Surface water pH measurements — theory and practice

Reliable measurement of pH in dilute and poorly buffered aqueous solutions is problematic. Of particular concern are the errors introduced as a result of differences in ionic strengths between the calibration solutions and the test sample. Residual junction potentials, stream potentials, and the mod...

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Bibliographic Details
Published in:Science of the total environment 1987, Vol.64 (1), p.211-230
Main Authors: Jones, Claire, Williams, David R., Marsicano, Fabrizio
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Natural water pollution
Pollution
Rainwaters, run off water and others
Water treatment and pollution
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Summary:Reliable measurement of pH in dilute and poorly buffered aqueous solutions is problematic. Of particular concern are the errors introduced as a result of differences in ionic strengths between the calibration solutions and the test sample. Residual junction potentials, stream potentials, and the mode of construction of the liquid junction have been implicated. Errors of 0.2 pH units and higher are commonplace. The relative merits of the calibration of various electrode systems with standard buffer solutions, dilute buffers, and dilute hydrochloric acid solutions on the precision and accuracy of electrode responses were investigated. A simplified free diffusion junction reference electrode was developed and tested. The dilute acid calibration technique appears to be significantly more accurate than the calibration with buffers. The free diffusion junction in its present form does not lead to significant improvements in accuracy or reproducibility.
ISSN:0048-9697
1879-1026
DOI:10.1016/0048-9697(87)90132-X