Magnetic ZIF-8 extraction using supramolecular solvent based on ferrofluid and vortex-assisted liquid–liquid microextraction of cationic dyes in beverage and river water samples

In this work, a new type of magnetic ZIF-8 based on ferrofluids (FFs) and supramolecular solvents (SUPRASs) was prepared and applied as an extraction phase in vortex-assisted liquid–liquid microextraction of cationic dyes (chrysoidin, auramine O and rhodamine B) in beverage and river water samples. The FFs comprised sodium dodecyl sulfate (SDS)-coupled titanium dioxide-coated MZIF-8 and hexafluorobutanol-geraniol SUPRAS (MZIF-8/SDS-TiO2@HFB-Ger). The prepared extraction phase exhibited high extraction recoveries of these cationic dyes owing to strong interaction mechanisms, including hydrogen-bonding, hydrophobic, π-π and electrostatic attractions, between the FFs and the analytes. The optimum extraction conditions of cationic dyes were as follows: Ger content was 4 %, HFB content was 6 %, MZIF-8/TiO2-SDS was 25 mg, vortex time was 3 min, solution pH was 6–8, salt concentration was 5 % (m/v), elution solvent was ethanol and elution solvent volume was 500 μL. Under the optimized conditions, cationic dyes were linear in 5–1000 ng mL−1 with determination coefficients higher than 0.9957. The limits of detection ranged from 1 to 1.5 ng mL−1, and the limits of quantification were between 3.5 and 5 ng mL−1. Finally, the developed method was applied to determine the target analytes in beverage and river water samples, achieving extraction recoveries ranging from 93.1 % to 104.3 %, with relative standard deviations between 1.1 % and 8.1 %. Compared with MZIF-8, MZIF-8/SDS-TiO2@HFB-Ger exhibited higher extraction efficiency for cationic dyes. Therefore, the developed method has great potential in extracting various analytes from various food and water samples.