Metrohm tiamo 2.1 (ProcessLab) - Manual (Page 873)

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tiamo 2.1 (ProcessLab) ￭￭￭￭￭￭￭￭ 857
5.6.3.9.4 Gran evaluation
Parameters: Method ▶ DET/MET ▶ Properties... ▶ Additional evaluations ▶ Gran
evaluation
The Gran evaluation can be used to determine S-shaped DET and MET titra-
tion curves. Two different procedures can be selected for this which are
referred to as Normalized and Standard.
In the normalized procedure, the titration curves are linearized in 2 parts:
the first part is before, the second after the equivalence point. The Gran
function G is then plotted vs. the reagent consumption to get the Gran
endpoint GP.
In the standard procedure, which is only available for 5.6.3.2.2.7DET pH -
Additional evaluations and 5.6.3.3.2MET pH, only the part before the
equivalence point will be linearized, and afterwards the intersection point
with the y axis is determined as the endpoint GP.
The Gran evaluation is only suitable for curves with a single jump. All of the
jumps are evaluated together as a group when a curve has several jumps.
This may be desirable, as for example if 2 EPs are very close to one another
in a steep jump and one wishes to have only one GP evaluated, e.g. with
titrations of NaOH that contain carbonate.