Comparative chemotype determination of Lamiaceae plants by means of GC-MS, FT-IR, and dispersive-Raman spectroscopic techniques and GC-FID quantification

Three different techniques: the classical gas chromatography-mass spectrometry (GC-MS) and two “green” alternative techniques to the classical chromatography, the spectroscopic techniques Fourier transform infrared (FT-IR), and dispersive-Raman were employed to characterize the main chemotypes of different essential oils from plants of the Lamiaceae family and to compare between techniques. Gas chromatography-flame ionization detector (GC-FID) was also employed to quantify the main compounds present in essential oils isolated by hydrodistillation (HD) and semi-quantify essential oil composition isolated by HD and simultaneous steam distillation - solvent extraction (SDE). While GC cannot differentiate between pure and mixed chemotypes of a compound, FT-IR, and Raman methods allow the creation of libraries, through which chemotype determination is feasible even for mixed chemotypes, thus combining robustness with being rapid and non-destructive techniques.