Determination of carboxyatractyloside, the main toxic component of Xanthium strumarium L., and alkaloid toxins in soybean by liquid chromatography tandem mass spectrometry.

The presence of carboxyatractyloside (CAT) in Xanthium strumarium L. (cocklebur weed) presents a high risk for both human and animal health. In this paper, we report a liquid chromatography tandem mass spectrometric (LC-MS/MS) method for the determination of CAT in soybean intended for animal feed. The herein described approach involves a fast sample preparation utilising QuEChERS extraction followed by dSPE clean-up. The optimised mobile phase composition flowing through an HPLC column packed with C18 fused-core particles consisted of alkaline conditions (pH = 8.8) in the aqueous eluent and pure methanol as the organic modifier. In this manner, it was also suitable for the analysis of tropane and ergot alkaloids together with CAT, which was attempted for the first time and may improve the analysis efficiency and reduce costs. During the method validation the matrix effect was also investigated, which clearly showed that matrix-matched calibration or standard addition is needed for appropriate quantification, mainly at low levels. The recoveries were between 94 % and 115 %, and the RSD % varied from 2.0 % to 7.3 %. The limits of quantification for alkaloids and CAT were 1 µg/kg and 100 µg/kg, respectively. The method implementation in other LC-MS/MS instruments was also tested. Finally, the validated method was successfully applied on soybean samples naturally contaminated with cocklebur.