Extraction efficiency definition

[Christelle Guillo]

Could anyone give me the definition of extraction efficiency for solid phase extraction. Is it:

= amount recovered/amount loaded

or

= amount recovered/[amount loaded - (amount recovered from load + wash)]

The last suggestion derives from the fact that an equilibrium exists between the solid phase and the load buffer and therefore not 100% of the analyte sticks to the SPE column.

And also is there a difference between recovery and extraction efficiency?

Thanks for your suggestions!

[HW Mueller]

To a person who learned the trade prior to GLP, etc., for whom science had the connotation of knowledge rather than fulfilment of regulations, both definitions are acceptable if it is clearly stated what was done to arrive at the figures (it would be better to call your second method a "corrected" recovery, though). If you present your extraction efficiency via your second definition, without stating the calc method, I would consider that cheating.
In that context recovery and extraction efficiency are synonyms. In regulatory terms the answer is apparently different.

[Uwe Neue]

I can not see another definition except for the first definition. The only other thing that is possible is to analyze all the fractions and sum up the amounts found in the different fractions.

The real problem is that there should be no loss during sample loading. There is a need to optimize the sample loading step. There could be several reasons for a loss of sample during sample loading. One could be related to the chemistry of the loading step. Another could be related to the speed with which the sample is loaded. In SPE one often needs to slow down the sample loading (for example by using a smaller vacuum) to reduce losses during the loading step.

[pawan ratra]

I agree that the first definition is correct way of calculating recovery. the sample loading technique has to be optimized to minimize the losses.