Collaborative Study of Two-Dimensional Thin Layer Chromatographic Analysis of Aflatoxin B1 in Peanut Butter Extracts, Using the Antidiagonal Spot Application Technique

Abstract

A collaborative study has been carried out among 20 laboratories in The Netherlands, representing governmental and industrial institutes, on the determination of aflatoxin B1 in peanut butter extracts. Blank peanut butter extracts prepared according to the proposed official Dutch method were spiked with aflatoxin B1, representing contamination levels of 0, 3, 6, and 12 μg B1/kg. Samples and standards were spotted on silica gel G TLC plates by the antidiagonal spot application technique described herein. Spotted plates were developed by 2-dimensional TLC with diethyl ether-methanol-water (94+4.5+1.5; lined tank) in the first direction and chloroform-acetone (90+10; unlined tank) in the second direction. Separated B1 spots from sample and standards developed in both directions were free from background interference. The quantity of aflatoxin B1 present in the sample was established by visual comparison of the fluorescent intensities of sample and standard B1 spots. For this procedure the variability of measurements within and between laboratories was statistically investigated: 80–90% of the complete results given by the participants were correct for the hlank and spiked extracts (contamination level of 12 μg B1/kg). For contamination levels of 3 and 6 μg B1/kg an approximate coefficient of variation of 35% was calculated for within- and between-laboratory results. Results obtained in this investigation were compared with those found by previous investigators who used the one-dimensional TLC technique. It is concluded that, with the antidiagonal procedure, small amounts of aflatoxin B1 (lowest level tested, 3 ppb) may be detected.