No abstract

An interlaboratory study of a negative ion chemical ionization mass spectrometric (MS) confirmation procedure for aflatoxin B1 was conducted in laboratories in the United States, England, and West Germany. Twelve partially purified, dry film extracts from naturally and artificially contaminated roasted peanuts, cottonseed, and ginger root containing varying quantities of aflatoxin B1 were distributed to the participating laboratories. The extracts required additional cleanup before MS analysis, using either an acidic alumina column and preparative thin layer chromatography (TLC) or a 2-dimensional TLC procedure. Recovery of purified aflatoxin B1 was influenced by the degree of recovery of sample from acid alumina and/or the TLC plate and incomplete elution of aflatoxin Bt from silica gel. Factors affecting MS confirmation included the purity and recovery of aflatoxin and MS instrument sensitivity. Aflatoxin Bi identity was confirmed in 19.5, 90.9, and 100% of samples containing <5,5-10, and >10 ng aflatoxin B1/g product, respectively, by solid probe introduction using full mass scans. The MS method has been adopted official first action.

No abstract

Two official first action methods for the determination of aflatoxins in peanuts and peanut products, method I (26.015-26.020) and method III (26.026-26.030), were modified slightly for the analysis of pistachio nuts. Thirteen collaborators analyzed naturally contaminated in-shell pistachio nuts, aflatoxin-free pistachio nuts, and pistachio nut composites spiked with known amounts of aflatoxins. The extraction and cleanup in method III are relatively simple and require no chromatography, whereas the lengthier method I employs column chromatography, producing a cleaner thin layer chromatographic extract. On the basis of the collaborative results obtained, both methods have been adopted as official first action for the determination of aflatoxins in in-shell pistachio nuts.

The minicolumn screening method for aflatoxins was collaboratively tested on naturally contaminated almonds. The nuts were extracted, and the extract was cleaned up and applied to a Velasco-type minicolumn. This permits the detection of total anatoxins (B1, B2, G1, G2) as a fluorescent band on the Florisil layer of the column. The results of 20 collaborators are presented. Samples containing 0, 2, 5, 10, and 25 ng aflatoxin/g were analyzed. Ninety-six per cent of the samples containing 5—25 ng total aflatoxins/g and 83% of the negative samples were correctly identified. The method has been adopted as official first action for detection of total aflatoxin levels of ≥5 ng/g.