Metrohm 797 VA Computrace - Manual (Page 152)

5 Determination mode
797 VA Computrace – Software
140
aid of these measured maxima and minima values, the Peak volt-
age and Peak width values are determined for each peak. After the
peak detection a baseline is constructed. The Peak height is deter-
mined from the value of the peak maximum minus the value of the
baseline at the position of the peak voltage.
Peak width
Minimum peak width
Peak position ± Tolerance
Peak voltage
Peak height
Umax Umin
Minimum peak height
i
di/dU
U
U
Derivative
• Peak voltage = (Umax +
Umin) / 2
• Peak width = ⎥ Umin - Umax ⎥
•
Peak height = Peak height at peak
voltage
The peaks found are assigned to defined substances with the aid of
these approximate values and the recognition parameters specified
for the substances on the
Substances tab. The following three rec-
ognition tests are performed:
Peak voltage test:
Peak voltage = Peak position ± Tolerance
Peak width test: Peak width > Minimum peak width
Peak height test: Peak height > Minimum peak height
If all three test conditions are met, this peak is assigned to the cor-
responding substance and thus recognized as a substance peak. In
the curve display, this peak is marked with the substance name
"
Substance ".
If only the last two test conditions are met, this peak is recognized
as an unknown peak but not assigned to a substance. In the curve
display, this peak is marked with "
Unk ".
Baseline calculation
Recognized peaks are evaluated using approximated baselines. The
calculation of a baseline for a smoothed substance peak is deter-