Xylem SI Analytics TitroLine 5000 Mode D'emploi page 110

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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 slope). 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 0.02 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 during the titration, the step sizes will decrease down to minimum step size, for
instance 0.02 ml. In the example below (Fig. 59) titration was performed between 100 and 300 mV
with the smallest step sizes (in the present case 0.02 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.
Fig. 59
Dynamic titration is possible for mV and pH titrations.
4.6.2.3 End-point titration
The goal of end-point titration consists in titrating as precisely as possible to one or two end points
given in terms of pH or mV. Consumption in the end points will be used as a result. The classical
examples of pH end-point titration include total acidity in wine or beverages and the p+m value
(alkalinity).
The first stage of end-point titration consists in the continuous dosing up to a delta value away from
the set end point. The dosing speed can be adjusted. Subsequently, titration is performed in a drift-
controlled manner with linear step sizes between the delta value and the end point.
Example: Determination of the alkalinity (m value)
pH in the point:
delta pH value:
linear step width:
dosing speed:
end-point delay:
drift:
Up to a pH value of 5.30, titration is performed with the set dosing speed. Subsequently, the method
will change to a linear step size of 0.02 ml, until the end point of pH 4.30 is either reached or fallen
short of. Should this value raise again to above pH 4.30 within 10 seconds, another titration step of
0.02 ml will be added. Consumption will be determined precisely at pH 4.30.
4.30
1.00
0.02
12 %
10 s
medium (20 mV/min)