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What's the pH Electrode?

What's the pH Electrode?

2022-03-25

What’s the pH Electrode?

pH electrodes are constructed from a special composition glass that senses the hydrogen ion concentration. This glass is typically composed of alkali metal ions. The alkali metal ions of the glass and the hydrogen ions in the solution undergo an ion exchange reaction, generating a potential difference.

 

In a combination pH probe, the most widely used variety, there are actually two electrodes in one body. One portion is called the measuring pH electrode, the other the pH reference electrode. The potential generated at the junction site of the measuring portion is due to the free hydrogen ions present in the solution.

 

The potential of the reference portion is produced by the internal element in contact with the reference fill solution. This potential is always constant. In summary, the measuring pH electrode delivers a varying voltage and the reference electrode delivers a constant voltage to the meter.

 

Industrial pH Electrodes The voltage signal produced by the pH probe is a very small, high impedance signal. The input impedance requires that it be interfaced only with equipment with high impedance circuits.

 

pH electrodes in BOQU Instrument are available in a variety of styles for both laboratories, portable and industrial applications. All pH electrodes are composed of glass and are therefore subject to breakage.

 

pH Electrodes are designed to measure mostly aqueous media. They are not designed to be used in solvents, such as CCI4, which does not have any free hydrogen ions.

 

The pH electrode, due to the nature of its construction, needs to be kept moist at all times. In order to operate properly, glass needs to be hydrated.

 

Hydration is required for the ion exchange process to occur. If a pH sensor should become dry, it is best to place it in some tap water for a half-hour to condition the glass.

 

pH electrodes have junctions that allow the internal fill solution of the measuring electrode to leak out into the solution being measured. This junction can become clogged by particulates in the solution and can also facilitate poisoning by metal ions present in the solution.

 

If a clogged junction is suspected it is best to soak the sensor in some warm tap water to dissolve the material and clear the junction. pH testers should always be stored in a moistened condition. When not in use it is best to store the electrode in either buffer 4.0 or buffer 7.0. Even if an electrode is not used it still ages. On the shelf, the pH probe should last approximately a year if kept in a moistened condition.

 

pH Electrode demise can usually be characterized by a sluggish response, erratic readings, or a reading which will not change. When this occurs an electrode can no longer be calibrated. pH electrodes are fragile and have a limited lifespan. How long an electrode will last is determined by how well the probe is maintained and the pH application.

 

The harsher the system, the shorter the lifespan. For this reason, it is always a good idea to have a backup pH sensor on hand to avoid any system downtime.

 

pH sensor Calibration is also an important part of electrode maintenance. This assures not only that the electrode is behaving properly but that the system is operating correctly.

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