Determination of Water Content in Mascara Using Karl Fischer Titration

Product Group

Cosmetics

General Information concerning the product group

Cosmetics

Cosmetics on an aqueous and alcoholic basis can be titrated without problems according to the Karl Fischer (KF) method. Due to the often high water concentration of the emulsions small samples are required. The accuracy of analysis is determined through exact sampling, weighing and adding. The coulometric method is unsuitable for most emulsions. Fatty and oily preparations are insoluble in methanolic KF solvents and require the addition of a solubiliser, or respectively titration with specific KF solvents for oils and fats.

Special Information concerning the sample and the methods

The solubility of Mascara in methanolic solvents is limited. Therefore an external dissolution in a mixture of CombiMethanol and Chloroform (ratio CombiMethanol : Chloroform = 2:1) is necessary. The measurement result has to be corrected for the blank value of the solvent mixture.

Titration one component system

Reagents:

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

Solvent
50 mL 188009 Aquastar™ - CombiMethanol - Solvent for volumetric Karl Fischer titration with one component reagents, max. 0.01 % water

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

Sample size:
blank value: 5 gsample: 1 g aliquot of the external dissolution (2 g Mascara in 50 g solvent)

Procedure:
The titration medium is first placed into the cell and titrated dry by means of the titrant. Then the externally dissolved sample is added with a syringe (exact sample weight determination by weighing of syringe before and after injection) and the titration is started. It is possible to analyse approx. 5 g solution before the KF solvent must be changed.

Materials

     
Related Links