Werickson Fortunato de Carvalho Rocha

Fingerprinting of sildenafil citrate and tadalafil tablets in pharmaceutical formulations via X-ray fluorescence (XRF) spectrometry.

The production of counterfeited drugs is a criminal problem that carries serious risks to public health in the worldwide. In Brazil, Viagra and Cialis are the most counterfeit medicines, being used to inhibit the phosphodiesterase type 5 (PDE-5), treating thus, problems related to erectile dysfunction. X-ray fluorescence (XRF) is a suitable technique to control the quality of new pharmaceutical formulations and distinguish between authentic and counterfeit tablets. XRF has advantageous features like multielemental capability, good detectivity, high precision, short analysis times, and is nondestructive, which makes it suitable to be extended to a great variety of samples. In this work, the inorganic fingerprinting chemical of forty-one commercial samples (Viagra, Cialis, Lazar, Libiden, Maxfil, Plenovit, Potent 75, Rigix, V-50, Vimax and Pramil) and fifty-six counterfeit samples (Viagra and Cialis) were obtained from XRF data. XRF presented an excellent analytical methodology for semi-quantitative determination of active ingredient (in case of sildenafil citrate that presents S in its structure) and excipients such as calcium phosphate, titanium oxide and iron oxide (P, Ca, Ti and Fe). The matrix data were allied to chemometric methods (Principal Component Analysis and Hierarchical Cluster Analysis) to classify the tablets investigated between authentic and counterfeit, grouping the samples into of seven groups: A, B, C, D and E (counterfeit group) and F and G (authentic group).

Classification of soil samples based on Raman spectroscopy and X-ray fluorescence spectrometry combined with chemometric methods and variable selection

Soil classification is crucial for its cultivation preparation in countries that export several agricultural commodities. The soil classification system adopted in Brazil is based on chemical parameters and physical and morphological changes. This system possesses disadvantages because many analyses are time-consuming, especially during the sample preparation stage. Raman spectroscopy is a non-destructive technique that enables rapid soil sample characterisation. In this study, Raman spectroscopy was used to discriminate different soil samples. Although the Raman spectra of a substance can be used as a phase fingerprint due to its specificity, this technique is not adequate for sample discrimination and suffers from matrix interferences, especially during the analyses of soil samples. However, a synergic effect with satisfactory results regarding prediction and classification problems occurs when this method is coupled with chemometric tools. In this research, a robust classification method for analysing soil samples using Raman spectroscopy combined with a support vector machines (SVM-C) method and genetic algorithm (GA) for variable selection was developed. The results obtained from the combination of the proposed GA–SVM-C based on the figures of merit were sensitivity (1.000), specificity (1.000), and misclassification error (0.0%) in the validation step. This soil discrimination methodology was validated using X-ray fluorescence spectrometry. These tools can be used in routine analyses, reducing laboratory costs with good efficiency.

Multivariate control charts based on net analyte signal (NAS) and Raman spectroscopy for quality control of carbamazepine

Raman spectroscopy and control charts based on the net analyte signal (NAS) were applied to polymorphic characterization of carbamazepine. Carbamazepine presents four polymorphic forms: I-IV (dihydrate). X-ray powder diffraction was used as a reference technique. The control charts were built generating three charts: the NAS chart that corresponds to the analyte of interest (form III in this case), the interference chart that corresponds to the contribution of other compounds in the sample and the residual chart that corresponds to nonsystematic variations. For each chart, statistical limits were developed using samples within the quality specifications. It was possible to identify the different polymorphic forms of carbamazepine present in pharmaceutical formulations. Thus, an alternative method for the quality monitoring of the carbamazepine polymorphic forms after the crystallization process is presented.

Viagra® and Cialis® blister packaging fingerprinting using Fourier transform infrared spectroscopy (FTIR) allied with chemometric methods

The production of counterfeit drugs is a criminal problem that carries serious risks to public health worldwide. Herein, the chemical fingerprinting of blister packaging using Fourier transform infrared spectroscopy (FTIR) of authentic and counterfeit samples of Viagra® and Cialis® is demonstrated. Fifteen commercial samples (Viagra® and Cialis®) and thirty two counterfeit samples (Viagra and Cialis) were analyzed, and the FTIR data was subjected to chemometric treatment via unsupervised pattern recognition methods (principal component analysis, and hierarchical cluster analysis) and a supervised pattern recognition method (partial least squares discriminant analysis). ATR-FTIR spectra of the blister packaging of authentic Cialis® and counterfeit Cialis samples showed bands at 2976, 2904, 1431, 1326, 1243, 973, 691 and 608 cm−1, suggesting the presence of polyvinyl chloride (PVC) in its chemical composition. For authentic Viagra® and counterfeit Viagra samples, several distinct chemical profiles were observed in the ATR-FTIR spectra. Using unsupervised methods, samples were separated into three large groups: (i) counterfeit Viagra (seven samples made of PVC); (ii) authentic Viagra® (three samples made of poly(ethylene terephthalate)); (iii) Cialis (authentic and counterfeit) and some samples of Viagra (thirty seven made of PVC with additives of stearic acid derivatives, butyl hydroxy toluene or bisphenol A). Therefore, this suggests that three different types of forming films are used in the market for blister packaging used to contain inhibitors of PDE-5. Using supervised methods, all samples were correctly classified into their respective classes.

Final report on key comparison CCQM-K92: Electrolytic conductivity at 0.05?S?m?1 and 20?S?m?1

The aim of the key comparison CCQM-K92 was to demonstrate the capabilities of the participating NMIs to measure electrolytic conductivity of an unknown sample. Two samples with nominal electrolytic conductivity values of 0.05xa0Sxa0m−1 and 20xa0Sxa0m−1 have been prepared for comparison. For the first time a conductivity value larger than those given in the IUPAC document [1] was measured in a CCQM comparison. Thus no calibration standards with similar conductivity value were available. The comparison was an activity of the Electrochemical Working Group (EAWG) of the CCQM and was coordinated by SMU. In the comparison NMIs from fifteen countries took part. The higher conductivity (20xa0Sxa0m−1) was measured by ten participants. Good agreement of the results was observed for the majority of participants. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).