Quick and reliable determination of matrine and oxymatrine in vegetable products by Liquid Chromatography and Mass Spectrometry

A rapid LC/tandem MS method for the quantitative determination of matrine-based biopesticides is proposed for the analysis of fruit and vegetable samples. A simple extraction process by acidified methanol was selected, ensuring reduced solvent consumption and time, and allowing a simultaneous preparation of multiple sample extracts. Excellent chromatographic results were obtained in terms of peak shape and efficiency, in less than 10 min. Method validation was performed according to the European directives through the evaluation of selectivity, linearity, detection and quantification limits, recovery, and precision. Under the optimal extraction and chromatographic conditions, good responses were observed in the range of 5–200 μg L−1, with correlation coefficients higher than 0.9984. Instrumental limits of detection were 0.032 and 0.033 μg L−1 for matrine and oxymatrine, respectively. Detection limits in oranges, apples, fennels, and tomatoes, calculated for matrine and oxymatrine on spiked samples, were in the range 0.13–1.5 μg kg−1 and 0.17−0.30 μg kg−1, respectively. The validated method was then successfully applied to the determination of matrine and oxymatrine in 102 commercially available samples of fruit and vegetables.