Metrohm tiamo 2.1 Manual - Manual (Page 443)

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tiamo 2.1 ￭￭￭￭￭￭￭￭ 429
Evaluation
Equivalence points EP are determined atuomatically in a similar manner to
that described in the Tubbs method (C.F. Tubbs; Anal. Chem 26 (1954)
1670–1671, quoted in Ullman 5 (1980) 659). The volume of the equivalence
point VE is shifted from the inflection point towards the smaller circle of
curvature for real asymmetric titration curves.
The figure shows that the evaluation also requires measuring points from
the measuring point list after the equivalence point as well.
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 first
derivative of the titration curve combined with a mathematical function
which is more sensitive for flat jumps than for steeper ones. EPs whose ERC
is smaller than the set EP criterion will not be recognized.
Commands
Depending on the measured value one of the following four DET commands
can be selected:
￭ DET pH
Potentiometric pH measurement with pH electrodes (measured quantity
pH).
￭ DET U
Potentiometric voltage measurement with metal electrodes (measured
quantity voltage U).