Improved analysis of fatty acid anilides: application to toxic and to aniline and citric acid-containing oils.

Abstract

The Spanish Toxic Oil Syndrome (TOS) was traced to the consumption of some cheap oils sold at retail by street salesmen (Tabuenca 1981; Kilbourne et al. 1992). These oils contained different proportions of a refined batch of rapeseed oil initially denatured with 2% of aniline and imported from France for industrial use (Tabuenca 1981). However, although most of the free aniline was effectively extracted during the refining processes, a significant part of it reacted with fatty acids yielding the corresponding fatty acid anilides (FAAs) (Guitart and Gelpi 1992). Although toxicological data on FAAs are very controversial, they had been proposed as the causative agents of the illness or, at least, are considered as the best markers of toxic oils (Bernert Jr. et al. 1987; Kilbourne et al. 1991). Four gas chromatographic methods have been published for the analysis of FAAs in oils (Diachenko et al. 1982; Vazquez Roncero et al. 1983; Artigas et al. 1983; Balley et al. 1983). The chemical similarity with the methyl esters of fatty acids makes gas-liquid chromatography (GLC) the method of choice for the analysis of FAAs, although their higher molecular weights limited up to now the use of the more resolutive polar stationary phases. Since the introduction of cross-bonded polar phases which can be run at higher temperatures than columns available in the last decade, the possibility to obtain a better separation of FAAs is raised. This paper reports the development of such a method and its application to 10 case oil samples and to the study of the generation rate of FAAs in aniline-denatured rapeseed oils containing citric acid. This additive was used in some refineries that handled the TOS-suspected oils in 1981 as a stabilizer, preservative and antioxidant, and was added normally before the deodorizing process at a l-2% concentration (Special Investigation Team 1981).