Metrohm tiamo 1.2 Manual - Handbuch (Seite 456)

430 Method
Titration rate
Titration rate
50 µL/min, [ 100 µL/min ], 500 µL/min, user
Three predefined sets of parameters can be selected for the titration rate:
50 µL/min , 100 µL/min and 500 µL/min . For these sets the parameters for
the Control are not displayed. In order to edit these parameters the value
user must be selected.
Control
(only visible for Titration rate = user )
Dynamics pH
0.001 ... [ 1.000 ] ... 20.000, off (Titrando)
0.01 ... [ 1.00 ] ... 20.00, off (Titrino)
Dynamics defines the measured value range before the given endpoint.
This parameter has an important influence on the titration rate and with it on
the accuracy. Within the control range the steps which are added are con-
trolled by the Min. rate . The nearer the endpoint the slower the dosing takes
place until the Min. rate has been reached. Outside the range the dosing
takes place with Max. rate ) (see Control range).
Max. rate
0.01 ... [ 0.25 (50 µL/min) ] ... [ 0.75 (100 µL/min) ] ... [ 2.00 (500 µL/min) ] ...
166.00 mL/min, maximum
(Titrando)
0.01 ... [ 0.25 (50 µL/min) ] ... [ 0.75 (100 µL/min) ] ... [ 2.00 (500 µL/min) ] ...
150.00 mL/min, maximum
(Titrino)
Speed of addition outside the control range. The maximum dosing speed
depends on the cylinder volume of the exchange unit or dosing unit used.
Rule of thumb for the maximum rate:
Max. rate in mL/min = 0.005 • Ex-
pected rate of reaction in µL/min
Min. rate
0.01 ... [ 5.00 (50 µL/min)] ... [ 10.00 (100 µL/min) ] ... [ 40.00 (500 µL/min) ]
... 9999.00 µL/min
Speed of addition at the start and finish of the titration. The slower the
minimum rate that is selected, the slower the titration and the higher the ac-
curacy. the longer it takes until the control point is reached for the first time.
The following rule of thumb should be considered in order to obtain as con-
stant a dosing at the control point as possible: Min. rate in µL/min = Ex-
pected rate of reaction in µL/min / 10.
Note
Outside the control range the dosing rate is mainly characterized by the Max. ra-
te . The parameters Max. rate and Dynamics pH should be optimized together in
such a way that the titration does not overshoot too much when reaching the
control point. The control range should be set so that the measured value re-
mains within this range while it is kept constant. A slightly larger control range
should be defined for slow reactions (e. g. pH = 3). A SET pretitration is fre-
quently used to reach the control point before the substrate is added. This
means that the STAT titration can be started with a small variation from the
control point. Within the control range the dosing rate is mainly characterized by
the
Min. rate .