Pharmaceutical tablets contain a variety of active substances and excipients which could be monitored by Raman spectroscopy/microscopy. Raman microscopic spectra are affected not only by the sample
composition but also by preparation/measurement conditions. The character and variability of surface morphology (of tablet slices), the appropriate levels of focusing and other adjustable settings of
the measurement instrumentation represent important parameters to be considered for obtaining relevant and reliable results by Raman microscopic mapping/imaging analysis in the pharmaceutical
practice. The aim of the study is to determine the effect of levels of the spotlight, and other instrumental parameters for mapping industrially manufactured pharmaceutical tablets and to find out
suitable, preferably robust, parameters for routine analyses. The role of roughnesses produced by commonly used microtome slices of tablets was investigated experimentally by different focusing
levels showing relatively weak (statistical) influence on data sets. The spectral quality was evaluated by signal–to–noise ratio. The data sets were processed using two multivariate statistical
methods (Principal Component Analysis, Soft Independent Modeling of Class Analogy). Direct Classical Least Squares statistical modeling was optimized to show the distribution of active pharmaceutical
ingredient and excipients in Raman maps. The applied different types of data evaluation confirm that the most suitable position regarding the focusing is the middle of tablet's cross-section
roughness. However, we have shown that the selection of microscopic measurement modes plays a much more significant role. The selection of proper measurement mode is crucial to describe the actual
sample variability and to obtain relevant data for real pharmaceutical samples. The time–consuming requirements of measurement modes need to be considered, as well, to obtain as reasonable data as
possible in the given time frame in the applied pharmaceutical analysis.
