Direct FTIR Analysis of Free Fatty Acids in Edible Oils Using Disposable Polyethylene Films

Determination of the acid values of edible oils via FTIR spectroscopy based on the OH stretching band

“…From a sample handling perspective, the attenuated total reflectance (ATR) attachment, which allows one to simply place the oil onto an exposed crystal surface and record the spectrum, is one of the most viable alternatives (Filho, 2014;Sherazi, Mahesar, Bhanger, Voort, & Sedman, 2007). Polyethylene and polytetrafluoroethylene films, which contain microcrystalline pores capable of absorbing liquids into the polymer matrix via capillary action, have also been employed as single-use, disposable infrared-transparent substrates for measuring the infrared spectra of oils (Dong, Li, Sun, Chen, & Yu, 2015;Xu, Zhu, Chen, Sun, & Yu, 2015).…”

“…By adding a spectral maker, such as methylcyclopentadienyl manganese tricarbonyl (MMT), to oils, the relative intensity of the peak at 1942 cm À1 , corresponding to the C@O stretching of MMT, could be used for spectral reconstitution to remove the spectral contributions from diluents, to eliminate the influence of oil film thickness on the spectra and to correct the characteristic band of free fatty acids (Yu, Voort, Sedman, & Gao, 2011). To avoid the necessity of using a marker, Dong and coworkers normalized the path length of each oil film to a fixed path length of 0.15 mm with the absorbance at 4334 cm À1 , which is fairly constant in intensity, irrespective of the type of oil being analysed and corresponds to a maximum of the broad absorption band that oils exhibit in the CH combination band region (Dong et al, 2015). Another quantitative calibration technique is the chemometric method, which is capable of providing precision, accuracy, and analytical information and has been widely used in recent years.…”

Analysis of Reaction Kinetics of Edible Oil Oxidation at Ambient Temperature by FTIR Spectroscopy

“…[ 24 ] The vibrational regions of these characteristic absorption peaks have been found to correspond to the following wavenumbers: ROOH bonds occur in the range of 3650–2700 cm −1 ; C═O bonds from FFAs vibrates within the range of 1720–1700 cm −1 ; TDBs conform to the peak at 969–967 cm −1 approximately; and CCS vibration is accord with the region within 723 cm −1 . [ 25–28 ] The absorption of ROOH bonds, C═O bonds, TDBs, and CCS in the corresponding spectral regions is related to hydroperoxides, FFAs, TFAs, and carbon chains of fatty acids in the oils. [ 20 ]…”

Authentication of <i>Eucommia ulmoides</i> Seed Oil Using Fourier Transform Infrared and Synchronous Fluorescence Spectroscopy Combined with Chemometrics

“…The conventional ATR-FTIR methods provide weak signals due to short path length of ATR cell 18,33,34 . By the PE-FTIR procedure, spectra of the oil films were collected using a PE film as background spectrum, and effective path lengths of oil film spectra were normalized to a fixed path length of 0.15 mm by a path length calibration equation attributed to CH combination band 35 . Therefore, the PE-FTIR method is a feasible alternative for accurate analyses of EUSO adulteration because of simple procedure using a disposable PE film as a spectral acquisition accessory.…”