Automated Strong Cation Exchange Extraction of Fatty Acid Esters of 3-(N-Phenylamino)-1,2-propanediol from Oil Samples for Routine Quantification by HPLC-APCI/MS/MS

Abstract

Fatty acid esters of 3-(N-phenylamino)-1,2-propanediol are currently considered the best chemical markers of toxic oils related to the Spanish toxic oil syndrome. Recent research in this area has undertaken the exhaustive and quantitative characterization of these compounds in oils collected during the epidemic outbreak. Current methods developed in this laboratory are based on solid phase extraction (SPE) using SCX cartridges followed by HPLC-APCI/MS/MS quantification. To circumvent the long and tedious extraction procedure, the SPE protocol was adapted for automatic extraction and the problems derived from the use of the immiscible solvents required for the SCX extraction were solved. Linearity of the analytical method was found in the same range as for the manual method. Extraction recoveries were 87 and 75% for 2-hydroxy-3-(N-phenylamino)propyl linoleate and 2-(linoleyloxy)-3-(N-phenylamino)propyl linoleate, respectively, and the corresponding coefficients of variation were approximately 1%, greatly improving reproducibility over manual procedures.

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

“…Owing to the complexity of the oil extract and the low concentrations at which PAPs are found, a preconcentration technique based on SCX was applied. This technique, developed by Calaf et al ,14, 15 had demonstrated to be very efficient in improving the detection limits of the minor amine‐containing compounds in oils 14. In addition, the fraction of volatile compounds recovered from the chemical reactor was also analyzed.…”

“…An approximation to the relative proportions of representative compounds in the oil samples studied here calculated relative to the concentration of oleanilide (OA), the most abundant aniline derivative in oil, shows that except for the major FAAs (oleyl or linoleyl anilides) and a few PAPs, all other known aniline derivatives were found at concentrations lower than 0.4%. Quantitative details on the analysis of over 2600 samples over a two‐year period have been reported in the literature 14, 15. The majority of these samples contained OA at 8–100 ppm 14…”

“…In the latter work,15 we used an extraction protocol based on SCX purification to eliminate interfering nonionic compounds from the samples. This extraction technique produced a very selective purification of the amine‐containing compounds from the oil matrix, while other less polar compounds were not retained in the extraction column.…”

“…The extraction procedure was based on an SCX solid‐phase extraction (SPE) method (as summarized in Scheme ) and adapted to the HPLC‐MS system requirements, as reported by Calaf et al 15…”

“…The aim of this study was to account for all possible combinations of triglyceride‐ and fatty‐acid‐related aniline by‐products through selective separation and identification procedures. While the major FAAs and some PAP esters had been previously identified,14–16 available experimental data suggested other aniline‐containing classes of compounds (Fig. 1) that needed to be fully accounted for, searching at the same time for previously undetected new compounds, or classes of compounds, if any.…”