11. If you are sure all cell leads are connected, turn the CELL switch to ON.
12. When the electrode is first turned on, you should see a large current signal. This is the
“charging and transient background current” and will gradually decay to a steady-state
background. You can gradually increase the current amplification (go to smaller
RANGE numbers) on the RANGE switch. You will see a temporary increase in signal
with each change in RANGE. Go only as far down in RANGE as you need for the assay
at hand. There is no benefit in placing the detector on the lowest possible setting when
this is not needed.
13. When the background stabilizes, turn the AUTO ZERO on and momentarily push the tog-
gle switch to the ZERO position to rezero the output.
The system is now ready for standards and samples.
Shutdown and Storage
If the detector will be used every day or every few days, leave it on. A bacteria-resistant mo-
bile phase (such as monochloroacetic acid) may be recycled when the system is not in use.
Mobile phases that promote bacterial growth (acetates, citrates, phosphates) should not be
recycled, and should be changed every few days (generally every two days). Pump these at
low flow rates when the system is not in use.
If the detector will be unused for more than 2 or 3 days, the controller should be turned off
and the electrodes stored properly. By following these recommended procedures, consider-
able extension of electrode, column, and system lifetime will be gained.
1.
Turn the CELL switch to STBY position.
2.
Pump about 50 mL 40:60 acetonitrile:water through the system. This will remove corro-
sive mobile-phase salts from the plumbing and the column. Turn off the pumping sys-
tem.
3.
Turn off the main POWER to controller.
4.
Disconnect electrodes (thin-layer cell and reference). Store the reference electrode as rec-
ommended in the separate electrode manual shipped with the instrument. Rinse off the
working-electrode block with deionized water, air dry, and store it in the plastic box
used in shipping. Clean and dry the auxiliary-electrode block, and plug the column
ends.
Section 4. Operating the Electrochemical Detector
33
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