23
HTEC-500
11-2. Working Electrode
There are six types of working electrodes. Please select the working electrode based on the Eicom
technical information. Each application/technical note provides a guide for the working electrode
selection. The gasket (GS-25) has a 25 micron meter thickness and this allows for higher sensitivity.
However, coupling this with other electrodes, other than the WE-3G, induces higher noise.
Working Electrode
Graphite
Platinum
Glassy Carbon
Pure Graphite
Gold
Silver
Code
WE-3G
WE-PT
WE-GC
WE-PG
WE-AU
WE-AG
Gasket
GS-25
GS-25P for ø2.0 mm
AC-GEL column
and E-GEL.
GS-50P for ø4.6 mm
AC-GEL column.
GS-50
GS-50
GS-50
GS-50
Description
Standard.
Methanol in mobile phase is
less than 35%.
For acetylcholine analysis or
online glutamate analysis
only. (for OPA-Amino Acids,
use graphite)
OPA-GABA analysis at 50%
methanol in mobile phase.
High applied voltage
analyses.
Thiol analyses only.
Iodine analyses.
11-3. Applied Potential
Please refer to the Eicom technical information to determine the best applied potential for your target
substance.
Applied potential is set in the following way:
• Push the display key until the ECD screen appears.
• Push the edit key until ‘ ’ is displayed in front of applied potential.
• Input the target potential with the number keys (+/– is set with the select key).
• Push the edit key again to fix the input potential.
The potential set here is called the setting applied potential. The actual applied potential can be
different from the setting potential in the following cases:
• If the inside of the reference electrode is dry and the electrical resistance increases. In this case, the
reference electrode should be exchanged with a new one.
• If the surface of the reference electrode is dirty. In this case, clean its surface (See Fig. 23, next page).
Substances that are detected by an ECD (at a constant potential) are oxidized at the surface of a
working electrode. The oxidation potential differs according to the substance. Most substances are
detected under a higher applied potential. If the potential is higher than the appropriate value,
impurities will be detected and disturb the detection of the target substance.
Oxidation-reduction potential varies with the pH of the mobile phase. When the pH of the mobile phase
increases by 1, the
actual
applied potential decreases by 60 mV.
