Products > Electrodes
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
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.
- 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.
- 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
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.
a product range below: