Methods to measure the moisture content and water content and factors, calculations of Loss on Drying
Karl Fischer Titration
Karl Fischer Titration is the chemical method that measures only the water content in a product. Here the sample is added with reagent where water gets converted to nonconductive chemical on reaction in the product.
Loss on Drying:
Loss on drying is a method used to measure the moisture content along with volatile constituents in a sample under specified conditions. It generally refers to the total change in the weight of the material due to drying. In few products fat and alcohol components evaporate with water hence LOD also measures volatile impurities along with water content.
It compares the weight of the product before and after drying and the difference in weights is considered as moisture percentage in the product.
Loss on drying depends on various factors like
Calculation of Loss on Drying
1. % Loss on drying (LOD) = W start - W dry/ W start - W tare * 100
(Or)
2. % Volatiles (%LOD) = (B –D) x 100 / C
3. % Solids = (D- A ) x 100 / C
A = Weight of bottle/cover
B= Sample + bottle/ cover (initial weight)
C= Sample Weight.
D= Sample + bottle/ cover (final weight)
(Or)
%LOD = Mass of water in sample / Mass of wet sample * 100
% Moisture content = Mass of water in sample / mass of dry sample * 100
Even though loss on drying is the most commonly used method but still Karl Fischer method is more suitable as it produces consistent results when product has high level constituents or volatile impurities which impact moisture and also when the product has less moisture content.
Karl fischer titration, loss on drying, lod, moisture content
