Rinse sampling is generally used when the sampling part is either very small to take the swab or is inaccessable.
In case it is a small part we can use the swabbing solvent ( water or solvent or a mixture in some proportion )for rinsing of the partof the equipment.
But in case of larger surfaces like pipes of powder conveying system, the surface is very large( around 40 fts ) and the inner surface of the pipe is inaccessable. In that case to ensure the cleaning we have to go for rinse sampling.
Since we perform cleaning validation only for the worst case molecules and worst case molecules are insoluble in water so we cannot use water for rinsing , as the recovery will be almost zero in that case.
If we are using some solvent for rinsing in which the molecule is soluble , then we have to use a large quantity of solvent again which we need to remove from the equipment surface.
Please suggest what is to be used as rinsing solvent in such cases.
What is the general practice in industry for such situation?