Metrohm 916 Ti-Touch - Manual (Page 320)

28.2 Monotonic equivalence point titrations (MET)
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916 Ti-Touch
EP1
EP window 2
EP window 1
EP2
U/mV
V/mL
EP window 1
EP1
+
U/mV
V/mL
lower limit 1
upper limit 1
Figure 23 Equivalence point recognition and equivalence point num-
bering within windows
In the first example in the above figure, two equivalence points are recog-
nized in two different windows (EP1 in window 1 and EP2 in window 2).
In the second example, two equivalence points are found in one window,
but only the first one is recognized. In order to ensure that the user recog-
nizes that more than one equivalence point was found in the set window,
EP1 is marked with a "+" in the result view. In addition, a corresponding
message is entered in the message list.
Evaluation and equivalence point criterion with MET
The equivalence points (EPs) are localized by a method based on the For-
tuin method which has been adapted by Metrohm for numerical methods.
A search is made for the largest measured value modification ( ). The
exact EP is determined by using an interpolation factor which depends
on the
Δ values before and after .
: EP volume
: Dosed total volume before
: Volume increment
: Interpolation factor according to Fortuin
For the recognition of the EPs found the set EP criterion is compared with
the ERC (Equivalence point Recognition Criterion) found. The ERC is the
sum of the measured value modifications before and after the jump:
In certain cases only three or only a single summand are taken into
account.
EPs whose ERC is smaller than the defined EP criterion will not be recog-
nized. The ERC is displayed in the results dialog for each discovered and
recognized EP. If you adjust the EP criterion later in order to recognize