Application Manual
KF - Titration
1
KF Titration Application Manual
Contents
1
2
Page
Introduction............................................................................................................................................. 1
Main part................................................................................................................................................. 1
2.1
Basics of KF titration ....................................................................................................................... 1
2.1.1
The chemical reaction.............................................................................................................. 1
2.1.2
Side reactions .......................................................................................................................... 2
2.1.3
The influence of temperature and reaction medium ................................................................ 3
2.1.4
Titration curves ........................................................................................................................ 5
2.1.5
Volumetry and coulometry ....................................................................................................... 6
2.1.6
„Setting“ the titration................................................................................................................. 7
2.2
Working methods of KF titration...................................................................................................... 8
2.2.1
Sample properties.................................................................................................................... 8
2.2.2.1 Working with liquid samples................................................................................................. 8
2.2.2.2 Working with solid samples.................................................................................................. 9
2.2.2.3 Dry-heating of samples using the oven................................................................................ 9
2.2.2
Adaptation to the sample matrix ............................................................................................ 10
2.2.2.1 Working with other temperatures ....................................................................................... 10
2.2.2.2 Variation of the commercially available solvent ................................................................. 11
2.2.2.3 Setting the pH value ........................................................................................................... 12
2.3
Working specifications .................................................................................................................. 13
2.3.1
Titer determination ................................................................................................................. 13
2.3.2
Use of single-component reagents ........................................................................................ 14
2.3.3
Use of two-comonent systems............................................................................................... 15
2.3.4
Working with liquid samples .................................................................................................. 16
2.3.5
Working with solid samples and direct input.......................................................................... 17
2.3.6
Working with solid samples and solid lock............................................................................. 18
2.3.7
Working with solid samples and homogenizer ...................................................................... 19
2.3.8
Working with raised temperature ........................................................................................... 20
2.3.9
Working with external extraction............................................................................................ 21
2.3.10 Working with the oven............................................................................................................ 22
2.2.3.1 General form of working specifications .............................................................................. 23
2.3.11 Inspection of the titration system ........................................................................................... 24
2.4
Error and their consequences....................................................................................................... 26
2.4.1
The titration takes too long .................................................................................................... 26
2.4.2
The titration solution turns brown........................................................................................... 26
2.4.3
Detected water contents is too low ........................................................................................ 26
2.4.4
Detected water contents is too high....................................................................................... 27
2.4.5
Brown titration solution is leaking .......................................................................................... 27
2.4.6
Titration proceed fast and without stopping ........................................................................... 27
2.4.7
Wrong output of the result ..................................................................................................... 27
2.5
Validation of the KF titration .......................................................................................................... 27
2.5.1
Validation scheme and evaluation of general features.......................................................... 28
2.5.2
Inspection of testing means ................................................................................................... 29
2.5.3
Tests to be made ................................................................................................................... 30
2.6
KF titration and normative documents .......................................................................................... 32
2.7
KF titration and quality assurance................................................................................................. 34
3 List of keywords.................................................................................................................................... 36
4 Annexes........................................................................................... Fehler! Textmarke nicht definiert.
4.1
Documents ............................................................................... Fehler! Textmarke nicht definiert.
1
1
Introduction
The water contents or the humidity is an important factor for many products, since it influences the product
properties or the quality of the products. Butter, for instance, contains up to 16 % of water. If the water
contents is too high, butter does no longer meet the legal regulations. In this way, the microbiological
composition is exposed to considerably higher risks. If the water contents is too low, the manufacturer
simply gives away money. The determination of the water contents, in addition to its mere necessity, is in
many cases an important commercial factor to reduce costs.
There are countless applications in which the water determination is inevitable: The pourability of
products, the processing of plastics in injection moulding, or else, tablets will disintegrate if they are too
dry, or they will deliquesce if they contain too much humidity. This list could be continued without ever
reaching an end.
In this context, the water contents may be located in the ppm range, such as is the case with insulating oil,
or in a high percentage range, for instance in the case of alcoholic extracts of natural matters (plants). Karl
Fischer titration with its methods can cover this wide sector without any problems.
Karl Fisher reaction was published in 1935 by Karl Fischer as a method of water determination. He used
pyridine, iodine, methanol, and SO2 as single-component compounds for his determinations. The
underlying reaction equation was based on Bunsen’s equation. Stoichiometry of the reaction equation,
however, was corrected in subsequent publications.
A titration can only be performed if the end point of the reaction is clearly marked or if the reaction is
recorded in the form of a titration curve and the transformation can be calculated on this basis. In the case
of Karl Fischer titration the end of the titration can be seen in the colour change to brown, caused by the
iodine surplus. The own colour of the reaction, however, does not change in the course of the titration.
Whereas the first titration clearly shifts from almost colourless to dark brown, the colour shift of many
titrations may be from dark yellow to brown. This is based on the assumption that a multitude of samples
is being titrated in one and the same solution. This is common practice today.
Modern titrators recognise the end of titration in an electrochemical way. In the case of Schott titrators, the
indication is done in a bi-amperometric process. A voltage is applied between two platinum pins. As long
as water is present in the solution, only iodide is present in the solution, and no current is flowing. As soon
as the water is titrated away, the solution contains a small iodine surplus. The oxidation of the iodide to
iodine occurring at the anode, and the reduction of the iodine to iodide occurring at the cathode is
reversible and indicated by a flow of current.
2
Main part
2.1
Basics of KF titration
4.1.1
The chemical reaction
The precise nature of the mechanism of Karl Fischer reaction was the subject of tedious discussions.
Even the stoichiometry of the reaction was not clear for a long time.
In principle, titration would not be possible with it. Recently, the mechanism has been the object of several
investigations which resulted in the following reaction equation:
ROH + SO2 + R´N Æ [R´NH]SO3R
H2O + J2 + [R´NH]SO3R + 2 R´N Æ [R´NH]SO4R + 2 [R´NH]J
Equation 1: KF equation according to [1]
Legend:
ROH An alcohol, for instance, methanol, ethanol, ethylene-glycol-mono-ethyl-ether
R´N
A caustic solution, for instance imodazol (formerly often pyridine
The investigations of the mechanism show a change in stoichiometry if work is done in other solvents. The
addition of other solvents should therefore be limited to 50 volume %.
2
The basic components of the reaction are as follows:
• Alcohol
• Base
• SO2
• Iodine
A distinction in 2 fundamental working techniques is made: Either all components are combined within one
titration reagent (single-component reagent), or else, alcohol, base, and SO2 are patterned in a solvent
component and titrated with iodine in alcohol (two-component reagent). Since, in contrast to the singlecomponent reagent, base and SO2 are present in a surplus in the case of the two-component reagent, and
since the system is moreover buffered, the reaction is clearly quicker. To achieve this effect for the singlecomponent reagent, too, an additional auxiliary solvent is added in some cases.
Single-component reagent
•
Pattern
Titration agent
Methanol
•
•
•
•
Alcohol
Base
SO2
Iodine
2-component reagent
Pattern
•
•
•
Alcohol
Base
SO2
Titration agent
•
•
Iodine
Alcohol
The single-component reagent is mainly used to enable special samples to be dissolved by a variation of
the solvent. With many polar samples, formamide is added, whereas chloroform is added with many nonpolar samples. It is also possible to add long-chained alkanes or alcohols. Any addition of other solvents
to alcohol should not exceed 50 volume %.
Intense investigations show the pH dependency of the reaction, and this is to be expected before the
background of the reaction equation. The optimum pH is between pH 6 and 7. If the pH is lower, the
reaction speed will slow down clearly. And if the pH value is higher than pH = 8.0, side reactions will give
the illusion of an excessive consumption.
Therefore please note:
• When determining acids, check the pH value and add imidazol if required.
•
When determining bases, neutralise using benzoic acid or salicylic acid.
4.1.2
Side reactions
In the given the circumstances, KF titration is water selective to a far-reaching extent. Nevertheless, there
is of course a number of restrictions caused by a series of side reactions. These side reactions can be
classified according to the following types.
a) Reactions producing water
b) Reactions requiring water
c) Redox side reactions of the iodine
d) External water
Some examples will be quoted here. In many cases, the side reactions can be avoided by corresponding
working conditions or an appropriate selection of the reagents.
a) Reactions producing water
The best known water-producing reaction is the formation of acetals and ketals. The alcohol required for
this reaction and used as the solvent reacts with carbonyl groups (C=0) under formation of water. This
water is also captured in the titration. The titration seems to be endless. The result is a high permanent
"drift".
3
The formation of acetals or ketals can be avoided, however, if special reagents for aldehydes and ketones
are used. An alternative possibility would consist in working at a reduced temperature. In this case, work is
done at temperatures below 0°C. The ionic KF reaction proceeds almost unaffected, while the formation of
acetals or ketals is clearly slowed down. The lower temperature limit is determined by the viscosity of the
pattern and the settlement by crystallisation of side components.
Under certain circumstances, aldehydes may also enter into a bi-sulfite addition with SO2. If the pH value
is correctly set, this reaction should be largely suppressed. This reaction would not produce or bind any
water, but reduce the available SO2 quantity.
Other reactions involving the formation of water include the reaction of carbonyles with amines to form
Schiff’s bases, the formation of enamines, and the esterification of acids with the alcohol of the solvent. If
methanol-containing solvents are used, the risk is reduced.
In the case of certain neutralisation reactions with the bases, water giving the illusion of an increased
water contents may be formed.
b) Reactions requiring water
Ester decomposition would be a typical reaction requiring water. A temperature decrease should solve the
problem. This problem is hardly of any practical importance, since most esters do not react under the
conditions of KF titration.
c) Redox side reactions of the iodine
This involves a series of possible reactions. Peroxides react with iodine [1, 2]. Other oxidants such as
chlorine, nitrogen oxides, dichromate have to be reduced before use. Reductives such as ascorbic acid,
tin(II)-salts, and mercaptan have to be oxidised prior to titration. [1, 2] contains a description of numerous
side reactions and possible solutions.
d) External water
External water is the most frequent source of error with KF titration. There are various possible causes for
its entrance into the titration cell. As a matter of course, the solvent or the pattern component have to be
dry-titrated first. This process is referred to as conditioning. If water still enters the titration cell, it is
assigned as external water together with the sample.
External water enters the titration cell in one of the following ways:
• A titration cell is not tight. External particles, for instance, may be stuck in the ground surfaces.
• Defective O-rings at the screwed connections of the titration cell may be another possibility.
• The septum for the addition of liquid samples is not tight and worn out.
• The molecular sieve in the drying tube for pressure equalisation is used up and has to be dried.
• The pumping system contains damp air. The air for the addition of the solvent should also be dried
using a molecular sieve.
4.1.3
The influence of temperature and reaction medium
The Karl Fischer reaction is a fast reaction. It depends much less on the temperature than a lot of the side
reactions. The acetal and ketal formation, for instance, is reduced by a decrease of the temperature to
such a degree that a Karl Fisher water determination is still possible in many cases. By suitable cooling
facilities, the temperatures can be reduced down to – 30 to – 40 °C. The possible cooling agents include:
dry ice with a matching organic solvent, ice/salt mixtures, or the connection of a cryostat to a temperaturecontrollable titration vessel. The increased duration of the titration with temperatures as low as these
remains practicable if work is done with two-component reagents.
Titration at increased temperatures is mainly used to improve and accelerate the process of dissolving a
sample or to extract the water from a sample more speedily. The temperatures can be regulated to
40 – 50 °C without any problems. If the temperature is further increased, a cooler is to be used in the
position of the drying tube. The drying tube is then placed on top of the cooler. Temperature equalisation
is simply done by using a small, heatable magnetic stirrer which is placed under the titration cell.
4
The titer of the titration agent will change if the working temperatures clearly differ from 20 °C. Literature
quotes a titer change of 1 % per 10 °C [2]. In principle, it is recommended to determine the titer under the
same conditions under which the sample is titrated.
In addition to the variation of the temperature, the use of different solvents enables an adaptation to the
matrix. Considering that the alcohol participates in the chemical reaction, it cannot be fully substituted. The
alcohol components used include: methanol, ethanol, 2-chloroethanol, ethylene-glycol-monomethyl ether.
Owing to its solubility properties, methanol can be used on a broad basis, but is classified as poisonous
(poison class 3). Likewise, some of the alternatives are poisonous, and if used, the required safety
measures have to be taken. They are indicated on the reagent bottles (R and S sentences).
The alcohol component should be contained by a minimum of 50 % in the titration cell. Other solvents are
added to improve or enable the solubility of samples:
Solvents
Application
Observations
Formamide
Polar substances,
Please observe hazards information and safety advice!
sugar, salts, proteines Formamide can cause damage to the unborn child!
Chloroform,
dichloromethane
Fats/greases, oils,
hydrocarbons
Please observe hazards information and safety advice!
Long-chained alcohols, Fats/greases, oils,
1-propanol, 1-butanol, hydrocarbons
decanol
Please observe hazards information and safety advice!
Alkanes (ligroines,
petrol ether)
Fats/greases, oils,
hydrocarbons
Please observe hazards information and safety advice!
Ethylene glycol
Absorption of gases
Please observe hazards information and safety advice!
Acetic acid
Amines, inorganic
compounds
Please observe hazards information and safety advice!
Toluene, Xylene
Plastics, lubricating
fats/greases, oils
Please observe hazards information and safety advice!
The use of formamide and chloroform accelerates titration, but may change the titer in the process. In this
case, too, it is generally valid that the titer has to be determined under the same conditions under which
the sample is later on titrated.
5
4.1.4
Titration curves
KF titration is controlled by the magnitude of
•
•
•
the current flow between the platinum pins of the electrode [µA]
the reagent consumption [ml]
the duration of the titration [s]
The current curve is required for the indication of the titration end. In addition, the titration control tries to
titrate as quickly as possible after a check at the beginning of titration, in order to hit the endpoint of the
titration as accurately as possible when the end of the titration is approaching.
KF titration current curve
Strom [µA]
25
20
15
10
5
0
0
1
2
3
4
5
Titration agent [ml]
Fig. 2: Current curve of a KF titration
Figure 2 shows an indication curve showing the consumption on the x axis and the current in µA on the
y axis. The almost completely flat course of the current curve with a sudden rise towards the end of
titration is typical. Considering that this curve gives only little information on the reaction, it makes sense in
practice to record that time versus consumption. On the x axis, the time is recorded, whereas the y axis
shows the consumption as a function of time (Figure 3).
KF titration curve
Nicht zu scharfer Knick
5
Verbrauch [ml]
Steile Kurve
4
Flacher, paralleler
Verlauf zur x-Achse
3
2
1
0
20
40
60
80
100
120
140
Titration duration [s]
Fig. 3: Current curve of a KF titration
As you can see from the curve, approx. 95 % of the titration agent have been dosed within approx.
50 seconds after approx. 20 seconds of solving or extraction time. In the course of the remaining
70 seconds, titration was performed carefully and in minute quantities in order to achieve a result as
accurate as possible. Titration will end as soon as no more reagent is being titrated within a defined period
of time (mostly 10 or 20 seconds).
The following criteria are indicative of a "good" titration curve:
Steep rise means fast titration (too flat = too slow)
• A round, but not too steady bow without bends (too round = too slow; bend = overtitration)
• A flat course, parallel with the x axis (further rise = drift).
6
KF titration curve with a clear drift caused
by side reactions
Drift mit kontinuierlichem Anstieg
Verbrauch ohne Drift
Verbrauch [ml]
2,5
2
1,5
Hohe Drift von ca.
240 µl/min zeigt
Nebenreaktion
1
0,5
0
20
70
120
170
220
270
Time [s]
Fig. 4: KF titration curve with a clear drift caused by side reactions
The high drift may be indicative of a side reaction or of a leaking titration cell. From the example in figure 4
you can see a titration curve which is characterised by a high drift of approx. 240 µl/min caused by side
reactions. The proportionate consumption of the sample can be read off on the y axis by a backward
extension of a straight line leading through the rise of the drift. In the present example, the side reaction
was caused by a too high pH value (< pH 8).
4.1.5
Volumetry and coulometry
KF titration can be performed in two different ways: in a volumetric or in a coulometric process. The
reaction equation and the indication of the titration end are the same in both cases. The difference is
found in the addition of the iodine solution. Whereas, in the case of volumetric titration, the reagent
addition is done automatically using a motor-driven piston burette of the titrator, the reagent is generated
electrochemically from iodide in the case of coulometry.
The practically relevant differences are derived directly there from:
Volumetry
Reagents with different concentrations are
available (1, 2, 5 mg/ml)
For all quantities from 0.5 mg of water
Solid, liquid, and gaseous samples
A variation of the solvent is possible
Certain samples can be titrated in one and
the same cell without change of solvent
Titration to dry of the cell will occur very
quickly
Used as:
Universal method
Coulometry
Iodine generation according to Faraday’s law,
electrochemically
For small quantities of water only
Liquid and gaseous samples
A variation of the solvent is hardly possible
A great lot of samples can be titrated one after the other in
the same solvent
The drying process of the cell and the solvent will take very
long, since the newly generated quantity of the reagent is
only small
Used as:
Micro method
The smallest quantity of water which can be determined by way of volumetry can be derived easily by
some reflections:
• Smallest dosable reagent volume: 0,5 ml (works very well in practice)
• Titer of the reagent:
1 mg water / ml
• Soluble sample quantity:
10 g
In many cases, this is still practicable without any problems. If the solubility of the samples becomes
worse, i.e. if less sample can be used, consumption decreases. With some practice, sensible results may
still be achieved with a consumption of 0.1 ml.
7
The following table shows the relationships between water contents,
sample quantity under the above conditions:
Sample quatity
[g]
0.05
0.1
1
1
1
1
1
10
Consumption
[ml]
10
5
5
5
1
1
0.5
0.5
Titer
[mg/ml]
5
5
5
2
2
1
1
1
Water content
[ppm]
1 000 000
250 000
25 000
10 000
2 000
1 000
500
50
Water content
[%]
100
25
2.5
1.0
0.2
0.1
0.05
0.005
So the smallest water contents which can be titrated volumetrically is approx. 50 ppm, the highest is 100 %.
4.1.6
„Setting“ the titration
In principle, KF titration requires three different "methods":
• Titer determination to establish the exact concentration of the titration agent. By way of a titration
using an accurate standard, the exact concentration of the titration agent is determined. The
concentration of the titration agent is subject to changes over time. The titer determination should be
repeated approx. every week.
• Blank value: Determination for working with the oven or for longer opening times of the titration cell. A
blank value is particularly required for samples which are heated to dry using an oven. As a result of
the gas flow through the oven, atmospheric water is entrained, thus leading to a blank value. If the
sample is heated to dry for approx. 10 minutes, the blank value of approx. 10 minutes should be
deducted from the titration result.
•
Sample titration for the determination of the water contents of the samples.
This is the actual method for determining the water in a sample.
These "methods" are distinguished by the formula, but not by the setting of the parameters. The settings
of the parameters involve:
• Breaking current in [µA] ; if this current is flowing between the indicator electrodes, the end criterion
has been reached.
• The default setting is 20 µA. Values from 10 – 30 µA make sense.
• Switch-off time in [s]; if the breaking current has exceeded this switch-off time, the titration will be
ended.
• The default setting is 10 s. Time spans between 0 – 10 s make sense. With a few special applications,
e.g. applications involving the introduction of gases, other settings may make sense.
• Drift in [µl/min]; titration will be ended as soon as the addition of the titration agent falls short of the set
drift value. The default setting is 10 µl/min. Values from 3 – 30 µl/min make sense.
• Applied voltage between the platinum electrodes in [mV]: As a rule, this value does not have to be
changed. The default setting is 100 mV. Values between 20 – 150 mV make sense.
• An adaptation to the sample matrix is made possible by the extraction time in [s], to ensure a complete
water yield of the sample. Values between 10 and 600 s make sense.
• An adaptation to the sample matrix is made possible by the max. titration duration in [s]. In this way, a
KF titration can also be made possible with a high drift. A titration should not last longer than
10 minutes.
• The min. titration duration in [s] will accelerate the extraction of the water, without there being the risk
that the titration is cancelled prematurely. The extraction behaviour is improved by a continuous
addition of the iodine.
For all of these parameters, meaningful settings are defaulted on the TitroLine KF Titrator, so that hardly
any change of these values is required. All settings should possibly be the same for a certain type of
application, since otherwise the results cannot be compared exactly. The titer may change by differing
settings of the parameters.
8
2.2
Working methods of KF titration
4.2.1
Sample properties
The working methods of KF titration are highly dependent on the properties of the sample. Working with
gaseous, liquid, low-viscous, high-viscous, and solid samples is distinguished by:
• Sample input
• Solubility
• Sample quantity
• Sample volume
• Water yield
2.2.2.1 Working with liquid samples
In general, liquid samples are injected through a septum into the titration cell using a one-way syringe.
The size of the syringe depends on the sample volume. Syringes from 1 ml to 20 ml can be used. The
needles of these syringes have a diameter from 0 .6 to 1.2 mm. The thinner needles are or only available
for low-viscous samples, whereas the thicker needles should be used for samples with a higher viscosity.
The thicker the needle is, the higher will be the degree of the effect on the septum. In this case, it has to
be replaced sooner. The length of the needles is between 50 and 90 mm. In this way it can be ensured
that no drops remain adhered to the walls. The needles should not be immersed into the solvent.
Particularly high-viscous samples, such as oils, are transferred into the titration cell without a needle,
directly, and without the use of a septum.
The septum consists of a polymer which has to have the three following major properties:
• The proper size.
• It has to close again directly after being pierced.
• This point can only be realised with certain restrictions. The silicon discs used have to be replaced on a
regular basis.
We recommend the use of original spare parts.
As a rule, the samples have to be weighed in using an analytical weighing-balance.
The working process is as follows:
⇒ Put a 150 ml beaker glass on the balance.
⇒ Draw up the liquid sample into the syringe.
⇒ Put the needle protector on again.
⇒ Place the syringe with the needle up into the beaker glass.
⇒ Gauge the weighing-balance.
⇒ Carefully take the syringe from the balance, then remove the needle protector.
⇒ Inject the sample through the septum into the titration vessel.
⇒ Remove the syringe from the septum, put on the needle protector again.
⇒ Place the syringe with the needle up in the beaker glass on the weighing-balance.
⇒ Read off the weight as a negative number on the weighing-balance, then enter it as an absolute value
on the titrator.
Working with sample volumes is unusual. When drawing up the sample into the syringe, please proceed
carefully and slowly to avoid air (including air-borne humidity) being unnecessarily drawn through the
samples.
Figure 5 shows the sample opening with the septum and a syringe:
Plug
Cover
Needle
Fig. 5: Sample input through septum
Septum
9
2.2.2.2 Working with solid samples
The following working methods are common for solid samples:
• Direct sample input by opening the plug in the cover of the titration vessel
• Use of a solid lock
Direct sample input by opening the plug is certainly the most simple way of introducing solid samples in
the KF titration vessel. During the opening time of the cell, humidity of the ambient air may lead to a blank
value. This blank value, however, can be determined by way of a separate titration and then be
automatically taken into account in arithmetic form. The smaller the water quantity to be determined, the
less favourable is this method of sample addition. As a rule, the blank value should not be greater than the
water quantity to be determined.
The samples may be weighed with a weighing boat made of glass or aluminium to be transported to the
titration vessel. After weighing, the samples are no longer touched by hand.
Using the solid lock, it is possible to re-condition after the titration vessel was opened, prior to introducing
the sample in the solvent. The sample quantity is limited to small sample quantities in the range of one
gram. The working sequence is based on the following scheme:
⇒ The sample is weighed inside the solid lock.
⇒ Pull the outer part of the solid lock over the inner part containing the sample, until the part containing
the sample is fully closed.
⇒ Open the titration vessel, then place the outer part of the solid lock with the built-in NS 19 ground
surface in the opening.
⇒ Start conditioning.
⇒ Push down the inner part, so that the sample can be dissolved away.
⇒ Start titration with a longer extraction time for solving the sample. As an alternative, a minimum titration
duration can be specified.
Working with the solid lock may involve a higher drift.
This can be taken into account accordingly in the titration methods.
2.2.2.3 Dry-heating of samples using the oven
In many cases a direct determination is impossible because:
• The samples are insoluble (plastics).
• The samples release the water only in heat.
• The samples enter into side reactions.
The samples are placed in the oven, heated up, and the water being released is transferred to the titration
vessel by dried gas. In this process, the major quantity of water is released at the beginning. The following
graph shows the way in which the water contained in the sample is released. At the end of titration, the
added quantity is limited by the drift value. On the graph, a side reaction is indicated by a high residual
drift. The x axis shows the duration of the titration, the first y axis shows the drift, the second y axis shows
the consumption.
After a approx. five minutes, the major part of the water is released. We recommend a dry-heating time of
10 minutes. This time is set as a waiting time on the titrator. Subsequently, the water quantity absorbed in
the solvent is titrated within a short period of time. If the preceding drift is not reached again, or almost not
reached again, this is indicative of a side reaction.
10
With the titration in the graph it was proven that thermal decomposition leads to the generation of
formaldehyde, which reacts with the methanol in the titration cell to acetal, with water being separated.
300
1,4
250
1,2
1
200
0,8
150
0,6
100
0,4
50
Verbrauch [ml]
Wasserabgabe [µl/min]
Water yield
0,2
0
0
1
6
Time [min]
11
The set-up and the connection of the oven will be illustrated by the figure below:
N2
Drying
Oven
Titration cell
The gases to be preferred include inert gases, such as nitrogen, since side reactions, e.g. oxidations,
cannot occur.
The set-up and the connection of the oven will be illustrated by the figures below.
(Hier die Anleitung Ofenanschluss)
4.2.2
Adaptation to the sample matrix
The sample matrix has a major influence on the water determination. Direct water titration is not possible
in all cases. Some samples release the water only very slowly or, under certain circumstances, do not
release it at all. The possibilities for getting the water out of the samples in a definable form include, for
instance:
• The variation of the temperature
• Comminution
• Internal or external extraction
• Variation of the solvent
• Setting the pH value
• Oven
2.2.2.1 Working with other temperatures
A variation of the temperature of KF titration is simple method to:
• Slow down temperature-dependent side reactions in such a manner that the KF titration can run off
without disturbance
• Improve the input of volatile substances
• Accelerate the extraction of the water contained in samples at a higher temperature
• Accelerate titration
At low temperatures, many organic reactions go off clearly slower. KF titration is not that temperaturedependent. This means, for instance, that many ketones and aldehydes can still be titrated which would
tend to disturbing side reactions at normal temperature. Cooling may be done by the external application
of ice or by organic solvents with dry ice.
One problem of cooling is the condensation of atmospheric air during the process of opening the cell. It is
therefore recommendable to work with a syringe through the septum or, in the case of solid samples, with
a solid lock.
11
Working at raised temperatures is opposed to this. The high air temperature enables a better extraction of
water from the samples. Moreover, the reaction is speeded up. The most simple way of heating is the use
of a heatable magnetic stirrer. Working without an additional cooler is possible in a temperature range
from 40 – 50 °C. Methanol boils at approx. 65 °C. A reflux cooler can be set into the NS 14.5 ground
opening of the dry air capillary. Subsequently, the desiccant tube is set on top of the cooler.
Pre-drying of the cooler in the drying oven is not required. If overtitration occurs during conditioning, for
instance caused by a short-term removal of the electrode from the solution, the entire titration vessel plus
the cooler can be "rinsed" with this solution. Particular care should be taken in this process. All apertures
are to be closed (with plugs). Please observe all safety regulations applicable to the handling of the
chemicals being used and the work in the laboratory. After the "rinsing" process, the plugs have to be
replaced by desiccant tubes!
Particular care should be taking to ensure the thorough drying of the desiccant. Best results were
achieved using a molecular sieve of the 0.3 nm size, which was dried in the drying oven at approx. 250 °C
for at least three hours. A possibly present indicator reacts clearly too late. Replacing and drying on a
regular basis will ensure a low drift inside the titration vessel.
2.2.2.2 Variation of the commercially available solvent
As was already mentioned in Chapter 2.1.3., the adaptation of the solvent to the sample properties
enables many applications to be performed which would otherwise be excluded from classic KF titration.
The table in Chapter 2.1.3. provides some information on this topic. In many cases, additives to the
reagents mentioned below are also possible. In case of doubt, please contact the manufacturer.
The manufacturers offer a number of commercially available solvents for specific applications:
Manufacturer
Solvent
Riedel de Haen Hydranal Solvent E
MERCK
Application
Observations
Lösungsmittelkomponente zu
dem entsprechenden Titriermittel Hydranal Titrant 5 E
Hydranal Solvent
Lösungsmittelkomponente zu
dem entsprechenden Titriermittel Titrant 2/5
Hydranal Composolver Lösungsmittel für die Titration
Beschleunigt die Titration und
mit Hydranal Composite 1/2/5
ergibt bessere Resultate
Hydranal Methanol dry Besonders trockenes Methanol Absorbiert besser Wasser,
benötigt weniger Reagenz
zum Konditionieren
Hydranal Solvent Oil
Löst viele Öle und Fette
Chloroform frei
Hydranal Solvent CM
Löst die meisten Öle und Fette Enthält halogenierte
Kohlenwasserstoffe
Hydranal Ketosolver
Lösungsmittel für Ketone und
Ohne halogenierte
Aldehyde
Kohlenwasserstoffe
Hydranal Arbeitsmedium Lösungsmittel für Ketone und
K
Aldehyde
Karl-Fischer-Reagenz S Lösungsmittelkomponente zu
dem entsprechenden Titriermittel Karl-Fischer-Reagenz T (TU)
Karl-Fischer-Reagenz
Löst die meisten Öle und Fette Enthält halogenierte
SF
Kohlenwasserstoffe
Karl-Fischer-Reagenz
Lösungsmittel für Ketone und
SK
Aldehyde
Methanol getrocknet
Besonders trockenes Methanol Absorbiert besser Wasser,
benötigt weniger Reagenz
zum Konditionieren
12
Manufacturer
Solvent
Application
Observations
Fisher
AquaStar Anhydrous
Methanol
Besonders trockenes Methanol
Absorbiert besser Wasser,
benötigt weniger Reagenz
zum Konditionieren
AquaStar Solvent KN
Lösungsmittelkomponente
zu dem entsprechenden
Titriermittel Comp 5/2K
Lösungsmittelkomponente
zu dem entsprechenden Titriermittel Titrant 5
AquaStar Solvent S
Important note:
These solvents can normally only be used together with the appropriate titration
agents. It is not possible to use the methanol as a solvent and to titrate using a
two-component titration agent. In this case the S02 base components are missing, without which a KF reaction cannot take place!
2.2.2.3 Setting the pH value
In Chapter 2.1.1 point, reference is already made to the pH-dependency of KF titration. The KF reaction
requires a base to be functioning at all. The original composition used by Karl Fischer included pyridine,
allegedly because it was just standing on the shelf. Pyridine has a pKs value of 5.25 and thus leads to a
solvent which has a too low pH value for a fast reaction. Imidazol, which is often used today, has a pKs
value of 6.95, and this means that a favourable pH value for a speedy titration is set. Other bases with
comparable pKs values are also possible. The use of imidazol as a base for KF titration is under patent
protection.
If the pH value is too high, side reactions will lead to incorrect results. With a too low pH value, titration will
take too long. It is therefore essential to estimate of, or better verify, the pH value for a specific type of
sample. Most pH electrodes contain an aqueous electrolyte which may give the illusion of an incorrect
water contents of the sample.
13
2.3
Working specifications
4.3.1
Titer determination
Method
No. 1
Application
Titer determination of KF titration agents
†
†
†
†
†
†
†
†
†
†
†
TitroLine KF Titrator or TitroLine alpha
TM KF Titration Stand (TL KF scope of delivery)
TZ 1770 Titration vessel (TL KF scope of delivery)
TZ 1106 Double platinum electrode (TL KF scope of delivery)
TZ 1721 Solid lock
5 ml one-way syringe with needle length approx. 60 mm plus needle protector
3 or 4-digit weighing-balance
Beaker glass
Titration agents: Single- or two-component titration agents
Pattern: Methanol, Composolver, or solvent depending on the titration agent
Standard: Depending on the standard, please refer to table
Sample input
⇒
⇒
†
†
†
Through the septum using a syringe and needle
Using a solid lock
Directly, by opening the plug
Connection of an oven
Introduction of gas
Description
The “titer determination” method is selected, and the calculation factor is checked.
Liquid standard:
The standard is weighed in in the one-way syringe (water in a microliter syringe).
The consumption to be expected should be approx. 5 ml.
With reagent 5 mg water/ml this would be:
Standard 10 mg water / ml:
2.500 g
Standard 5 mg water / g:
5.000 g
Tare the weighing-balance, transfer the sample through the septum in the titration
vessel, then weigh the empty syringe again. Enter the weight on the titrator. Start
titration.
Equipment
Reagents
Sample preparation
Calculation
Parameter
Solid standard:
Tare the weighing-balance. The standard (approx. 160 mg of sodium tartratehydrate) is weighed in the inner part of the solid lock using the weighing-balance.
Carefully push the inner part of the solid lock into the outer part until the standard
disappears completely in the lock and cannot fall off. The closed solid lock is then
placed in the opening of the titration vessel, start conditioning. Upon completion of
the conditioning process, push the inner part fully down so it can dissolve. Place
the weighed-in quantity in the titrator, then start titration.
Liquid standard:
Concentration titration agent [mg/ml] = weighed-in quantity [g] * standard [mg
water/g] * factor 1 / ((consumption [ml] – blank value [ml]) * factor 2)
Water:
Concentration titration agent [mg/ml] = weighed-in quantity [mg]
((consumption [ml] – blank value [ml]) * factor 2)
Sodium tartrate-hydrate:
Concentration titration agent [mg/ml] = weighed-in quantity [g] * 1000 * 0.1566
((consumption [ml] – blank value [ml]) * factor 2)
End value:
20 µA
Switch-off time: 10 sec
Potential:
100 mV
14
4.3.2
Use of single-component reagents
Method
No. 2
Application
Equipment
Reagents
Titration with single-component reagents
†
†
†
†
†
†
†
†
†
†
TitroLine KF Titrator or TitroLine alpha
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
TZ 1721 Solid lock
5 ml one-way syringe with needle length approx. 60 mm plus needle protector
3 or better 4-digit weighing-balance
Glass beaker
Titration reagent: Single-component reagent
Pattern: Methanol, composolver or Combi solvent and mixtures
Sample preparation Feste Proben werden ggf. zerkleinert, flüssige Proben mit einer Spritze direkt aufgenommen, hochviskose Proben mit der Spritze ohne Nadel aufgezogen.
Sample input
⇒
⇒
†
†
†
Description
The „sample titration“method is selected, and the calculation factor is checked.
Liquid and high-viscous standards:
Der Probe wird in der Einwegspritze eingewogen. Die Waage wird tariert, die Probe
durch das Septum in das Titrationsgefäß überführt und die leere Spritze zurückgewogen. Das Gewicht wird am Titrator eingegeben. Die Titration wird gestartet.
Solid standard:
Tare the weighing-balance. Die Probe wird im Innenteil der Feststoffschleuse auf
der Waage eingewogen und die Einwaage notiert. Carefully push the inner part of
the solid lock into the outer part until the standard disappears completely in the lock
and cannot fall off. The closed solid lock is then placed in the opening of the
titration vessel, start conditioning. Upon completion of the conditioning process,
push the inner part fully down so it can dissolve. Place the weighed-in quantity in
the titrator, then start titration.
Calculation
% Water = (consumption [ml] – blank value [ml]) * 100 /
(weighed-in quantity [g] * 1000)
Parameters
End value:
20 µA
End point delay: 10 sec
Potential:
100 mV
Notice
⇒ Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter denen
die Probe titriert wird, z. B. das gleiche Lösungsmittelgemisch
Through the septum using a syringe and needle
Using a solid lock
Directly, by opening the plug
Connection of an oven
Introduction of gas
⇒ Für unpolare Substanzen (Fette und Öle) kann dem Methanol zugesetzt werden: Chloroform (bis etwa 50 %), Petrolether oder Ligroin (bis etwa 40 %),
langkettige Alkohole (bis etwa 50 %)
⇒ Für polare Substanzen (Zucker, Salze,..) kann Formamid (bis etwa 35 %) zugegeben werden. Höhere Formamidgehalte können zu einer veränderten Stöchiometrie führen.
15
4.3.3
Use of two-comonent systems
Method
No. 3
Application
Equipment
Reagents
Titration with two-component systems
†
†
†
†
†
†
†
†
†
†
†
TitroLine KF Titrator or TitroLine alpha
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
TZ 1721 Solid lock
5 ml one-way syringe with needle length approx. 60 mm plus needle protector
3 or better 4-digit weighing-balance
Glass beaker
Titration agent: two-component agent
Pattern: Two-component agent
ACHTUNG: Die Lösungsmittelkomponente enthält für die chemische Reaktion
notwendige Bestandteile. Deshalb nur vom Hersteller empfohlene Zusammen
setzungen einsetzen!
Sample preparation
Feste Proben werden ggf. zerkleinert, flüssige Proben mit einer Spritze direkt
aufgenommen, hochviskose Proben mit der Spritze ohne Nadel aufgezogen.
Sample input
⇒
⇒
†
†
†
Description
Es wird die Methode „Probentitration“ ausgewählt und die Auswerteeinheit ausgewählt.
Liquid and high-viscous standards:
Der Probe wird in der Einwegspritze eingewogen. Die Waage wird tariert, die
Probe durch das Septum in das Titrationsgefäß überführt und die leere Spritze
zurückgewogen. Das Gewicht wird am Titrator eingegeben. Die Titration wird gestartet.
Through the septum using a syringe and needle
Using a solid lock
Directly, by opening the plug
Connection of an oven
Introduction of gas
Solid standard:
Die Waage wird tariert. Die Probe wird im Innenteil der Feststoffschleuse auf der
Waage eingewogen und die Einwaage notiert. Carefully push the inner part of the
solid lock into the outer part until the standard disappears completely in the lock
and cannot fall off. The closed solid lock is then placed in the opening of the
titration vessel, start conditioning. Upon completion of the conditioning process,
push the inner part fully down so it can dissolve. Place the weighed-in quantity in
the titrator, then start titration.
Calculation
% Water = (sonsumption [ml] – blind value [ml])* 100 /
(weighed-in quantity [g] * 1000)
Parameters
End value:
20 µA
Switch-off time:10 sec
Potential:
100 mV
Notice
•
•
•
Der Titer muss unter den gleichen Bedingungen bestimmt werden,
unter denen die Probe titriert wird, z.B. das gleiche Lösungsmittelgemisch
Es sind Zusätze andere Lösungsmittel in geringem Maße möglich.
Die Titration ist sehr schnell. Die Probe sollte daher bei Beginn der
Titration schon möglichst vollständig gelöst sein. Bei Proben mit
langsamer Wasserabgabe muss die Abschaltzeit verlängert werden.
16
4.3.4
Working with liquid samples
No. 4
Method
Titration with liquid samples
Application
Equipment
Reagents
†
†
†
†
†
†
†
†
†
†
TitroLine KF Titrator or TitroLine alpha
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
TZ ???? Solid lock
5 ml one-way syringe with needle length approx. 60 mm plus needle protector
3 or 4-digit weighing-balance
Beaker glass
Titriermittel: Ein- oder Zwei-Komponenten Titriermittel
Vorlage: Methanol, Composolver or Solvent je nach Titriermittel
Sample preparation
Die flüssige Proben mit einer Spritze direkt aufgenommen, hochviskose Proben
mit der Spritze ohne Nadel aufgezogen.
Sample input
⇒
†
⇒
†
†
Description
The „sample titration“ method is selected, and the calculation factor is checked.
Through the septum using a syringe and needle
Using a solid lock (solid standards)
Directly by openiung the plug (high-viscous standards, solid standards)
Connection of an oven
Introduction of gas
Liquid and high-viscous standards:
Der Probe wird in der Einwegspritze mit Nadelschutz eingewogen. Die Waage
wird tariert, die Probe nach Entfernen des Nadelschutzes durch das Septum in
das Titrationsgefäß überführt und die leere Spritze zurückgewogen mit Nadelschutz. Das Gewicht wird am Titrator eingegeben. Then start titration.
Calculation
% Water = (consumption [ml] – blank value [ml]) * 100 /
(weighed-in quantity [g] * 1000)
Parameters
End value:
20 µA
Switch-off time:10 sec
Potential:
100 mV
⇒ Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter denen die Probe titriert wird, z. B. das gleiche Lösungsmittelgemisch
Notice
⇒ Für unpolare Substanzen (Fette und Öle) kann dem Methanol beim Einko
monentenreagenz zugesetzt werden: Chloroform (bis etwa 50%), Petrolether
oder Ligroin (bis etwa 40 %), langkettige Alkohole (bis etwa 50 %)
⇒ Für polare Substanzen (Zucker, Salze,..) kann Formamid (bis etwa 35 %) zugegeben werden. Höhere Formamidgehalte können zu einer veränderten Stöchiometrie führen.
⇒ Beim Zweikomponentensystem kann in begrenztem Maße Lösungsvermittler
zugefügt werden.
17
4.3.5
Working with solid samples and direct input
Method
No. 5
Application
Titration with single-component reagents
Equipment
†
†
†
†
†
Reagents
† Titriermittel: Ein- oder Zwei-Komponenten Titriermittel
† Vorlage: Methanol, composolver or Solvent je nach Titriermittel
TitroLine KF Titrator
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
3 or 4-digit weighing-balance
Sample preparation Feste Proben werden ggf. zerkleinert und in einem Wägeschiffchen oder
Becherglas eingewogen und direkt in die Zelle überführt.
Through the septum using a syringe and needle (liquid standard)
Using a solid lock (solid standard)
Directly, by opening the plug
Connection of an oven
Introduction of gas
Sample input
†
†
⇒
†
†
Description
Es wird die Methode „Probentitration“ gewählt und die Auswerteeinheit ausgewählt.
Solid standard:
Die Waage wird tariert. Die Probe wird in einem Wägeschiffchen oder Becherglas
eingewogen. Das Konditionieren wird gestartet. Nach der Beendigung des Konditionieren wird die Probe durch Öffnen des Stopfens direkt in die Titrationszelle
gegeben. Wenn Reste nicht in die Zelle überführt werden können, wird die
Einwaage wie bei flüssigen Proben durch Rückwägung ermittelt. Die Einwaage
wird in den Titrator eingegeben und die Titration gestartet. In vielen Fällen wird in
einer Wartezeit die Probe aufgelöst oder extrahiert, dann beginnt die Titration.
Calculation
% Water = (consumption [ml] – blank value [ml]) * 100 /
(weighed-in quantity [g] * 1000)
Parameters
End value:
20 µA
Switch-off time: 10 sec
Potential:
100 mV
Notice
⇒ Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter
denen die Probe titriert wird, z. B. das gleiche Lösungsmittelgemisch.
⇒ Viele feste Proben brauchen eine gewisse Zeit, bis sie sich lösen oder
das Wasser komplett abgeben.
⇒ Es empfiehlt sich, vorher einen Blindwert zu bestimmen und diesen
automatisch zur Korrektur des Ergebnisses zu verwenden.
18
4.3.6
Working with solid samples and solid lock
No. 6
Method
Titration with solid samples and solid lock
Application
TitroLine KF Titrator
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
TZ 1721 Solid lock
3 or 4-digt weighing balance
Beaker glass
Equipment
†
†
†
†
†
†
†
Reagents
† Titriermittel: Ein- oder Zwei-Komponenten Titriermittel
† Vorlage: Methanol, Composolver oder Solvent je nach Titriermittel
Sample preparation Feste Proben werden ggf. zerkleinert und in den inneren Teil der Feststoffschleuse überführt. Es hat bis etwa ein Gramm darin Platz. Großvolumigere Proben
müssen direkt in die Zelle überführt werden.
† Through the septum using a syringe and needle (liquid standard)
Sample input
⇒
†
†
†
Description
Using a solid lock (solid standard)
Directly, by opening the plug (hochviskose Proben, solid standards)
Connection of an oven
Introduction of gas
Es wird die Methode „Probentitration“ ausgewählt und die Auswerteeinheit ausgewählt.
Solid standard:
Tare the weighing balance. The standard is weighed in the inner part of the solid
lock using the weighing-balance. Carefully push the inner part of the solid lock
into the outer part until the standard dissapears completey in the lock and cannot
fall off. The closed solid lock is then placed in the opening of the titration vessel.
Start conditioning. Upon completion of the conditioning pocess, push the inner
part fully down so it can dissolve. Place the weighed-in quantity in the titrator,
then start titration.
Calculation
% Water = (consumption [ml] – blind value [ml]) * 100 /
(weighed-in quantity [g] * 1000)
Parameters
End value:
20 µA
Switch-off time: 10 sec
Potential:
100 mV
⇒ Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter denen die Probe titriert wird, z. B. das gleiche Lösungsmittelgemisch
Notice
⇒ Die Arbeit mit der Feststoffschleuse kann mit einer höheren Drift verbunden
sein (statt 3-5 µml/min bis zu 5-10 µml/min).
⇒ Es empfiehlt sich, vorher einen Blindwert zu bestimmen und diesen automa
tisch zur Korrektur des Ergebnisses zu verwenden.
19
4.3.7
Working with solid samples and homogenizer
Method
Application
No. 7
Titration with solid samples, die mit homogenizer zerkleinert werden müssen
TitroLine KF Titrator
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
3 or 4-digit weighing balance
Beaker glass
Homogenisator e.g. CAT X 620/520 mit Tool T 10
Gewinderohr GL 18 mit NS Kern 19/26 (SCHOTT 24 841 71)
Schraubkappenverschluss GL 18 (SCHOTT 29 227 06)
Silikondichtung GL 18 with 9-11 mm I.D. (SCHOTT 29 235 10)
Equipment
†
†
†
†
†
†
†
†
†
†
Reagents
† Titriermittel: Ein- oder Zwei-Komponenten Titriermittel
† Vorlage: Methanol, Composolver oder Solvent je nach Titriermittel
Sample preparation Feste Proben werden ggf. zerkleinert und direkt durch die Homogenisatoröffnung
in die Titrierzelle gegeben.
Sample input
Through the septum using a syringe and needle (liquid standard)
Using a solid lock (solid standard)
Directly by opening the plug (der Homogenisator wird an der Stativstange angehoben und nach Probenzugabe wieder in die Öffnung gesenkt).
Connection of an oven
Introduction of gas
Decription
Es wird die Methode „Probentitration“ gewählt und die Auswerteeinheit ausgewählt.
Solid standard:
Tare the weighing-balance. Die Probe wird in einem Wägeschiffchen oder Becherglas eingewogen. Das Konditionieren wird gestartet. Nach der Beendigung des
Konditionieren wird die Probe durch Anheben des Homenisators direkt in die Titrationszelle gegeben. Wenn Reste nicht in die Zelle überführt werden können, wird
die Einwaage wie bei flüssigen Proben durch Rückwägung ermittelt. Die Einwaage
wird in den Titrator eingegeben und die Titration gestartet. In vielen Fällen wird in
einer Wartezeit die Probe aufgelöst oder extrahiert, dann beginnt die Titration.
Calculation
% Water = (consumption [ml] – blank value [ml]) * 100 /
(weighed-in quantity [g] * 1000)
Parameters
End value:
20 µA
Switch-off time: 10 sec
Potential:
100 mV
Notice
⇒ Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter denen
die Probe titriert wird, z. B. das gleiche Lösungsmittelgemisch
⇒ Es empfiehlt sich, vorher einen Blindwert zu bestimmen und diesen automatisch
zur Korrektur des Ergebnisses zu verwenden.
20
4.3.8
Working with raised temperature
Method
Application
Equipment
No. 8
Titration single-component reagent
TitroLine KF Titrator
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
TZ 1721 Solid lock
5 ml one-way syringe with needle length approx. 60 mm plus needle protector
3 or 4-digit weighing balance
Beaker glass
Temperierbarer Magnetic Stirrer CAT ECM 6;
Die Titrationszelle wird an der Stativstange des TM KF befestigt und
direkt daneben auf den Magnetrührer gestellt.
† Dimroth-Kühler NS 14/23 160 mm
† Titriermittel: Ein- oder Zwei-Komponenten Titriermittel
Reagents
† Vorlage: Methanol, Composolver oder Solvent je nach Titriermittel
Sample preparation Feste Proben werden ggf. zerkleinert, flüssige Proben mit einer Spritze direkt
aufgenommen, hochviskose Proben mit der Spritze ohne Nadel aufgezogen.
Sample input
⇒ Through the septum using a syringe and needle (liquid standards)
⇒ Using a solid lock (solid standards)
⇒ Directly by opening the plug (hochviskose Proben, feste Proben)
† Connection of an oven
† Introduction of gas
Description
Es wird die Methode „Probentitration“ gewählt und die Auswerteeinheit ausgewählt.
Temperatureinstellung:
Die Temperatur wird langsam hochgeregelt, so dass 50 °C nicht überschritten werden. Wenn mit höheren Temeraturen gearbeitet werden soll, muss mit einem Rückflusskühler gearbeitet werden.
Arbeiten mit Kühler:
Der Kühler wird in die Öffnung NS 14 des Trockenröhrchens gesteckt.
Das Trockenröhrchen wird auf den Kühler gesetzt.
Der Kühler wird an Kühlwasser angeschlossen.
Flüssige und hochviskose Probe:
Der Probe wird in der Einwegspritze eingewogen. Die Waage wird tariert, die Probe
durch das Septum in das Titrationsgefäß überführt und die leere Spritze zurückgewogen. Das Gewicht wird am Titrator eingegeben. Die Titration wird gestartet.
Solid standard:
Die Waage wird tariert. Die Probe wird im Innenteil der Feststoffschleuse auf der
Waage eingewogen und die Einwaage notiert. Das Innenteil der Feststoffschleuse
wird vorsichtig in das äußere Teil geschoben, bis der Standard komplett in der
Schleuse verschindet und nicht herausfallen kann. Die Feststoffschleuse wird geschlossen in die Öffnung des Titrationsgefäßes gegeben. Das Konditionieren wird
gestartet. Nach der Beendigung des Konditionieren wird des innere Teil bis zum
Anschlag heruntergeschoben, damit er sich auflösen kann. Die Einwaage wird in
den Titrator eingegeben und die Titration gestartet.
†
†
†
†
†
†
†
†
†
†
Calculation
% Water = (consumption [ml] – blank value [ml]) * 100 /
(weighed-in quantity [g] * 1000)
Parameters
End value:
20 µA
Switch-off time: 10 sec
Potential:
100 mV
Notice
⇒ Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter denen
die Probe titriert wird, z.B. das gleiche Lösungsmittelgemisch.
⇒ Es empfiehlt sich, vorher einen Blindwert zu bestimmen und diesen
automatisch zur Korrektur des Ergebnisses zu verwenden.
21
4.3.9
Working with external extraction
Working specifications, calculation models, solvent mix to be prepared and dried before. Blank value to be
taken into account.
Method
No. 9
Application
Equipment
Reagents
Titration with external extracton
†
†
†
†
†
†
†
†
†
†
TitroLine KF Titrator
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
5 ml one-way syringe with needle length approx. 60 mm plus needle protector
3 or 4-digit weighing balance
Beaker glass
Extraktionsgefäß für externe Extraktion, z.B. Flaschen mit Septen
Titriermittel: Ein- oder Zwei-Komponenten Titriermittel
Vorlage: Methanol, Composolver oder Solvent je nach Titriermittel
Sample preparation Die Probe wird genau gewogen in ein Gefäß mit Septum gegeben und eine (zum
Beispiel durch Wiegen) exakt definierte Menge (z.B. 20 ml) möglichst trockenes
Lösungsmittel hinzugefügt. Der Restwassergehalt des Lösungsmittel muss als
Blindwert separat bestimmt werden. Die Probe wird über längere Zeit in dieser
Flasche belassen. Der Zeitraum kann 1 – 10 Stunden betragen. Er hängt von
Wasserabgabe der Probe in dem gewählten Lösungsmittel ab.
Sample input
⇒
⇒
⇒
†
†
Description
Es wird die Methode „Probentitration“ gewählt und die Auswerteeinheit ausgewählt.
Probenabmessung:
Mit der Einwegspritze wird ein Teil der extrahierten Probe im Lösungsmittel
entnommen und gewogen. Die Waage wird tariert, die Probe durch das Septum in
das Titrationsgefäß überführt und die leere Spritze zurückgewogen. Der Anteil der
Probe am Gesamtgewicht Probe und Lösungsmittel wird am Titrator eingegeben.
Example:
1.000 g Probe genau gewogen werden mit exakt 20 g Lösungsmittel extrahiert. Das
Wasser der Probe befindet sich nach der Extraktion vollständig im Lösungsmittel.
Es werden 10 g Lösungsmittel (jetzt mit dem Wasser) entnommen und in die Zelle
überführt.
Die Probeneinwaage [g] ist:
Probenmenge [g] * Lösungsmittel in Titrierzelle [g] / Gesamtlösungsmittel [g]
In unserem Beispiel wäre die Probenmenge 0,500 g!
Der Blindwert ist in aller Regel niedrig und wird mit ca. 10 g Lösungsmittel bestimmt. Then start tiration.
Calculation
% Water = (consumption [ml] – blind value [ml])* 100 /
(weighed-in quantity [g] * 1000)
Parameters
End value:
20 µA
Switch-off time: 10 sec
Potential:
100 mV
Notice
• Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter denen
die Probe titriert wird, z. B. das gleiche Lösungsmittelgemisch
• Es empfiehlt sich, vorher einen Blindwert zu bestimmen und diesen automatisch
zur Korrektur des Ergebnisses zu verwenden. Die Menge für den Blindwert und
die Probentitration müssen identisch sein.
Through the septum using a syringe and needle (liquid standards)
Using a solid lock (solid standard)
Directly by opening the plug (hochviskose Proben, solid standard)
Connection of an oven
Introduction of gas
22
4.3.10
Working with the oven
Method
No. 10
Application
Equipment
Reagents
Titration with the oven
†
†
†
†
†
†
†
†
†
†
†
†
TitroLine KF Titrator
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
5 ml one-way syringe with needle len approx. 60 mmplus needle protector
Wägeschiffchen
3 or 4-digit weighing-balance
Beaker glass
TZ 1052 Drying oven
TZ 1050 Accessories
Titriermittel: Ein- oder Zwei-Komponenten Titriermittel
Vorlage: Methanol, Composolver oder Solvent je nach Titriermittel
Trägergas (z.B. Stickstoff)
Sample preparation Feste Proben werden ggf. zerkleinert, flüssige Proben mit einer Spritze direkt aufgenommen, hochviskose Proben mit der Spritze ohne Nadel aufgezogen.
Sample input
⇒ Mit Spritze und Nadel in das Schiffchen des Ofens (liquid standard)
⇒ Using a solid lock (solid standard)
⇒ Durch Öffnen des Stopfens direkt in das Schiffchen des Ofens (high-viscous
standards, solid standards)
⇒ Connection of an oven
⇒ Introduction of gas
Description
Der Ofen wird auf die erforderliche Temperatur aufgeheizt. Die Temperatur hängt
von der Art der Probe ab.
Es wird etwa 250 ml/min getrocknetes Gas (z.B. Stickstoff) durch den Ofen geleitet
(die besten Erfahrungen liegen zwischen 150 – 500 ml/min). Im Titrationsgefäß
können noch gut die einzelnen aufsteigenden Luftblasen unterschieden werden.
Wenn der Ofen aufgeheizt ist, wird der Gasstrom abgeschaltet und konditioniert.
Nach dem Konditieren wird das Gas wieder eingeschaltet und der Blindwert wird
über den gleichen Zeitraum bestimmt, den später die Probe im Ofen sein wird.
Für die Probentitration wird konditioniert wie vor. Die Probe wird eingewogen und in
den Ofen auf das Schiffchen gegeben. Das Schiffchen wird mit der Handkurbel in
den heißen Teil des Ofens geschoben. Die Probenmenge wird eingegeben und die
Titration gestartet. Der Gasstrom wird auf die gleiche Menge eingestellt, wie beim
Blindwert. Die Titration beginnt nach einer Wartezeit von üblicherweise 10 Minuten.
Calculation
% Water = (consumption [ml] – blind value [ml]) * 100 /
(weighed-in quantity [g] * 1000)
Parameters
Waiting time: 10 minutes or 600 seconds
End value:
20 µA
Switch-off time: 10 sec
Potential:
100 mV
Notice
• Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter denen
die Probe titriert wird, z.B. das gleiche Lösungsmittelgemisch
• Der Blindwert hat bei dieser Methode einen großen Einfluss und muss unter den
gleichen Bedingungen bestimmt werden, unter denen die Proben titriert werden.
23
2.2.3.1
General form of working specifications
Method
Application
No. 11
†
†
†
Blind value
Titer determination
Sample titration
TitroLine KF Titrator
TM KF Titration Stand
TZ 1770 Titration vessel
TZ 1106 Double platinum electrode
TZ 1721 Solid lock
5 ml one-way syringe with needle length approx. 60 mm plus needle protector
Wägeschiffchen
† 3 or 4-digit weighing-balance
† Beaker glass
† TZ 1052 Drying oven
† TZ 1050 Accessories
† Further accessories
† Titriermittel: Ein- oder Zwei-Komponenten Titriermittel
Reagents
† Vorlage: Methanol, Composolver oder Solvent je nach Titriermittel
† Trägergas (z.B. Stickstoff)
† Standard 10 mg water / g or other standard
† Andere Reagenzien: Lösungsmittel
Sample preparation † Direkte Eingabe der Probe in das Titrationsgefäß
† Aufnahme der Probe mit einer Spritze mit Kanüle
† Aufnahme der Probe mit einer Spritze
† Interne Extraktion durch Wartezeit vor der Titration
† External extraction
† Ausheizen mit dem Ofen
† Mit Spritze und Nadel in das Schiffchen des Ofens (flüssige Proben)
Sample input
† With solid lock (solid standards)
† Durch Öffnen des Stopfens direkt in das Schiffchen des Ofens (high-viscous
standards, solid standards)
† Connection of an oven
† Introduction of gas
Beschreibung der Vorgehens mit folgenden Kriterien:
Description
† Blindwert wichtig
† Ermittlung und Begrenzung der Probenmenge
† Art und Menge Lösungsmittel
Calculation
† Probe:
% Water = (consumption [ml] – blind value [ml]) * 100 /
(weighed-in quantity [g] * 1000)
† Liquid standard:
Concentration titration agent [mg/ml] = weighed-in quantity [g] *
Standard [mg water/g] * factor 1 / ((consumption [ml] – blind value [ml]) * factor 2
† Water:
Concentration titratin agent [mg/ml] = weighed-in quantity [mg]
((consumption [ml] – blind value [ml]) * factor 2)
† Sodium tartrate-hydrate:
Concentration titration agent [mg/ml] = weighed-in quantity [g] * 1000 * 0,1566
((consumption [ml] – blind value [ml]) * factor 2)
Equipment
†
†
†
†
†
†
24
Parameters
Notice
4.3.11
Waiting time:
________ min
End value:
________ µA
Switch-off time: ________ sec
Potential:
________ mV
† Der Titer muss unter den gleichen Bedingungen bestimmt werden, unter denen
die Probe titriert wird, z.B. das gleiche Lösungsmittelgemisch.
† Der Blindwert hat bei dieser Methode einen großen Einfluss und muss unter
den gleichen Bedingungen bestimmt werden, unter denen die Proben titriert
werden.
† Weitere Hinweise
† Warn- und Sicherheitshinweise
Inspection of the titration system
Regulations concerning titration and the standard enclosed with the delivery. Desired results, error
descriptions.
Method
No. 12 a
Application
Inspection of the titration system Part I: Titerstellung
Equipment
† TitroLine KF Titrator
† TM KF Titration Stand
† TZ 1770 Titration vessel
† TZ 1106 Double platinum electrode
† 5 ml one-way syringe with needle length approx. 60 mm plus needle protector
† 3 or 4-digti weighing-balance
† Beaker glass
† Titration agent: Two-component titration agents
† Pattern: Solvent according to titration agent
† Standard 10 mg water / g or other standard
Die Spitze der Ampulle mit dem Standard wird aufgebrochen. Aufnahme des Standards
(ca. 2 ml auf 3 oder 4 Stellen genau) mit einer Spritze mit Kanüle. Der Nadel-Schutz wird
aufgezogen und die Spritze mit der Nadel nach oben in ein Becherglas auf die Waage gestellt. Die Waage wird tariert.
Der Nadelschutz wird abgenommen und die Probe langsam ohne Eintauchen durch das
Septum in das Titrationsgefäß gespritzt. Den Nadelschutz wieder aufziehen und die Spritze
zurückwiegen. Das an der Waage angezeigte Gewicht wird am Titrator eingegeben.
Es wird aus der Lösungsmittelflasche so viel Solvent in das Titrationsgefäß gepumpt, bis
die Stifte der Doppelplatinelektrode vollständig eintauchen. Die Methode Titerstellung wird
gewählt und gestartet. Der Titrator konditioniert. Wenn die Zelle trocken ist, wird das
Konditionieren beendet.
Der Nadelschutz wird abgenommen und die Probe langsam ohne Eintauchen durch das
Septum in das Titrationsgefäß gespritzt. Der Nadelschutz wird wieder aufgezogen und die
Spritze zurückgewogen. Das an der Waage angezeigte Gewicht wird am Titrator eingegeben. Die Titration wird gestartet. Nach Beenden der Titration wird das Ergebnis angezeigt
bzw. ausgedruckt. Diese Titration wird drei mal wiederholt.
Reagents
Sample
preparation
Sample input
Description
Calculation
Parameters
Notice
Die Ergebnisse sollten den Titer der Titrierlösung angeben:
Type
reagent [mg water/ml]
rel. standard deviation [%]
1
0.8 .. 1.2
<2
2
1.5 .. 2.5
<1
2.5
2.0 .. 3.5
<1
5
4.0 .. 5.5
< 0.5
Liquid standard: Concentration titration agent [mg/ml] = weighed-in quantity [g] * 10,00
((consumption [ml] – 0,0) * 1,00
Waiting time:
5 min;
End value: 20 µA
Switch-off time: 10 sec;
Potential: 100 mV
Warning and safety information
25
Method
No. 12 b
Application
Überprüfung des Titrationssystems Teil II: Testtitration
Equipment
† TitroLine KF Titrator
† TM KF Titration Stand
† TZ 1770 Titration vessel
† TZ 1106 Double platinum electrode
† 5 ml one-way syringe with needle length approx. 60 mm plus needle protector
† 3 or 4-digti weighing-balance
† Beaker glass
Reagents
† Titration agent: Two-component titration agents
† Pattern: Solvent according to titration agent
† Standard 10 mg water / g or other standard
Sample preparation Die Spitze der Ampulle mit dem Standard wird aufgebrochen. Aufnahme des
Standards (ca. 2 ml auf 3 oder 4 Stellen genau) mit einer Spritze mit Kanüle. Der
Nadel-Schutz wird aufgezogen und die Spritze mit der Nadel nach oben in ein
Becherglas auf die Waage gestellt. Die Waage wird tariert.
Sample input
Der Nadelschutz wird abgenommen und die Probe langsam ohne Eintauchen
durch das Septum in das Titrationsgefäß gespritzt. Der Nadelschutz wird wieder
aufgezogen und die Spritze zurückgewogen. Das an der Waage angezeigte Gewicht wird am Titrator eingegeben.
Description
Es wird aus der Lösungsmittelflasche so viel Solvent in das Titrationsgefäß
gepumpt, bis die Stifte der Doppelplatinelektrode vollständig eintauchen.
Die Methode Probe wird gewählt und gestartet. Der Titrator konditioniert. Wenn die
Zelle trocken ist, wird das Konditionieren beendet.
Die Nadelschutz wird abgenommen und die Probe langsam ohne Eintauchen durch
das Septum in das Titrationsgefäß gespritzt. Der Nadelschutz wird wieder aufgezogen und die Spritze zurückgewogen. Das an der Waage angezeigte Gewicht wird
am Titrator eingegeben.
Die Titration wird gestartet.
Nach Beenden der Titration wird das Ergebnis angezeigt bzw. ausgedruckt.
Diese Titration wird dreimal wiederholt.
Die Ergebnisse sollten den Wassergehalt des Standards in % Wasser angeben.
Der Wassergehalt des Standards ist 1,00 %.
Die relative Standardabweichung sollte < 0,5 % sein.
Calculation
Probe:
% Water = (consumption [ml] – 0.00) * 100 / (weighed-in quantity [g] * 1000)
Parameters
Waiting time:
5
End value:
20
Switch-off time: 10
Potential:
100
Notice
Warning and safety information
min
µA
sec
mV
26
2.4
Error and their consequences
4.4.1
The titration takes too long
If the titration takes too long (> 5 minutes), something is not in order in most cases. The causes may be of
a quite trivial nature. The following list shows causes for an excessive duration of titration and provides
information on how to detect and eliminate the individual causes.
† Wrong solvent
In particular with the two-component reagents, it happens from time to time that, for instance, methanol
alone is used instead of a correct solvent including the required reaction partners. KF titration cannot
take place.
† Cell open or leaking
The drift is extraordinarily high. If its general value is around 4 µl/min, and suddenly it is in the range of
10 µl/min, this is a frequent cause of error.
† Titration agent used up
Trivial, yet not uncommon. The dark brown bottles and the light-protected units make it difficult to see
whether there is enough reagent contained in the bottle or in the unit.
† Side reactions
In addition to the actual KF reaction, a side reaction is taking place which is also consuming titration
agent. Towards the end, the drift remains constant on a certain value, for instance at 20 µl/min.
† Chemicals too old
A “best before” date which should not be exceeded is printed on most reagents. If their use cannot be
avoided, the titration should be observed closely.
† No more drying effect of desiccant
The molecular sieve should be re-dried on a regular basis (> = 250 °C over more than three hours).
Used molecular sieve makes itself noticeable by an above-normal drift (e.g. 6 instead of 4).
4.4.2
The titration solution turns brown
If the titration solution turns brown, one of the following problems is present as a rule:
† Overtitration
The titration reaches the end point too early, and therefore overtitration occurs. In order to determine
the overtitration quantity, use the syringe to introduce drops of standard through the septum until a
discoloration takes place. Count the drops, then determine the water contents for the drop number
separately.
† Microtip has come off
The titration reaches the end point too early, and therefore overtitration occurs. In order to determine
the overtitration quantity, use the syringe to introduce drops of standard through the septum until a
discoloration takes place. Count the drops, then determine the water contents for the drop number
separately.
† No water in sample
If the titration begins with no water being contained in the sample, (insignificant) overtitration will occur
as a matter of course.
4.4.3
Detected water contents is too low
There are many causes for incorrect titration results. Below are just a few examples of causes of errors.
† Wrong titer
The titer was not determined correctly or has changed.
† Wrong reagent
The new reagent has a different factor, or it is a different titration agent.
† Sample not dissolved (or only partially)
If the sample is not fully dissolved, then only a part of the water can be determined.
† Sample not comminuted
If samples are not disintegrated the water in the sample may often not be released to a sufficient degree.
† Titration conditions are not ideal
Under non-optimum titration conditions (polarity, solvent, pH value, temperature, ...), it may e.g. happen
that too little water is found in the sample.
27
4.4.4
Detected water contents is too high
† Side reactions
A side reaction will always lead to an excessive value (please refer to the side reactions chapter).
† Wrong titer
The titer was not determined correctly, or it has changed.
† Wrong reagent
The titer was not determined correctly, or it has changed.
† Sample not homogenous
A part of the sample with a higher water contents may have been taken.
† Incorrect formula
The results may be incorrect owing to wrong blank values, titer. Is “sample titration” actually the current
method? An incorrect result unit was selected.
4.4.5
Brown titration solution is leaking
† Leakage
After cleaning a unit it may happen from time to time that the hoses are not tightened firmly enough. A
thread may have been damaged as a result of an excessive tightening of the hoses.
† Microtip off
The micro titration tip with the valve is only plugged on the hose. It may have been pushed out, e.g. by
clogging. The risk of clogging is particularly high after longer periods without operation.
† Overpressure or vacuum within the system
If the openings in the titration vessel are clogged, a vacuum may build up in the titration vessel during
the evacuation process. Likewise, an overpressure may occur during the dosage of the solvent or the
titration agent.
4.4.6
Titration proceed fast and without stopping
† With two-component system: no solvent
With two-component reagents the solvent has to contain the SO2, base, and alcohol components,
otherwise the KF reaction cannot take place. Please make sure that the matching components are
being used.
† Excessive sample quantity
The sample contains so much water that the consumption is too high. The titration should be repeated
with a smaller sample quantity after sucking the sample off.
† Excessive water contents
The sample contains so much water that the consumption is too high. The titration should be repeated
with a smaller sample quantity after sucking the sample off.
† Contaminated solvents
The solvents contain so much water that the conditioning process consumes too much reagent and
lasts too long. The solvents should be pre-dried. This also improves their water extraction properties.
4.4.7
Wrong output of the result
† Incorrect formula
An incorrect output unit was selected.
† Wrong method
Instead of the sample titration mode, titration was performed in the blank value or titer determination
mode.
2.5
Validation of the KF titration
The sounding of the term might imply truth. This would mean that “validation” would be supposed to
ensure the veracity of an analysis result. However, Latin “validere” means “to correspond”, and this leads
to the logic, official definition, DIN EN ISO 8402:
“Confirmation on the basis of an investigation and by the provision of an objective proof of the fact that the
special requirements imposed on a particular, intended use are met".
Proof: provable information based on facts gathered by way of observation, measurement, a test, or in a
similar form.
28
4.5.1
Validation scheme and evaluation of general features
The validation of a method requires a series of validation features which are identical for all methods. The
individual items, however, are not of the same importance in each case. So it is, for instance, that the
detection limit may certainly be particularly significant with regard to a method of trace analytics, whereas
it is most likely to be irrelevant with regard to the contents determination in the high % range. In the
following table, the validation features are evaluated including comments.
Validation feature
Importance
Significance for titration
Accuracy
++
the strong point of titration
Correctness
++
to be evidenced for each method
Traceability
+
as a rule, no sample preparation is necessary
Linearity
+
titration is a method with a high degree of linearity. The
concentration range being used should have been verified.
Selectivity
o
usually of no importance
Robustness
++
importance for the applicability to other methods
Detection limit
o
usually omitted
Determination limit
o
The range in which samples occur is defined and checked. As
a rule, however, the sample is adapted to achieve an uniform
consumption.
Titration analysis methods
Chemical reaction
Reagent and dosage
Indication
• Applicability
Titer stability of the titration agent • Sensor functions according to specifications
• Stoichiometry
• Accurate dosability with accurate
volumes of the burette
• Sensor is suitable for the indication of the
chemical transformation (selectivity,
sensitivity)
• Reaction speed
• Accurately known composition
and contents of the reagent
• End of the chemical reaction
• Side reactions
Chemical reaction
• Equivalent transformation can be read off or
calculated from the curve
Reagent and dosage
Reagent • Research and
publication
• Ensures composition
Manufact. • Patents
• Ensures durability
Device
• Experience
• Ensures accurate dosing
• Ensures indication function
• Applications
• Declaration of conformity
• Declaration of conformity
• Manufacturer’s test certificate
• Manufacturer’s test certificate
• Titer determination
• Curve analysis
• Inspection of testing means
• Inspection of testing means
Manufactu
rer
User
Indication
• Validation
29
4.5.2
Inspection of testing means
The manufacturer of a titration device warrants the proper functioning of his device. He verifies this, for
instance, on the bases of the criteria contained in the appropriate tables (table 4 to 8). The user can adopt
these features for his own testing-means inspection or make a selection which he considers useful for his
own purposes.
Visual inspection
Table 4:
Display
Check segments: completeness, brightness, uniformity; check special characters
Plug
connections
Corrosion, solidity, bending, completeness, damage to the plug casings
Switches + pots
Corrosion, smooth running, latching and end positions, mechanical stability,
inscriptions
Casing
Damage, impaired function
Cylinder, piston
Damage, wear and tear, dull glass, glass surfaces (interior and exterior)
Piston rod
Corrosion, damage
Seals
Liquid leakage, cracks, deformation
Hoses
Bends, damage, connection / threading, liquid leakage, air intake
Internal structure General condition
Printed boards
Damage, in particular corrosion of the printed circuits, the components, the soldered
points, the plugs
Functioning mechanical
system
Corrosion of and damage to the driving system, especially the spindle, play of the
mechanical system
Interfaces
Table 5:
RS-232-C
Functional check: Transmission of data to a test PC using terminal program
others
Practical functional check, e.g. SGH interface with connected SGH device
Recorder output
Measurement of 3 voltages, distributed across the range
Controller input
Practical functional check with the corresponding device
Stirrer connection Practical functional check with connected stirrer
Centronics
Connect printer, transmit 5 values
Table 6:
Electronics
Measurement amplifier
Inspection and readjustment according to alignment
instructions
Controlling behaviour
Visual inspection of the safety-relevant connections
Electrical safety
Measurement based on standards
Table 7:
Dialogue system
Keyboard function
Menu scrolling, check of the function keys
Parameter input
Menu scrolling with a stop at 5 positions previously
determined at random. At these positions: Input of
meaningful
parameters.
Check
whether
the
values/characters displayed correspond to those input.
30
Additionally with QA inspections
Table 8:
Certificate
A quality certificate according to DIN 55350-18-4.2.2 is issued. This document can be
used in quality management systems according to DIN EN ISO 9000 ff. The certificate
must only be issued by persons being nominated by the management and the quality
management department.
Spindle travel
To be measured in three points using an altimeter: 10 %, 50 %, 100 %,
variance comparison
Spindle force
Measurement of the maximum in a force-sensing device
pH/mV ranges
Variance comparison of the measurement deviation in 3 points each
Temperature
range
as pH/mV range
Dead-Stop range
as pH/mV range
Volume according
DIN
Weighing with water according to DIN 12 650, Part 5, at 10 %, 50 %, 100 %,
variance comparison
With regard to titration, the accurate dosage of the reagent is unquestionably the most important point.
This is checked according to DIN 12650, Part 6. In the course of three dosing processes with approx.
10 %, 50 %, and 100 %, each value must not deviate by more than 0.3 % (or as per manufacturer’s
specification) from the desired value, referred to the total volume of the cylinder of the burette.
The new ISO 8655 (under preparation) requires 10 identical volumes each for nominal volume, 50 %
nominal volume and the smallest selectable volume or 10 % of the nominal volume. The correctness of
the volume with a 10 ml burette has to be ± 0.20 %, the precision has to be ± 0.10 per cent of the
command volume
The difference is found in the detail: whereas none of the single values must drop out according to the
DIN, the news ISO makes weighing across a Gauss curve in which a individual value actually may be a
"maverick".
Considering that most of the motor piston burettes do not have to be calibrated, a volumetric inspection
according to these norms is only seldom required. As a matter of experience, visual inspections at shorter
intervals make sense. The more comprehensive volumetric inspection should be performed once per year
or at shorter intervals if the device is subject to great load or if a deviation has been detected.
A practice-oriented alternative (i.e. not according to any normative regulation) consists in a titer
determination using a standard or a titrimetic standard in which different titration volumes are used. In this
process the volumes are selected in such a way that the same quantity range as with the samples is
recorded and, at the same time, different positions of the piston burette are present.
In this way the electronics and many other items including the sensor are inspected automatically as well.
The individual elements have a different influence on the different types of titration. For this reason,
validation is discussed at this point on the basis of two examples. If specific particularities of the testingmeans supervision are of any significant importance, a special reference will be made.
4.5.3
Tests to be made
Test list including example:
Procee- Elements
ding
Preconditions
What has to be done
Reactions A sample is titrated, the titration curve is analysed. Chapter XX shows the major
features of a Karl Fischer titration curve. If the expected contents is smaller or greater
than the first result, one has to reckon with a side reaction.
Reagent
and
dosing
A multiple determination (e.g. 10-fold) is performed using a standard, a titrimetric
standard (di-sodium-tartrate dihydrate), or water (with microliter syringe, weigh if
necessary). If different quantities are being used, which cover different burette
volumes as well, this means that the proper functioning of the titrator is largely
ensured. An additional testing-means supervision is only required if problems occur or
if a basic inspection of the titrator is to be performed.
31
Proceeding
Elements
Preconditions
Tightness
of the
titration
vessel
What has to be done
The titration vessel has to be tight since the air contains a considerable amount of
humidity. This is indicated by the drift. The drift should be less than 5 µg of water per
minute. The drift will be greater if the oven is being used. The drift can be read off
directly on the device, or it is easily obtainable by waiting for one hour after
conditioning (drying of the solvent), followed by a start of a titration.
The drift is calculated as follows:
Drift [ µg/min] = consumption [ml] * titer [mg water/ml] * 1000 / 60 [min]
Indication The proper functioning of the indication can by be established easily:
• Remove the double platinum electrode from the titration vessel
• Start titration: no current is flowing, or no voltage is being indicated
• Use a metal office clip to short-circuit the two platinum pins: a current is flowing,
and titration will disrupt after the switch-off time.
If this test is functioning, the indication system is working properly.
Validation Accuracy Multiple determination of a sample (e.g. 10-fold),
determination of mean value and standard deviation
Correctness
• In the course of each determination, a defined quantity of water (or standard) is
added several times to the sample. This quantity must be retraced completely.
Mean value and standard deviations of the individual retraced quantities are noted.
Less water is indicative of an incomplete transformation. A higher water contents
indicates a drift or side reactions..
• The tests for linearity inspection are analysed. The straight line must show a slope
(if the command consumption is recorded versus the actual consumption) of
approx. 1.00. The straight line must lead through the zero point. The correlation
coefficient should be close to 1.00. Deviations indicate a drift, side reactions, or
incomplete transformations.
• Comparison to the standard the water contents and properties of which are known
and which behaves identically to the sample. The standard has to be certified.
Retracing • In the course of each determination, a defined quantity of water (or standard) is
added several times to the sample. This quantity must be retraced completely.
Mean value and standard deviations of the individual retraced quantities are noted.
• Other samples with a known contents are added to the sample with a known
contents. This sample quantity must be the retraced completely.
Linearity
A number of samples with an increasing contents is titrated. In this process, for
instance, 10 titrations are performed for each contents. The smallest and the greatest
water contents should correspond to the practical requirements. The straight line
must show a slope (if the command consumption is recorded versus the actual
consumption) of approx. 1.00. The straight line must lead through the zero point. The
correlation coefficient should be close to 1.00. Mean value and standard deviation of
the individual titrations are calculated.
Selectivity Karl Fischer titration is selective for water. The method is tested for almost all types of
samples. Side reactions have to be excluded (correctness, linearity, retracing).
Robustness
• Robustness may be determined in the form of an inter-laboratory test.
• All the relevant paramters of Karl Fischer titration are varied:
Electrode, solvent quantities, temperature, steering speed, titration paramters,
titration device
Detection The detection limit is no criterion in contents determination. It can be defined similar
limit
to the determination limit.
Determina The determination limits result from linearity inspection. The smallest and greatest
tion limit sample volumes which are located inside the linear range and meet the required
standard deviation are defined as determination limits.
32
2.6
KF titration and normative documents
KF titration is contained in numerous normative documents. The following table will give you an overview
of these standards.
Document number
BS EN ISO 10101-1
BS EN ISO 10101-2
BS EN ISO 10101-3
DIN 10252
DIN 53715
DIN 53979
DIN EN ISO 10101-1
DIN EN ISO 10101-2
DIN EN ISO 10101-3
DS PD 3201
EN 60814 (BS)
IEC 60814
IP 356
ISO 760
ISO 10101-1
ISO 10101-1 FRENCH
ISO 10101-2
ISO 10101-2 FRENCH
ISO 10101-3
ISO 10101-3 FRENCH
ISO 10336
ISO 10336 FRENCH
ISO 10337
ISO 10337 FRENCH
ISO 10362-2 FRENCH
ISO 11021
ANSI C59.53
Title
NATURAL GAS – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD – PART 1. INTRODUCTION
NATURAL GAS – DETERMINATION OF WATER BY KARL FISCHER
METHOD – PART 2. TITRATION PROCEDURE
NATURAL GASES – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD PART 3. COULOMETRIC PROCEDURE
ANALYSIS OF TOBACCO AND TOBACCO PRODUCTS; DETERMINATION
OF WATER CONTENT; KARL FISCHER METHOD
DETERMINATION OF WATER CONTENT OF PLASTICS BY THE KARL
FISCHER METHOD
TEST OF AIDS FOR DRY-CLEANING; DETERMINATION OF THE WATER
CONTENT ACCORDING TO THE METHOD OF KARL FISCHER
NATURAL GAS – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD – PART 1. INTRODUCTION
NATURAL GAS – DETERMINATION OF WATER BYTHE KARL FISCHER
METHOD – PART 2. TITRATION PROCEDURE
NATURAL GAS – DETERMINATION OF WATER BY KARL FISCHER
METHOD – PART 3. COULOMETRIC PROCEDURE
DETERMINATION OF WATER BY THE KARL FISCHER METHOD.
DETERMINATION OF WATER IN KETONES
INSULATING LIQUIDS – OIL-IMPREGNATED PAPER AND PRESSBOARD –
DETERMINATION OF WATER BY AUTOMATIC COULOMETRIC KARL
FISCHER TITRATION
DETERMINATION OF WATER IN INSULATING LIQUIDS BY AUTOMATIC
COULOMETRIC KARL FISCHER TITRATION
WATER IN CRUDE OILS BY VOLUMETRIC KARL FISCHER TITRATION
DETERMINTN.WATER-KARL FISHER METHOD (GENERAL METHOD)
NATURAL GAS – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD – PART 1: INTRODUCTION
NATURAL GAS – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD – PART 1: INTRODUCTION
NATURAL GAS – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD – PART 2: TITRATION PROCEDURE
NATURAL GAS – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD – PART 2: TITRATION PROCEDURE
NATURAL GAS – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD – PART 3: COULOMETRIC PROCEDURE
NATURAL GAS – DETERMINATION OF WATER BY THE KARL FISCHER
METHOD – PART 3: COULOMETRIC PROCEDURE
CRUDE PETROLEUM – DETERMINATION OF WATER – POTENTIOMETRIC
KARL FISCHER TITRATION METHOD
CRUDE PETROLEUM – DETERMINATION OF WATER – POTENTIOMETRIC
KARL FISCHER TITRATION METHOD
CRUDE PETROLEUM – DETERMINATION OF WATER – COULOMETRIC
KARL FISCHER TITRATION METHOD
CRUDE PETROLEUM – DETERMINATION OF WATER – COULOMETRIC
KARL FISCHER TITRATION METHOD
CIGARETTES – DETERMINATION OF WATER IN SMOKE CONDENSATES –
PART 2: KARL FISCHER METHOD
ESSENTIAL OIL – DETERMINATION OF WATER CONTENT – KARL
FISCHER METHOD
WATER IN INSULATING LIQUIDS (KARL FISCHER METHOD)
33
Document number
API MPMS C10 S7 *E
ASTM D 1123
ASTM D 1364
ASTM D 1533
ASTM D 1744
ASTM D 4017
ASTM D 4377
ASTM D 4928
ASTM D 5530
ASTM E 203
ASTM E 700
ASTM F 1214
BS 2511
BS 3156 S11.3
SS11.3.1
BS 3156 S11.3
SS11.3.2
BS 3156 S11.3
SS11.3.3
BS 4993 P5
BS 5202 P15
BS 5202 P19
BS 5711 P8
BS 5752 P13
BS 6725
BS 684 P2 S2.1
ISO 11021 FRENCH
ISO 11817
ISO 11817 FRENCH
Title
MEASUREMENT STANDARDS CHAPTER 10: SEDIMENT AND WATER
SECTION 7: STANDARD TEST METHOD FOR WATER IN CRUDE OILS BY
KARL FISCHER TITRATION (VOLUMETRIC)
TEST METHOD FOR WATER IN ENGINE COOLANT CONCENTRATE BY
THE KARL FISCHER REAGENT METHOD
STANDARD TEST METHOD FOR WATER IN VOLATILE SOLVENTS (KARL
FISCHER REAGENT TITRATION METHOD)
STANDARD TEST METHODS FOR WATER IN INSULATING LIQUIDS (KARL
FISCHER REACTION METHOD)
TEST METHOD FOR DETERMINATION OF WATER IN LIQUID PETROLEUM
PRODUCTS BY KARL FISCHER REAGENT
STANDARD TEST METHOD FOR WATER IN PAINTS AND PAINT
MATERIALS BY KARL FISCHER METHOD
WATER IN CRUDE OILS BY POTENTIOMETRIC KARL FISCHER TITRATION
WATER IN CRUDE OILS BY COULOMETRIC KARL FISCHER TITRATION
TEST METHOD FOR TOTAL MOISTURE OF HAZARDOUS WASTE FUEL BY
KARL FISCHER TITRIMETRY
TEST METHOD FOR WATER USING VOLUMETRIC KARL FISCHER
TITRATION
WATER IN GASES USING KARL FISCHER REAGENT
WATER SOLUBILITY IN LIQUID PETROLEUM BY KARL FISCHER
METHODS FOR THE DETERMINATION OF WATER (KARL FISCHER
METHOD)
ANALYSIS OF FUEL GASES - PART 11. METHODS FOR NONMANUFACTURED GASES - SECTION 11.3 DETERMINATION OF WATER IN
NATURAL GAS BY THE KARL FISCHER METHOD - SUBSECTION 11.3.1
INTRODUCTION
ANALYSIS OF FUEL GASES - PART 11. METHODS FOR NONMANUFACTURED GASES - SECTION 11.3 DETERMINATION OF WATER IN
NATURAL GAS BY THE KARL FISCHER METHOD - SUBSECTION 11.3.2
TITRATION METHOD
ANALYSIS OF FUEL GASES - PART 11. METHODS FOR NONMANUFACTURED GASES - SECTION 11.3 DETERMINATION OF WATER IN
NATURAL GAS BY THE KARL FISCHER METHOD - SUBSECTION 11.3.3
COULOMETRIC METHOD
METHODS OF TEST FOR ALUMINIUM FLUORIDE FOR INDUSTRIAL USE DETERMINATION OF MOISTURE CONTENT (KARL FISCHER METHOD)
METHODS FOR CHEMICAL ANALYSIS OF TOBACCO AND TOBACCO
PRODUCTS - PART 15. DETERMINATION OF WATER IN SMOKE
CONDENSATE OF CIGARETTES (KARL FISCHER METHOD)
METHODS FOR CHEMICAL ANALYSIS OF TOBACCO AND TOBACCO
PRODUCTS - PART 19. DETERMINATION OF WATER CONTENT (KARL
FISCHER METHOD)
DETERMINATION OF WATER CONTENT: KARL FISCHER METHOD
METHODS OF TEST FOR COFFEE AND COFFEE PRODUCTS - PART 13.
ROASTED GROUND COFFEE: DETERMINATION OF MOISTURE CONTENT
[KARL FISCHER METHOD (REFERENCE METHOD)]
METHOD FOR DETERMINATION OF WATER IN LIQUID DIELECTRICS BY
AUTOMATIC COULOMETRIC KARL FISCHER TITRATION
METHODS OF ANALYSIS OF FATS AND FATTY OILS - PART 2: OTHER
METHODS - SECTION 2.1: DETERMINATION OF WATER BY THE KARL
FISCHER METHOD
ESSENTIAL OIL - DETERMINATION OF WATER CONTENT - KARL FISCHER
METHOD
ROASTED GROUND COFFEE - DETERMINATION OF MOISTURE CONTENT
- KARL FISCHER METHODS (REFERENCE METHOD)
ROASTED GROUND COFFEE - DETERMINATION OF MOISTURE CONTENT
- KARL FISCHER METHODS (REFERENCE METHOD)
34
Document number
ISO 4317
ISO 6488-1
ISO 6488-1 FRENCH
ISO 8534
ISO 8534 FRENCH
JIS K0113
Title
SURFACE-ACTIVE AGENTS AND DETERGENTS - DETERMINATION OF
WATER CONTENT - KARL FISCHER METHOD
TOBACCO - DETERMINATION OF WATER CONTENT - PART 1:
KARL FISCHER METHOD
TOBACCO - DETERMINATION OF WATER CONTENT - PART 1:
KARL FISCHER METHOD
ANIMAL AND VEGETABLE FATS AND OILS - DETERMINATION OF WATER
CONTENT - KARL FISCHER METHOD
ANIMAL AND VEGETABLE FATS AND OILS - DETERMINATION OF WATER
CONTENT - KARL FISCHER METHOD
GENERAL RULES FOR METHODS OF POTENTIOMETRIC,
AMPEROMETRIC COULOMETRIC, AND KARL-FISCHER TITRATIONS
On the Internet, these normative documents or standards can be investigated and also ordered as titles or
abstracts. The following addresses are intended to give you a starting point for your own excursion to the
Internet:
ASTM
Information Services GmbH
DIN-Normen
VDE
Technischer Fachbuch-Vertrieb
http://www.astm.org
http://www.global.ihs.com
http://www.din-normen.de
http://www.vde-verlag.de
http://www.tfv.ch
Further working specifications are contained in the Phamakopoeen (Ph. Eur. II; DAB 96, USP XXI).
2.7
KF titration and quality assurance
As a rule, KF titration is used within the framework of quality assurance. Many aspects have already been
mentioned in the validation section, such as the testing-means supervision.
In order to enable the account for the current trends, it is not intended to list the features of all different
quality systems. We rather include some important organisations including their Internet addresses.
Some features, however, should be noted here:
ISO 9000: A testing-means supervision made ensure the eligibility for use of a KF titrator. In the preceding
chapter as well as in the annex you will find some practical information. The attributality to a national or
other standard is important. KF titration offers some certified standards. The scope of delivery of the
TitroLine KF Titrator contains standards of this type. The manufacturer of the reagents will offer you
detailed information in this context.
GLP/GMP This is focused on the contents and form of the documentation regarding the use of the
TitroLine KF Titrator. The comprehensibility of the result is the most important requirement in this context.
Validation: Please refer to chapter XX
For the GLP and GMP range you will find a number of good tips on the Internet compiled by the DGGF
association.
DGGF (Deutsche Gesellschaft für Gute Forschungspraxis)
http://www.dggf.de
BARQA (British Association for Research Quality Assurance)
http://www.barqa.com
BIRA (British Institute of Regulatory Affairs)
http://www.bira.org.uk
DIA (Drug Information Association)
http://www.diahome.org
ESRA (European Society of Regulatory Affairs), viele Links zu internationalen Behörden
http://www.esra.org
ISQA (International Society of Quality Assurance)
http://www.quality.org/isqa.info.txt
35
Almost all industrial association meanwhile have set up their own homepages. As a rule, you will find there
information on the industry being served as well as on the economic importance plus links to the member
companies.
International
ICH (International Conference on Harmonisation)
http://www.ifpma.org/ich1.html
Die Homepage der international abgestimmten Arzneimittelprüfrichtlinien
Deutschland
BAH (Bundesfachverband der Arzneimittel-Hersteller, Bonn)
http://www.bah-bonn.de
BPI (Bundesverband der Pharmazeutische Industrie, Frankfurt)
http://www.bpi.de
VCI (Verband der chemischen Industrie, Frankfurt)
http://www.chemische-industrie.de
EU (European Union)
http://europa.eu.int/eur-lex
The wording of all major laws of the European Union can be obtained here. You will get free access to
publications of the gazette of the EU from the past 20 days as well as to the European Treaties,
consolidated versions of the currently applicable EU law, and judgements of the European Court, and this
in all official languages of the EU. They are updated on a daily basis.
OECD (Organisation for Economic Co-Operation and Development, Paris, Frankreich)
http://www.oecd.org/ehs
A brief English text on the OECD activities in the range of GLP as well as the complete English wording of
the new edition of the "OECD Principles of GLP" and the consent documents can be found at
http://www.oecd.org/ehs/glp.htm
US-FDA (U.S. Food & Drug Administration)
http://www.fda.gov/fdahomepage.html
Food and Drug Administration
Center for Drugs and Biologics
Office of Drug Research and Review (HFN-100)
5600 Fishers Lane
Rockville, Maryland 20857
(301-443-4330)
D-BgVV (Bundesinstitut für gesundheitlichen Verbraucherschutz und Veterinärmedizin, Berlin)
http://www.bgvv.de
Die GLP-Bundesstelle (z.Zt. ohne eigene Homepage) ist Teil des Fachbereichs 8 'Chemikalienbewertung'.
D-UBA (Umweltbundesamt, Berlin)
http://www.umweltbundesamt.de
US-EPA (U.S. Environmental Protection Agency)
http://www.epa.gov
36
3
List of keywords
4
Annexes
4.1
Applications
Liste von etwa 10(-20) Applikationen
4.2
Documents
4.2.1
DQ Specimen
The pharmaceutics and medical sector, but increasingly the food range, too, are requesting various
qualifications describing a suitable and properly functioning analysis system. In this context, the following
abbreviations have the meaning opposite to them:
DQ
IQ
OQ
PQ
Design Qualification
Installation Qualification
Operational Qualification
Performance Qualification
4.2.2
IQ Specimen
4.2.3
OQ Specimen
4.2.4
PQ Specimen
„Pflichtenheft“
„Installations-Qualifizierung“
„Arbeitsweisen-Qualifizierung“
„Leistungs-Qualifizierung“
Prior to purchase
Required dor installation
Operation of the device
Inspection of the device