Coupon Swabbing

Hi all,

I’m looking at cleaning validation through coupon swabbing. My analyte is albumin and will be analyzed through a previously validated ELISA. I have a few questions regarding the process.

It seems that polyester swabs are the best for capture and release of analytes for cleaning validation. Does anyone have experience with them or knows of a better option?

Coupon treatment for recovery testing:
I see that typically a swab area of 10cm x 10cm or 5cm x 5cm is used for analyte recovery. Is the analyte deposited evenly on this area, left to dry, and then recovery swabbing performed? Or is the coupon normally submerged in a solution of known concentration, allowed to dry, and then swabbed? If the latter is the case, how does one determine the expected amount of analyte in the area?

Expected Recovery:
It seems that 80% is the magic number for recovery by chemical analysis, and this number changes considerably for microbiological assays. Does anybody have experience with ELISA and expected recovery in this type of assay?

Thank you for your help,


Dear Mr. Ben,

Hope that following answers might be of help:

Swab Type:
There is no straight-forward answer to your query regarding the type of swab to be used for cleaning validation studies. There doesn’t exist a single type of swab which could be used for every swab sampling. The type of residue, possible intereference with residue testing (giving false positive results), and % recovery desired are some of the factors which affect the choice of swab. You should optimise your swab sampling method by using different type of swabs. You may select the swab which gives you highest recovery. For optimisation of swab sampling you may refer to this article:
. In my opinion, simply using cotton swabs will help you as albumin is water soluble molecule.

Coupon treatment for recovery testing:
The first method is the preferred method for swab sampling recovery studies i.e. spike residue on to coupons, dry and then perform swab sampling.

Expected Recovery:
% recovery >= 50% is considered acceptable for cleaning validation studies. If you managed to get 80% or more using polyester swabs then it is perfectly fine to use it for swab sampling. In your case it should be expectable to get more than 80% recovery as the residue you are using is water soluble (which I expect is easily recoverable as compared to water insoluble residues).

Polyester swabs are generally considered ideal for sampling where the method of analysis, used for testing the swabs, is TOC. However, they can also be used if you need any intereference-free testing of residues (as may be the case with ELISA).

Hope this helps.