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

Instruction Manual Nitrate Ion Electrode
12
their effect on the junction potential with any concentration of equitransferent salt. One must either
calibrate the electrodes in the same pH range as the sample or use a known incremental 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 plastic-ware, the electrodes, the standards & 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 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 section
Measuring Hints
. Repeat the slope
check.
3.
If the electrodes still fail to respond as expected, substitute another nitrate 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 standards or 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.
- Use the proper filling solution.
- Adjust the pH and the ionic strength of the solution by the use of the proper ISA.
- Measure correctly and accurately.
- Review TROUBLESHOOTING HINTS .
Standards and Reagents
Whenever problems arise with the measuring procedure that has been used successfully in the past, be
sure to check the standard and reagent solutions. If in doubt about the credibility of any of the
solutions, prepare them again. Errors may result from contamination of the ISA, incorrect dilution of
standards, poor quality distilled/deionized water, or a simple mathematical miscalculation.