K. Ma et al., STOICHIOMETRIC DETERMINATION OF HYDROPEROXIDES IN FATS AND OILS BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY, Journal of the American Oil Chemists' Society, 74(8), 1997, pp. 897-906
A primary Fourier transform infrared (FTIR) spec troscopic method for
the determination of peroxide value (PV) in edible oils was developed
based on the stoichiometric reaction of triphenylphosphine (TPP) with
hydroperoxides to produce triphenylphosphine oxide (TPPO). Accurate qu
antitation of the TPPO formed in this reaction by measurement of its i
ntense absorption band at 542 cm(-1) provides a simple means of determ
ining PV. A calibration was developed with TPPO as the standard; its c
oncentration, expressed in terms of PV, covered a range of 0-15 PV. Th
e resulting calibration was linear over the analytical range and had a
standard deviation of +/-0.05 PV. A standardized analytical protocol
was developed, consisting of adding similar to 0.2 g of a 33% (w/w) st
ock solution of TPP in hexanol to similar to 30 g of melted fat or oil
, shaking the sample, and scanning it in a 100-mu m KCI IR transmissio
n cell maintained at 80 degrees C. The FTIR spectrometer was programme
d in Visual Basic to automate scanning and quantitation, with the reac
tion/FTIR analysis taking about 2 min per sample. The method was valid
ated by comparing the analytical results of the AOCS PV method to thos
e of the automated FTIR procedure by using both oxidized oils and oils
spiked with tert-butyl hydroperoxide. The two methods correlated well
. The reproducibility of the FTIR method was superior (+/-0.18) to tha
t of the standard chemical method (+/-0.89 PV). The FTIR method is a s
ignificant improvement over the standard AOCS method in terms of analy
tical time and effort and avoids solvent and reagent disposal problems
. Based on its simple stoichiometry, rapid and complete reaction, and
the singular band that characterizes the end product, the TPP/TPPO rea
ction coupled with a programmable FTIR spectrometer provides a rapid a
nd efficient means of determining PV that is especially suited for rou
tine quality control applications in the fats and oils industry.