pH-Testing – a No-Brainer?

Collaborative Efforts to Improve Environmental Monitoring - Session 2
Oral Presentation

Prepared by C. Prokisch
MACHEREY-NAGEL, Neumann-Neander-Str. 6-8, Dueren, NRW, 52355, Germany

Contact Information: [email protected]; +49204219690


pH testing using test strips is widely applied and generally thought to not require any explanation. The author dealt with pH-papers for more than 20 years and never felt the necessity to provide in-depth-knowledge as pH-tests are seemingly self-explanatory. Yet, the last NEMC-meeting in Jacksonville revealed that pH testing might not be as well understood as generally assumed. For example it seems to „feel wrong“ that – in contrast to most other analytical methods – the uncertainty for pH-testing may be highest in the middle of the range (pH=7).
This presentation will provide an overview of different pH-paper concepts like universal indicator papers, pH-test strips and indicator solutions along with the limits of application. Data will show, that it is well possible to reliably check sample conservation at pH 2 but that determining the pH of surface water at pH5-6 with good precision is often difficult. The influence of buffering will be discussed as well as the influence of interfering substances like protein, salt or surfactants will be addressed. The information will also be contributed to ASTM work item WK65181 „Standard practice for estimating pH to verify status of laboratory samples“.