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Direct infusion electrospray ionization mass spectrometry (ESI-MS) is shown to provide an efficient tech- nique for the investigation of polar composition of forensic tablets for male erectile dysfunction. ESI-MS fingerprinting of 41 commercial sildenafil samples (Viagra®, Cialis®, Lazar®, Libiden®, , Maxfil®, , Plenovit®, Potent 75®, Rigix®, V-50®, Vimax®, Pramil 75® and Pramil®) and 56 counterfeit samples (Viagra and Cialis) were obtained. The spectra for the authentic Viagra® tablets showed abundant ions exclusively corresponding to the sildenafil (SLD) molecule: [SLD + H]+ of m/z 475; [SLD + Na]+ of m/z 497; and [2SLD + H]+ of m/z 949. The spectra for com-mercial sildenafil samples also showed predominat SLD ions. Tablets of authentic Cialis® showed mainly ions of m/z 343, 365 and 707 from the lactose molecule (the excipient); as well as a minor ion of m/z 390 corresponding to the active ingredient tadalafil (TAD) in its protonated form [TAD + H]+. For counterfeit Cialis samples, how-ever, normally TAD ions of much high abundances was observed, together with ions corresponding to sildenafil analogues such as those of m/z 489 (homosildenafil) and 505 (hydroxyhomosildenafil). Principal component analysis was applied to ESI-MS fingerprint data, placing samples according to their contents of active ingredients hence authentic and counterfeit samples are easily recognized

Chemical Fingerprinting of Counterfeits of Viagra and Cialis Tablets and Analogues via Electrospray Ionization Mass Spectrometry