Attention:

Certain features of Sigma-Aldrich.com will be down for maintenance the evening of Friday August 18th starting at 8:00 pm CDT until Saturday August 19th at 12:01 pm CDT.   Please note that you still have telephone and email access to our local offices. We apologize for any inconvenience.

Determination of Water Content in Tensides 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

According to ISO 4317 the one component titration with methanol as solvent is carried out. For solubility problems 1-propanol may for instance be added as solubiliser. The two component titration can also be carried out. Alkali metal silicates, carbonates, hydroxides and borates cause side reactions with the Karl Fischer reagent and simulate higher water concentrations. Therefore, detergents and other cleaning materials that contain such compounds cannot be determined by direct titration. Here the KF oven technique is employed.

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 188009 Aquastar™ - CombiMethanol - Solvent for volumetric Karl Fischer titration with one component reagents, max. 0.01 % water
or
30 mL / 20 mL 188009 / 100997 Aquastar™ - CombiMethanol / 1-propanol - Solvent mixture for one component titration

Titration Parameters:
Stirring time: 60 sec.
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
0.2 - 10 mL (depending on the expected water content).

Procedure:
The titration medium is first placed into the cell and titrated dry by means of the titrant. Then the sample is added with a syringe (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 60 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. 2 mg water

Solvent
50 mL 188015 Aquastar™ - Solvent - Solvent for volumetric titration with two component reagents
or
50 mL 188016 Aquastar™ - Solvent oils & fats - Solvent for volumetric Karl Fischer titration with two component reagents for oils & fats

Titration Parameters:
Stirring time: 60 sec.
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
0.2 - 10 mL (depending on the expected water content).

Procedure:
The titration medium is first placed into the cell and titrated dry by means of the titrant. Then the sample is added with a syringe (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 60 seconds is recommended.

Materials

     
Related Links