pH and Ion Selective Electrodes
pH electrodes
The vast majority of pH electrodes comprise a thin
glass bulb as the measuring electrode. They also require a reference
electrode which may be incorporated into the measuring electrode (which
is then known as a combination electrode). These are suitable for use
with the:
- pH Amp suitable for combination electrodes, or electrodes with a separate reference
- pH Pod suitable for combination electrodes only.
We also supply the:
- pH Electrode combination 'double junction' design resists fouling and is easily cleaned - especially good for biological samples. Supplied with guarded tip for general purpose use, and micro tip for use with small samples (about 0.5 mL or more). Good quality laboratory electrode.
- pH 'TuffTip' electrode. Specially hardened glass bulb for use in student laboratories
Manufacturers of other pH electrodes include:
- Microelectrodes Inc, miniature, needle and flexible pH electrodes,
- DiamondGeneral, needle and flexible electrode
- Ionode, electrodes
- Innovative Instruments, all plastic electrodes from 0.4 mm tip diameter
- Metrohm meters and electrodes
- Mettler-Toledo meters and electrodes
- Phoenix Electrode Company
- RadiometerAnalytical meters and electrodes
- ThermoOrion meters and electrodes
Ion Selective electrodes
Although there are several methods of construction most of these electrodes work by changing their potential (voltage) in response to changes in ionic concentration. They usually require a pH meter, and normally they require a separate reference electrode (usually a silver/silver chloride reference is suitable), and so are suitable for use with the eDAQ pH Amp. Make sure you have a combination-type electrode if you want to use it with an eDAQ pH Pod.Electrodes are available for many ionic species including sodium, potassium, calcium, chloride, nitrate, sulfide, etc, and are available from:
- Microelectrodes Inc miniature, flow thru, and needle electrodes for sodium, potassium, and calcium
- DiamondGeneral, miniature sodium electrode
- Ionode, chloride, bromide, and iodide
- Metrohm meters and electrodes, wide variety of ions
- Mettler-Toledo meters and electrodes
- NICO Scientific mono and combination ion selective electrodes, flow through configurations.
- Phoenix Electrode Company, wide variety of ions
- RadiometerAnalytical meters and electrodes, wide variety of ions
- ThermoOrion meters and electrodes, wide variety of ions
pHFET and ISFET electrodes
Occasionally you may come across pHFET (pH field effect transistor) and ISFET (ion selective field effect transistor) electrodes. In general these electrodes require a specially designed meter (they will NOT work with the pH Amp or pH Pod, or most other standard pH meters). Usually the pHFET or ISFET electrode and meter will be obtained from the same manufacturer - you will need to check the meter specification to see is an analog signal is provided that is compatible with e-corder.- Sentron, TitanX meter and electrodes
Fibre Optic probes
It is possible to monitor pH by the use of fibre optic technology. The tip of the fibre optic probe is coated in a special dye which changes colour in a known way with changes in pH. A special meter must be used with the probe and both are usually bought from the same manufacturer.
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