# Last rinse

Hi all,

I have been working in several firms in cleaning validation and I don’t understand the aproach for rinsing sampling. In one of them, the rinse sample was token of the last mL of the last rinse of water use to clean (ie, there were three rinses and the sample was token of the third one, in the end), and in other company, the rinse sample was token from a rinse performed after clean. Which do you think that is the correct form?

In the same way, for calculating the acceptance limit in rinse water, what volume have I to introduce in the ecuation? The total volume of the rinse water used in my cleaning method or the water used to do a rinse extra for sampling?

Thanks in advance, folks!

Dear Anuki…
First, calculate the MACO. Let’s assume it is 100 mg.
Calculate the quantity of water required to rinse the entire product contact surface area. Here, rinsing is collection of sample but not cleaning of equipment. Let’s assume it is 5 litre. Then the content of your product in rinse water should be less than 2 ppm or 2 µg
Then clean your equipment as per your standard cleaning procedure.
Then rinse the entire product contact surface area with 5 litres of water and collect the entire rinses into a bucket. Mix it well and collect 100 ml of sample from the bucket.

RAJU

Thank you very much! :o

Is it 2 ppm or 20 ppm[ 100 mg rinsed with 5 liters of water ]

Regards,
Bujji Kanchi.

Yes, you are right
Its a typo error
Thank you

RAJU