Magnetic metal-organic frameworks for fast and efficient solid-phase extraction of six Sudan dyes in tomato sauce

Magnetic solid-phase extraction is an effective and useful technique to preconcentrate trace analytes from food samples. In this study, a magnetic trimeric chromium octahedral metal-organic framework (Fe 3 O 4 -NH 2 @MIL-101) was fabricated and characterized. Fe 3 O 4 -NH 2 @MIL-101 was applied as an adsorbent of magnetic solid-phase extraction combined with high performance liquid chromatography to effectively isolate and simultaneously determine six Sudan dyes (Para Red, Sudan I–IV, and Sudan Red 7B) from tomato sauce. Potential factors affecting the MSPE were investigated in detail, and adsorption efficiency of Fe 3 O 4 -NH 2 @MIL-101 was compared with those of conventional adsorbents, such as neutral alumina, HLB, and C 18 . The developed method facilitated the extraction with using only 3 mg of adsorbent in 2 min. In addition, enhancement factors of 50, linear range of 0.01–25 μg/mL, and detection limit (S/N = 3) of 0.5–2.5 μg/kg were obtained. The intra-day and inter-day recoveries for spiked Sudan dyes were in the range of 72.6%–92.9% and 69.6%–91.6%, respectively, with relative standard deviations of ≤9.2%.