Quantitation and identification of fumonisins by liquid chromatography/mass spectrometry

A method was evaluated for the quantitation and identification of fumonisins by on-line liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization. A linear response in the full-scan mode with positive ion detection was obtained for fumonisin B1 (FB1) over the range of 5-5000 ng injected on-column. Purified FB1, FB2, and half-hydrolyzed FB1 showed equimolar responses. Fully hydrolyzed FB1 did not show a similar molar response profile and produced a signal which was approximately 2 times that obtained for an equal quantity of FB1. Most known fumonisins and preparative by-products such as methyl esters were chromatographically resolved and identified by MS by using an acetonitrile gradient and positive ion detection. Negative ion electrospray was used to differentiate fumonisin amides from esters on the basis of differences in response. Response factors for FB1 and the acetyl amide of FB1 in the negative ion mode at pH 4.5 were approximately 1:3, respectively.