Post cleaning rinsing

Can I please ask people for their thoughts, I am trying to separate rumour, current practice and regulation.
I am performing a clean-in-place operation with the final stages being a phosphoric acid wash and then a water rinse to eliminate the acid. Do I need to validate the rinse with a set volume / time of water flow, it is acceptable (to FDA standards) to continue rinsing with water until the conductivity is within limits, or, can I use such an automated system that only feeds sufficient phosphoric acid into to system as necessary to nutralise previous sodium hydroxide stages (I know that there will be salts formed that will need to be rinsed away before conductivity drops, but I am trying to establish the principle here).
Many thanks

Dear Trefor,

as with every material that is not part of the product formula, you will have to prove that it has been eliminated to scientifically justified levels. What you need to demonstrate is that, regardless if you use a preset rinsing volume or if you rinse until conductivity drops below a preset level, remaining contamination is below a justified level. In any case, measurement of the rinsewater conductivity (to detect Phosphoric acid, sodium phosphate or whatever) is suitable only as monitoring but not for validation because you measure what is eliminated from the equipment but not what remains in it. My advice is to carry out a recovery test for phosphoric acid or sodium phosphate (swabbing or rinsing), then clean the equipment, measure the conductivity of the rinsate, sample the equipment (by the method chosen) and verify that the equiment is clean. When you have validated the cleaning procedure you will have conductivity data which support conductivity as the monitoring method.

Best regards


In addition to what Alfred said, it is essential that we also need to measure the pH of the rinsate to demonstrate that the Phosphoric acid and Sodium phosphate are neutralized or removed from the equipment surface.