Determination of Water Content in Oregano 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

Oregano contains very firmly bonded water. Extraction in methanol is very slow and dragging. The presence of formamide  accelerates the release of water. Additionally the use of a homogeniser is favourable. Alternatively the KF oven technique can be used in combination with coulometry. For the release of water a temperature of approx 130 °C is 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

Solvent
30 mL 188009 Aquastar™ - CombiMethanol - Methanol-free solvent for volumetric Karl Fischer titration with one component reagents
and
20 mL 109684 Formamide - as Solubilizer

Titration Parameters:
Stirring time: 180 sec.
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min

Sample size:
0,1 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 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 the sample a stirring time of at least 180 seconds is recommended.

Materials

     
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