Effect of temperature on thermal oxidation of palmitic acid studied by combination of EPR spin trapping technique and SPME-GC-MS/MS

Effect of temperatures on thermal oxidation of palmitic acid was studied by the combination of EPR and GC-MS/MS. DMPO was used as the spin trap. The experimental spectrum was simulated with alkyl and alkoxyl spin adducts. Total amount of spins, a parameter to indicate radical concentrations, detected at 180 degrees C was nearly 10 times higher than that at 175 degrees C. Besides, total amounts of spins detected at 180 degrees C decreased rapidly because of the reaction between radical adducts and newly formed radicals. Signal intensities of alkyl radical adducts increased rapidly from 0.405 to 4.785 from 175 degrees C to 180 degrees C. Besides, more palmitic acid degraded to oxidized compounds from 175 degrees C to 180 degrees C than that of other temperature ranges. The C-C linkages between carbons 2 to 6 were easier to be oxidized at 180 degrees C. The results all implied that oxidation rates of palmitic acid samples increased rapidly from 175 degrees C to 180 degrees C. (C) 2017 Elsevier Ltd. All rights reserved.