Ionode IJ ORP - Manual (Page 2)

Calibration
Unlike pH electrodes, ORP electrodes do not require
asymmetry potential and slope correction. However, an
offset can develop if the sensor tip or the reference junction
becomes contaminated. To assure correct operation, check
ORP electrodes with an ORP standard as detailed below.
Checking ORP Electrodes IJ64/IJAu
• Set pH/mV meter to mV and connect electrode.
• Place the electrode in a stirred ORP standard, allow time to
stabilise, and observe the reading.
• Note mV reading and compare to the correct value.
• If reading is not within ±20mV of the correct value, clean
the electrode, replenish the electrolyte and repeat the procedure.
• Rinse the electrode in distilled water before use.
ORP Standards
We recommend the use of either Light’s (476mV @25 oC ) or
Zobell’s (229mV @25 oC ) solution for checking ORP electrodes.
Checking Silver Electrode
• A simple procedure for checking the silver electrode is
to check the mV potentials in two (2) chloride standards a
decade apart in concentration.
• The more dilute solution should read higher (more +ve mV)
than the more concentrated one.
• Rinse in distilled water before use.
Helpful Hints
• ORP standards are generally unstable—measure samples
on site whenever possible.
• Most ORP reactions are not reversible—solutions should be
stirred for best results.
• Clean the sensing tip regularly.
• Allow adequate time for stabilisation.
• Always use fresh standards.
• DO NOT leave IJAg in the titrated solution after silver
nitrate (argentimetric) titrations.
• Acidify samples with dilute nitric acid before argentimetric
titrations (pH should be around 2-3).
• Expected endpoint for argentimetric chloride titration is
approximately 280mV.
Maintenance
• When not in use (short term), store the electrode in
2-3M KCl.
• Replace sleeve electrolyte when necessary.
The frequency of this is best determined by
experience, however this should be done more often
when measuring contaminated samples.
• For long term storage, remove and clean the
sleeve. Replace the sleeve (without electrolyte) and
attach the wetting cap.
• From time to time, excess AgCl deposits should
be removed from the silver rod (IJAg) by wiping
with a tissue. The rod can be cleaned with 0.1M nitric
acid or dilute ammonia.
Cleaning
Cleanliness of the sensor and junction is critical for
accurate measurement. Drift and long response
times are often due to an unclean sensor/junction.
Remove the sleeve, clean the sensor wire, ground
glass stem and sleeve periodically by the following
methods. DO NOT use abrasive materials.
Method One: Alkaline samples and scale: Soak
membrane in 1M HCl for an hour. Wash well with
water and condition in 20% KCl before use.
Method Two: Grease and oil: Wipe the membrane
and ground stem with cotton or tissue soaked in
acetone followed by methylated spirits. Wash with
distilled water before use.
Method Three: Plated metals: Metals such as
copper and zinc can plate onto the Pt or Au tip.
These can be removed by soaking in dilute (approx
0.1M) nitric acid for 15-20 minutes, followed by soaking
in 2-3M KCl before use.
www.ionode.com.au
Introduction
This guide contains the basic information for correct use
and maintenance of your new ORP/Metal electrode.
A more comprehensive manual is available for download
from www.ionode.com.au
Preparation
IJ series electrodes are shipped without sleeve electrolyte,
and must be fi lled prior to use. To fi ll, hold the electrode
by the sleeve and gently ease off the rubber wetting cap.
Prepare as follows:
2. Fill the annular space with gel
or electrolyte to approximately
half to three quarter full.
(use potassium nitrate in IJAg).
1. 2.
1. Invert the electrode. Hold the
electrode just below the sleeve
and with careful rotation and
pulling along the axis of the
electrode, remove the sleeve.
DO NOT BEND.
3. Slide the sleeve back onto the electrode ensuring the black
O-ring is well seated within the electrode body. Do not exert
sideways force. Any excess electrolyte will be expelled from the
end of the electrode through the ground junction. Ensure there
are no air bubbles in the sleeve.Wash off any excess electrolyte
and store in 2-3M KCl before use.
3.