Thermo Fisher Scientific Ion Selective Electrodes Chloride - Manual (Page 17)

Instruction Manual Chloride Electrode
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.
Strongly acidic (pH = 0-2) and strongly basic (pH = 12-14) solutions are particularly troublesome
to measure. The high mobility of hydrogen and hydroxide ions in samples make it impossible to
mask their effect on the junction potential with any concentration of an equitransferent salt. One
must either calibrate the electrodes in the same pH range as the sample or use a known increment
method for ion measurement.
TROUBLESHOOTING GUIDE
The goal of troubleshooting is the isolation of a problem through checking each of the system
components in turn: the meter, the glassware, 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.
Glassware
Clean glassware is essential for good measurement. Be sure to wash the glassware well with a mild
detergent and rinse very well with distilled or deionized water. Clean glassware will drain without
leaving water droplets behind.
Electrodes
The electrode 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 chloride 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
Standards and 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.
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