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29.1 Dynamic equivalence point titrations (DET) ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
Volume after EP
This volume will be added when the number of equivalence points defined under Stop EP has been found. The curve shape after the equivalence point can also be seen this way.
Input range
Selection
Default value
0.01000 to 9999.99 mL off off
Stop time
The titration is stopped when the specified time has elapsed since the start of the titration.
Input range
Selection
Default value
0 to 999999 s off off
Filling rate
Rate at which the dosing cylinder is filled.
Input range
Selection
Default value
0.01 to 166.00 mL/min maximum maximum maximum
The maximum filling rate depends on the cylinder volume (see chapter
29.1.4 Potentiometric evaluation
The parameters for the evaluation of the titration curve are defined under
[Potentiometr. evaluation] .
EP criterion
The Equivalence point Recognition Criterion (ERC) found is compared with this value. Equivalence points whose ERC is less than the value defined here will be ignored.
Input range
Default value
0 to 200
5
EP recognition
This parameter allows you to filter out only the equivalence points that are being sought.
Selection
Default value all | greatest | last | ascending | descending | off all
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All equivalence points will be recognized.
greatest
Only the equivalence point with the greatest ERC value, i.e. the steepest jump, will be recognized.
last
Only the last equivalence point will be recognized.
ascending
Only equivalence points with a positive slope of the titration curve will be recognized.
descending
Only equivalence points with a negative slope of the titration curve will be recognized.
off
No evaluation takes place.
Set windows
This parameter allows to recognize equivalence points only in a particular range (so-called window) of the curve. Equivalence points outside this window will not be recognized. A maximum of 9 windows can be defined. Setting windows is advisable when interference and unnecessary equivalence points are to be suppressed.
Selection
Default value
Measured value | Volume | off off
Measured value
The windows are defined on the measured value axis.
Volume
The windows are defined on the volume axis.
off
The entire titration curve is being evaluated.
Setting windows
The list of defined windows is opened with [Set window] .
When the list is opened for the first time, a window over the entire measured value range or volume range is already defined. The windows must not overlap, they only may lie next to one another. For each window, own criteria can be defined for the equivalence point recognition.
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29.1 Dynamic equivalence point titrations (DET) ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
NOTICE
When you define a result variable instead of a numerical value as limit
value (see chapter 32.6, page 496) , then just one window can be
defined.
[New]
[Delete]
[Edit]
Define a new window. This is only possible when not the entire range is covered yet.
Delete the selected window.
Edit the settings of the selected window.
Lower limit
Measured value or volume for the lower limit.
The values that are actually measurable may vary from the values specified here, depending on the hardware. The binding measurement value ranges can be found in the "Technical specifications" chapter for the control instrument used.
Measured value (measuring mode pH):
Input range
Default value
–20.000 to 20.000
–20.000
Measured value (measuring mode U, Ipol):
Input range –2000.0 to 2000.0 mV
Default value –2000.0 mV
Measured value (measuring mode Upol):
Input range
Default value
–200.00 to 200.00 µA
–200.00 µA
Volume:
Input range
Default value
0.00000 to 9999.99 mL
0.00000 mL
Upper limit
Measured value or volume for the upper limit.
The values that are actually measurable may vary from the values specified here, depending on the hardware. The binding measurement value ranges
288 ￭￭￭￭￭￭￭￭ 900 Touch Control
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Measured value (measuring mode pH):
Input range –20.000 to 20.000
Default value 20.000
Measured value (measuring mode U, Ipol):
Input range
Default value
–2000.0 to 2000.0 mV
2000.0 mV
Measured value (measuring mode Upol):
Input range –200.00 to 200.00 µA
Default value 200.00 µA
Volume:
Input range
Default value
0.00000 to 9999.99 mL
9999.99 mL
EP criterion
The Equivalence point Recognition Criterion (ERC) found is compared with this value. Equivalence points whose ERC is less than the value defined here will be ignored.
Input range
Default value
0 to 200
5
EP recognition
This parameter allows you to filter out only the equivalence points that are being sought.
Selection
Default value first first
| greatest | last | ascending | descending first
Only the first equivalence point will be recognized.
greatest
Only the equivalence point with the greatest ERC value, i.e. the steepest jump, will be recognized.
last
Only the last equivalence point will be recognized.
ascending
Only equivalence points with a positive slope of the titration curve will be recognized.
descending
Only equivalence points with a negative slope of the titration curve will be recognized.
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29.1 Dynamic equivalence point titrations (DET) ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
Only one equivalence point will be recognized in a window. The numbering of the equivalence points (EP) is defined by the numbering of the windows (e.g. EP2 in window 2), so that even if EPs are missing, the calculations will still be carried out with the correctly assigned EP volumes.
U/mV U/mV
EP window 2
EP window 1 EP1
EP2
EP window 1 upper limit 1
+
EP1 lower limit 1
V/mL V/mL
Figure 13 Equivalence point recognition and equivalence point numbering within windows
In the first example in the above figure, two equivalence points are recognized in two different windows (EP1 in window 1 and EP2 in window 2).
In the second example, two equivalence points are found in one window, but only the first one is recognized. In order to ensure that the user recognizes that more than one equivalence point was found in the set window,
EP1 is marked with a "+" in the result view. In addition, a corresponding message is entered in the message list.
Evaluation and equivalence point criterion with DET
The equivalence points (EP) are localized in a way similar to the Tubbs method [1][2]. The volume value of the equivalence point (V
E
) is shifted from the inflection point (see arrow) towards the smaller circle of curvature for real asymmetric titration curves.
[1] C. F. Tubbs, Anal. Chem.
1954 , 26 , 1670–1671.
[2] E. Bartholomé, E. Biekert, H. Hellmann, H. Ley, M. Weigert, E. Weise,
Ullmanns Encyklopädie der technischen Chemie , Vol. 5, Verlag Chemie,
Weinheim, 1980, p. 659.
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Key Features
- Dynamic equivalence point titration (DET)
- Monotonic equivalence point titration (MET)
- Endpoint titration (SET)
- Water determination according to Karl Fischer (KFT)
- Titration with constant maintenance of the measured value (STAT)
- Manual titration (MAT)
- Coulometric water content determination according to Karl Fischer (KFC)
- Bromine index determination (BRC)
- Intuitive touch-sensitive screen for easy operation
- Comprehensive user administration for secure data management