Metrohm 794 Basic Titrino - Manual (Page 36)

2.7. Parameters, key
794 Basic Titrino
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Reagent feeding and EP evaluation of DET
The reagent feeding of DET is similar to the controlling, a human being would apply in
manually controlled titrations: Great volume increments are dosed far away from the EP,
small increments in the region of the equivalence point.
The size of the volume increments dosed by the Titrino is determined by the following
parameters:
meas.pt.density
The measuring point density is entered as a relative
value from 0...9. Input of a low number means small
volume increments, i.e. a large measuring point density
on the curve. A curve results which reproduces all fine
details. "Fine details", however, also include signal noise,
which can easily lead to unwanted equivalence points. A
high number, i.e. low measuring density, on the other
hand, allows a more rapid titration. The standard value of
4 is suitable for most cases.
If you work with small cylinder volumes (1 or 2 mL), a
small measuring point density may be advisable. In
these cases you should also lower the drift for
meas.value acquisition and set a higher EPC.
min.incr.
Defines the minimum possible increment. This minimum
increment is dosed at the beginning of the titration and
in the region of the equivalence point (for steep curves).
Use low minimum increments only, if small volumes of
titrant consumption are expected, e.g. in micro titrations;
otherwise unwanted equivalence points may arise. The
standard value of 10.0 µL is suitable for most cases.
EPC
The EP's are evaluated according to a special
METROHM procedure which is so sensitive that even
weak equivalence points are determined correctly.
Equivalence Point Criteria.
The preset EPC is compared to the found ERC
(Equivalence point Recognition Criteria) for each
evaluated equivalence point. The ERC is given in the
following reports: deriv (1 st derivative), comp (combined
titration and derivative curves) as well as in the mplist
(measuring point list). The ERC is the first derivative of
the titration curve overlaid with a mathematical function
so that small maxima become higher and great maxima
smaller. EP's whose ERC is below the preset EPC will
not be recognized. For most cases the standard value of
5 is suitable. The evaluation can be repeated at any time
after the titration in a "dry run" with changed evaluation
criteria. The old titration data are not deleted until a new
titration is started.