[Preparation and identification of aflatoxin B2a under laboratory conditions].

The method of preparing and identifying small quantities of aflatoxin B2a after Pohland et al. (1968) was verified as it was necessary to differentiate various types of aflatoxins in analytic practice. Aflatoxin B2a was prepared by the hydroxylation of aflatoxin B1 in acid medium and was identified by thin silica gel layer chromatography (TLC) and by spectral analysis in methanol medium and in a mixture of methanol with ammonium hydroxide (14 + 1). The results of both methods of identification were in keeping with the results of earlier works. At TLC in the system of chloroform + methanol (95 + 5) the Rf values were as follows: Rf AFB1--0.68 and Rf AFB2a--0.32; in the system of chloroform + acetone + isopropyl alcohol (85 + 10 + 5) the respective values were Rf AFB1--0.46 and Rf AFB2a--0.22. Spectral analysis demonstrated a shift in the absorption maximum in the methanol + ammonium hydroxide medium from 362 nm to 404 nm in aflatoxin B2a. The yield rate of AFB2a was about 50 to 55%.