Karl Fischer Titration and Loss on Drying (LOD) are both methods for determining moisture content in a product.
That’s where the similarities end, though. Here’s the difference between Karl Fischer and Loss on Drying:
What Moisture Does It Measure?
Karl Fischer Titration is a method measures only the water content (i.e. it's water-specific) in a product sample.
Loss on Drying, on the other hand, measures the total change in weight of a material as a result of drying. For some products, components such as alcohol or fat evaporate with the water. Therefore, the LOD method measures both the water and volatile impurities such as those mentioned previously.
How Do They Get at the Moisture?
Karl Fischer titration is a chemical method. It involves adding a reagent to the sample to cause a reaction that converts the water in a product to a non-conductive chemical.
Loss on Drying compares the weight of a product before and after it is dried. This difference in weight is taken as the percentage of moisture in the product.
How Do You Choose the Best Method?
Choosing the right method of moisture determination can be tricky, and there is no one-size-fits-all answer to this question. However, there are a few things that would lead you to favor Karl Fischer titration over the more commonly used LOD method.
Does your product contain a high level of constituents, which can distort the moisture reading? (In other words, does it contain more than trace amounts of those “volatile impurities” mentioned earlier, enough to significantly alter the results?)
If “yes”, Karl Fischer would most likely be a better method, as this measurement is not affected by impurities.
Does your product have a very low moisture content?
- If “yes”, Karl Fischer frequently provides more consistent results.
Loss-on drying is the most commonly used of the methods. In order to help answer the question "Will Loss-On Drying Work for Me?" we have created a chart that rates materials/products based on how effective the LOD method will be for determining moisture content.
Loss-on Drying Effectiveness for Common Applications:
I hope this has been helpful to you. Please share your opinions and/or questions in the comments section below!
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P.P.S Here is a set of questions and answers about Karl Fischer.