Ion-Selective Electrode Issues and What to Check

Cole-Parmer® Combination Ion Selective ElectrodesCole-Parmer® Combination Ion Selective Electrodes

Ion-selective electrodes are used in end point determinations in potentiometric titrations or for continuous monitoring of specific ions. But what happens when you encounter issues? Here are five problems and possible solutions:

Cole-Parmer® Combination Ion Selective Electrodes

  1. Slow response. Check to see if the electrode was stored in the wrong solution or if it may have been poisoned by the sample.
  2. Noisy response. Is the controller grounded? Perhaps there is an air bubble on the surface of the electrode? If not, is the electrode plugged into the controller properly? Is there enough fill solution left in reference? Is the electrode in the sample solution?
  3. Out-of-range reading. Perhaps the electrode is not plugged into the controller properly or there is an air bubble on the surface of the electrode. Check to see if there is enough fill solution left in reference and if the electrode is in the sample solution.
  4. Measurements are not reproducible. Determine if there is sample carryover or sample interferences. Or, the reference electrode junction may be contaminated.
  5. Readings continuously change. Is there excessive leaking at the reference electrode junction or is it clogged? Was the sensing membrane poisoned by the sample? Is the sample too concentrated or are there temperature fluctuations? Does the sensing membrane need conditioning?

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