Development of a Sensitive Analytical Method for the Determination of Sulforaphane in Vegetables by Automated Online In-Tube SPME/LC–MS/MS

Sulforaphane (SFN), an isothiocyanate abundant in cruciferous vegetables, possesses well-documented anticancer, antioxidant, and anti-inflammatory properties, and has attracted interest as a dietary chemopreventive agent. However, sensitive and fully automated methods for its quantification in foods remain limited. In this study, we developed an automated analytical system coupling in-tube solid-phase microextraction (IT-SPME) with high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) to determine SFN in vegetable samples. Vegetable samples were autohydrolyzed in aqueous solution at 37 °C to generate SFN, which was then extracted with methanol by sonication. The extract was concentrated onto a Carboxen 1006 capillary column by IT-SPME, separated within 5 min on an Inertsil C8 column, and detected in positive electrospray ionization mode using multiple reaction monitoring. The detection limit was 5.6 pg/mL, with good linearity (R2 = 0.9995) over 0.1–100 ng/mL, intra- and inter-day precisions below 2.9% and 3.9%, respectively, and accuracy of 98–102%. SFN was detected at concentrations of 600 μg/g or higher in broccoli sprouts, florets, and stems, but was found at less than one-tenth of these levels in other vegetables tested. This method provides a simple, sensitive, and solvent-efficient tool for SFN quantification in vegetables, with potential application in food functionality assessment and chemopreventive research.