David Pollard

This study reported a combined use of ordinary Fourier transform-infrared spectroscopy (FT-IR) in conjunction with partial-least-square (PLS) multivariate regression for accurate determination of the percent compositions of four essential oils (EOs) (wintergreen, tea tree, rosemary, and lemon eucalyptus oils) that were adulterated either with lemongrass essential oil (LO) or peppermint essential oil (PO). The FT-IR spectra of the calibration sample sets of known compositions of adulterated EOs with LO or PO were measured and subjected to PLS multivariate regression analysis. The simplicity, low-cost, and high accuracy of the protocol makes it appealing for routine industrial quality assurance of consumable goods.

The peppermint oil results are presented in this supplementary section.