7.4 Some voltammetric troubles in detail
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60
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Problem
Cause
Remedy
Interfering substances
mask the analyte.
■
A second peak of an interfering substance
overlaps with the analyte peak. It depends
on the individual case whether the interfer-
ence can be eliminated. More information
may be available in the respective applica-
tion documentation.
■
Organic complexing agents or the forma-
tion of insoluble compounds prevent the
presence of the analyte in ionic form.
Whether and in which way a sample prep-
aration is possible depends on the applica-
tion problem.
Sample volume not correct.
Verify that the sample was correctly diluted
and the correct sample volume was pipetted
into the measuring vessel. Also check that the
correct
Sample volume
is specified in the
method parameters on the tab
Determina-
tion
.
Standard addition not cor-
rect.
See
Calibration curve - the calibration curve is
not linear or poorly reproducible.
and
Calibra-
tion curve - the standard addition is too
small / too big.
7.4
Some voltammetric troubles in detail
7.4.1
Linear working range
The quantification in voltammetric measurements is often carried out by
the standard addition technique. A linear relation between the concentra-
tion and the peak height is a basic requirement for this calibration techni-
que. The normal calibration function (
) is linear over a
certain concentration range. At higher concentrations the curve starts to
flatten. When the standard additions are carried out take care that the
sample peak as well as the peaks for the standard addition are within the
linear range, otherwise the calculated concentration will be too high, as
shown in
Summary of Contents for 2.946.0010
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