API Manufacturing: Do you do rinse recovery studies?

Whereas recovery studies for swabbing do make sense to me (spike a coupon, swab and analyse), I have more difficulties to see the benefit of rinse recovery studies. Please convince me they are useful!
Thanks for every contribution.

The selection of an appropriate extraction solution is an important step in establishing a swab or rinse procedure. Your decision should be based on the solubility of the cleaning detergent residue or pharmaceutical product residue in the selected solution. Various alcohols, water, buffers, or combinations of the three are common extraction solutions used for cleaning procedures. Once an extraction solution is chosen, equipment surfaces may be extracted using a swabbing or rinse method.

Rinsing is suitable for small surface areas where traditional swabbing procedures may be difficult. The specified area should be rinsed long enough to ensure complete coverage of the entire surface and sufficient removal of the target residue. Rinsing methods provide a more simplistic sampling approach because they avoid possible swab interference in the detection method or extraction issues in removing the residue from the swab surface.

Swabbing is ideal for hard-to-clean areas and can physically remove insoluble residues. Swabs are selected for their ability to recover the monitored residue from a given surface and their ability to release the residue to an extraction solution for analysis. The selected swab should not contribute excessive interference or background during analysis. Another consideration in swab selection is whether the area being swabbed is easily accessible or hard to reach. Swabs that are long with small heads are excellent for general purposes and hard-to-reach areas. Other swabs with larger heads are better suited for cleaning broad, flat areas.

Advantages of Rinsing:

·Adaptable to on-line monitoring

· Easy to sample

· Non-intrusive

· Less technique dependent than swabs

· Applicable for actives, cleaning agents and excipients

· Allows sampling of a large surface area

· Allows sampling of unique (e.g., porus) surfaces

Limitations of Rinsing:

· Limited information about actual surface cleanliness in some cases

· May lower test sensitivity

· Residues may not be homogeneously distributed

· Inability to detect location of residues

· Rinse volume is critical to ensure accurate interpretation of results

· Sampling methodology must be defined since rinse sampling method and location can influence results

· May be difficult to accurately define and control the areas sampled, therefore usually used for rinsing an entire piece of equipment, such as a vessel

· Reduced physical sampling of the surface

Dear Durga,

Thank you for the extensive reply. I fully agree to your point of view.
I guess my question was not clear!

Assume you have a cleaning procedure based on rinsing and which you would verify or validate by taking samples of the rinse(s) to show your cleaning is effective.

Some people will say you must do a preliminary study, i.e. a rinse recovery study (most probably on lab scale), to show that rinsing will effectively remove the contaminant(s) from the equipment’s surface and to what extent.

My question is about such lab studies. Are they really needed? How representative can they be? My opinion is they are not of great value. I find it better to do it on commercial scale right away and to show the contamination is decreasing with repeated rinses and to take swabs to assess the surface directly.

You must do a rinse study at Pilot level rather than at lab level.The reason is pilot level will be a representative size before you actually sacleup to your production level.You need to show that the rinsing solvent properly recovers all the material with in the limits that you intend for. If this fails here you must chose an alternative solvent or method. I think proving is must.There will be no shortcuts for any cleaning procedures and you must have a scientifical methodology to prove.