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. In this article, I will explain the difference between Karl Fischer Titration and Loss-on Drying, and offer some suggestions to help you choose the right method for your application.
What Moisture Does It Measure?
Karl Fischer Titration is a method that measures only water content in a product sample. In other words, it's water-specific.
Loss-on Drying, on the other hand, measures the total change in weight of a material when the sample is dried. For some products, components such as alcohol or fat will evaporate along with water. Therefore, the LOD method measures both water and volatile impurities such as the ones I've just mentioned.
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 the product into 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 more than trace amounts of volatiles, which can distort the moisture reading?
If “yes”, Karl Fischer Titration would most likely be a better method for testing your product, as this measurement is not affected by these impurities.
- Does your product have a very low moisture content?
If “yes”, Karl Fischer Titration frequently provides more consistent results for products with very low moisture content.
Loss-on Drying is still the more commonly used of these 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.