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 2-Methoxynaphthalene Using Karl Fischer Titration

Product Group

Ethers

General Information concerning the product group

Ethers

In most cases ethers can be determined after Karl Fischer standard methods analogously to hydrocarbons. Long-chain compounds require the addition of solubilisers, e.g. long-chain alcohols or chloroform. Recommended methods are both, the volumetric titration with one or two component reagents, as well as the coulometric analysis. The latter is predominantly applied for low water concentrations (< 0.1 %). One exception are the vinyl ethers, which cause an interfering side reaction with methanolic Karl Fischer reagents.

Special Information concerning the sample and the methods

This substance is only slowly soluble in alcoholic media. In order to improve solubility a solubiliser is added to the KF solvent. Titration at 50 °C is favourable.

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

Titration Parameters:
Stirring time: 3 mins.
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
2 g

Procedure:
The titration medium is first placed into the cell and titrated dry by means of the titrant. Then the sample is added from a weighing boat (exact sample weight determination by weighing of weighing boat before and after addition) and the titration is started. For complete dissolution of the sample a stirring time of three minutes 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 188016 Aquastar™ - Solvent oils & fats - Solvent for volumetric Karl Fischer titration with two component reagents for oils & fats

Titration Parameters:
Stirring time: 3 mins.
Titration temperature: 50 °C
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
2 g

Procedure:
The titration medium is first placed into the cell and titrated dry by means of the titrant. Then the sample is added from a weighing boat (exact sample weight determination by weighing of weighing boat before and after addition) and the titration is started. For complete dissolution of the sample a stirring time of three minutes is recommended.

Materials

     
Related Links