3D hierarchical magnetic hollow sphere-like CuFe2O4 combined with HPLC for the simultaneous determination of Sudan I-IV dyes in preserved bean curd.

Three-dimensional (3D) hierarchical magnetic hollow sphere-like CuFe2O4 (3D HMHS-CuFe2O4) were designed to sensitively detect four Sudan dyes combined with HPLC-DAD. The formation mechanism of 3D HMHS-CuFe2O4 is also discussed. Compared to the particle-like CuFe2O4 (PL-CuFe2O4), the as-obtained 3D HMHS-CuFe2O4 provided a higher extraction efficiency for the four Sudan dyes (I, II, III and IV) due to its hierarchical hollow structure with properly interconnected pores where the targets can easily diffuse into the reaction sites. Thus, a magnetic solid-phase extraction (MSPE)-HPLC method was established for the simultaneous measurement of the four Sudan dyes. Under optimized conditions, good linearity (5-4000ngg-1, r2≥0.9991), limits of detection (LODs, 0.56-0.60ngg-1), recoveries (91.1%-99.3%) and precision (RSDs≤4.9%) for the four Sudan dyes were obtained. The proposed MSPE-HPLC-DAD method is a convenient, effective, sensitive and time-saving method for the rapid isolation and determination of four Sudan dyes in preserved bean curd.