Titration Mode; Linear Titration; Dynamic Titration - Xylem SI Analytics TitroLine 6000 Manual De Instrucciones

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4.6.2

Titration mode

In the case of an automatic titration, you can make a selection between the following modes:
• Linear titration (pH and mV)
• Dynamic titration (pH and mV)
• End-point titration (pH, mV)
• Dead Stop titration (µA)
• pH Stat Titration (pH)

4.6.2.1 Linear titration

In the case of linear titration, the step size remains identical over the entire titration cycle. Linear titration is often
used for complicated or unknown samples. Complicated examples include, for instance, chloride in the trace
range (-> very flat curve pattern) or titrations in non-aqueous media. If one would use a dynamic titration control
in these cases, this would not yield any benefit. Depending on the parameters, the step sizes used in excessively
flat curves would either be too small or too large. Below an example of a flat and rather unsteady course of a
curve (Fig. 68).
Fig. 68
Titration was performed as a linear titration with a step size of 0.05 ml. In this case, dynamic titration control with
a step size adapted to the curve slope would generate an even more unsteady course of the curve.
Linear Titration is only available for mV und pH titrations.

4.6.2.2 Dynamic titration

in the case of dynamic titration, the titration steps are adapted to the change of the measurement readings/ml
(slope, curve gradient). Small slope values mean a large step sizes, and large slope values indicate small step
sizes. Within that section, this leads to the inclusion of most of the measurement points which are later on of
importance with regard to the evaluation of the equivalence point (EQ).
Dynamic titration begins with three identical small step sizes, for instance 0.01 ml, and this value is then doubled
until the maximum step width is reached, for instance 0.5 or 1 ml. Should the slope values now increase in the
course of titration, the step sizes will decrease down to minimum step size, for instance 0.01 ml. In the example
below (Fig. 69) titration was performed between 100 and 300 mV with the smallest step sizes (in the present
case 0.01 ml). With linear titration control involving step sizes of 0.05 or even 0.1 ml, only 1-2 measurement
points would be recorded between 100 and 300 mV. This would result in an inaccurate calculation of the
equivalence point.
Chapter 4 Method Parameters