Identification and Quantitation of Volatile Organic Compounds from Oxidation of Linseed Oil

Abstract

Solid phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) served to identify and quantitate the volatile organic compounds (VOCs) formed in the degradative oxidation of linseed oil. SPME involved experiments under nitrogen and oxygen atmosphere, two oil types (raw and boiled), and two different methods of sampling the head space to differentiate between the oxidation products and the oil impurities. Further experiments entailed the oxidation of neat linoleic and linolenic acids to assist with the development of a detailed reaction mechanism. The majority of the detected product species originated from the oxidation of linolenic compounds, which dominate the composition of linseed oil, while 2-propenal, pentanal, hexanal, 2,4-decadienal, and hexanoic acid, among others, were released from linoleic compounds. The concentration of hexanal (7-26), 2-pentenal (25-39), 1-penten-3-ol (3.1-4.8), trans,trans-2,4-heptadienal (33-50), trans,trans-2,4-decadienal (0.7-0.8), 3,5-octadien-2-one (2.5-6.2; relative area), ethanoic acid (137-195), and hexanoic acid (18-29) increased with the progress of oxidation; the numbers in the parentheses indicate initial and final concentration (ppm) of the species in the oil in 6 h experiments.