53

1

96-101.

Division of Food Chemistry and Technology, Food and Drug ADministration, Washigton, D.C. 20204, USA.

Title in English;

Meausrements of molar absorptivities in methanol were carried out by two laboratories on samples of aflatoxins B1 and G1 prepared and purified independently in four laboratories and on samples of aflatoxins B2 and G2 prepared and purified independently in three laboratories. Molar absorptivities of pure aflatoxins B1, B2, G1, and G2 in benzene-acetonitrile (98+2) were determined in two laboratories. With the exception of aflatoxin G2, no significant difference between aflatoxin samples could be demonstrated. Molar absorptivity values and absorbance ratios for each aflatoxin, based on these data, are given. Statistical 95 per cent confidence limits were established for a single determination of molar absorptivity. A statistical study was made of the components of variance which contribute to the accuracy of the determination of molar absorptivity. A comparison of the fluorescence intensities of spots of various aflatoxin preparations, developed on silica-gel coated thin-layer plates, with the amount of aflatoxin in each spotting solution as determined by absorbance measurements, demonstrated the validity of using absorbance and fluorescence comparison measurements for aflatoxin quantitation.