In most sources i found Loss on drying /LOD (w/w %)of a sample is determined by putting about 1g of a powdered sample into an oven at about 105°C for some hours.
Afterwards it is placed in a desiccator while cooling.
This is not only used in most papers i found - but also mentioned in Pharmacopoeias or Certificates of Analysis.
In a few articles i found vacuum desiccators mentioned. But so far nothing about how those two methods compare. Or if it is even possible to get comparabe/accurate results when using a vacuum desiccator with siliga gel instead of an oven?
Does anyone of you have experience in drying powdered samples (e.g. herbal extracts) and determing LOD via vaccum desiccator?
How do the two methods compare? How long does it need roughly to dry?
Hi Daryl,
what you initially describe is indeed a standard procedure, however its suitability always depends on your requirements. Drying in an oven, e.g. at 105 °C for several hours, may be faster for removal of moisture. However, it may not be effective enough. For instance, you may consider wether you wish to remove moisture or water of crystallization. After drying in an oven, if the dried material is hygroscopic, you may wish to store it in a desiccator under vacuum to keep it dry. If your material is sensitive to oxygen, not an oven but a vacuum desiccator may be the method of choice, especially if the latter is equipped with a heating device which will speed up the drying process and probably make it more effective.
Wishing you best of success,
Johannes
it is put into desiccator for cooling with some dessicant in desicator so that it could trap moisture again
We generally use vacuum drying when a sample are heat-sensitive, or when high temperature cause gelling in the sample. 50C at overnight is the generally accepted method. Keep in mine that water can be produced by thermal reactions, misleading your results. If your sample is not heat-sensitive, then you should be no worry since you use one of the standart methods. I used 3 methods to comapre LOD in a food sample. I found that thermogravimetri was the best one among them (oven and vacuum oven)
Good luck
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