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). Both combination electrodes and electrodes with a separate reference are suitable for use with the:

• EP353 pH & ISE isoPod with an e-corder and Chart software.
• EPU353 pH/ISE isoPod with USB for direct connection to a computer with Pod-Vu or third-party software.
• EPU452 Quad MF isoPod and EU168 Quad pH Amp to measure four pH values simultaneously, USB connection, Pod-Vu or third-party software.

We also supply a:

• ET042 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.
• ET060 Redox Electrode combination redox electrode (oxidation/reduction potential, ORP, electrode), featuring an easy to clean double junction and a platinum wire sensor.
• ET5733 pH 'Tuff Tip' electrode. Specially hardened glass bulb for use in student laboratories.
• ET044 Flow Thru pH electrode. Small internal volume; suitable for biological fluids.

Manufacturers of other pH electrodes include:

• Microelectrodes Inc, miniature, needle and flexible pH electrodes,
• Ionode, electrodes
• Innovative Instruments, all plastic electrodes from 0.4 mm tip diameter
• Analytical Sensors & Instruments, electrodes
• Metrohm meters and electrodes
• Mettler-Toledo meters and electrodes
• Phoenix Electrode Company
• Radiometer Analytical meters and electrodes
• Thermo Scientific 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, Many pH meter are suitable and they are often marketed as 'pH/ISE meters'. Often these electrodes require a separate reference electrode (usually a silver/silver chloride reference is suitable). 

eDAQ makes suitable amplifiers for these electrodes:

• EP353 pH & ISE isoPod with an e-corder and Chart software.
• EPU353 pH/ISE isoPod with USB for direct connection to a computer with Pod-Vu or third-party software.
• EPU452 Quad MF isoPod and EU168 Quad pH Amp to measure four pH values simultaneously, USB connection, Pod-Vu or third-party software.

Ion selective 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
• Ionode, chloride, bromide, and iodide
• Analytical Sensors & Instruments, wide variety of ions
• 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
• Radiometer Analytical meters and electrodes, wide variety of ions
• Thermo Scientific meters and electrodes, wide variety of ions

Combination and half cell electrodes

'Combination' pH electrodes and ISEs have an internal reference and can be directly connected to the BNC socket on the back of an eDAQ pH & ISE isoPod.

'Half cell' pH electrodes and ISEs must be used with a separate reference electrode. In this case the reference electrode is connected to the shell of the BNC socket on the back of an eDAQ pH & ISE isoPod, while the sensor electrode is connected to the center pin of the socket. You may find the following adaptors useful in connecting such electrodes to the isoPod:

• EC010 BNC T-piece
• EC009 BNC to 4 mm Banana Plug Adaptor

 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/ISE isoPods, 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.

DISCLAIMER: The appearance of a third party company or product on this page is for informational purposes and constitutes neither a recommendation nor an endorsement.