Determination of Water Content in Silicone oil Using Karl Fischer Titration

Product Group

Technical products

General Information concerning the product group

Technical products

This product group comprises the most diverse products. Depending on solubility, their behaviour in the KF solution and water content, different Karl Fischer methods apply.

Special Information concerning the sample and the methods

Oils show inadequate solubility in methanolic KF solvents. Oils on silicone basis require the addition of long chain alcohols or chloroform as solubilisers or utilisation of specific KF solvents for oils. In the case of complete dissolution of the sample both the volumetric as well as the coulometric KF method may be used. The most suitable method will depend in that case on the water concentration of the sample. Volumetry is prefered in case of titration in suspended solution.

Titration one component system

Reagents:

Titrant
188005 Aquastar™ - CombiTitrant 5 - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 5 mg water
or
188002 Aquastar™ - CombiTitrant 2 - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 2 mg water

Solvent
50 mL 188020 Aquastar™ - CombiSolvent oils - Solvent for volumetric Karl Fischer titration with one component reagents for oils
or
30 mL / 30 mL 188009 / 102445 Aquastar™ - CombiMethanol / Chloroform - solvent mixture for one component titration

Titration Parameters:
Stirring time: 120 sec.
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
appr. 5 g

Procedure:
The titration medium is first placed into the titration cell and titrated dry by means of the titrant. Then the sample is added with a syringe with or without hollow needle (exact sample weight determination by weighing of syringe before and after injection) and the titration is started. For complete dissolution of the sample a stirring time of 120 seconds is recommended.

Titration two component system

Reagents:

Titrant
188010 Aquastar™ - Titrant 5 - Titrant for volumetric titration with two component reagents, 1 mL = approx. 5 mg water
or
188011 Aquastar™ - Titrant 2 - Titrant for volumetric titration with two component reagents, 1 mL = approx. 5 mg water

Solvent
50 mL 188016 Aquastar™ - Solvent oils & fats - Solvent for volumetric Karl Fischer titration with two component reagents for oils & fats
or
30 mL / 30 mL 188015 / 102445 Aquastar™ - Solvent / Chloroform - solvent mixture for two component titration

Titration Parameters:
Stirring time: 120 sec.
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
appr. 5 g

Procedure:
The titration medium is first placed into the titration cell and titrated dry by means of the titrant. Then the sample is added with a syringe with or without hollow needle (exact sample weight determination by weighing of syringe before and after injection) and the titration is started. For complete dissolution of the sample a stirring time of 120 seconds is recommended.

Coulometry with diaphragm

Reagents:

Catholyte
5 mL 109255 Aquastar™ - CombiCoulomat frit - Coulometric Karl Fischer reagent for cells with diaphragm

Anolyte
80 mL 109255 Aquastar™ - CombiCoulomat frit - Coulometric Karl Fischer reagent for cells with diaphragm
and
40 mL 803463 Decanol - as solubiliser

Titration Parameters:
stirring time: 60 sec
Default coulometer settings for cell with diaphragm:
For end point indication, e.g.:
I(pol) = 5 - 10 µA, U(EP) = 50 - 100 mV
Stop criterion: drift < 10 µg/min

Sample size:
1 mL

Procedure:
The Karl-Fischer reagent is placed into the cathode and anode compartment of the titration cell with diaphragm. The coulometer is started and the solvent is titrated dry. After preliminary titration and stabilisation of drift the sample is injected into the titration cell with a syringe (exact sample weight determination by weighing of syringe before and after injection) and the water determination is started. A stirring time of 60 sec is recommended.

Coulometry without diaphragm

Reagents:

Working medium
80 mL 109257 Aquastar™ - CombiCoulomat fritless - Coulometric Karl Fischer reagent for cells with or without diaphragm
and
20 mL 803463 Decanol - null

Titration Parameters:
stirring time: 60 sec
Default coulometer settings for cell without diaphragm:
For end point indication, e.g.:
I(pol) = 5 - 10 µA, U(EP) = 50 - 100 mV
Stop criterion: drift < 10 µg/min

Sample size:
1 mL

Procedure:
The Karl-Fischer reagent is placed into the titration cell without diaphragm. The coulometer is started and the solvent is titrated dry. After preliminary titration and stabilisation of drift the sample is injected into the titration cell with a syringe (exact sample weight determination by weighing of syringe before and after injection) and the water determination is started. A stirring time of 60 ec is recommended.

Materials

     
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