Effect of the inclusion of adsorbents on aflatoxin B1 quantification in animal feedstuffs

The extraction efficiency of aflatoxin B₁ (AFB₁) in cattle feed containing nine adsorbents (ADSs) was investigated using two organic/aqueous solvents composed of methanol/water (80/20 v/v; MeOH) and acetone/water (85/15 v/v; AC). Samples were obtained including a highly AFB₁-contaminated (HC) and a low-level AFB₁-contaminated (LC) feedstuff (15.33 and 7.57 µg kg^–1, respectively), nine ADSs (four clay minerals; one yeast cell wall-based product; one activated carbon and three commercial ADS products) at two different levels of inclusion (10 and 20 g kg^?1). After solvent extraction and immunoaffinity column clean-up, all samples were analysed for AFB₁ by high-performance liquid chromatography (HPLC) with fluorescence detection. For each contamination level (HC and LC), the data obtained were analysed using a factorial arrangement in a completely randomized design. Means were compared with the correspondent controls using the Dunnett's test. No statistical difference was found in AFB₁ levels of feedstuffs not containing ADSs when extracted with AC or MeOH, even if numerically higher values were obtained with AC. A dose-dependent effect (p < 0.01) of ADSs inclusion was observed on AFB₁ recoveries that were lower when the higher ADS level (20 g kg^?1) was included in the HC and LC feedstuffs. Higher AFB₁ recoveries were obtained using AC compared with MeOH, both in HC (75.0% versus 12.0%, respectively) and in LC (84.0% versus 22.8%, respectively) ADSs containing feedstuffs. However, when the activated carbon and the sodium bentonite were included in feeds, lower AFB₁ concentrations with respect to control values (p < 0.001 and <0.05, respectively) were obtained also using AC. The data obtained in this study indicate that routine use of the MeOH solvent for AFB₁ analysis of unknown feedstuffs, can produce misleading results if they contain an ADS.