Aim - To evaluate the use of vibrational spectroscopy in tandem with chemometric data analysis as a fast and low-cost alternative method for the quality control of TTO. Methodology - Spectral data were acquired in both the mid infrared (MIR) and near infrared (NIR) wavelength regions and reference data obtained using GC–MS–FID. Principal component analysis (PCA) was used to investigate the data by observing clustering and identifying outliers. Partial least squares (PLS) multivariate calibration models were constructed for the quantification of the seven major constituents.
Results - High correlation coefficients (R2) of ≥ 0.75 were obtained for the seven major compounds and 1,8-cineole showed the best correlation coefficients for both MIR and NIR data (R2= 0.97 and 0.95, respectively). Low values were obtained for the root mean square error of estimation (RMSEE) and root mean square error of prediction (RMSEP) values indicating accuracy.
Conclusion - The accurate prediction of the external dataset after introduction into the models confirmed that both MIR and NIR spectroscopy are valuable methods for quantification of the major compounds of TTO when compared to the reference data obtained with GC-MS.