Determination of aflatoxins in beer

Aflatoxins B-1, B-2, G(1), and G(2) were determined at parts-per-trillion levels in beer by immunoaffinity column cleanup and reversed-phase liquid chromatography (LC) with fluorescence detection after trifluoroacetic acid derivatization. Silanized vials were necessary for the evaporation step in order to obtain good recoveries of aflatoxins from spiked beer samples. Recoveries averaged 90-104%, 94%, 84-87%, and 89% for aflatoxins B-1, B-2, G(1), and G(2), respectively, at levels of 9.7-133 ng B-1, 46 ng B-2, 35-140 ng G(1), and 41 ng G(2)/L. Detection limits were 19-20 ng/L for aflatoxins B-1 and G(1) and 15-16 ng/L for aflatoxins B-2 and G(2) (signal-to-noise ratio = 3:1) obtained by using an excitation wavelength of 360 nm; at 340 nm these detection limits were lowered to about 2 ng/L. Analysis of 24 beer samples, the majority from the United States and Mexico, showed natural contamination of one sample of Mexican beer at 49 ng B-1/L when determined at 360 nm excitation, but reanalysis of 23 of the samples using 340 nm excitation indicated that an additional 4 Mexican samples and one Brazilian sample contained aflatoxin B-1 at low levels (<10 ng/L).