karl fischer

1 INTRODUCTION

Karl Fischer was the scientist who in 1935 developed the original Karl Fischer

method for water determination in various compounds

Water content or moisture content needs to be determined at all stages of the

manufacturing process from raw materials to finished goods Mostly it is determined in

Quality Control Labs Process Labs General Chemistry RampD Labs Analytical Labs and

Manufacturing department as quality of the product depends on it In the pharmaceutical

industry it is essential to know the amount of water contained in the ingredients of a drug in

order to correctly predict its lifetime stability and effectiveness In the food industry the

water content of both raw materials and the finished foodstuff needs to be carefully

monitored

The Karl Fischer titration is a direct method that is almost specific for water The

method is especially useful for low moisture levels (lt1) and also levels lt001 are

achievable

Sheth M N Science College Patan Page no - 1

KARL - FISCHER Analysis Water Content Determination

2 Theory of Karl - Fischer Technique

A Karl Fischer titration determines the water content in a sample based on an

iodineiodide redox reaction The titration is based on the oxidation of sulphur dioxide by

iodine in the presence of water It is the same reaction as the iodometric titration of sulphur

dioxide in water Titration may be defined as ndash ldquoA technique to determine the concentration

of a substance in solution by adding to it a standard reagent of known concentration in

carefully measured amounts until a reaction of definite and known proportion is completed

as shown by a color change or by electrical measurement and then calculating the unknown

concentrationrdquo

In this method water reacts with iodine until the water is consumed and the

endpoint is reached Overall reaction can be written as ndash

H2O + SO2 + I2 harr 2HI + SO3

or

2H2O + SO2 + I2 harr2HI + H2SO4

In 1935 Karl Fischer published a description of ldquoa new procedure for the titration of waterrdquo

using the above reaction in an anhydrous nonaqueous solvent However in order to shift the

equilibrium to the right it was necessary to neutralise the acids produced Originally

pyridine was used as the neutralising base Later on diethanolamine followed by imidazole

were used as buffers Recent studies show that methanol which is the most commonly used

solvent contributes in the reaction Ethanol-based reagents have recently emerged These

have the advantage of being less toxic offering more stable endpoints and faster kinetics

Actually Karl Fischer reaction occurs in two stages

(1) SO2 + CH3OH + B harr CH3SO3- + HB+

(2) CH3SO3- + H2O + I2 + 2B harr CH3SO4

- + 2HB+ + 2I-

Where B = Base

Since water and I2 are consumed in equimolar amounts in reaction 2 if you know

the amount of I2 consumed you know the amount of water that was present in the sample



3 Factors to consider in Karl ndash Fischer Titration

A pH considerations

The Karl Fischer reaction can only take place in a certain pH range between 5 and 7

In this pH range the reaction remains constant If the pH drops too low end point

attainment becomes sluggish or an end point will not be reached at all If the pH is too high

side reactions occur making the titration non-stoichiometric We can therefore say that

errors occurring during a KF titration may be due to a change in the pH of the titration

solvent Use acid base or buffer if necessary

pH dependence of the Karl ndash Fischer reaction [K = Reaction kinetic constant]

The pH of the titration solvent can be tested using a combined pH electrode and a

pH meter The electrode is first calibrated with aqueous buffer solutions and afterwards the

pH of the titration solvent is measured

Note do not place the pH electrode directly into the KF cell because excessive moisture

will be introduced along with the electrode For further information consult the userrsquos

manuals of the main manufacturers of Karl Fischer reagents

B Aldehydes and ketones

Use special reagents to prevent side reactions which generate or consume water and prevent

good endpoints



C Water content

Consider when choosing auto-titrator

D Sample size

Choose sample size that is large enough for precise determination but not so large as to

prolong the titration exceed the capacity of the reagent or be insoluble

The sample size should be small so that as many samples as possible can be titrated in the

same electrolyte solution and the titration time kept short However take care that the

sample contains at least 50 μl water The following table provides guidelines for the sample

weight

Water content of Sample Sample size Water to be determined

100000 ppm = 10 50 mg 5000 microg

10000 ppm = 1 10 mg ndash 100 mg 100 microg ndash 1000 microg

1000 ppm = 01 100 mg ndash 1 g 100 microg ndash 1000 microg

100 ppm = 001 1 g 100 microg

10 ppm = 0001 5 g 50 microg

E Frequency of SolventWorking Medium Change

When the vessel is full when the methanol content is lt25 when the capacity of the

solvent in exceeded (generally not more than 1 mg water per 1 ml methanol)

F Exclusion of background water

Maintain desiccant tubes keep reagents dry good seals on instrument and reagent bottles

G Pre-titration conditioning of working solution

Solventworking solution must be dry but not over titrated before the sample titration to

avoid positive or negative bias to results

H Solubility of the sample

Sample Solubility is Extremely Important to Obtain Total Water Content Sample must be

completely dissolved prior to the start of the titration to obtain accurate and reproducible

results

Total Water = Surface Water + Bound Water



Different methods to improve sample solubility are

i Choose the right solvent

ii Allow sufficient time for dissolution (extract time)

iii Grind sample

iv Co-solvent additions

v Elevating solvent system temperature and

vi Adding homogenizer to system

I Conductivity

Conductivity of the solvent and added sample has to be sufficient to support proper function

of the electrodes in order to detect the endpoint andor generate the iodine titrant (by

coulometric type)

J Influence of the Base

Pyridine was the original Karl-Fischer base Pyridine because of its weak basicity cannot

totally neutralize the methylsulfurous acid The equilibrium in reaction at stage-1 is not

completely shifted to the right The reaction with pyridine is therefore slow and the

endpoint is not stable often making the repeatability using pyridine very poor

Pyridine Imidazole

Imidazole was chosen to replace pyridine as it shifts the reaction at stage-1

completely to the right reaction is swift and endpoints clear and stable Imidazole also does

not have the unpleasant odor and toxicity of pyridine



K Stability of the Reagent

The stability of the original Karl Fischer reagent initially prepared with an excess of

methanol was found to be fairly poor and hence evidently needed frequent standardization

However it was established subsequently that the stability could be improved significantly

by replacing the methanol by 2-methoxyethanol It has been observed that the titer of the

Karl Fischer reagent which stands at 35 mg of water per milliliter of reagent falls rapidly

upon standing with the passage of time Hence the following precautions must be observed

rigidly using the Karl Fischer reagent namely

(a) Always prepare the reagent a day or two before it is to be used

(b) Great care must be taken to prevent and check any possible contamination either of the

reagent or the sample by atmospheric moisture

(c) All glassware(s) must be thoroughly dried before use

(d) Standard solution should be stored out of contact with air and

(e) Essential to minimise contact between the atmosphere and the solution during the course

of titration



4 Types of Karl ndash Fischer titrations

There are two determination methods different in iodine-providing principle

(1) Volumetric titration method and

(2) Coulometric titration method

In the volumetric titration method iodine required for reaction with water is

previously dissolved in water determination TS and water content is determined by

measuring the amount of iodine consumed as a result of reaction with water in a sample It

is good for high level moisture determination

In the coulometric titration method first iodine is produced by electrolysis of the

reagent containing iodide ion and then the water content in a sample is determined by

measuring the quantity of electricity (Coulombs) which is required for the electrolysis (ie

for the production of iodine) based on the quantitative reaction of the generated iodine with

water It is good for low level moisture determination

1048707Volumetric titration ndashwater determination based on volumetric measurement of reagent

Good for high level moisture determinations

1048707Coulometrictitration ndashwater determination based on measurement of time and current (in

coulombs) used to generate the iodine Good for low level moisture determinations

Instrument Type Volumetric Coulometric

Best for Solids and Liquids Low moisture samples

Water content limit 50 ppm to 100 water 1 ppm to 100 water

Matrices Solid Liquid and Gas Liquid only

Advantages All around performance Low detection limit



(Two compartment system possess separate solvent and titrating solutions)



5 Advantages

A Karl Fischer moisture determination is advantageous as compared to a

determination based on weight loss because KF is not affected by volatile compounds The

popularity of the Karl Fischer titration is due in large part to several practical advantages

that it holds over other methods of moisture determination including

i High accuracy and precision

ii Selectivity for water

iii Small sample quantities required

iv Easy sample preparation

v Short analysis duration

vi Nearly unlimited measuring range (1ppm to 100)

vii Suitability for analyzing Solids Liquids and Gases

viii Independence of presence of other volatiles

ix Suitability for automation

In contrast loss on drying will detect the loss of any volatile substance



6 Instrumentation

Following Figure illustrates a simple dead-stop end-point assembly or a Karl Fischer

titration apparatus The titration vessel is fitted with a pair of identical platinum electrodes

a mechanical stirrer with adjustable speed and a burette It will be observed that absolutely

little or no current may flow unless and until the solution is totally free from any polarizing

substances this could perhaps be due to the absorbed layers of oxygen and hydrogen on the

anode and cathode respectively

However the current shall flow only when the two electrodes get depolarized The

Karl Fischer reagent is pumped into the burette by means of hand bellows the access of

moisture is usually prevented by employing an appropriate arrangement of desiccant tubes

Alternatively the stirring may also be accomplished either by using a magnetic stirrer or by

means of suitably dried nitrogen passed gently through the solution during the course of

titration

The end-point is achieved by employing an eiectrical circuit comprising of a

microammeter (A) platinum electrodes together with a 15 V to 20 V battery connected

across a variable resistance of about 25 kΩ First of all the resistance is adjusted in such a

manner that an initial current passes through the platinum electrodes in series with a

microammeter (A) After each addition of reagent the pointer of the microammeter gets

deflected but quickly returns to its original position At the end of the reaction a deflection

is obtained which persists for 10-15 seconds

7 Water Determination Methodology



71 Volumetric titration method

Apparatus

Generally the apparatus consists of an automatic burette a backtitration flask a stirrer and

equipment for amperometric titration at constant voltage or potentiometric titration at

constant current

Because water determination TS is extremely hygroscopic the titration apparatus

should be protected from atmospheric moisture Silica gel or calcium chloride for water

determination is usually used for moisture protection

Procedure

As a rule the titration of the sample with water determination TS should be performed at

the same temperature as that at the standardization of the TS while protecting from

moisture

The apparatus is equipped with a variable resistor in the circuit and the resistor is

adjusted to apply a definite voltage (mV) between a pair of platinum electrodes immersed in

the solution to be titrated The change in current (1048707A) is measured during the dropping of

water determination TS (Amperometric titration at constant voltage) As titration continues

the abrupt change in current in the circuit occurs but returns to the original state within

several seconds At the end of a titration the change in current persists for a certain time

(usually longer than 30 seconds) The end point of titration is determined at this electric

state

Otherwise by adjusting the resistor a definite current is passed between the two

platinum electrodes and the change in potential (mV) is measured during dropping water

determination TS (Potentiometric titration at constant current) With the progress of

titration the value indicated by the potentiometer in the circuit decreases suddenly from a

polarization state of several hundreds (mV) to the nonpolarization state but it returns to the

original state within several seconds At the end of titration the non-polarization state

persists for a certain time (usually longer than 30 seconds) The end point of titration is

determined when this electric state attains

In the case of back titration when the amperometric titration method is used at

constant voltage the needle of microammeter is out of scale while an excessive quantity of

water determination TS remains It returns rapidly to the original position when the titration

reaches the end point



Similarly when the Potentiometric titration method at constant current is used the

needle of the millivoltmeter is at the original position while an excessive quantity of water

determination TS remains A definite voltage is applied when the titration reaches the end

point Unless otherwise specified the titration of water with water determination TS is

performed by either of the methods below Usually the end point of the titration can be

observed more clearly in the back titration method than in the direct titration method

711 Direct titration

Unless otherwise specified proceed as directed below Take 25ml of methanol for water

determination in a dried titration flask and titrate with water determination TS to the end

point Unless otherwise specified weigh accurately a quantity of the sample containing 10

to 50 mg of water transfer it quickly into the titration flask and dissolve by stirring Titrate

the solution with water determination TS to the end point under vigorous stirring When the

sample is insoluble in the solvent powder the sample quickly weigh a suitable amount of

the sample accurately and transfer it quickly into the titration vessel stir the mixture for 30

minutes while protecting it from moisture

Perform a titration under vigorous stirring When the sample interferes with the Karl

Fisher reaction water in the sample can be removed by heating and under a stream of

nitrogen gas and introduced into the titration vessel by using a water-evaporation device

712 Back titration


determination in the dried titration vessel and titrate with water determination TS Weigh

accurately a suitable quantity of the sample containing 10 to 50 mg of water transfer the

sample quickly into the titration vessel add an excessive and definite volume of water

determination TS stir for 30 min protecting from atmospheric moisture and then titrate the

solution with Water Methanol Standard Solution under vigorous stirring



Wheref = the number of mg of water (H2O) corresponding to 1 ml of water determination

TS

Where

f = the number of mg of water (H2O) corresponding to 1 ml of water determination TS

f rsquo = the number of mg of water (H2O) in 1 ml of Water Methanol Standard Solution

713 General Remarks

Volumetric Karl Fischer titration requires the determination of the titre (t) of the Karl

Fischer reagent It is usually quoted in mg of water per ml of Karl Fischer reagent Modern

reagents allow direct titration of water in the sample The sample may be introduced

directly into the KF cell or after an extraction or dissolution with a suitable solvent The

water concentration of the solvent must be determined previously in order to be subtracted

from the sample analysis In Radiometer Analytical titrators all these operations are

simplified and the different results are accounted for automatically The volumetric titration

of water allows the analysis of water concentrations between 01 and 100 If an aliquot

contains less than 1 mg of water coulometric determination will result in a more accurate

result For reasons of precision the titre of the titrant should be chosen so that the titration is

completed with a titrant demand between 1 and 10 ml

The working medium (ie the solvent required) can be freely chosen by the user

depending on the dissolution properties of the sample to be investigated For methanol-

based reagents the stoichiometry 11 of the Karl Fischer reaction is only fulfilled if there is

more than 25 methanol in the reaction mixture A methanol-free working medium can be

used however it is important to determine the titre of the KF reagent in the same working

medium The modern solvents available today present a high buffer and dissolution

capacity These solvents consist of sulphur dioxide a base and methanol or ethanol The

main advantages of these solvents are

bull A more rapid titration due to better reaction kinetics an advantage especially for the

titration of large amounts of water

bull A better reproducibility because the reaction environment is stable The pH and the

sulphur dioxide concentration remain constant



For the titration of samples producing side reactions (aldehydes ketones and

silanols) it is necessary to use an appropriate solvent Most reagent manufacturers include

the letter K in the commercial name of such solvents

72 Coulometric titration

Apparatus

Usually the apparatus is comprised of an electrolytic cell for iodine production a stirrer a

titration flask and a potentiometric titration system at constant current The iodine

production device is composed of an anode and a cathode separated by a diaphragm The

anode is immersed in the anolyte solution for water determination and the cathode is

immersed in the catholyte solution for water determination Both electrodes are usually

made of platinum-mesh


should be protected from atmospheric moisture For this purpose silica gel or calcium

chloride for water determination is usually used Procedure Take a suitable volume of an

anolyte for water determination in a titration vessel immerse in this solution a pair of

platinum electrodes for potentiometric titration at constant current

Then immerse the iodide production system filled with a catholyte for water

determination in the anolyte solution Switch on the electrolytic system and make the

content of the titration vessel anhydrous Next take an accurately weighed amount of the

sample containing 15 mg of water add it quickly to the vessel and dissolve by stirring

Perform the titration to the end point under vigorous stirring When the sample is insoluble

in the anolyte powder it quickly and add an accurately weighed amount of the sample to

the vessel After stirring the mixture for 5 to 30 minutes while protecting from atmospheric

moisture perform the titration with vigorous stirring Determine the quantity of electricity

(C) [electric current (A) and time (s)] required for the production of iodine during the

titration and calculate the content () of the water in the sample by the formula

When the sample interferes with the Karl Fisher reaction water in the sample can be

removed by heating under a stream of nitrogen gas and introduced into the titration vessel

by using a water-evaporation device



8 Interference and Limitations of Karl Fischer Method

Interferences in the water determinations by Karl Fischer method are associated with

condensation or oxidation ndash reduction reactions with a number of substances and

compounds or by side reactions Other possible interferences to the KF reagent are certain

active metals metal oxides metal hydroxides chromates melamines etc

The Karl Fischer titration has a number of serious limitations due to possible

interferences tantamount to erroneous results namely

(i) Oxidizing agents for instance chromates Cu(II) Fe(III) Cr2O7 2ndash peroxides salts

higher oxides

Example MnO2 + 4C5H5NH+ + 2Indash rarr Mn2+ + 4C5H5N + I2 + H2O

(ii) Reducing agents such as Sn (II) salts sulphides and S2O32ndash and

(iii) Compounds that have a tendency to form water with the ingredients of the Karl Fischer

reagent for instance

(a) Basic oxides eg ZnO

Example ZnO + 2C5H5NH+ rarr Zn2+ + C5H5N + H2O

(b) Salts of weak oxy-acids eg NaHCO3

Example NaHCO3 + C5H5NH+ rarr Na+ + H2O + CO2 + C5H5N

[Note As H2CO3 carbonic acid is very unstable hence it splits up to yield a mole each of

water and CO2]

Use of certain reagents will minimize or eliminate the interferences of many classes

of compounds For example the use of non-methanol containing KF reagent and solvent will

reduce the interference from aldehyde and ketones Ammonia and amines can be eliminated

by the addition of salicylic acid to the solvent



9 Side reactions

Side Reactions are classified as

(1) Reactions Influenced by Methanol

(2) Reactions with Iodine


It includes

bull Aldehydes react to form acetals also undergo Bisulfite addition

bull Ketones react to form ketals

bull Amines undergo methylation

bull Siloxanes undergo esterification


It includes

bull Halogenated Hydrocarbons containing free halogens

bull Mercaptans (Thiols)

bull Phenols

bull Peroxides

Testing for Iodine Reactivity

bull Dissolve a few Iodine Crystals in Methanol and Introduce Sample

bull Watch for Solution to Change Color if Clear Iodine Reaction is Present



1 Mercaptans (Thiols) are oxidized by iodine Suppress this side reaction by treating

sample with N-ethylmaleimide in a buffered solvent system

2 Inhibition of Thiol Oxidation by Iodine

Most Phenols do not react with KF reagents higher molecular weight phenols and

Amino-phenols are most problematic Volumetric method is most suitable since the

Oxidation potential is high in coulometry or Acidify Solvent system to reduce interference



10 Applications of Karl Fischer method for determination of Water in

pharmaceutical analysis

101 PREDNISOLONE SODIUM PHOSPHATE

Materials Required Karl Fischer Reagent 100 ml prednisolone sodium phosphate

02gm anhydrous methanol 200 ml

Procedure Add about 20 ml of anhydrous methanol to the titration vessel and titrate to the

Amperometric End-point with the Karl Fischer reagent Quickly add 02 g of prednisolone

sodium phosphate sample stir for 1 minute and again titrate to the amperometric end-point

with the Karl Fischer reagent The difference between the two titrations gives the volume

(v) of Karl Fischer reagent consumed by the sample

The minimum water equivalent is 35 mg of water per ml of Karl Fischer reagent

Hence the percentage of water ww in the given sample may be calculated by the

following

Precautions

(1) The reagents and solutions used must be kept anhydrous and necessary care should be

taken throughout to prevent exposure to atmospheric moisture

(2) The Karl Fischer reagent should be protected from light and preferably stored in a bottle

fitted with an automatic burette and

(3) The water equivalent of Karl Fischer reagent should always be determined before use

102 COGNATE ASSAYS

A number of other official pharmaceutical substances may be assayed for their water

content by the Karl Fischer method as summarized in the following Table



11 Automated Electrochemical Karl Fischer Analysis

Commercially available Modern KF-Titrators are usually equipped with specifically

designed titration vessels that are exclusively meant to check and prevent the contact with

atmospheric moisture Quite a few such devices are armed with microprocessors that will

perform the requisite operations sequentially in a programmed manner automatically and

may also dish out a print-out of the desired results including the percentage moisture

content In fact these Modern KF-Titrators not only afford greater accuracy and precision

in results but also offer much ease and convenience in routine analysis as compared to the

classical techniques based on either caulometry or controlled current potentiometry using

two indicator electrodes

Thus the basis of the analysis rests upon the quantitative relationship existing

between charge passed and iodine produced by the reagent according to the above reaction

Therefore the generation of iodine is automatically stopped when an excess of it is detected

by the indicator electrode It essentially consists of two platinum electrodes across which an

AC is applied and subsequently a marked drop in voltage between the electrodes takes place

as soon as an excess of iodine is present Normally such automated instruments make use of

proprietory reagents exclusively

The major advantage of this approach to KF-analysis being that no calibration is

required as the method is absolute and is entirely based on the stoichiometry of the

aforesaid equation It is noteworthy that one may determine the amounts of water ranging

between 10 mcg and 10 mg in solid as well as liquid samples



12 Some of the innovative brands in Karl Fischer Auto ndash titrator

instruments





13 References

1 Chapter 14 Karl fishcer method for determination of water Page no 223-227

Pharmaceutical Drug Analysis Ashutosh Kar New age international limited publishers

2 Aqua Stars Karl fischer instruments wwwemdchemicalscom

3 Karl Fischer Volumetric Titration Theory and Practice by Radiometer analytical

SAS wwwradiometer-analyticalcom

4 MettlerToledo AG Analytical Switzerland wwwmtcom

5 Summary of Karl fischer titrations by Orion products Baverly MA Thermofischer

Scientific wwwthermocomwater

6 Moisture determination by Karl Fischer titration background of chemistry and

recent advances SupelcoSigma-Aldrich Bellefonte Pa wwwsigma-aldrichcom

7 Karl Fischer Titration Methods Methodology and water determination in 442

different substances European Pharmacopoeia (PharmEurope) 4th Edition plus

Supplements 2002 International Electrotechnical Commission Geneva

8 Karl ndash fischer titration wwwwikipediacom



2 Theory of Karl - Fischer Technique

A Karl Fischer titration determines the water content in a sample based on an

iodineiodide redox reaction The titration is based on the oxidation of sulphur dioxide by

iodine in the presence of water It is the same reaction as the iodometric titration of sulphur

dioxide in water Titration may be defined as ndash ldquoA technique to determine the concentration

of a substance in solution by adding to it a standard reagent of known concentration in

carefully measured amounts until a reaction of definite and known proportion is completed

as shown by a color change or by electrical measurement and then calculating the unknown

concentrationrdquo

In this method water reacts with iodine until the water is consumed and the

endpoint is reached Overall reaction can be written as ndash

H2O + SO2 + I2 harr 2HI + SO3

or

2H2O + SO2 + I2 harr2HI + H2SO4

In 1935 Karl Fischer published a description of ldquoa new procedure for the titration of waterrdquo

using the above reaction in an anhydrous nonaqueous solvent However in order to shift the

equilibrium to the right it was necessary to neutralise the acids produced Originally

pyridine was used as the neutralising base Later on diethanolamine followed by imidazole

were used as buffers Recent studies show that methanol which is the most commonly used

solvent contributes in the reaction Ethanol-based reagents have recently emerged These

have the advantage of being less toxic offering more stable endpoints and faster kinetics

Actually Karl Fischer reaction occurs in two stages

(1) SO2 + CH3OH + B harr CH3SO3- + HB+

(2) CH3SO3- + H2O + I2 + 2B harr CH3SO4

- + 2HB+ + 2I-

Where B = Base

Since water and I2 are consumed in equimolar amounts in reaction 2 if you know

the amount of I2 consumed you know the amount of water that was present in the sample




A pH considerations
















good endpoints



C Water content


D Sample size






weight


100000 ppm = 10 50 mg 5000 microg



100 ppm = 001 1 g 100 microg

10 ppm = 0001 5 g 50 microg












results







iii Grind sample




I Conductivity



coulometric type)






Pyridine Imidazole




















of titration






























5 Advantages

















6 Instrumentation












titration












Apparatus



constant current




Procedure



moisture








state

































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References


















A pH considerations
















good endpoints



C Water content


D Sample size






weight


100000 ppm = 10 50 mg 5000 microg



100 ppm = 001 1 g 100 microg

10 ppm = 0001 5 g 50 microg












results







iii Grind sample




I Conductivity



coulometric type)






Pyridine Imidazole




















of titration






























5 Advantages

















6 Instrumentation












titration












Apparatus



constant current




Procedure



moisture








state

































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References

















C Water content


D Sample size






weight


100000 ppm = 10 50 mg 5000 microg



100 ppm = 001 1 g 100 microg

10 ppm = 0001 5 g 50 microg












results







iii Grind sample




I Conductivity



coulometric type)






Pyridine Imidazole




















of titration






























5 Advantages

















6 Instrumentation












titration












Apparatus



constant current




Procedure



moisture








state

































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References




















iii Grind sample




I Conductivity



coulometric type)






Pyridine Imidazole




















of titration






























5 Advantages

















6 Instrumentation












titration












Apparatus



constant current




Procedure



moisture








state

































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References































of titration






























5 Advantages

















6 Instrumentation












titration












Apparatus



constant current




Procedure



moisture








state

































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References












































5 Advantages

















6 Instrumentation












titration












Apparatus



constant current




Procedure



moisture








state

































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References

















6 Instrumentation












titration












Apparatus



constant current




Procedure



moisture








state

































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References


















Apparatus



constant current




Procedure



moisture








state

































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References



































712 Back titration










TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References


















TS

Where



713 General Remarks






























Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References





















Apparatus



































higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References

























higher oxides










water and CO2]







9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References

















9 Side reactions





It includes






It includes



bull Phenols

bull Peroxides


























following

Precautions






102 COGNATE ASSAYS





























instruments





13 References





































following

Precautions






102 COGNATE ASSAYS





























instruments





13 References









































instruments





13 References



















13 References

















karl fischer

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