Counterfeit Cialis and Viagra fingerprinting by ATR-FTIR spectroscopy with chemometry: Can the same pharmaceutical powder mixture be used to falsify two medicines?

ATR-FTIR characterization of generic brand-named and counterfeit sildenafil- and tadalafil-based tablets found on the Brazilian market

“…Although several studies based on infrared profiling [12,[14][15][16][17][18][19][20] have been published over this decade concerning identification of counterfeit samples of Viagra and Cialis, most of these works do not consider nor discuss the compositional characteristics of the samples, employing spectral profiling mostly as a data source for chemometrical analysis, an approach which, although very powerful and useful, is usually beyond practical use in most forensic laboratories. The present approach was based on more direct and comparative practical analyses of the spectral profiles of tablet cores, applied not only to identify the AI of each tablet, but also the major excipients/adjuvants present.…”

Detection of Counterfeit Durateston® Using Fourier Transform Infrared Spectroscopy and Partial Least Squares - Discriminant Analysis

“…13,15,17 It reduces the number of variables by making linear orthogonal combinations of the original variables, called the principal components (PCs), which progressively explain the remaining variability in the data. 13,15 In this study, PCA was performed with all available spectra for exploratory analysis. Preprocessing included baseline offset correction, first derivative smoothing (Savitzky-Golay, fourth order polynomial, 5 smoothing points) and data mean centering.…”

“…17,20 PLS-DA is also based on the PCA decomposition, the difference being that the combinations of variables, called PLS factors or latent variables, are defined in such a way that the covariance of the instrumental data with the response variable (predefined classes) are maximized, leading to quantitative methods with low errors and high discrimination power between the different classes in discriminant analysis. 13,15,18,20 PLS-DA is performed using binary coding, in which a dummy discrete response vector y is attributed to the data set, such as 0 for counterfeit samples and 1 for original samples. 14,17,21,22 In the training stage, the method is trained to assign "membership values", one for each class; a test sample is then assigned to a specific class if its y value surpasses a specific prediction threshold that may be estimated by establishing confidence limits for each sample classified.…”

“…[8][9][10][11][12] Spectroscopic techniques such as Raman, near infrared, and Fourier transform infrared (FTIR), together with chemometric tools, are being successfully used to analyze suspected counterfeit medicines. [13][14][15][16][17][18][19] They have the advantage of being less time-consuming than chromatographic methods, with little or no sample preparation. [13][14][15]19 However, to the best of our knowledge, only one work using spectroscopic methods to analyze anabolic steroid medicines has been published so far, describing the investigation of the composition of methandrostenolone-containing tablets by near infrared and Raman spectroscopy.…”

“…[13][14][15][16][17][18][19] They have the advantage of being less time-consuming than chromatographic methods, with little or no sample preparation. [13][14][15]19 However, to the best of our knowledge, only one work using spectroscopic methods to analyze anabolic steroid medicines has been published so far, describing the investigation of the composition of methandrostenolone-containing tablets by near infrared and Raman spectroscopy. 20 The aim of this work was to develop a simple, fast, low-cost and reliable method for the detection of Durateston ® counterfeits using FTIR and partial least squares -discriminant analysis (PLS-DA).…”