Monitoring peroxide value in fatliquor manufacture by Fourier transform infrared spectroscopy

A Fourier transform infrared (FTIR) spectrometer equipped with an attenuate d total reflectance (ATR) sample handling accessory was used to rapidly mon itor the peroxide value (PV) of oils undergoing catalytic oxidation to prod uce sulfonated fatliquors used in the leather industry. PV quantitation was based on the stoichiometric reaction of triphenylphosphine (TPP) with hydr operoxides to produce triphenylphosphine oxide (TPPO). By using a germanium ATR accessory that has a very short effective pathlength, the spectral con tributions of the base oil could be subtracted out, eliminating any oil-dep endent interferences as well as providing a facile means of observing the s pectral changes associated with the TPP/TPPO reaction. A calibration was de vised by adding a constant amount of TPP-saturated chloroform to oils conta ining varying amounts of tert-butyl hydroperoxide (TBHP) to produce TPPO th at had a measurable band at 1118 cm(-1). This band was linearly related to TBHP concentration, and the calibration devised had an SD of similar to 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 au tomated FTIR-ATR method was found to be a convenient means of tracking PV o f oils undergoing oxidation, and the results correlated well with the PV va lues 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 productio n of sulfonated oils for the leather industry.