Metrohm 757 VA Computrace - Manual (Page 43)

3.2 VA measurement modes
757 VA Computrace – Software
33
SqW – Square Wave
General:
SqW or Square Wave voltammetry is primarly suitable for re-
versible electrode processes. It is used particularly for sensitive
stripping voltammetric determinations at the HMDE or RDE. The
SqW measurement mode can be set for the exploratory and de-
termination mode by selecting
SqW - Square wave for the Mode pa-
rameter in the EXPLORATORY SPECIFICATION or WORKING
METHOD SPECIFICATIONS window.
Description:
For SqW voltammetry, a square wave alternating voltage with a
small, constant amplitude is superimposed on a stepwise rising
direct voltage ramp. The current
i is measured as a function of the
voltage U at the maximum and minimum of the square wave volt-
age. The phase dependent differences between the two current
measurements give peak-shaped curves which are evaluated us-
ing linear, polynomial or exponential baselines.
U
i
U
Start potential
Voltage step
Voltage step time = 1 / Frequency
Peak voltage
Peak
height
Amplitude
i = i2 - i1
t (i1) t (i2) t (i1) t (i2)
t