Aflatoxin G1

A method based on reversed-phase high-performance liquid chromatography (RP-HPLC) with amperometric detection with a glassy carbon electrode at a constant potential of 1.4 V is reported for the separation and identification of aflatoxins B1, B2, G1 and G2 in a model mixture. The chromatography was performed on a PAH-Baker column with a ternary mobile phase containing methanol, acetonitrile and aqueous LiClO4 electrolyte. Aflatoxin G1 showed the highest electroactivity in the compound series studied. Calibration curves of aflatoxins G1 and B2 were linear up to 0.2 and 0.3 mmol/l, respectively. Sensitivity varied between 7 and 10 ng for the different aflatoxins. The combination of different HPLC detectors in the analysis of these compounds was applied to investigate the stability of aflatoxins G1 and B2.

A short-term test for carcinogens has been developed based on the interaction of chemical carcinogens with tRNA(FMet) in vitro. Transfer RNA from rat or rabbit liver is pre-treated with compounds to be tested in the presence of microsomal enzymes and NADPH. Re-isolated tRNA is then charged with L-methionine by aminoacyl-tRNA synthetases from E. coli B. Carcinogens induce a stimulation of tRNA charging whereas chemically similar non-carcinogenic compounds do not show this effect. Experiments with model substances N-methyl-N'-nitro-N-nitrosoguanidine (strong carcinogen) and aflatoxin G1 (weak carcinogen) revealed some differences in dose effect relationships. It is advisable to test unknown compounds at three different concentrations (10(-5), 10(-7) and 10(-9) mg/ml) with at least two different quantities of microsomal enzymes. Tests on greater than 150 different compounds performed so far indicate that the evaluation of results as % of stimulation (when compared with the control value obtained with the charging of tRNA treated with the solvent only) may allow a quantitative discrimination between weak and intermediate, and strong carcinogens. The procedure is rapid, well reproducible and relatively inexpensive and may be used to complement the other short-term tests for carcinogenicity.

Graphene-based materials have been studied in many applications, owing to the excellent electrical, mechanical, and thermal properties of graphene. In the current study, an environmentally friendly approach to the preparation of a reduced graphene oxide-gold nanoparticle (rGO-AuNP) nanocomposite was developed by using L-cysteine and vitamin C as reductants under mild reaction conditions. The rGO-AuNP material showed a highly selective separation ability for 6 naturally occurring aflatoxins, which are easily adsorbed onto traditional graphene materials but are difficult to be desorbed. The specificity of the nanocomposite was evaluated in the separation of 6 aflatoxin congeners (aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, aflatoxin M1 and aflatoxin M2) from 23 other biotoxins (including, ochratoxin A, citrinin, and deoxynivalenol). The results indicated that this material was specific for separating aflatoxin congeners. The synthesized material was further validated by determining the recovery (77.6-105.0%), sensitivity (limit of detection in the range of 0.05-0.21 μg kg;-1;), and precision (1.5-11.8%), and was then successfully applied to the separation of aflatoxins from real-world maize, wheat and rice samples.