Thermo Fisher Scientific Ion Selective Electrodes Cyanide - Manual (Page 14)

Cyanide Electrode Instruction Manual
14
ions diffuse at different rates. When making measurements, it is important to remember that this
potential be the same when the reference is in the standardizing solution as well as in the sample
solution or the change in liquid junction potential will appear as an error in the measured electrode
potential.
The composition of the liquid junction filling solution in the reference electrode is most important.
The speed with which the positive and negative ions in the filling solution diffuse into the sample
should be equitransferent. No junction potential can result if the rate at which positive and negative
charge carried into the sample is equal.
TROUBLESHOOTING GUIDE
The goal of troubleshooting is the isolation of a problem through checking each of the system
components in turn: the meter, the plastic-ware, the electrodes, the standards and reagents, the
sample, and the technique.
Meter
The meter may be checked by following the check-out procedure in the instrument instruction
manual.
Plastic-ware
Clean plastic-ware is essential for good measurement. Be sure to wash the plastic-ware well with a
mild detergent and rinse very well with distilled or deionized water.
Electrodes
The electrodes may be checked by using the procedure found in the sections entitled
Electrode
Slope Check.
1. Be sure to use distilled or deionized water when following the procedures given in
Electrode Slope Check
.
2.
If the electrode fails to respond as expected, see the sections
Measuring Hints
and
Electrode Response
. Repeat the slope check.
3.
If the electrodes still fail to respond as expected, substitute another cyanide ion electrode
that is known to be in good working order for the questionable electrode. If the problem
persists and you are using an electrode pair, try the same routine with a working reference
electrode.
4.
If the problem persists, the reagent may be of poor quality, interferences in the sample may
be present or the technique may be faulty. See
Reagents, Sample,
and
Technique
sections below.
5.
If another electrode is not available for test purposes, or if the electrode in use is suspect,
review the instruction manual and be sure to:
- Clean and rinse the electrodes thoroughly.
- Prepare the electrodes properly.
- Use the proper filling solution.
- Adjust the pH and the ionic strength of the solution by the use of the proper ISA.