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Chapter 7 Optimization of working potential 75
Fig. 31. Example of the mass spectra of 10

mol/L amodiaquine oxidized
at a glassy carbon working electrode, at a scan speed of 10 mV/s.
Optimization using a voltammogram
Sometimes, when interfering peaks appear in the chromatogram, it is pos-
sible to optimize the method with regard to selectivity. If the interfering
compound has a higher oxidation potential, a working potential is chosen
that gives the best selectivity, i.e. the largest difference in peak height. In
the example of Fig. 32 the selectivity for compound X is improved consid-
erably by decreasing the potential to E
2
or E
1
. Obviously, if compound Y is
the compound of interest, optimization of selectivity in this way is not pos-
sible and the chromatography has to be optimized.
Electrochemical detection differs from most other LC detection methods in
that a reaction takes place in the detection cell. Due to reaction kinetics an
increased temperature speeds up the oxidation/reduction reaction. How-
ever, this not only holds for the analyte but also for the background current
and possible interferences. An elevated temperature will therefore not au-