Measurement of Peroxide Values (PV) in Oils by Triphenylphosphine/Triphenylphosphine Oxide (TPP/TPPO) Assay Coupled with ATR-FTIR Spectroscopy

One of the first indicators of oxidation in oils and fats is the presence of hydroperoxides (LOOH); therefore, it is important to find a reliable method to quantify these oxidation products. Herein, we propose a procedure to measure oxidation levels of oils using Fourier transform infrared (FTIR) spectroscopy with an attenuated total reflectance (ATR) mode based on the stoichiometric conversion of triphenylphosphine (TPP) into triphenylphosphine oxide (TPPO) by LOOH. ATR-FTIR spectroscopy allows for simple and accurate detection of the TPPO formed by selective reaction with LOOH, with measurement of its specific adsorption band at 542 cm−1. Calibration was made with TPPO solubilized in butan-2-one and covers a range of peroxide values (PV) from ~2 to ~800 mEq/kg of fat. This method is simple and fast while limiting the use of toxic solvents and is suitable for routine analysis of oils and fats.