Determination of fumonisins in rodent feed using HPLC with electrospray mass spectrometric detection

A method based on liquid chromatography with electrospray ionization mass spectrometry was validated for analysis of low-level contamination of rodent feed by fumonisins B-1 (10-200 ppb) and also applied to the analysis of fumonisin B-2 and B-3. The quantitation limit for a fumonisin B-1 standard was 1.1 ppb using the protonated molecule signal (m/z 722), and similar sensitivity was observed for protonated molecules for fumonisins B-2 and B-3 in feed. To increase specificity of the mass spectrometric analysis, two fragment ions for fumonisin B-1 (m/z 352 and 334) were also acquired by using rapid sampling cone-skimmer potential switching in concert with acquisition of the respective ion. This permitted the use of ion intensity ratios for structural confirmation of fumonisin B-1 at levels > 10 ppb. Intra-assay precision for fumonisin B-1 determination in feed (6-16% relative standard deviation) was comparable to inter-assay precision (7.7-16.0%) and appeared to be affected most by the variability in recovery of analytes from the immunoaffinity cleanup column. A survey of fumonisin contamination in rodent feed from 12 U.S, biomedical research institutions showed median contamination of 237 ppb and a range from 46 to 923 ppb of total fumonisin B congeners.