Absorption spectrophotometry hydroperoxide determination

The analytical procedures applied in the study were fluoromet-ric determination of chlorophyll pigments / /, absorption spectrophotometry for the analysis of carotenoids /2/. Hydroperoxides were determined by the iodometric titrational or spectro-photometric procedures /3,4/. 

Hydroperoxide formation by the ene reaction path may lead to formation of conjugated double bonds in polyunsaturated fatty acids (see Section V.A) this reaction is concurrent with POV increase. An increase of the CDV, as measured from the absorbance at 233 nm, therefore indicates oxidation of polyunsaturated lipids. A strong correlation exists between CDV predicted from the absorbance in the 1100 to 2200 nm NIR region and CDV determined by the Ti Ia-64 AOCS official method , by UV spectrophotometry at 233 nm. The method was applied to determine CDV for oxidized soybean oil. A secondary absorption maximum of lesser intensity appears in the 260-280 mn range, and is assigned to ketone dienes . 

Ferric Ion Complexes Other chemical methods based on the oxidation of ferrous ion (Fe ) to ferric ion (Fe ) in an acidic medium and the formation of iron complexes have also been widely accepted. These methods spectrophotometri-cally measure the abihty of lipid hydroperoxides to oxidize ferrous ions to ferric ions, which are complexed by either thiocyanate or xylenol orange (23, 28, 29). Ferric thiocyanate is a red-violet complex that shows strong absorption at 500-510 nm (8). The method of determining PV by coloremetric detection of ferric thiocyanate is simple, reproducible, and more sensitive than the standard iodometric assay, and has been used to measure hpid oxidation in milk products, fats, oils, and liposomes (8, 23). 

Conjugated terpene hydrocarbons ultraviolet spectra 2,6-di-tert-butyl-p-cresol in edible fats and oils by a combined chromatographic-ultraviolet method Waxes ultraviolet absorptivity tests, ASTM ES 50 [ ]. Hydroperoxide (00-H) determination by near-infrared spectrophotometry... 

---