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pH measurement is usually done with the use of a combination electrode. The combination electrode is an electrode system formed by a glass sensing half-cell and an internal reference half-cell. As the reference junction acts as the medium of conductor between the reference electrolyte and the sample to be measured, it must allow free movement of electrons through the junction and into the sample.

A potential develops on the membrane surface when a pH electrode comes into contact with a sample and its value varies with the pH of the sample. This variation in potential is measured in mV by a meter and is converted to direct pH values.

The selection of a suitable electrode depends on the types of application.

Eutech Instruments has a comprehensive range of electrodes for laboratory and process applications.

Electrode selection criteria includes:

1. Electrode Body - Glass body is more resistant to corrosive materials and solvents and withstands high temperatures beyond 100 C. In contrast, plastic body electrodes are not recommended for temperatures above 80 C but are more durable for rugged use. As such the glass body electrode is most suited for routine pH measurements for accuracy, high temperature and ease of cleaning while the plastic body electrode is a good choice for more rugged applications.

2. Reference Construction - Refillable electrodes allows replenishment of reference electrolyte for repeated usage. Conversely a sealed electrode usually has gel reference electrolyte and replacement of electrode is necessary when there is contamination.
The reproducibility and potential stability of the calomel reference electrode is superior to those of the Ag/AgCl electrode at a constant and relatively low temperature. The calomel reference electrode has a temperature limitation of 80 C and is recommended for clinical measurements and samples containing protein, tris buffers and high purity water applications. The Ag/AgCl reference electrode is good for general purpose applications with a wide temperature range of -5 to 110 C.

3. Junction - The single junction electrode is ideal for general purpose applications while the double junction electrode is suitable for use with biological samples and can be used to replace calomel reference electrodes.

4. Applications - General purpose electrodes are economical combination electrodes ideal for general-purpose applications in the lab or field. They have the impact-resistant qualities of a plastic body. Electrodes provide a fast, stable response and are ideal for prolonged use. Most electrodes come in different lengths and diameters for specific applications. Refillable electrode extends the useful life and is ideal for measurement of viscous samples and pH samples with low conductivity.

Electrodes (Size: 110 mm (L) x 12 mm (D) are supplied with 1-metre cable and BNC connector and can withstand temperatures up to 80 C.

Please select a product range below:

Laboratory Electrodes
Process Electrodes


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