Confocal micro-X-ray fluorescence analysis as a new tool for the non-destructive study of the elemental distributions in pharmaceutical tablets.

Chemical imaging studies of pharmaceutical tablets are currently an important emerging field in the pharmaceutical industry. Finding the distribution of the different compounds inside the tablet is an important issue for production quality control but also for counterfeit detection. Most of the currently used techniques are limited to the study of the surface of the compacts, whereas the study of the bulk requires a time-consuming sample preparation. In this paper, we present the use of 3D micro-X-ray fluorescence analysis (3D μXRF) for the non-destructive study of pharmaceutical tablets. Based on two different examples, it was shown that it was possible to measure the distribution of several inorganic elements (Zn, Fe, Ti, Mn, Cu) from the surface to a depth of several hundred microns under the surface. The X-ray absorption, depending on both matrix composition and energy, is one of the most critical factors of this analytical method while performing depth profiling or mapping. Therefore, an original method to correct the absorption, in order to accurately measure the true elemental distribution, was proposed. Moreover, by using the presence of titanium dioxide in a pharmaceutical coating, we proved that this technique is also suited to the non-destructive measurement of coating thickness.