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4.12 Shift in Ag/AgCl Reference Potential
•
Faulty reference electrode
A shift in reference potential causes a shift in the effective potential applied to
the working electrode. For example, an applied potential of 0.1V, using an
electrode with a shift of 50 mV, is equivalent to an applied potential of 0.15V
for a new reference electrode with no shift.
Following the steps below, measure the Ag/AgCl reference electrode potential
shift by comparing it to the potential shift of a new electrode. You should
always keep a spare reference electrode (P/N 046333) on hand for this
purpose.
Using a Digital Voltmeter
1. If you have a digital voltmeter, connect the voltmeter's test probes to
the center sockets of the standard and test reference electrodes.
2. Immerse both reference electrodes in a solution of 0.1M KCl.
3. Read the potential difference (in mV) between the standard and test
electrodes. If it is greater than 50 mV, try regenerating the electrode
by soaking it in a solution of 1M KCl plus 1M HCl. If this does not
reduce the potential shift, replace the electrode.
Using the Dionex ED50A Electronics
If you do not have a digital voltmeter, follow this procedure:
1. Turn off the cell.
2. Remove the reference electrode from the cell body, unplug the
electrode, and rinse it in deionized water. See Figure B-3 for cell
assembly drawings.
3. Locate the reference electrode connector (J2) on the cell pre-amp
board (see Figure 5-7). Short the two pins of the connector together,
using a short piece of wire or a metal clip. Do not allow the wire or
metal clip to contact the cell body or any other conductor.
4. Select
"pH 7 Calibration Complete" message appears, remove the wire or
clip from J2.
Doc. 065551-01 6/13
on the
CAL
pH CALIBRATION
4 • Troubleshooting
screen and press
Enter
. When the
4-7
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