Incomplete recoveries of fumonisins present in naturally contaminated corn foods from an immunoaffinity column.

Following previous observations of apparent instability of fumonisin B1 in corn starch and corn meal, immunoaffinity column (IAC) cleanup, of the type used in the analysis of commercial starch-containing corn foods for fumonisins, was investigated. Foods analyzed for naturally occurring fumonisins B1, B2, and B3 included corn flour (3 different products), corn meal, and corn flakes. In 2 series of experiments, fractions were eluted by gravity or vacuum from narrow- or wide-bore Fumonitest IACs either with 2 x 2 mL methanol, followed by 2 mL methanol-water (8 + 2, v/v), or with 2 mL methanol, then 2 mL methanol-water (8 + 2, v/v). The ratio (%) of fumonisin B1 concentration in the first methanol eluate to the total concentration measured from all eluates in most cases varied from 25-70%. Incomplete recoveries were also observed for fumonisins B2 and B3. It is concluded that there can be a major underestimation of naturally occurring fumonisins in methods using only methanol elution for IAC cleanup, as in AOAC INTERNATIONAL Official Method 2001.04 (accuracy of these methods had been determined only by spiking the food with fumonisins). Elution with 2 x 2 mL methanol-water (8 + 2, v/v) was chosen as a practical procedure; means of 81-98% of the total fumonisin B1 concentration were found in the first eluate, except for corn flakes and 2 experiments with corn meal.