Raman Spectroscopic Differences between Ephedrine and Pseudoephedrine

Differentiation of white architectural paints by microscopic laser Raman spectroscopy and chemometrics

A feasible, effective and non-destructive method that could be used to differentiate architectural paints was proposed by Microscopic laser Raman spectroscopy and chemometrics. A total of 252 white architectural paints from 7 different manufacturers were prepared for evaluating the potential of differentiating them. 5th Newton interpolation polynomial combined with Savitzky-Golay 7-point and 1st or 2nd polynomial smoothing under the 1st-order derivative were considered as the optimal pre-processing method for MLRM data. The Bayes discriminant analysis model realized 100% accuracy based on discriminant functions Z₁, Z₂ and Z₃, which was the more useful and practical method for differentiating white architectural paints than that of multilayer perceptron and radial basis function neural network models. All samples were differentiated exactly, which was rapid and non-destructive. The designed method demonstrated the potential of Microscopic Laser Raman spectroscopy in combination with pre-processing and chemometrics as a universal, confirmatory, and accurate method for the white architectural paint differentiation in forensic science.

Raman spectral characterization of silver metal-based complexes of different benzimidazolium ligands

In this study, Raman spectroscopy has been employed for the characterization of two structurally different monodentate N-heterocyclic carbene ligands (ligand-1 and ligand-2) and their respective complexes (complex-1 and complex-2). The Raman spectral features are found helpful for the confirmation of formation of complexes. The significant Raman spectral features are identified for benzimidazole ring with higher intensities in carbene complexes having more polarizability as compared to their ligands, providing the evidence for the formation of coordinate covalent bond. The successful complexation is further supported by using multivariate data analysis technique, Principal Component Analysis (PCA), which is found very helpful to highlight the variability of Raman spectral data of both ligands and their respective metal complexes from each other. Moreover, the coordination of carbene with Ag(I) is confirmed from the dominant spectral markers of higher intensities at 359 cm^-1 in complex-1 and 338 cm^-1 in complex-2. The effective and reliable characterization and confirmation of metal complexes indicates the potential of Raman spectroscopy for its use for the characterization of the organometallic complexes and other chemical products.