An automated on-line method for the quantitative detection of fumonisins B1, B2, and B3 and hydrolyzed fumonisin B1 in corn-based feed was developed using a combination of immunoaffinity capture (IAC)/cleanup, coupled with reversed phase liquid chromatography and electrospray ionization mass spectrometry. Blocking the C2 amine of fumonisin B1 with 9-fluorenylmethylchloroformate allowed coupling to keyhole limpet hemocyanin through the tricarballylic end, leaving the amino terminus exposed on the immunogenic conjugate after removal of the blocking group. Antiserum had specificity for the C1−C10 fumonisin domain and was used for ELISA and to prepare immunoaffinity columns. The quantitation limit (s/n = 10) for fumonisin B1 standard was 250 pg using the protonated molecule signal (m/z 722). Similar sensitivity was observed for fumonisins B2 and B3 (m/z 706) and hydrolyzed fumonisin B1 (m/z 406). The on-line IAC/LC/ESI-MS method provided a linear response from the detection limit to 5 ng for fumonisin B1 and has the capability to analyze low-level contamination of rodent feed samples for fumonisins. The dynamic range can be adjusted as necessary by varying the volume of the sample injected for IAC capture. Keywords: Analytical immunology; fumonisins; immunoaffinity; mass spectrometry; immunoassay; site-directed coupling; ELISA; mixtures

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