ELIT Brand Electrochemical Sensors and Computer-based Instrumentation.
Innovative technology at highly competitive prices.


Ion Selective Electrodes, Reference Electrodes, Electrode Heads, Mini ISEs
pH Electrodes, ORP Electrodes, D.O. Electrodes, Conductivity Cells, Temperature Sensors

At the heart of ELIT Electrochemical Measuring Systems

Want to Learn More About Ion Selective Electrodes ?

Scroll down to see introductory text and diagrams.

Also see our comprehensive
Information and Education pages
Click Picture for enlargement & Explanation

Use ELIT plug-in all-solid-state Ion-Selective Electrodes with our 8mm Reference Electrodes and dual Electrode Heads for a practical and cost-effective alternative to conventional combination electrodes.

Click any ion name below for details of the method for measuring
the ion concentration in aqueous solutions and electrode specifications.

NH4+ (NH3)

Br -



















Click Here for a summary table of specifications for all ELIT Ion Selective Electrodes.

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The main advantages of Ion Selective Electrodes are:

  • Inexpensive and simple to use, in the field as well as the laboratory.

  • Wide concentration range - typically from less than one to several thousand parts per million.

  • Unaffected by sample colour or turbidity.

  • Ideal for monitoring environmental pollution or water quality etc. - where the operator simply wants to be sure that a certain ion is below a particular threshold value, or where only the order of magnitude may be required.

  • Ideal for long term monitoring of changes in ion concentration (e.g. for measuring rates of reaction or nutrient uptake etc.) - particularly when used in conjunction with an ELIT Ion Analyser (electrode-computer Interface), to link electrodes directly to a desk-top or lap-top PC.

Note: ISEs are not generally used as precise analytical tools. Nevertheless, routine, rapid measurements can usually be expected to have an accuracy of around � 10% and with careful analysis under ideal conditions some can achieve an accuracy and precision of better than � 2% (1-sigma) - see chapter on Accuracy and Precision in our Beginners Guide to ISE measurements.

Ion-Selective Electrodes measure the activity (or effective concentration) of ions in a solution, rather than the actual concentration; the activity is always less than the concentration because of
inter-ionic interactions and the difference between concentration and activity increases as the
Ionic Strength increases. (Note that the Ionic Strength is a measure of the total effect of all the ions in the solution, both positive and negative, of the measured ion as well as any other contaminants.) In practice, however, the measured activity is not significantly different from the concentration in dilute solutions (i.e. with total Ionic Strength of less than about 0.01 Molar for monovalent ions and 0.001 Molar for divalent ions), and steps can be taken to minimize the difference at higher concentrations (e.g. by adding Ionic Strength Adjustment Buffer, diluting the sample, or, most effectively, by using Standard Addition or Sample Addition techniques).

Other Essential (included) Components of an ELIT Ion Analyser:

Optional Extras:
  • Electrode stand with articulated arm - or a laboratory clamp stand may suffice.
  • Magnetic stirrer.

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ELIT ion selective electrodes

These electrodes have a solid state membrane and a solid internal contact - i.e. they do not contain any liquid or gel electrolytes. Their characteristics and advantages are:
    All solid-state construction.
    Simple gold-plated plug-in connectors.
    Robust and Durable.
    Easy to handle.
    Stable electrochemical potential.
    Fast response time.
    Function in any position.
    No leaking of fluids.
    Long shelf life and working life.
    Can be stored and transported below 0�C.

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The ELIT Electrode Head System

A practical and cost effective way to combine Ion Selective and Reference Electrodes

ELIT Electrode Heads are manufactured from a robust plastic material and fitted with low noise cables and connectors which are compatible with any standard mV/pH/ion meter.
The standard version, for use with an ELIT Ion Analyser / Computer Interface, has a BNC plug, but DIN, US or S7 versions are available if required.
The sockets on the head and the pins on the plug-in electrodes are gold plated to assure good contact.

Advantages of this 'electrode combination' over conventional combination electrodes:

  • Use of one reference electrode for several ion-selective electrodes.
  • Replacement of a defective reference system without sacrificing the more expensive ISE.
  • Expensive low-noise cable and connector are attached to the re-usable head and do not need to be replaced if the ISE becomes defective.
  • ISE is less expensive than conventional types which have the cable & connectors permanently attached.
  • ISE can be stored dry and the RE wet.
  • Increased distance between the ISE and the reference system reduces electrical interference and increases the precision of measurement.

   Six types of ELIT Heads are currently available:
  • Mono Head for inserting one ELIT ISE or Redox electrode, for use with a conventional reference electrode
    (or a combination pH electrode).

  • Mono Head with 2mm plug connector for using one ELIT reference electrode with any ISE which is not compatible with an ELIT head.

  • Dual Head for use as an electrode combination: one ISE or Redox and one ELIT reference electrode.

  • Triple, Four or Seven-electrode head for connecting up to six sensors with one reference, for use in simultaneous multi-component analysis using an ELIT four or eight-channel Ion Analyser / computer interface.

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Nico2000 Ltd can also supply Mini ISEs with a range of tube diameters and lengths for special applications. These electrodes are fitted with a simple wire connector to allow maximum flexibilty for connecting to other equipment and are not suitable for use with the ELIT electrode head system.

  • Diameter range 6 to 12 mm.
  • Length 20 to 130 mm.
  • The attached wire can be from 2 to 5 cm in length and must be soldered to a screened cable for connecting to an ion meter or computer interface. Due to the high resistance of an ISE (>20 MOhm), the maximum length of this screened cable should not exceed 3 metres.
  • Delivery 7 weeks from receipt of order.

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    ELIT Reference Electrodes

    These electrodes are of a robust design with 8mm diameter PVC bodies and gel electrolytes. Made to be compatible with ELIT ISEs, they must also be connected to the measuring system via an ELIT Electrode Head.
    Leak rates are very low and the electrolytes do not require replacing, therefore these electrodes are manufactured as maintenance-free sealed units which should have an active (or shelf) life of several years - provided that the porous frit is kept moist by immersing in a solution with the same composition as the gel electrolyte when not in use. This is normally done by keeping a few drops of solution in the protective black plastic cap which must always be replaced when the electrode is not in use.

    Two types of Reference electrodes are available.
    (Click on code number for operating instructions - pdf files).

    • Single Junction potassium/silver chloride.
      (code number ELIT 001n ) This has traditionally been the preferred option because the simple design allows fast and reproducible stabilisation - but it is only suitable for Ba, Ca, F, NO2, Na, ClO4) due the possibility of interference from the internal electrolyte on other ionophores. However, it must be noted that the introduction of gel electrolytes means that this risk is very much reduced and some users prefer to use this for all ions - particularly for quick measurements or in free-flowing open systems

    • Double Junction lithium acetate ( 003n) - suitable for all Ion Selective Electrodes.
      The double junction Reference was developed to avoid contamination of samples from the concentrated KCl internal electrolyte by introducing a bridging solution which is less concentrated and does not contain any ions which would interfere with the sample ISE. Traditionally several different bridging solutions have been used for different ions but Nico2000 Ltd recommend only Lithium Acetate because neither ion interferes with any ISE and both have virtually the same mobility (equi-transferrent solution) which minimises the liquid junction potential and stabilises almost as quickly as the single junction.

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    ELIT pH Electrodes

    ELIT pH electrodes are basic combination electrodes with glass membranes and AgCl reference systems. They are fitted with cable and BNC connector for connection to any type of measuring system and do not require an ELIT electrode head connector or separate reference electrode.

    pH measuring range: 0 - 14. Dimensions: 120mm long by 12mm diameter.

    ELIT P11 has a glass body, refillable liquid electrolyte and annular ceramic junction.
    Temp Range 0 - 80�C.

    ELIT P2011 is a low-maintenance version with an epoxy body, non-refillable gel electrolyte and porous teflon junction.
    Temp Range 0 - 60�C.

    For more details please see individual Operating Instructions: PH2011

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    ELIT Redox Electrodes
    also known as ORP (Oxidation-Reduction Potential)

    Three types are available. All are Cost effective Combination Electrodes fitted with 1 m Cable and BNC Connector. Dimensions 12 x 120 mm. Temperature Range 0�C to 80�C. Suitable for Laboratory, Field and light Industrial Applications where the electrode is not submersed or under pressure.

    1) Type ORP-31C

    Platinum-Rod ORP Electrode for General Applications. Has Gel-filled Plastic Body, Protective Skirt, Single Junction Ag/AgCl Gel Reference with Fiber/Pellon liquid junction.

    2) Type ORP-32C

    For More Demanding Applications. Platinum-Band (wrapped around a glass dome) ORP Electrode with Gel-filled Plastic Body, Protective Skirt, Single Junction Ag/AgCl Gel Reference with Fiber/Pellon liquid junction.

    3) Type ORP-33C

    For High Precision Applications. Platinum-Band (wrapped around a glass dome) ORP Electrode with Re-fillable Glass Body, Single Junction Ag/AgCl Solution Reference with annular Ceramic liquid junction.

    To prevent the electrodes from drying-out they must be stored in an O-Ring sealed bottle filled with Soaking solution.

    For more details please see individual Operating Instructions:
    ORP-31C , ORP-32C , ORP-33C

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    ELIT Dissolved Oxygen Electrodes (DO)

    Click Elit Order Code for more details: Galvanic DO Sensor, DO-003

    ELIT Conductivity Cells

    Cost-effective Conductivity Cells for General Applications: Lab, Field and light Industrial use, where the cells are not submerged or under pressure.

    Five versions are available:

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    CCR,   Nico2000 Ltd,  Last Update: 02 May 2017