Kim and colleagues employed time-resolved IR (TRIR) spectroscopy to scrutinize excited-singlet-state aromaticity from the viewpoint of molecular geometry. The interconvertible spectral features were observed in the IR spectra between the ground and excited singlet states; the contrasting spectral features of simple and complicated Fourier transform IR spectra between aromatic and anti-aromatic hexaphyrins were reversed in their TRIR spectra. Qualitative analyses revealed that the interconvertible spectral features arise from aromaticity-driven structural changes, demonstrating aromaticity reversal in the excited singlet states.
A solvent-free headspace gas chromatography – mass spectrometry (SF-HS-GC/MS) method was developed and validated for screening of N-nitrosodimethylamine (NDMA) in various active pharmaceutical ingredients (APIs) and drug products. Experimental parameters...
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