title: Detection of counterfeit Viagra® by Raman microspectroscopy imaging and multivariate analysis.
abstract: During the past years, pharmaceutical counterfeiting was mainly a problem of developing countries with weak enforcement and inspection programs. However, Europe and North America are more and more confronted with the counterfeiting problem. During this study, 26 counterfeits and imitations of Viagra® tablets and 8 genuine tablets of Viagra® were analysed by Raman microspectroscopy imaging. After unfolding the data, three maps are combined per sample and a first PCA is realised on these data. Then, the first principal components of each sample are assembled. The exploratory and classification analysis are performed on that matrix. PCA was applied as exploratory analysis tool on different spectral ranges to detect counterfeit medicines based on the full spectra (200-1800 cm⁻¹), the presence of lactose (830-880 cm⁻¹) and the spatial distribution of sildenafil (1200-1290 cm⁻¹) inside the tablet. After the exploratory analysis, three different classification algorithms were applied on the full spectra dataset: linear discriminant analysis, k-nearest neighbour and soft independent modelling of class analogy. PCA analysis of the 830-880 cm⁻¹ spectral region discriminated genuine samples while the multivariate analysis of the spectral region between 1200 cm⁻¹ and 1290 cm⁻¹ returns no satisfactory results. A good discrimination of genuine samples was obtained with multivariate analysis of the full spectra region (200-1800 cm⁻¹). Application of the k-NN and SIMCA algorithm returned 100% correct classification during both internal and external validation.
authors.affiliation: Laboratory of Drug Analysis, Scientific Institute of Public Health, Brussels, Belgium.
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Sacré
authors.forename: Eric
authors.initials: E
authors.lastname: Deconinck
authors.forename: Lien
authors.initials: L
authors.lastname: Saerens
authors.forename: Thomas
authors.initials: T
authors.lastname: De Beer
authors.forename: Patricia
authors.initials: P
authors.lastname: Courselle
authors.forename: Roy
authors.initials: R
authors.lastname: Vancauwenberghe
authors.forename: Patrice
authors.initials: P
authors.lastname: Chiap
authors.forename: Jacques
authors.initials: J
authors.lastname: Crommen
authors.forename: Jacques O
authors.initials: JO
authors.lastname: De Beer
mesh_terms: D000465:Algorithms; D002626:Chemistry, Pharmaceutical; D058110:Counterfeit Drugs / Q000737:chemistry*; D016002:Discriminant Analysis; D005079:Excipients / Q000737:chemistry; D005240:Feasibility Studies; D005607:Fraud / Q000517:prevention & control*; D007785:Lactose / Q000737:chemistry; D015591:Microspectrophotometry / Q000592:standards; D015999:Multivariate Analysis; D058986:Phosphodiesterase 5 Inhibitors / Q000737:chemistry*; D010879:Piperazines / Q000737:chemistry*; D025341:Principal Component Analysis; D011687:Purines / Q000737:chemistry; D012015:Reference Standards; D015203:Reproducibility of Results; D000068677:Sildenafil Citrate; D013059:Spectrum Analysis, Raman / Q000592:standards; D013450:Sulfones / Q000737:chemistry*; D013607:Tablets; D013678:Technology, Pharmaceutical / Q000379:methods*
chemical_list: D058110:Counterfeit Drugs; D005079:Excipients; D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D013607:Tablets; D000068677:Sildenafil Citrate; D007785:Lactose