Determination of Aflatoxins B1 and M1 in Milk

Abstract

Cows fed contaminated rations containing the mold metabolite aflatoxin B1 secrete low levels of aflatoxin B1 and its metabolite aflatoxin M1 in milk. To establish the relationship between ingested aflatoxin and milk-secreted aflatoxin, a sensitive method is needed to determine aflatoxins B1 and M1 in milk. A method is presented by which good recoveries, within the limits of visual comparison, were obtained from samples containing 0.5 parts per billion aflatoxin.Deproteinized milk (80% methanolic filtrates) was adjusted to 50% by addition of 4% salt solution and defatted by extraction with hexane. Aflatoxins were extracted from the alcoholic phase with chloroform which was removed in vacuo. The residue was dissolved in benzene :hexane (1:1) and chromatographed on a partition column of Celite coated with an aqueous solution of calcium chloride to separate aflatoxins B1 and M1. The eluted B1 was passed through another partition column of Celite coated with methanol :water (1:1) for additional cleanup. Aflatoxin eluates were evaporated to dryness and residues were dissolved in chloroform and spotted on thin-layer chromatographic plates for fluorescence comparisons.