Metrohm 726 Titroprocessor - Manual (Page 106)

7.2 DET Dynamic equivalence point titration
726 Titroprocessor, Instructions for use 100 100
7.2 DET Dynamic equivalence point titration
Application:
DET modes are universal titration modes which can be used for most
(unproblematic) titrations. Their features are a dynamically titration algo-
rithm, variable dosing steps, drift-controlled measurement acceptance and
automatic equivalence point recognition.
They also recognize potential jumps which lie close together or which are
not very distinct.
Important: as the addition of the reagent depends on the measuring data
the titration should not vary too greatly from an S-shaped curve.
7.2.1 Measuring mode
A dynamic equivalence point titration can be carried out with four different
types of measurement:
• potentiometric pH measurement (DET_PH*)
• potentiometric voltage measurement (DET_U*)
• amperometric measurement with selectable polarization voltage (DET_UPOL*)
• voltametric measurement with selectable polarization current (DET_IPOL*)
7.2.2 Reagent addition and measurement acceptance
The reagent addition and measurement acceptance are very closely related.
The optimal size of a dosing increment is always determined by the change
in the measurement following the preceding addition. The addition of titrant
therefore depends on the slope of the titration curve. After the addition of the
particular dosing increment the potential of the sample solution is meas-
ured. Acceptance of a measurement in the measuring point list can also
take place with controlled drift. In drift-controlled measurement acceptance
the measurement drift of the measured potential must be lower than a pre-
defined amount for it to be accepted as a valid measurement. If after a de-
fined waiting period has elapsed this measurement drift has not been un-
dercut then the momentary measurement will be accepted and included in
the list of measuring points together with the corresponding value for the
volume.
V [mL]
U [mV]
DET: "equilibrium titration"
Reagent addition:
variable volume increments,
depending on the slope of the
curve
Measurement acceptance:
drift-controlled and/or after wait-
ing period