Through its Active Pharmaceutical Ingredient Working Group (API-WG) the General European Official Medicines
; Control Laboratory (OMCL) Network (GEON), co-ordinated by the European Directorate for the Quality of
; Medicines & HealthCare (EDQM), regularly organises market surveillance studies for specific APIs for conformity
; to their monograph in the European Pharmacopoeia. During the past years some studies were combined with a
; fingerprint study of the APIs. The idea is to obtain a fingerprint for each manufacturer of the API under investigation,
; allowing the OMCL network to identify future samples as well as to detect substandard and falsified
; APIs.
; This paper reports the results of the latest fingerprint study, organised on sildenafil citrate API samples.
; Seventy-nine samples from 14 different manufacturers were collected throughout the Network. Fingerprint data
; was collected through Mid-Infrared spectroscopy, Raman spectroscopy, liquid chromatography for related substances,
; gas chromatography for residual solvents, X-ray diffraction and Nuclear Magnetic Resonance (NMR)
; spectroscopy. Chemometrics applied to the collected data showed that all manufacturers could be discriminated
; based on the data of only three of these tests, i.e. gas chromatography for residual solvents, X-ray diffraction and
; proton NMR. Suspicious API samples for sildenafil citrate will therefore be analysed in the future with the
; selected techniques in order to link the sample to a manufacturer or demonstrate the absence of such link. If the
; sample cannot be attributed to one of the manufacturers, further analysis and research on provenance and
; identity will be required. Of course, if the suspected sample claims to originate from one of the manufacturers
; included in the study, analysis can be limited to the test distinguishing this manufacturer.