Determination of α-guaiene and azulene chemical content in patchouli aromatic oil (Pogostemon cablin Benth.) from Indonesia by Near-infrared spectroscopy

Abstract

This study evaluated the α-guaiene and azulene chemical composition of patchouli aromatic oil from Indonesia by Near-infrared Spectroscopy (NIRS) combined with chemometric treatments. 84 oil samples collected around Indonesia were used, Konawe, Kolaka, Bogor, Garut, Aceh, Jambi, and Masamba. The spectral data were obtained using Fourier Transformed Near-infrared (FT-NIR) spectrometer in 1000 to 2500 nm. Several pretreatments processed the resulted transflectance spectra, and then partial least squares regression (PLSR) was applied. The data obtained from the spectra were evaluated based on the physical and chemical properties of the oil. α-guaiene and azulene chemical content were measured by liquid chromatography-mass spectrometry as a reference method. The best calibration for α-guaiene and azulene was second derivative with normalization mean centre, as data pretreatments. Both models had a high correlation coefficient (r>0.90), a low coefficient of variation (CV<2.98%), and an elevated ratio of standard error of prediction to standard deviation (RPD >3), which proved the applicability of NIRS to quality evaluation of patchouli oil.