Moisture determination is important in foods for various reasons including; economic, food quality, microbial stability, labeling requirements etc. this may be done by several methods depending on several factors such as water type, decomposition of other food component among others. One such method of moisture determination is the Karl-Fischer Titration Method (KF).
Titration is a technique used to determine the concentration of a known volume of solution. A titrant; that is a solution of known concentration is added slowly in the presence of an indicator until the solution neutralizes. Neutralization is said to occur when the indicator undergoes a color change. ("Titration", 2013) According to S. Nielson the Karl Fischer titration is compatible for foods …show more content…
I2 + SO2 + 3 Py + H2O → 2 Py-H+ I – + Py•SO3 –
2. Py•SO3 + CH3OH → Py-H+CH3SO4
The stoichiometric ratio of iodine and water is important to not; for alcoholic solutions it is 1:1 whereas for non -alcoholic solutions it is 1:2. The reaction rate is maximum when all the sulphur dioxide ions have been converted into methyl sulphite; the optimum pH for this is 5.5-8. Side reactions are possible resulting in high I2 consumption as well as a slower reaction.
The KF titration maybe done by two methods either volumetric or coulometric. KF titration generally occurs as follows:
1. Add reagent (“titrant”) to a burette [include alcohol, SO2, a base and I2 ]
2. Add sample solvent to the titration vessel
3. Begin stirring the vessel
4. Zero the instrument by titrating unwanted moisture in the system
5. Add the weighed sample to the titration vessel
6. Begin adding reagent from the burette while stirring
7. When the endpoint is reached, the electrode will detect no change in current upon addition of more reagent
8. By knowing how much titrant was added, the water content can be calculated
9. Normally, the K-F instrument does the calculations and reports the results as “% water” or “ppm water.” (Aurand,
Titration is a technique used to determine the concentration of a known volume of solution. A titrant; that is a solution of known concentration is added slowly in the presence of an indicator until the solution neutralizes. Neutralization is said to occur when the indicator undergoes a color change. ("Titration", 2013) According to S. Nielson the Karl Fischer titration is compatible for foods …show more content…
I2 + SO2 + 3 Py + H2O → 2 Py-H+ I – + Py•SO3 –
2. Py•SO3 + CH3OH → Py-H+CH3SO4
The stoichiometric ratio of iodine and water is important to not; for alcoholic solutions it is 1:1 whereas for non -alcoholic solutions it is 1:2. The reaction rate is maximum when all the sulphur dioxide ions have been converted into methyl sulphite; the optimum pH for this is 5.5-8. Side reactions are possible resulting in high I2 consumption as well as a slower reaction.
The KF titration maybe done by two methods either volumetric or coulometric. KF titration generally occurs as follows:
1. Add reagent (“titrant”) to a burette [include alcohol, SO2, a base and I2 ]
2. Add sample solvent to the titration vessel
3. Begin stirring the vessel
4. Zero the instrument by titrating unwanted moisture in the system
5. Add the weighed sample to the titration vessel
6. Begin adding reagent from the burette while stirring
7. When the endpoint is reached, the electrode will detect no change in current upon addition of more reagent
8. By knowing how much titrant was added, the water content can be calculated
9. Normally, the K-F instrument does the calculations and reports the results as “% water” or “ppm water.” (Aurand,