In the spectra of TFA-free oils (Fig. 3), the area at 1670–
1625 cm1 was directly proportional to the area at the wavelength
typically employed in TFA quantitation. The quantitative relationship
(Eq. (2)) can be considered to determine the TFA absorption in
the spectrum of an oil sample that needs interference from an
inherent ester to removed. However, such correction is not valid
when other factors (such as free fatty acid presents) in the oil sample
perturb the absorbance because of the overtone at 1670–
1625 cm1
. Despite this requirement, when the relation in Eq. (2)
was applied in the calibration curve displayed in Fig. 1 (Eq. (1)),
the resulting correlation obtained from the corrected calibration