Metrohm 757 VA Computrace - Manual (Page 57)

3.4 General operation sequence
757 VA Computrace – Software
47
Purging
Purging means saturation of the analysis solution with an inert
gas and is used to remove the electrochemically active and
hence interfering oxygen. With the inert gas flow rate of ca. 20 l/h
set on the 757 VA Computrace Stand, a purging time of ca. 3...5
min usually suffices. For an effective purging of the analysis solu-
tion, the solution should also be stirred.
Initial purge time (s) [ 0...80600 s ; 300 s ]
Time of inert gas purging before the first measurement of
the sample solution.
Conditioning of solid state electrodes
Solid state electrodes (particularly carbon electrodes) can be
electrochemically regenerated by a freely selectable number of
conditioning cycles. For every cycle, the voltage is changed at a
sweep rate of 1 V/s to the
end potential and then decreased at the
same rate back to the start potential .
Start potential (V) [ -5...+5 V ; -1.2 V ]
Start voltage for the cyclic conditioning sweep.
End potential (V) [ -5...+5 V ; -0.1 V ]
Final voltage for the cyclic conditioning sweep.
No. of cycles [ 0...X ; 0 ]
Number of conditioning cycles.
Pretreatment
The pretreatment of the electrode before starting a sweep can
consist of the following three steps:
• The cleaning potential can be used to clean solid state
electrodes with a stationary surface which are contami-
nated with the products of the electrode redox processes.
• The deposition potential is used for electrochemical en-
richment in stripping voltammetry.