10. Ultrasonic-Assisted Dispersive Solid Phase Microextraction (UA-DSPME) Using Silica@Multiwalled Carbon Nanotubes Hybrid Nanostructures Sorbent for Preconcentration of Trace Aflatoxin B₁ in Liquid Milk Samples

A reliable, simple, rapid and cost-effective extraction method based on ultrasonic-assisted dispersive solid phase microextraction (UA-DSPME) method using silica@multiwalled carbon nanotubes hybrid nanostructures combined with spectrophotometric detection was developed for the first time for preconcentration and determination of aflatoxin B₁ (AFB1) in liquid milk samples. Two level factorial design and central composite design in combination with response surface methodology were used to evaluate the factors affecting extraction and preconcentration procedure. The influence of different variables including mass of adsorbent, extraction time, eluent volume and sample volume was investigated in the optimization study. Under the optimal conditions, a dynamic linear range of 0.3–250 μg L⁻¹ with detection limit of 0.1 μg L⁻¹ was obtained. The intraday and interday precisions expressed as relative standard deviations were 3.2% and 4.3% respectively. The developed UA-DSPME/UV-Vis method was applied for extraction and preconcentration of AFB1 in real milk samples. As a result of relatively high enrichment factor (108), satisfactory extraction recoveries (96.8–99.2%) using only 62 mg of an adsorbent were achieved.