Separation and determination of aflatoxins B1, B2, G1 and G2 in pistachio samples based on magnetic solid phase extraction followed by high performance liquid chromatography with fluorescence detection

A simple and fast method based on magnetic solid phase extraction (MSPE) followed by high performance liquid chromatography with a post column derivatization-fluorescence detection system has been developed for simultaneous separation and determination of aflatoxins (AFs) B-1, B-2, G(1) and G(2) in pistachio. After primary extraction, purification of AFs was carried out by a MSPE procedure. Magnetic nanoparticles coated by 3-(trimethoxysilyl)-1-propantiol and modified with 2-amino-5-mercapto-1,3,4-thiadiazole were used for extraction and purification of AFs. Efficiency of modified magnetic nanoparticles has been validated as an antibody-free adsorbent. The experimental parameters affecting the extraction efficiency such as the pH, adsorption and desorption times, amount of adsorbent, type and volume of desorption solvent were investigated and optimized. Under the optimized conditions, the calibration curves were linear in the ranges of 0.10-15 mu g L-1 for AFB(1) and AFG(1) and 0.04-3.00 mu g L-1 for AFB(2) and AFG(2). Limits of detection (LODs) were in the range of 0.012-0.035 mu g L-1. The intra-day and inter-day precision (RSD%) were in the range of 2.3-5.4% and 2.8-5.9%, respectively. The developed method has been successfully applied to the determination of AFs in pistachio samples with good recoveries (92.5-103.2%). Also, the performance of the method was compared with the conventional method based on the immunoaffinity chromatography. The results demonstrated that the developed method is simple, rapid, inexpensive, accurate and selective.