If you are a pharma professional, then you must be familiar with the two terms, which are water content & LOD. These two terms create confusion for many professionals as they think both are the same, but the reality is that these terms are not the same, and there is a big difference between water content and LOD.
Now let’s have a look at the difference between these two terms, but first make it clear that moisture content is another term which is also used, so don’t be overconfused. The moisture content terminology is also used for LOD.
Water Content
Chemical test used to determine the quantity of only water present in the sample is known as the water content test.
Explanation
Water content test only gives the amount of water in the sample, meaning if we have a sample of raw material & we want to check its water content, then only the amount of water will be found by using the water content testing procedure.
Suppose if other volatile solvents like alcohol are also present in the sample, then we can’t determine its value by using the water content test.
LOD
LOD or loss on drying is the physical test which is performed to check the water & other volatile components present in the sample.LOD is also known as moisture content.
Explanation
LOD or loss on drying test gives the total moisture content present in the sample & it includes the amount of water in the sample as well as all other volatile components present in the sample.
If we have a sample of raw material & we want to check its LOD, then the LOD test will give us the amount of water as well as other volatile solvents like IPA in the sample.
Equipment Used For Moisture Content
To determine the water content Carl Fisher titrator is used, where a chemical reaction takes place by using Karl Fischer reagent.
Equipment Used For LOD
The official method to measure LOD is by using the dry oven method, where a sample is heated at a defined temperature for a defined period of time.
The LOD or moisture content can also be determined by using the moisture analyser, where a halogen lamp is used to heat the sample.
The moisture determination by the oven method takes about 2 to 3 hours, but the use of a moisture analyser is faster, where we can check the moisture content in a short period of time.
Results Presentation
The results of water content are expressed as the percentage of water present in the sample.
The results of LOD are expressed as a percentage of water loss.
Formula
The formula used for LOD determination is given as
Sample weight before drying – Weight after drying ×100
Weight of the sample before drying
Conclusion
LOD & Water content methods are used in pharma quality control, where the water content method is used to measure the total amount of water present in a sample, and the LOD or moisture content method is used to measure the total amount of water and other volatile substances present in the sample.
Also Read