Characterization of sildenafil citrate tablets of different sources by near infrared chemical imaging and chemometric tools

In this paper the chemical imaging technique by near infrared spectroscopy was applied for characterization of drug formulations in tablets of sildenafil citrate of different sources. This work is original and has never been published because it was used the sildenafil citrate, including in the commercial one called "Viagra". In the first stage of the study, a chemometric method based on multivariate curve resolution was properly chosen for the development of the distribution map of concentrations of the active ingredient in tablets. In the second step, the normalized histograms of images from active ingredient were classified by hierarchical cluster analysis. Finally it was possible to recognize the patterns of homogeneity of images in sildenafil citrate tablet. This concept can be used to improve the knowledge of industrial products and processes, as well as, for characterization of counterfeit drugs.