pH Measurement Principles and Best Measurement Practices

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pH measurement is based on activity of H+ ion . Sample containing more of H+ ion is acidic and if the OH- is more than the sample becomes alkaline. Pls refer to chart below.

pH Chart

Glass bulb - pH sensor develops a voltage across its permeable membrane which is related to activity of H+ ion inside and outside of its membrane. pH electrode works on the principal of Nernst equation:-

•E = E0+ 2.303 R T log [ A

nF

Typical pH measuring device

Factors influences pH measurements are :-

a) Temperature - pH measurement is temp sensitive.

b) Reference electrode/its internal fill solution. Reference electrode is also known as

diaphragm, creates electrical contact between the reference and solution much like

reference electrolyte( fill solution)

c) Sample conditions/its type

d) Continuous stirring

e) Proper maintenance including cleaning & storage of sensor.

Lab and Process pH electrodes.

pH electrodes are manufactured with various offerings like Epoxy body, refillable, non refillable, same offerings are in case of glass body pH sensors. Some manufacturers offer with temp sensor built in. In this case one does not have to use temp. probe separately. pH electrodes are offered for Lab, in field as well for Industrial applications covering wide spectrum of its usage from Ultra pure to most dirty critical samples. These process electrodes work in line as well as at line sample streams.

Lab pH electrode Process pH sensor