CHAPTER 7 Optimisation of working potential
65
Fig. 29. The scanning voltammograms of 2,4-dimethylphenol (DMP), phenol
(P), 2-chlorophenol (2-CP) and 4-nitrophenol (NP).
The following procedure is used to obtain the voltammograms in Fig. 24 and
Fig. 29:
1. The column is removed from the LC system. The voltammogram is
recorded in the flow injection analysis (FIA) mode.
2. The pure compound is dissolved in (preferably) the HPLC buffer at a
concentration of ca. 10-100 µmol/l. When the analyte is already in solution,
it should be diluted in HPLC buffer until the desired concentration.
3. An injection loop of 100 µl is installed and the LC flow rate is set at 40
µl/min. The analyte plug will than be detected during approximately 2.5
minutes. The flow rate is lowered if more scanning time is needed.
4.
An initial run is started in the
DC mode
at a high potential to estimate the
required start and stop time of the scan after sample injection (Fig. 30). In
the scan mode, the scan is obtained at the flat top of an analyte plug.
The
analyte delivery should be constant. Fluctuations result in unreliable
results.
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