Monitoring peroxide value in fatliquor manufacture by Fourier transform infrared spectroscopy

Abstract

Abstract A Fourier transform infrared (FTIR) spectrometer equipped with an attenuated total reflectance (ATR) sample handling accessory was used to rapidly monitor the peroxide value (PV) of oils undergoing catalytic oxidation to produce sulfonated fatliquors used in the leather industry. PV quantitation was based on the stoichiometric reaction of triphenylphosphosphine (TPP) with hydroperoxides to produce triphenylphosphine oxide (TPPO). By using a germanium ATR accessory that has a very short effective pathlength, the spectral contributions of the base oil could be subtracted out, eliminating any oil‐dependent intereferences as well as providing a facile means of observing the spectral changes associated with the TPP/TPPO reaction. A calibration was devised by adding a constant amount of TPP‐saturated chloroform to oils containing varying amounts of tert ‐butyl hydroperoxide (TBHP) to produce TPPO that had a measurable band at 1118 cm −1 . this band was linearly related to TBHP concentration and the calibration devised had an SD of ∼3.4 PV over the range of 0–250 PV. The ATR‐PV method was standardized and the spectrometer programmed using Visual Basic to automate the analysis. the automated FTIR‐ATR method was found to be a convenient means of tracking PV of oils undergoing oxidation, and the results correlated well with the PV values obtained using the AOAC iodometric method ( r=0.94 ). The FTIR‐ATR PV methodology provides a simple means of monitoring the PV of oils undergoing rapid oxidation and could serve as a quality‐control tool in the production of sulfonated oils for the leather industry.