Analysis of fumonisins B1 and B2 in spices and aromatic and medicinal herbs by HPLC-FLD with on-line post-column derivatization and positive confirmation by LC-MS/MS

Abstract

Fumonisins are produced by the fungus Fusarium verticillioides, which are known to cause fatal diseases in some animals and humans. Here, we describe a sensitive, reproducible and reliable analytical method for the quantitative determination of fumonisins B₁ (FB₁) and B₂ (FB₂) in 112 spices and aromatic and medicinal herbs marketed in China. This method is based on high performance liquid chromatography and fluorescence detection (HPLC-FLD) coupled to a new on-line post-column derivatization using ortho-phthaldialdehyde with 2-mercaptoethanol and immunoaffinity column clean-up. Under the optimized experimental conditions, a complete separation of FB₁ and FB₂ was obtained using a Synergi C₁₈ column and a gradient elution at 0.8 mL min⁻¹ with methanol and 0.1 M phosphate buffer at pH 3.15. The limits of detection for FB₁ and FB₂ were both 40 μg kg⁻¹. Good recoveries were found for spiked samples with FB₁ and FB₂, ranging from 82.34% to 98.16% for FB₁ and from 72.58% to 97.10% for FB₂, with relative standard deviation (RSD) < 7.0%. 5 spices, 11 aromatic herbs and 96 medicinal herbs including 93 normal samples and 19 visibly moldy samples, which were spoiled artificially, were analyzed. The results showed that 8 (42.1%) visibly moldy samples and 8 (8.6%) normal samples were contaminated with FB₁ at mean contents of 129.0 and 165.9 μg kg⁻¹, and with FB₂ at 1745.0 and 256.8 μg kg⁻¹, respectively. Positive confirmation of detected samples was performed by liquid chromatography tandem electrospray ionization mass spectrometry (LC-ESI-MS/MS), using a triple quadrupole analyzer and operated in the multiple reaction monitoring mode.