5.5.5.2. DYNAMIC DOSING
The titrator determines the titrant dose by trying to maintain a certain potential change (delta E) with each addition.
After a titrant dose, if the potential change is lower than the set delta E, the next dose will be progressively increased until max Vol is
attained. If the potential change is still lower than the set value, the titration will continue with max Vol doses.
After a titrant dose, if the potential change is higher than the set delta E, the next dose will be progressively decreased until min Vol
is attained. If the potential change is still higher than the set value, the titration will continue with min Vol doses.
The titrant is added in volumes that depend on the proximity of the end point as shown in the graph below.
Dynamic dosing allows for larger doses far from the end point, reducing the total titration time. Closer to the end point, smaller doses
are made, providing more data and improved accuracy.
The following parameters must be set:
min Vol: The smallest dose to be dispensed during a titration.
The min Vol must be greater than or equal to:
0.001 mL for a 5 mL burette
0.001 mL for a 10 mL burette
0.005 mL for a 25 mL burette
0.005 mL for a 50 mL burette
max Vol: The largest dose to be dispensed during a titration.
The max Vol must be less than or equal to 4.000 mL.
delta E: Sets the fixed potential jump that has to be achieved after each titrant dose.
The allowed range is between 0.1 and 99.999 mV.
Recommendations for dosing parameters:
For steep and normal titration curves the recommended settings are:
delta E 3.5 to 9 mV
min Vol 0.010 to 0.025 mL (for a 25 mL burette)
max Vol 0.075 to 0.250 mL (for a 25 mL burette)
For flat titration curves the recommended settings are:
delta E 10 to 15 mV
min Vol 0.050 to 0.150 mL (for a 25 mL burette)
max Vol 0.400 to 0.600 mL (for a 25 mL burette)
To achieve the highest levels of accuracy and reproducibility, it is recommended that 20-80% of the nominal burette volume used for
each titration is consumed. If lower volumes of titrant are required, a smaller burette can be used.
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