Investigation of minor elemental species within tablets using in situ depth profiling via laser-induced breakdown spectroscopy hyperspectral imaging

Abstract

Laser-induced breakdown spectroscopy (LIBS) hyperspectral imaging allows for the determination of two-dimensional and three-dimensional spatial distributions of elemental species throughout complex samples. In this work, LIBS hyperspectral imaging was utilized to investigate minor elemental species within tablets. Representative LIBS spectra were initially collected on four complex, heterogeneous tablets, showing high concentrations of Ti in the tablet coating, with low and variable abundance of Na, Mg, and K. Principal component analysis revealed distinct resolution of the four tablets due to differences in Na, Mg, and K. Using two-dimensional LIBS hyperspectral imaging, spatial distributions of Na, Mg, and K within defined x and y regions of the tablet coating were generated. Subsequent three-dimensional LIBS hyperspectral imaging further elucidated the full x, y, and z spatial distributions of these minor elemental species within the tablet surface, tablet coating, and tablet core. As such, in situ depth profiling of the minor elemental species within each tablet was accomplished. Quantification of the homogeneity and uniformity of each tablet was determined. To our knowledge, this is the first report of multivariate analysis, LIBS, and LIBS hyperspectral imaging being utilized for the determination of both 2D and 3D spatial distributions of minor elemental species, along with quantification of tablet homogeneity, within tablets.