5.2.4. Tablet characterisation
Sˇ
asˇic [32] published findings from a study in which
Raman-CI was compared with NIR-CI for determining
spatial distribution of multiple components in tablets. Multivariate
Raman images could identify all of the components
in each tablet studied, while only two or three
components could be imaged using NIR imaging. It was
demonstrated that the eigenvalue-based criteria for choosing
principal components were ineffective for these Raman
Chemical Images, and the author remarked that the basic
postulates of PCA could pose a significant problem when
applied to Raman mapping spectra. For NIR mapping
spectra, interpretation of PCA proved difficult; problems
were associated with associating pure component spectra
and loadings. It was demonstrated that PCA was less efficient
for producing NIR-CIs than for Raman CIs.