In the context of cleaning validation reference is often made to the riboflavin test when it comes to wettability and spray shadows. But how is this test carried out? In this regard questions may arise concerning the concentration of the riboflavin solution, time for drying out, thickening agent etc. There does not exist any assistance by the authorities. The test is not required explicitly in the official regulations on cleaning validation.
The VDMA (German Process Plant and Equipment Association) has published an information sheet on this test that also is available in English. You can find details in the GMP News from January 2010.
In the (German) dissertation with the title "Prüfung der Effektivität eines CIP-Systems für die Reinigung und Desinfektion des Innenraums einer Tiefziehverpackungsmaschine" (Examination of the effectiveness of a CIP system for the cleaning and disinfection of the interior of a thermoforming machine) at the Faculty of Veterinary Medicine of Ludwig-Maximilian University, Munich form the year 2009 you can also find information on the execution of the riboflavin test. There it was employed to review the cleaning effectiveness of the CIP system. The basis was again the VDMA information sheet. In this dissertation you can also find alternative tests. Apart from the riboflavin test the NAD rapid detection test and the wet-dry swab testing procedure, a microbiological procedure, were used. Neither of the two tests is widespread in the pharmaceutical environment.
Relatively new is an alternative procedure to the riboflavin test, the P3-aquanta Blue-Test. By means of this test the wetting of the surface and especially the corresponding cleaning mechanics are tested. The cleaning mechanics must be suited very well for cleaning off the film. In contrast to the riboflavin test a light blue film remains if the mechanics of the heads is insufficient or if only water has flown across the relevant surfaces. This can be tested with the aid of a simple wipe test with white cloths. More information can be found here.