Fabrication of Magnetic Al-Based Fe3O4@MIL-53 Metal Organic Framework for Capture of Multi-Pollutants Residue in Milk Followed by HPLC-UV.

The efficient capture of multi-pollutant residues in food is vital for food safety monitoring. In this study, in-situ-fabricated magnetic MIL-53(Al) metal organic frameworks (MOFs), with good magnetic responsiveness, were synthesized and applied for the magnetic solid-phase extraction (MSPE) of chloramphenicol, bisphenol A, estradiol, and diethylstilbestrol. Terephthalic acid (H2BDC) organic ligands were pre-coupled on the surface of amino-Fe3O4 composites (H2BDC@Fe3O4). Fe3O4@MIL-53(Al) MOF was fabricated by in-situ hydrothermal polymerization of H2BDC, Al (NO3)3, and H2BDC@Fe3O4. This approach highly increased the stability of the material. The magnetic Fe3O4@MIL-53(Al) MOF-based MSPE was combined with high-performance liquid chromatography-photo diode array detection, to establish a novel sensitive method for analyzing multi-pollutant residues in milk. This method showed good linear correlations, in the range of 0.05-5.00 µg/mL, with good reproducibility. The limit of detection was 0.004-0.108 µg/mL. The presented method was verified using a milk sample, spiked with four pollutants, which enabled high-throughput detection and the accuracies of 88.17-107.58% confirmed its applicability, in real sample analysis.

Development and application of magnetic solid phase extraction in tandem with liquid-liquid extraction method for determination of four tetracyclines by HPLC with UV detection.

A novel HPLC-UV method was developed for the determination of four tetracyclines based on magnetic solid phase extraction in tandem with liquid-liquid extraction. The water-soluble amino functionalized magnetite nanoparticle (MNP-NH2) was used as an adsorbent for extraction/preconcentration of tetracycline, oxytetracycline, chlortetracycline, and doxycycline from bovine milk samples. Fourier transform infrared spectrometer, transmission electron microscope, X-ray diffraction, and elemental analyze techniques were used to characterize the material. Some key parameters which influence liquid-liquid extraction and magnetic dispersive solid-phase extraction procedure, including volume of extraction solvent, the amount of adsorbent, the pH, extraction and desorption time, the composition of the eluent, and elution frequency were investigated. The proposed method exhibited a linear range of 50.0-2500.0 µg L-1 (r2 = 0.9941) with and good reproducibility (RSD < 2.2%, n = 3). The limit of detection and quantification were 40.0 and 50.0 µg L-1. This method was verified using milk sample spiked with four tetracyclines (100.0-200.0 µg L-1), and accuracies of 87.8-107.5%, which confirmed its applicability in real-sample analysis. The proposed method also shows potential application prospects for other water-soluble adsorbents.

Graphene oxide composites for magnetic solid-phase extraction of twelve quinolones in water samples followed by MALDI-TOF MS.

Antibiotic compounds in natural waters are normally present at low concentrations. In this paper, an easy and highly sensitive screening method using graphene oxide-functionalized magnetic composites (GO@NH2@Fe3O4) combined with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) was established for twelve quinolone antibiotics. GO@NH2@Fe3O4 composites were utilized as adsorbents for magnetic solid-phase extraction. This method combines the advantages of magnetic solid-phase extraction and MALDI-TOF MS, which allows for fast detection of quinolones at low concentrations. To improve absorption efficiency, the following parameters were individually optimized: sample acidity, extraction time, amount of adsorbent used, eluent used, and desorption time. Under the optimum conditions, the established method gave a low detection limit of 0.010 mg/L and allowed the high-throughput screening of twelve quinolone antibiotics (enoxacin, norfloxacin, ciprofloxacin, pefloxacin, fleroxacin, gatifloxacin, enrofloxacin, levofloxacin, sparfloxacin, danofloxacin, difloxacin, and lomefloxacin). The proposed method, having an easily prepared sorbent with a high affinity for quinolones and a convenient, high-throughput detection step, has been shown to have merit for the detection of antibiotics in water samples. Graphical abstract Schematic illustration of the (A) preparation of GO@NH2@Fe3O4 and (B) operating procedure for the MSPE and MALDI-TOF MS detection of QNs.

Amorphous poly-N-vinylcarbazole polymer as a novel matrix for the determination of low molecular weight compounds by MALDI-TOF MS.

Traditional matrices for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) are usually crystalline small molecules. The heterogeneous co-crystallization of the analyte and the matrix creates a sweet spot effect and reduces point-to-point reproducibility. In this study, an amorphous poly-N-vinylcarbazole polymer (PVK) was studied as a novel matrix for MALDI-TOF MS to detect various low molecular weight compounds (LMWCs) in the negative ion mode. The PVK achieved excellent matrix action and showed high sensitivity, good salt tolerance, and reproducibility. These results significantly broaden the design rules for new and efficient polymeric MALDI matrices.