SOLVENT-EFFICIENT THIN-LAYER CHROMATOGRAPHIC METHOD FOR THE DETERMINATION OF AFLATOXIN-B1, AFLATOXIN-B2, AFLATOXIN-G1, AND AFLATOXIN-G2 IN CORN AND PEANUT PRODUCTS - COLLABORATIVE STUDY

An interlaboratory study of a solvent-efficient thin-layer chromatogra phic (TLC) method for the determination of aflatoxins B1, B2, G1, and G2 was conducted in laboratories located in the United States, France, Tunisia, and Denmark. Eighteen artificially contaminated samples plus blanks of raw peanuts and peanut butter and corn containing varying a mounts of aflatoxins B1, B2, G1, and G2 were distributed to participat ing laboratories. The method consists of elements of the U.S. Food and Drug Administration (FDA), Contaminants Branch (CB) (AOAC Method 968. 22) and FDA, Best Foods (BF) (AOAC Method 970.45) methods with reduced requirements for solvents. Participating laboratories used either vis ual or densitometric techniques during the final determinative step. S tatistical analysis of the data was performed to determine or confirm outliers and to compute repeatability and reproducibility of the metho d using either visual or densitometric techniques for the determinativ e step. Reported results from laboratories using a densitometer showed that, for corn, the relative standard deviation for repeatability (RS D(r)) for aflatoxin B1 ranged from 56.6 to 41.7% for contamination lev els ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSD, values for aflatoxin B1 ranged from 21.3 to 37.3% and 65.9 to 42. 1%, respectively, for the contamination levels ranging from 5 to 25 ng /g. RSD(r) ranges for aflatoxins B2, G1, and G2 were similar. For repr oducibility (R), the RSD(R) ranges for aflatoxin B1 were 41.7-56.6%, 5 6.6-84.8%, and 26.4-37.3% for corn, peanut butter, and raw peanuts, re spectively. Average recoveries for all aflatoxins at all levels were 9 5.3, 139.0, and 95.6% for corn, peanut butter, and raw peanuts, respec tively. When analysts determined aflatoxin concentrations in corn by v isual comparison to standards, the RSD(r) values for aflatoxin B1 were 47.8-11.4% for contamination levels ranging from 5 to 50 ng/g. For ra w peanuts and peanut butter, the RSD, values for aflatoxin B1 were 76. 3-12.6% and 33.4-8.8%, respectively, for the contamination levels rang ing from 5 to 25 ng/g. RSD(r) values for aflatoxins B2, G1, and G2 Wer e similar. The RSD(R) values for aflatoxin B1 were 34.6-90.2%, 45.5-59 .3%, and 31.8-78.3% for corn, peanut butter, and raw peanuts, respecti vely. Average recoveries for all aflatoxins at all levels were 111.0, 157.6, and 92.3% for corn, peanut butter, and raw peanuts, respectivel y. High recoveries were noted for aflatoxins in peanut butter determin ed by either a densitometer or comparison to standards. Generally, inc reased precision was observed with the method at higher contamination levels. On the basis of the results obtained in this AOAC/IUPAC collab orative study, the solvent-efficient TLC method using densitometry for the quantitative step was adopted first action by AOAC for the determ ination of aflatoxins B1, B2, G1, and G2 in com at levels within the r ange of 5-50 ng/g, 3-15 ng/g, 10-50 ng/g, and 3-15 ng/g, respectively, by densitometry; for aflatoxins B1 and B2 in raw peanuts at levels ra nging from 5 to 25 ng/g and from 1.5 to 7.5 ng/g, respectively, by den sitometry; and for aflatoxins B1 and G1 in corn at 10-50 and 50 ng/g, respectively, and aflatoxins B1, B2, and G1 in raw peanuts at 10-25 ng /g, 7.5 ng/g, and 10-25 ng/g, respectively. Because of high recovery v alues, additional study is recommended for peanut butter. The solvent- efficient TLC method for determination of aflatoxins B1, B2, G1, and G 2 in corn and peanuts has been adopted first action by AOAC INTERNATIO NAL.