LC-MS ion maps for the characterization of aniline derivatives of fatty acids and triglycerides in laboratory-denatured rapeseed oil

Abstract

In 1981 Spain went through a unique epidemic associated with a food-borne vector, affecting more than 20,000 people with over 800 deaths, which came to be known as the Toxic Oil Syndrome (TOS). Early epidemiological studies showed a link between this illness and the ingestion of rapeseed oil denatured with 2% aniline. This oil, originally aniline-denatured for industrial use, was fraudulently processed in an attempt to remove free aniline, and marketed as edible oil. Fatty acid anilides (FAA), monoesters and diesters of 3-(N-phenylamino)-1,2-propanediol (PAP) are present in oil samples as they arise in the refining process from reactions of aniline with constituent fatty acids and triglycerides of the oil matrix and are the only extraneous compounds found in these samples. To expand the search for the causative agents in TOS-associated oils and to look for new aniline-related compounds, an exhaustive characterization of laboratory-processed oils was undertaken. These oils, in the presence of aniline doped with 14C labelled aniline, were submitted to the laboratory conditions required for the generation of PAPs and FAAs. Laboratory-generated oil samples were submitted to a liquid-liquid extraction procedure to remove the unreacted aniline. The extract was processed by double solid-phase extraction to improve detection limits for minor amine-containing compounds in oils. The extracts enriched in aniline derivatives were submitted to on-line HPLC-UV-APCI-MS. Using two-dimensional ion maps, the components of several families of derivatives were readily identified. Additionally, the extracts were also fractionated by HPLC-UV and the fractions were analyzed by HPLC-APCI-MS/MS to obtain structural information. Standards of some of these compounds were synthesized and analyzed to confirm the results. A total of 115 aniline derivatives from 9 aniline-related families were identified in these oil samples. These included fatty acid anilides and an extensive array of phenylaminopropanediol esters distributed in eight major compound classes.