A novel method for the high preconcentration of trace amounts of the aflatoxins in pistachios by dispersive liquid–liquid microextraction after solid-phase extraction

Abstract

In the present study, a new approach which uses solid-phase extraction clean-up combined with dispersive liquid–liquid microextraction is proposed for the preconcentration of trace amounts of aflatoxins (B₁, B₂, G₁ and G₂). The aflatoxins were then determined using high-performance liquid chromatography coupled with a fluorescent detector. In this method, pistachio samples were extracted by ultrasound-assisted extraction followed by solid-phase extraction. Then, the solid-phase extract was used as the disperser solvent for the next dispersive liquid–liquid microextraction step for further purification and enrichment of the aflatoxins. The effects of various parameters on the extraction efficiency of the proposed method were investigated and optimized. A good linearity of the aflatoxins was obtained from 0.1 to 50.0 μg kg⁻¹ for B₁ and B₂, and from 0.2 to 50.0 μg kg⁻¹ for G₁ and G₂, respectively. The limits of detection (LODs) (S/N = 3) were 0.02 for B₁ and B₂, and 0.04 μg kg⁻¹ for G₁ and G₂, respectively. The relative recoveries at the three spiked levels ranged from 85 to 93% with the RSDs less than 13% (n = 3). The method was successfully applied to the determination of aflatoxins in pistachio samples.