Metrohm 746 VA Trace Analyzer - Manual (Page 381)

5.7 Program instructions
746 VA Trace Analyzer / 747 VA Stand
5-230
DPMODE Page: O, S Stand: M, A Abbreviation: DP
Instructions t/s Main parameters Auxiliary parameters
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## .. DPMODE ..... U.ampl ........mV t.meas ........ms
t.step ........s t.pulse ........ms
Function Measurement mode for differential pulse voltammetry.
Application Differential pulse voltammetry is the most universal and frequently used
voltammetric determination method. It is equally well suited for irreversi-
ble and reversible systems and offers a high sensitivity.
Parameter Range; Default value / Meaning
U.ampl -100...-1,1...100 mV; 50 mV
Pulse amplitude
Pulse amplitude of the voltage pulse superimposed on the direct
voltage.
t.step 0.05...9.9 s; 0.3 s
Time interval for voltage step
Time interval after which the voltage in the sweep is increased or
decreased by the amount
U.step .
The following condition applies to the definition of t.step :
t.step > t.pulse + t.meas + t.drop + 30 ms
t.meas 1.0...32.0 ms; 20/16.6 ms for 50/60 Hz
Measurement time
Time during which the current is measured. Measurement is performed
at the end of the time interval
t.step immediately before the pulse
start and at the end of the pulse.
t.pulse 1.0...330.0 ms; 40/33 ms for 50/60 Hz
Pulse time
Time interval during which a voltage pulse is superimposed on the
direct voltage.
The following condition applies to the definition of t.pulse :
t.pulse > t.meas + 2 ms
Description With the DPMODE measurement mode for differential pulse voltammetry,
square-wave pulses with a small, constant amplitude are superimposed
on a stepwise rising direct voltage ramp. The current I is measured as a
function of the voltage U immediately before the pulse and at the end of
the pulse. The nature of the measurement is shown below using the
SMDE as an example.
From the differences between the two current measurements, peak-
shaped curves are obtained which can be evaluated using the baselines
of type
linear , polynom or expon. (see section 5.6.3).