Supplementary Section: Purity Analysis of Adulterated Essential Oils by FT-IR Spectroscopy and Partial-Least-Squares Regression

The peppermint oil results are presented in this supplementary section.

The peppermint oil results are presented in this supplementary section. This section includes Figures 1–4 and Table I. 

Figure 1 (web): FT-IR spectra of calibration samples of (a, left) WO, (b, left) TTO, (c, left) RO, and (d, left) LEO. Cross sections of FT-IR spectra of (a, right) WO, (b, right) TTO, (c, right) RO, and (d, right) LEO adulterated with peppermint oil. (Peppermint oil adulteration ranged between 1% and 90% [wt/wt].)

 

Figure 2 (web): Typical score plot of PLS-1 regression of WO adulterated with peppermint oil.

 

Figure 3 (web): FT-IR spectra of independent validation samples of (a) WO, (b) TTO, (c) RO, and (d) LEO adulterated with with peppermint oil.

 

Figure 4 (web): Plots of actual and determined percent composition of independent validation samples of (a) WO, (b) TTO, (c) RO, and (d) LEO adulterated with peppermint oil.