Automated and Simultaneous Determination of Free Fatty Acids and Peroxide Values in Edible Oils by FTIR Spectroscopy Using Spectral Reconstitution

Abstract

This paper described an FTIR spectrometer coupled to an auto-sampler and some attendant methodologies for a direct free fatty acid (FFA) method and triphenylphosphine (TPP)-based method for determination of FFA and peroxide value (PV) of edible oils by FTIR spectroscopy using spectral reconstitution. The viscosity of oil samples is reduced by mixing them with a diluent; such lowered viscosity allows them to be readily loaded into a flow-through transmission cell. The spectra of the neat oil samples are then reconstituted from those of the diluted samples by using the absorption of a spectral marker present in the diluent to determine the dilution ratio. For the direct FFA analysis, quantification is achieved using the (COO^-) band at 1712 cm^-1, while PV is determined using triphenylphosphine oxide (TPPO) absorption bands at 542 cm^-1. Calibration procedures and data are presented. Validation and performance data obtained with this automated system demonstrate that it is capable of analyzing ∼90 samples/h, a rate commensurate with the throughput required by commercial contract or high-volume process control laboratories.