Metrohm 757 VA Computrace - Manual (Page 127)

5.8 Data processing and evaluation
757 VA Computrace – Software
117
Evaluation quantity calculation
The peak evaluation quantity is identical for all peaks of a deter-
mination and must be set on the
Substances tab of the EDIT
WORKING METHOD PARAMETERS window (see section 5.2). With
the aid of the calculated baselines, the set evaluation quantity
Height , Area or Derivative is determined for each substance peak
and displayed as a result.
Peak voltage
Peak height
i
di/dU
U
U
Derivative
Peak area
Content calculation
With polarographic and voltammetric methods, the measured
evaluation quantities (
Height , Area or Derivative ) for a substance
are proportional to its mass concentration. The relation between
evaluation quantity and mass concentration must be determined
by a calibration with reference solutions. The 757 VA Computrace
offers the following two techniques for this:
• Standard addition
Content determination using single or multiple addition of a
standard solution.
• Calibration curve
Content determination using a calibration curve previously de-
termined with reference solutions.
The goal of these calibration methods is to calculate the sample
mass concentration
c(s) which is defined by the found substance
mass Mass and the sample amount in the measuring vessel Sam-
ple amount :
c(s) = Mass / Sample amount