All of the MI-800-XXX Series combination electrodes are ready to use.  Carefully unwind the green tape and remove the probe from the protective glass tube.  The white sleeve which covers the fill hole should be moved down the glass barrel to ventilate the reference chamber and replaced after use.

A separate reference electrode is not required.

B.  Single Electrodes

All of the MI-800-XXX Series single electrodes are ready to use.  Carefully unwind the green tape and remove the probe from the protective glass tube (if appropriate).

A separate reference electrode is required.

Calibration

Since ORP is a characteristic measure of redox equilibrium, it should not require standardization or calibration.  However, it is desirable to check the electrode for proper operation and electrode poisoning.  Solutions of known potential can be made by saturating pH buffers with quinhydrone using the following procedure:

1.  Place 20 ml of pH 4 buffer into one beaker and 20 ml of pH 7 buffer into a second beaker.  Saturate each buffer with quinhydrone.  Quinhydrone is not readily soluble in the buffers so a few crystals stirred into the buffer is sufficient.  The resultant solution will be amber colored.  Saturated quinhydrone buffers need to made up fresh each time you want to check the electrode.

2.  Place the tip of the MI-800-XXX Series ORP Electrode (with an appropriate reference electrode such as our MI-401 / MI-402 if it is not a combination electrode) into the first beaker containing the quinhydrone/buffer solution.  Record the millivolt reading and the temperature of the solution.

3.  Rinse the electrode with distilled water and place it into the second beaker.  Record the millivolt reading and the temperature of the solution.

4.  The measured potentials will generally be within 10 mv of the theoretical values listed below.

Handling

For combination electrodes:  When necessary, the outer reference chamber of the electrode can be refilled using the 3 M KCl dispensing bottle provided with the probe.  This may be a slow process, but introducing syringe needles or plastic tubes into the fill hole generally results in breaking the inner glass capillary, rendering the probe inoperative.

Care must be taken that the delicate inner glass capillary is not cracked when refilling.  Do not apply pressure against the inner glass capillary tube.

Cleaning

Cleaning of the electrode can be accomplished by immersing the tip of the electrode into a chromic/sulfuric acid cleaning solution or nitric acid for a couple of minutes to remove the contaminants.  Rinsing the electrode thoroughly after cleaning is required.

Storing

Long-term (over 2 weeks):  Return the electrode to its original container and prepare it in the same condition in which you received it.  For combination type electrodes, this means simply moistening the sponge located in the bottom of the protective glass tube with distilled water.

Short-term:  The electrode can be left in a 0.1 M KCl solution.