Determination of Water Content in Cheese Using Karl Fischer Titration

Product Group

Foodstuffs

General Information concerning the product group

Foodstuffs

Foodstuffs encompass the most diverse products. Depending on whether carbohydrate-rich, fatty or proteinrich substances are under investigation, different working techniques are favourable. Complex matrices that dissolve slowly, or where the water can only be slowly extracted, necessitate the use of solubilisers. In addition, titration under heating and the application of a homogeniser to accelerate water release are expedient.

Special Information concerning the sample and the methods

To accelerate the release of water, Formamide is added to the titration medium in case of volumetric Karl Fischer titration. Additionally titration at elevated temperatures is advantageous. The coulometric method can not be recommended.

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
20 mL 188015 Aquastar™ - Solvent - Solvent for volumetric titration with two component reagents
and
20 mL 109684 Formamide - as solubiliser

Titration Parameters:
Stirring time: 120 sec.
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:
0.2 - 0.5 g (thoroughly reduced to small pieces)

Procedure:
The titration medium is first placed into the cell, heated up to 50°C 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 extraction of water a stirring time of at least 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
and
188011 Aquastar™ - Titrant 2 - Titrant for volumetric titration with two component reagents, max. 0.01 % water

Solvent
15 mL 188015 Aquastar™ - Solvent - Solvent for volumetric titration with two component reagents
and
15 mL 109684 Formamide - as solubiliser

Titration Parameters:
Stirring time: 120 sec.
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:
0.2 - 0.5 g (thoroughly reduced to small pieces)

Procedure:
The titration medium is first placed into the cell, heated up to 50°C 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 extraction of water a stirring time of at least 120 seconds is recommended.

Materials

     
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