Trace analysis of sulforaphane in bee pollen and royal jelly by liquid chromatography-tandem mass spectrometry

In this study, we investigate for the first time the presence of sulforaphane (SFN) residues in two of the most currently consumed food/dietary supplements, royal jelly and bee pollen. Chromatography-tandem mass spectrometry (LC-MS/MS) was the method employed, the mass spectrometer consisting of an ion-trap mass analyzer used with electrospray ionization (ESI) in positive ion mode. An efficient sample treatment involving a solvent extraction with methanol, centrifugation, and concentration in a rotary evaporator was proposed. In all cases average analyte recoveries were between 92 and 106%. Chromatographic analysis (16 min) was performed on a core-shell technology based column (Kinetex C18, 150 × 4.6 mm, 2.6 μm, 100 Å). The mobile phase consisted of 0.02 M ammonium formate in water and acetonitrile, with a flow rate of 0.5 mL/min in gradient elution mode. The fully validated method was selective, linear from 8 to 1000 μg/kg (bee pollen), or from 10 to 1250 μg/kg (royal jelly), precise and accurate; relative standard deviation (% RSD) and relative error (% RE) values were below 10%. Low limits of detection (LOD) and quantification (LOQ) were obtained, namely, 3 μg/kg (LOD) and 8 (bee pollen) and 10 (royal jelly) μg/kg (LOQ). The method was applied for SFN analysis in several royal jelly and bee pollen samples. SFN was detected at trace levels in some bee pollen samples (<23 μg/kg) examined, whilst SFN went undetected in the royal jelly samples analyzed.