Rinsing recovery for cleaning method validation

Hi there

I’m working on cleaning method for an equipment which requires rinsing for sampling

Can anyone suggest how can i mimic the rinsing process in the lab for 10*10 cm steel plates. i’m struggling to find an ideal way to rinse the plates using minimum amount of rinsing solvent ?

My guess- can i dip the steel plate in the petridish containg small amount of solvent n sonicate it ?

n also can anyone send me the link for the calculation of the acceptable residual limit for rinsing method /is it different from swabbing method / will we take volume of solvent into account b4 setting the limits

can you plz check if this right??

ARL=10mg/1kgMinimum batch size/shared surface area recovery factor.


Plz respond


Dear pallavi,

first question is why you use rinsing as the sampling method. If you are going to sample flat stainless steel surfaces which will be mimicked by the coupons, swabbing is the better choice. If you are going to sample pieces that cannot be swabbed, perform the recovery test on that same pieces to replicate adequately the rinsing of the piece during the cleaning test, because coupons will not be representative for these pieces. The amount of solvent for sampling by rinsing is normally around 0,5 - 1 ml/cm², and with a good solvent sonication is not necessary. Our method for rinsing is using a glass funnel (15 cm diameter), placing it in a flask, and then rinsing the piece in the funnel with a pipette covering the whole surface. Last step is adjusting the exact volume in the flask with solvent. The rinsing method is far more robust to small methodology variations than the swabbing method.

The calculation for the acceptable residual is exactly the same as for swabbing, what changes is the sample concentration, where the amount of sampling solvent needs to be taken into account.

To check if your formula is correct I need to know what do you call ARL and where the factor 10 mg/1 kg comes from, as i guess it stems from the units of the other figures. In my opinion there is one thing missing and it is the daily intake of the product which has the minimum batch size. Actually, what matters is not the batch size but the factor [(Minimum batch size)/(shared surface area x maximum daily intake)], which has to be the minimum among the products which share the equipment. To make it clear: it is worse to take 10 tablets/day of a contaminated product with a batch size of 500 kg, than 2 tablets/day of a contaminated product with a batch size of 300 kg, even if among both 300 kg is the smaller batch size, and the accepted limit will be lower for the 500 kg batch.

Best regards