No. of swabs

Is there any reference indicating the qty of no. of swabs in cleaning validation, in other means is there any limit how many swabs to be collected from equipment/machines. Please provide reference. Thanks

The number of swabs used:

Generally, only one or two swabs are used per target surface area. The concept behind using more than one swab is to increase the recovery of the target residue. One swab cannot pick up all of the residues, but it will leave behind a finite amount of solvent, which probably contains some of the target residue. A second swab will pick up an additional amount of the target residue. To enhance recovery, the second swab is sometimes used dry. The theory here is that a dry swab will “mop up” any of the solvent residues left behind, thus increasing recovery as compared to using a second wet swab. While a second swab works well in theory for target residues where the second swab does not interfere with the analytical method, care should be used in adding a second swab to a swabbing procedure where TOC is the analytical technique; the additional background carbon (and the resultant greater variability and larger LOQ) provided by the second swab may negate any benefit due to the additional residue recovered from the second swab, with the net result being little or no overall benefit to the swabbing recovery.

Swab recovery studies comparing the use of one swab to two swabs can confirm whether the added swab has any benefit in a given case.


Dear Prasad,

Thanks for the prompt reply. Is there any reference (guidline/best practice) for nos of swab available i.e FDA, MHRA or any other, if yes, can you provide me the same?


Honestly I do not have any reference documents about the subject matter either from MHRA or FDA.
I gave you reply based on books I read and my previous training and experience.
If I find any such thing I shall certainly provide regulatory documental evidence right here very soon.


Refer PDA Technical report No: 49
Points to consider for Biotechnology Cleaning & Validation
Released June/July :2010

Thanks Dear, I Will check it