วัสดุและวิธีการThe reference clay samples, SWy-2 (SWy) and SAz-1 (SAz), were obtained from the Source Clay Repository of the Clay Minerals Society located at Purdue University (West Lafayette, IN). The SWy sample is a low-charge montmorillonite from Wyoming and SAz is a high-charge montmorillonite from Arizona. Novasil plus (a low-charge montmorillonite) is a product of Trouw Nutrition, which is a division of Englehard Corporation, Chemical Catalysts Group (600 East McDowell Road, Jackson, MS 39204). The clay samples were Na-saturated by treatment with NaCl, the <2 μm clay fractions were separated by centrifugation, and the <2 μm clay fractions were freeze-dried. Activated carbon (alkaline Norit-A decolorizing carbon) was obtained from Fisher Scientific. Dispersions of the <2 μm clays and activated carbon were prepared using an ultrasonic probe and a vortex mixer. Corn flour was obtained from a local grocery. Aflatoxin B1, rabbit anti-aflatoxin B1 antibody, aflatoxin B1-BSA conjugate, goat anti-rabbit horse-radish peroxidase (HRP) conjugate, phosphate buffered saline with 0.05% Tween 20 (PBST), and o-phenylenediamine dihydrochloride (OPD) substrate tablets were obtained from Sigma-Aldrich. Stable AfB1 stock solutions were prepared in 95% toluene/5% acetonitrile and stored in a freezer [38]. The aflatoxin stock solutions were calibrated by measuring the UV absorbance of AfB1 dissolved in methanol at 360 nm [38]. Enzyme-linked immunoassay microplates were washed and read using a Bio-Tek ELx50 plate washer and a ELx800uv (Bio-Tek Instruments, Inc.; Highland Park, Box 998, Winooski, VT) plate reader.
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