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  1. #1
    Validation Analyst
    Join Date
    Jan 2011

    Default Question about recovery of swab sampling method for active residue

    Dear Sirs,

    I am performing the recovery of swab sampling method for active residue in cleaning validation. But we have many equipment with many acceptance limit (i.e, 1.12 microg/cm2, 4.14 microg/cm2, 7.77 microgam/cm2). How many point I need to study recovery. This very simple for only one acceptance criteria at 50%, 100%, and 150% of acceptance criteria. But for many acceptance criteria, I am really confusing in this case

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  3. #2
    Validation Analyst
    Join Date
    Jan 2012


    We have same problems
    In our company we have many equipment with many acceptance criteria

    So we decided to choose one equipment with lowest acceptance limit and hardest to clean.

    We performed recovery swab on that equipment

    Actually, we still learn and developing cleaning validation (TOC method), we are glad if you have some idea or correction about our method

  4. #3
    Cleaning Validation Expert
    Join Date
    Mar 2012


    Dear friend...
    Your idea regarding "equipment with lowest acceptance criteria" is nice. But, “hard to clean” points are ideal for sampling but not for recovery study. Hard to clean means hard to access. If you get 60% recovery in hard to clean location (since hard to access), you will compensate the actual results by adding 40%. But, in other locations, it may be up to 95%. So, better to choose three locations, which should contain hard to clean and easy to clean locations, and report the average as actual recovey


  5. #4
    Validation Analyst
    Join Date
    Aug 2009


    Hello Phucto

    I would suggest that as it’s the swab’s ability to recover the active that you are trying to prove (regardless of which piece of equipment or location the swabs are being taken from), use the range of acceptance criteria you have (assuming it’s the same active you are swabbing for from each piece of equipment and using the same swabbing method) for setting your recovery range i.e.

    Equipment piece 1 limit: 1.12 g/cm2
    Equipment piece 2 limit: 4.14 g/cm2
    Equipment piece 3 limit: 7.77 g/cm2

    Your “working” range is 1.12 g/cm2 to 7.77 g/cm2, so if you are using a +50% approach you could justify swab recoveries at the following (depending on your analytical method’s LOD,LOQ and linearity):

    50% = 0.56 g/cm2 i.e. (1.12 x 0.5)
    100% = 6.11 g/cm2 i.e (0.56 + 11.66)/2
    150% = 11.66 g/cm2 i.e. (7.77 x 1.5)

    However due to the range it may be worth considering recoveries at 75% and 125% as well.

    Remember it’s not the acceptance criteria your validating, it’s the swab’s ability to recover the active from the surface and the analytical method’s ability to extract the active from the swab.

    Just my thoughts.


    PS if there are different product contact materials present, you will need to demonstrate the swab recovery for each i.e. plastic, stainless steel, rubber, etc.
    Last edited by Paniel12; 07-03-2012 at 10:31 AM.

  6. #5
    Validation Analyst
    Join Date
    Apr 2012


    Hi Phucto,

    In case of swab analysis with variable acceptance criteria it is a good approach to prove the accuracy over a range. It will always be better from analytical method point of view if Recovery/accuracy & also linearity is proved from LOQ to a level of concentration just above which the residues are visible.An analyst will never have to be worried about the method accuracy with method validated in this range. You can know the concentration by spiking the solution on ss plate & drying it & then visually observing it. Find out the concn. beyond which API is actually visible & perform accuracy at that level. You may find it difficult to get required accuracy at very low concns.(LOQ) & high concn. but then in those cases find out actual recovery & apply a factor in calculation to compensate low accuracy. eg. if accuracy is 50 % multiply your residu value obtained in actual use of method by 2 to get correct result.

    I also agree with paniel 12 regarding recovery on diffrent contact surfaces


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