Hydroperoxides (LOOH) quantification in oils and fats is a well-used method to determine their degree of oxidation. Iodometric and colorimetric quantification methods are already widely used, but present limitations: relative measurement, manipulator dependent, complicated appreciation if pigmented samples, and variable responses depending on the structure of the LOOH. As a result, alternative method by measuring the oxidation level using FTIR-ATR, based on the stoichiometric conversion of triphenylphosphine (TPP) into triphenylphosphine oxide (TPPO) by hydroperoxides is explored. The detection of the TPPO formed by selective reaction with LOOH is measured thanks to its specific adsorption band at 542cm-1. This method consists in forming a homogeneous film of oil on the FTIR-ATR crystal. Several steps were required to develop and validate this method. Tests were carried out on different oils in order to evaluate the effects of pigmented molecules and the degree of unsaturation of fatty acids. Another test was carried out to optimize concentration, reactivity and sensitivity limits of the method. A concentration of 200 mg/mL of oil in solvent (butan-2-one) showed the best results for LOOH detection down to the nanomole order. This rapid method offers great promise in terms of reproducibility, robustness and veracity of results, with absolute quantification of LOOH.
OXI-008: Optimization of lipid hydroperoxides determination using triphenylphosphine/triphenylphosphine oxide (TPP/TPPO) assay coupled with FTIR-ATR spectroscopy
