation of cost-effective means of disseminating the primary measurement of pH via certified reference materials with compositions
nominally identical to the primary standards,
b) Development and validation of new pH measurement techniques and Equipment,
c) pH measurement in complex matrices, namely non-aqueous solutions, e.g. in seawater, physiological fluids, bioethanol,
d) Proposing actions, such as proficiency testing in pH measurement with the use of aqueous and non-aqueous pH reference buffer solutions.