The document discusses the Karl Fischer titration technique for determining water content in samples. It describes the history of the technique developed by Karl Fischer in the 1930s. The technique is based on a chemical reaction between water and other reagents like iodine, sulfur dioxide, and a solvent. Depending on the water content, either volumetric or coulometric Karl Fischer methods are used to determine water over different concentration ranges. Now the technique is performed using automated Karl Fischer titration instruments.

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Water Determination by Karl Fischer Titration
Presentation · November 2017
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2. Water Determination by
Karl Fischer Titration
Cosimo A. De Caro
Albert Aichert
Mettler-Toledo GmbH, Analytical
Switzerland

3. Karl Fischer Titration: An Introduction 1
Agenda
 Why water determination
 Methods for water determination
 History of Karl Fischer Titration
 Karl Fischer Titration

4. Karl Fischer Titration: An Introduction 2
Why Water Determination?
Sugar stored in silos
Too much surface moisture
will NOT
trickle down
Sugar removal with
pickaxes or
a hammer drill.

5. Karl Fischer Titration: An Introduction 3
Why Water Determination?
Flour
Too little moisture (less than 10% water).
dust explosion

6. Karl Fischer Titration: An Introduction 4
Why Water Determination?
Butter
Maximum water content is 16.5 % by law.
Optimization of the water content in the butter production, for
maximum profit.

7. Karl Fischer Titration: An Introduction 5
Why Water Determination?
Too much water. Decomposition of active agent.
The serum is not active anymore, when you need it!
Drugs: Lyophilized serum

8. Karl Fischer Titration: An Introduction 6
Why Water Determination?
Production needs plastic granulate with water < 5 ppm
Too much water Bad music quality
CD Disc

9. Karl Fischer Titration: An Introduction 7
Why Water Determination?
Brake fluid
Too much water Brakes do not work anymore.
On steep mountain roads brakes get too hot !

10. Karl Fischer Titration: An Introduction 8
Why Water Determination?
Absorbable Suture Material
Too much water Absorption too early
Complete absorption after 17 – 21 days.
Material: polyglycolic acid Water content max. 400 ppm.

11. Karl Fischer Titration: An Introduction 9
Why Water Determination?
Gun powder
Water content too low: Barrel burst
Water content is important
Water content too high

12. Karl Fischer Titration: An Introduction 10
Why Water Determination?
Kerosene in aircraft jet engine
Water content must be very low
High water content: Kerosene freezing, blockage of tubing

13. Karl Fischer Titration: An Introduction 11
Why Water Determination?
Water in transformer oil
Almost no water in transformer oil to avoid short-circuit
A too high water content will lead to a short circuit

14. Karl Fischer Titration: An Introduction 12
Agenda
 Why water determination
 Methods for water determination
 History of Karl Fischer Titration
 Karl Fischer Titration

15. Karl Fischer Titration: An Introduction 13
Methods for Water Determination
Drying oven
Dry sample in a drying oven at higher temperature until the mass is
constant.
Advantages: Large number of samples.
Large sample size possible.
Disadvantages: Long measurement time (some hours)
Large amount of manual effort.
Other volatile substances evaporate.

16. Karl Fischer Titration: An Introduction 14
Methods for Water Determination
Moisture analyzer
Dry sample by IR or halogen heater on a balance until the mass is
constant.
Advantages: Simple operation.
Short measurement time (5 – 15 minutes)
Disadvantages: Single sample at a time.
Other volatile substances evaporate.
Decomposition of the sample.
HR73 Halogen
Moisture Analyzer

17. Karl Fischer Titration: An Introduction 15
Methods for Water Determination
Karl Fischer Titration
 Fast (1 ... 2 minutes)
 Selective for water
 Accurate and precise
 Wide measuring range (ppm - 100%)
 No decomposition

18. Karl Fischer Titration: An Introduction 16
Agenda
 Why water determination
 Methods for water determination
 History of Karl Fischer Titration
 Karl Fischer Titration

19. Karl Fischer Titration: An Introduction 17
History of Karl Fischer Titration
Karl Fischer
His job:
Start up oil refineries all over the world.
His problem:
Water determination in oil.
Karl Fischer: Petroleum Chemist 1901 - 1958

20. Karl Fischer Titration: An Introduction 18
History of Karl Fischer Titration
Karl Fischer
Bunsen reaction:
2 H2O + SO2 + I2  H2SO4 +2 HI
Karl Fischer on the way to the next job overseas

21. Karl Fischer Titration: An Introduction 19
History of Karl Fischer Titration
Karl Fischer back in the Lab
Methanol as solvent
Pyridine as base
happened to be around in the Lab
Bunsen reaction:
2 H2O + SO2 + I2  H2SO4 +2 HI
1935 First publication by Karl Fischer
3 years hard work, backstrokes and success

22. Karl Fischer Titration: An Introduction 20
History of Karl Fischer Titration
 1935 Scientific publication by Karl Fischer
 1950 First Karl Fischer Titrator commercially available.
 1970 First coulometric KF Titrator commercially available.
 1980 Pyridine free Karl Fischer reagents.
 1984 DL18 first microprocessor controlled KF Titrator
with automatic drift compensation, from METTLER TOLEDO
 1990 DL37 first KF coulometer from METTLER TOLEDO
 1998 Introduction of the volumetric KF Titrators DL31 / DL38
 2001 Introduction of the coulometric KF Titrators DL32 / DL39
 2008 The new Compact KF V20/V30 Volumetric
and C20/C30 Coulometric Instruments
 Today One of the most used titration methods.
Over 1 million KF titrations every day!
Karl Fischer Petroleum Chemist 1901 - 1958

23. Karl Fischer Titration: An Introduction 21
Agenda
 Why water determination
 Methods for water determination
 History of Karl Fischer Titration
 Karl Fischer Titration

24. Karl Fischer Titration: An Introduction 22
Karl Fischer Titration
Karl Fischer Reaction
Iodine (I2) reacts with water 1:1
1. SO2 + RN + CH3OH  (RNH)SO3CH3
Two step reaction
2. (RNH)SO3CH3 + H2O + I2 + 2 RN  (RNH)SO4CH3 + 2 (RNH)I
Methylsulfate
A suitable base (RN) keeps the pH value between 5 – 7
In the past: Pyridine now: Imidazole
The solvent (methanol, CH3OH) is involved in the reaction.
50 % of the solvent must be methanol.
Methylsulfite

25. Karl Fischer Titration: An Introduction 23
Karl Fischer Titration
Volumetric Karl Fischer:
Iodine is added by burette during titration.
Water as a relevant component: 100 ppm - 100 %
Coulometric Karl Fischer:
Iodine is generated electrochemically during titration.
Water in trace amounts: 1 ppm - 5 %
+
-
Volumetric & Coulometric Karl Fischer Titration

26. Karl Fischer Titration: An Introduction 24
Summary
 The Karl Fischer titration is a quantitative analytical technique for the
determination of water in different samples.
 It is based on a chemical reaction between 5 components:
iodine, sulfur dioxide, an alcohol (methanol), a base (imidazole) and water.
 Depending on the water content, two kinds of Karl Fischer methods are
used:
- The volumetric technique (100 ppm-100%)
- The coulometric technique (1 ppm-5%)
 Nowadays, the water content is determined by means of fully automated
Karl Fischer titrators.
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