Metrohm 817 Bioscan - Manual (Page 60)

4 Basic principles
817 Bioscan
52
The scan voltammogram is recorded in the scan mode. The measur-
ing potential is varied backwards and forwards between two given limits
while the analyte is passed through the measuring cell. The actual cur-
rent is then measured for each potential.
The substance under investigation can be dissolved in the IC eluent
used (e.g. 10 ppm Sucrose in 0.1 M NaOH) and a larger amount (e.g.
100 mL) pumped through the flow cell without a separation column
connected. If you work on trace concentrations of your analyte and
worry about contamination of your IC system you can still inject the
substance into the eluent using a large sample loop (> 500 µL). The
eluent should then be pumped at a very low flow rate (e.g. 0.05
mL/min).
In principal, same conditions should be used as they are needed for the
chromatographic separation (e.g. temperature, pH, eluent etc.).
Fig. 13 shows a schematic example of a scan:
Fig. 13: Example of a scan of a substance (A) with the additional repre-
sentation of the scan of the pure eluent (B)
When using metal electrodes as the working electrode, such as the
gold electrode used here, the reaction products formed by the am-
perometric detection during the scan method can form an interfering
layer on the electrode surface and influence the results. For this reason
a hydrodynamic voltammogram is to be preferred in such cases.
The following table summarizes the requirements for and the advan-
tages and disadvantages of these two methods.