Knauer Azura ECD 2.1, Instructions Manual

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62 Optimization of the working potential
AZURA® Detector ECD 2.1 Instructions, V6685
Fig. 51 Scan (cycle: half) of a 20 µM Serotonin in mobile phase at a glassy
carbon working electrode. Scan speed 20 mV/s.
The following procedure is advised to record scanning voltammogram of
analytes:
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Use a voltammetry set-up as shown in Fig. 57 (preferably) in combi-
nation with the Elite Dialogue software and a syringe pump for direct
infusion of analyte in the flow cell.
If Dialogue is not used, connect an A/D converter to the analog out-
put of the detector to record the cell current. Set the A/D converter
sampling rate to 1 Hz. This is the same frequency as the voltage
steps during the scan. If a higher sampling frequency is chosen a
typical stepwise pattern may appear. Note that with such set-up only
‘I versus t’ curves can be obtained.
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Prepare a solution of the pure compound dissolved in (preferably) the
HPLC buffer with a concentration in the range of 10-100 µM.
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Set the lower (E1) and upper potential (E2), the scan rate (Spd), range
and scan cycle in the ‘SCAN SETUP’ menu or under the ‘detector’ tab
in Dialogue.
Typical scan settings to start with: E1 0 mV, E2 1000 mV, scan speed
10 mV/s, range 5 µA/V. Optimize the settings if required for your speci-
fic compounds.
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Prime a 1 mL glass syringe with analyte solution and install it in the
syringe holder of the pump.
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Program the syringe diameter and flow rate in the syring pump set-
tings menu. In case a syringe pump is used which can be controlled
in Dialogue the settings can be programmed under the ‘S pump’ tab.
A typical flow rate to start with is 10 µL/min. Optimize the flow rate if
required during the scan experiments.
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Start the syringe pump and before scanning assure that the flow cell is
sufficiently primed with analyte solution.