TITLE:
Chemical Fingerprinting of Counterfeits of Viagra and Cialis Tablets and Analogues via Electrospray Ionization Mass Spectrometry
AUTHORS:
Rafael S. Ortiz, Kristiane de Cássia Mariotti, Wanderson Romão, Marcos N. Eberlin, Renata P. Limberger, Paulo Mayorga
KEYWORDS:
ESI-MS, Fingerprinting, Counterfeiting, Viagra®, Cialis®
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.2 No.8,
December
7,
2011
ABSTRACT: 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.