Thin layer chromatographic analysis of possible aflatoxins within grain dusts

The National Institute for Occupational Safety and Health is interested in assessing the hazards to grain workers associated with respirable grain dusts of all types. One of these hazards could involve the occurrence of mycotoxin producing fungi either upon or within grains. Aflatoxins, types of mycotoxins produced by bothAspergillus flavus andA. parasiticus, are hepatocarcinogens, mutagens, teratogens and toxins. Here, we report an attempt to determine whether settled and/or airborne dusts from barley, corn, flax, oats and Durum as well as spring wheats contain aflatoxins. These dusts were collected at port grain terminals in the Superior-Duluth regions of the United States. The dusts were extracted with and chromatographed upon thin layer plates in a variety of solvents which have been approved for the separation of aflatoxins. Two acceptable aflatoxin B₁ confirmatory tests were employed to verify suspected aflatoxin B₁ within the extracts. Each dust contained a chloroform-soluble, blue fluorescent compound(s) which possessed an Rf similar to that of aflatoxin B₁ upon chromatography of chloroform extracts in chloroform/95% methanol. Methylene chloride/H₂O) extracted a blue fluorescent compound(s) from each dust, and the compound(s) possessed Rf intermediate between those of aflatoxin B₁ and B₂ upon chromatography in acetone/methylene chloride. The methylene chloride/H₂O extracted compounds failed to turn yellow upon spraying with 25% sulphuric acid in methanol and subsequent viewing with an ultraviolet source. Our results confirm those of Sorenson et al., who reported that aflatoxins were absent from airborne grain dusts collected from the Superior-Duluth areas of the United States in the fall of 1977. In conclusion, we stress the need for extracting, detecting, and identifying aflatoxins by a variety of analytical procedures including thin layer and high performance liquid chromatography and “approved” confirmatory tests.