Abstract: It has been discovered that certain minerals, particularly various naturally occurring forms of aluminum oxide, will preferentially bind selective mycotoxins from a mixture of mycotoxins. These adsorbants, when used in various combinations and/or in conjunction with the adsorbants of the prior art, permit the construction of detector tubes which can resolve mycotoxins in solution and provide a semi-quantitative fluorescent determination of their concentration in feed or foodstuff samples. The detector tubes comprise transparent tubes packed with isolated layers of selected minerals. A solvent extract from a sample potentially contaminated with mycotoxins is passed through the column. As the mycotoxin mixture passes through the detector tube and is contacted by the various mineral adsorbants, selected mycotoxins are immobilized on a specific mineral while other mycotoxins and co-extracted organic compounds pass through that layer to be immobilized on subsequent downstream mineral layers.