Xylem Si Analytics TitroLine 5000 Mode D'emploi page 112

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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. 59).
Fig. 59
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. 60) titration was performed between 100 and 300 mV with the smallest step sizes
(in the present case 0.01 ml).
Fig. 60
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.
Dynamic titration is only available for mV and pH titrations.