l-drying and freeze drying - (Mar/26/2008 )

I know that the main difference between freezedrying and l-drying is that when using l-drying, you do not freeze the product.

But are there other difference too?
I mean by this : is the proces a lot different or can you compare them ?
More energy needed for the l-drying? or less?

advantages? disadvantages?

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what is I-dry ?

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L-drying stands for liquid drying.

Its like freezedrying, but you do not freeze your sample.

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To me that means centrifugal evaporation, where you spin the samples in a centrifuge under vacuum. The liquid sublimates off while everything is in the liquid form. You need to centrifuge while evaporating so the boiling of the liquid doesn't cause sample to spit out as bubbles burst.
The process is essentially the same. If you reduce the atmospheric pressure of a container, the boiling point of liquids in it are reduced. With freeze-drying, you go from solid to gas, with centrifugal evaporation, you go from liquid to gas. Same net effect.
The decision to use one or the other can lie in a few variables including the effect of freezing on the compound, and the effect of heating on the compound. Centifugal evap typically leaves you with a liquid, whereas freeze-drying typically goes to dryness.

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I see.

you have experience with both techniques?

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Sure have. Anything in particular?

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Well Swanny, when working with L-drying, do you heat your samples or not?

And you also use the terms primary and secondary drying?

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You can, but you don't have to. Certain instruments, like the Speedy-Vac, have heating controls that warm the rotor (because heat transfer through the vacuum is very poor).

Primary and secondary drying are terms used in freeze-drying. The modern-day font of all knowledge, Wikipedia, has an article on freeze-drying, including primary and secondary drying.

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I know what primary and secondary drying etc is...

Thats not the problem, the problem is that at the moment I am involved in a discussion about secondary drying.

Some state they you do not have a secondary drying when you do not heat your samples when freezedrying.
Some state that you can have secondary drying without heating your samples (when using a manifold freezedyer, you use the heat of the room and you do not externaly heat your samples)

Now I was thiking about L-drying, because this is "almost the same" as freezedrying, when speaking about the physics.
So I was wondering when L-drying, you use external heat to heat the samples or not, to get that "secondary" drying...

On the other hand: when using L-drying, the samples stays fluid, so you do not remove that much as you do when working with a freezedrier.


ANyway, its getting confusing at the moment lol

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