Determination of N-(carboxymethyl)fumonisin B1 in corn products by liquid chromatography/electrospray ionization-mass spectrometry

It is well-known that fumonisin B-1 (FB1) in corn meal decreases during baking, frying, and cooking, but it is still not exactly clear how heating affects the formation of N-(carboxymethyl)fumonisin B-1 (NCM-FB1), the reaction product of FB1 and reducing sugars. In model experiments corn grits were spiked with FB1 (2 mg/kg) and D-glucose (50 g/kg) or sucrose (50 g/kg) and manufactured into extrusion products at various temperatures (160-180 degreesC) and moisture levels (16-20%). A liquid chromatography/electrospray ionization-mass spectrometry method using isotopically labeled fumonisin FB1-d(6) as an internal standard was developed for the determination of NCM-FB1. For sample cleanup solid-phase C18 cartridges were used. The detection limit achieved with this method was 10 ng/g (signal-noise ratio = 3:1) using the protonated molecule [M + H](+) signal of NCM-FB1 (m/z 780) in the selected ion monitoring mode. Low concentrations of NCM-FB1 (29-97 ng/g) were detected in all samples spiked with D-glucose and FB1, whereas those spiked with FB1 and sucrose showed only NCM-FB1 in samples produced at 180 degreesC (NCM-FB1 = 27 ng/g). Various corn-containing food samples from the German market were analyzed for the presence of NCM-FB1, FB1, and hydrolyzed fumonisin B-1 (HFB1). All samples were contaminated with FB1 (22-194 ng/g) and HFB1 (5-247 ng/g), Six of nine samples contained NCM-FB1 in low concentrations ranging from 10 to 76 ng/g. From these data and the low toxicity of NCM-FB1 it can be concluded that the significance of NCM-FB1 in food seems to be a minor one.