Laser-induced breakdown spectroscopy as a tool for homogeneity measurements in medicine tablets

In this work, we have used laser-induced breakdown spectroscopy (LIBS) in the analysis of commercial tablets. The samples were mainly composed of dipyrone, an analgesic and fever reliever consumed worldwide. At first, the physical parameters, temperature and electronic density of the plasma were calculated throughout the Boltzmann plot and Saha equation respectively, and the McWhirter criterion was achieved, which allows us to assert that the minimum criterion for local thermodynamic equilibrium is presented in the plasma generated. After that, the tablets' homogeneity was assessed using the whole LIBS spectra combined to correlation statistic methods, such as principal components analysis (PCA) and hyperspectral images. The results show high homogeneity, R  >  0.996, at the surface and some heterogeneity in the bulk. LIBS was also applied for major active pharmaceutical ingredients C, Na and Mg identification. (paper)