Facile synthesis of magnetic one-dimensional polyaniline and its application in magnetic solid phase extraction for fluoroquinolones in honey samples

Terbium-based dual-ligand metal organic framework by diffusion method for selective and sensitive detection of danofloxacin in aqueous medium

A water-dispersible Tb(III)-based metal organic framework (TBP) was produced by diffusion technique using benzene-1,3,5-tricarboxylic acid (BTC) and pyridine as easily accessible ligands at low cost. The as-synthesized TBP with a crystalline structure and rod-shaped morphology has exhibited thermal stability up to 465 °C. Elemental analysis confirmed the presence of carbon, oxygen, nitrogen, and terbium in the synthesized MOF. TBP was used as a fluorescent probe for detection of danofloxacin (DANO) in an aqueous medium with significant enhancement of fluorescence intensity as compared to various fluoroquinolone antibiotics (levofloxacin (LEVO), ofloxacin (OFLO), norfloxacin (NOR), and ciprofloxacin (CIPRO)) with a low detection limit of 0.45 ng/mL (1.25 nm). The developed method has successfully detected DANO rapidly (i.e., response time = 1 min) with remarkable recovery (97.66-101.96%) and a relative standard deviation (RSD) of less than 2.2%. Additionally, TBP showcased good reusability up to three cycles without any significant performance decline. The in-depth mechanistic studies of the density functional theory (DFT) calculations and mode of action revealed that hydrogen bonding interactions and photo-induced electron transfer (PET) are the major factors for the turn-on enhancement behavior of TBP towards DANO. Thus, the present work provides the quick and precise identification of DANO using a new fluorescent MOF (TBP) synthesized via a unique and facile diffusion technique.

Polyaniline and Polyaniline-Based Materials as Sorbents in Solid-Phase Extraction Techniques

Polyaniline (PANI) is one of the best known and widely studied conducting polymers with multiple applications and unique physicochemical properties. Due to its porous structure and relatively high surface area as well as the affinity toward many analytes related to the ability to establish different types of interactions, PANI has a great potential as a sorbent in sample pretreatment before instrumental analyses. This study provides an overview of the applications of polyaniline and polyaniline composites as sorbents in sample preparation techniques based on solid-phase extraction, including conventional solid-phase extraction (SPE) and its modifications, solid-phase microextraction (SPME), dispersive solid-phase extraction (dSPE), magnetic solid-phase extraction (MSPE) and stir-bar sorptive extraction (SBSE). The utility of PANI-based sorbents in chromatography was also summarized. It has been shown that polyaniline is willingly combined with other components and PANI-based materials may be formed in a variety of shapes. Polyaniline alone and PANI-based composites were successfully applied for sample preparation before determination of various analytes, both metal ions and organic compounds, in different matrices such as environmental samples, food, human plasma, urine, and blood.

A nanocomposite of silica coated magnetite nanoparticles and aniline-anthranilic acid co-polymeric nanorods with improved stability and selectivity for fluoroquinolones dispersive micro solid phase extraction

Adsorbents composed of polyaniline nanostructures or their derivatives immobilized on magnetic nanoparticles had gained increasing interest for application in dispersive micro-solid phase extraction. However, reproducible binding between polymeric PANI nanopaterials and magnetic nanomaterials are still a challenging task. Furthermore, other challenges are the enhancement of physical and chemical stability of adsorbent magnetic nanoparticles as well as improvement of polymeric PANI nanoparticles selectivity towards target analytes. This work described the reproducible preparation of a nanocomposite of aniline-anthranilic acid co-polymeric nanorods with silica coated magnetite nanoparticles by physical mixing of its basic components. The prepared nanocomposite had proven stability against chemical and atmospheric attack. The formed nanocomposite in this work had advantages regarding stability and selectivity towards fluoroquinolones as compared with analogues prepared from polyaniline polymers and/or uncoated magnetite nanoparticles. The selectivity of the formed adsorbent was further optimized for microextraction of four fluoroquinolone antibacterial agents. The application of the prepared nanocomposite was exemplified in microextraction of the studied fluoroquinolones from spiked milk samples to enable their detection down to their stated maximum residue limits.

Fast Determination of Carbamates in Environmental Water Based on Magnetic Molecularly Imprinted Polymers as Adsorbent

Magnetic molecularly imprinted polymers (MMIPs) were prepared with isoprocarb as template molecule and applied to extraction of carbamates pesticides in different water samples. This method based on magnetic solid-phase extraction (SPE) avoided the time-consuming column-passing process of loading large volume samples in conventional SPE. In the study, only 0.1 g MMIPs could be used to obtain satisfactory recoveries, due to the high-surface area and excellent adsorption capacity of these nano-magnetic adsorbents. Owing to the excellent selectivity of MMIPs, in high-performance liquid chromatography-mass spectrometry analysis, the matrix effects of this technique were obviously lower than the conventional SPE method. Under the optimal conditions, the detection limits of carbamates were in the range of 2.7-11.7 ng L-1. The relative standard deviations of intra-day and inter-day were 2.5-7.4% and 3.6-8.4%, respectively. At all the spiked level, the recoveries of four analyzed carbamates in environmental water samples were in the range of 74.2-94.2%. The significant positive results were achieved in the proposed method for the determination of four carbamates in water samples from different lakes and rivers. In the three samples we tested, the carbaryl was found in the lake water obtained from Yitong River, and the content was 2.4 ng L-1.

Polyethyleneimine-functionalized Fe3O4/attapulgite particles for hydrophilic interaction-based magnetic dispersive solid-phase extraction of fluoroquinolones in chicken muscle

Fluoroquinolone (FQ) residues in foods of animal origin may threaten public health but are challenging to determine because of their low contents and complex matrices. In this study, novel polyethyleneimine-functionalized Fe₃O₄/attapulgite magnetic particles were prepared by a simple co-mixing method and applied as hydrophilic sorbents for the magnetic dispersive solid-phase extraction (MSPE) of three FQs, i.e., ciprofloxacin, norfloxacin, and enrofloxacin, from chicken muscle samples. The preparation of the magnetic particles was of high reproducibility and the products could be reused many times with high adsorption capacity. The key experimental factors possibly influencing the extraction efficiencies, including sample solution, extraction time, sample loading volume, desorption solution, desorption time, and elution volume were investigated. Under optimum MSPE conditions, the analytes in chicken muscle samples were extracted and then determined by RPLC-MS/MS in MRM mode. Good linearity was obtained for the analytes with correlation coefficients ranged from 0.9975 to 0.9995. The limits of detection were in the range of 0.02-0.08 μg kg^-1, and the recoveries of the spiked FQs in chicken muscle samples ranged from 83.9 to 98.7% with relative standard deviations of 1.3-6.8% (n = 3). Compared with the traditional MSPE methods based on hydrophobic mechanism, this hydrophilic interaction-based method significantly simplifies the sample pretreatment procedure and improves repeatability. This method is promising for accurate monitoring of FQs in foods of animal origin.

Validation of two UHPLC-MS/MS methods for fast and reliable determination of quinolone residues in honey

Antibiotic usage for beekeeping, including quinolones, can lead to residues in honey and these residues usually result from the drugs used in the treatment of American or European foulbrood diseases. Residues in honey may cause allergic reactions as well as increased antibiotic resistance. Within this study, rapid and breakthrough analysis methods were developed using UHPLC-ESI-MS/MS and sample preparation processes were minimised. Practical, low cost, time-effective analysis was provided utilising 'dilute & shoot' methodology and a QuEChERS-based procedure has been developed alternatively for improved sensitivity. Recovery values were 85%-112% for the 'dilute & shoot' method, and 82%-117% for the modified QuEChERS method. For accuracy studies, RSD% values were between 0.7% and 13.4% for both methods in intra-day and inter-day precision studies. CCα (1.1 μg/kg and 0.6 μg/kg) and CCβ (1.2 μg/kg and 0.6 μg/kg) mean values were calculated for the 'dilute & shoot' and QuEChERS method, respectively. These novel methods achieved simultaneous quantification of 21 quinolones in 7 min with high specificity and were used to analyse 50 honey samples. Quinolone residues were found in samples, and enrofloxacin, danofloxacin, pipemidic acid, lomefloxacin, cinoxacin, and ciprofloxacin were quantified.

Determination of anabolic androgenic steroids in dietary supplements and external drugs by magnetic solid-phase extraction combined with high-performance liquid chromatography-tandem mass spectrometry

The widespread abuse of anabolic androgenic steroids by healthy people leads to the risk of major mood disorders and heart failure; thus, the determination of anabolic androgenic steroids is vital. In this study, 17 anabolic androgenic steroids in dietary supplements and external drugs were identified, and their concentration was determined. For this purpose, polyaniline-coated magnetic nanoparticles were prepared and then subjected to magnetic solid-phase extraction combined with high-performance liquid chromatography-tandem mass spectrometry. The experimental parameters of magnetic solid-phase extraction were studied in detail, and the optimal conditions were established. Under the optimal conditions, the limits of detection were in the range of 0.001-0.02 μg/L, with relative standard deviations of 5.52-11.6% (n = 7) for all the steroids, and the enrichment factors were in the range of 20.0-24.8. The developed method was then successfully applied for the determination of 17 anabolic androgenic steroids in real samples, and dehydroepiandrosterone (prasterone) was detected in a commercially available external drug.

Use of a magnetic covalent organic framework material with a large specific surface area as an effective adsorbent for the extraction and determination of six fluoroquinolone antibiotics by HPLC in milk sample

A magnetic covalent organic framework material was synthesized with a core-shell structure using a simple solvothermal method. It was prepared with Fe₃ O₄ as the magnetic core, covalent organic framework as the shell, which synthesized from 1,3,5-triformylphloroglucinol and p-phenylenediamine by Schiff base reaction. Transmission electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, vibrating sample magnetometry, and nitrogen adsorption-desorption were used to characterize magnetic adsorbent. It has showed a large specific surface area (505.6 m² /g), which can provide many adsorption sites. Moreover, the saturation magnetization value was 48.4 emu/g enough to be separated by external magnet. Six kinds of fluoroquinolones (enoxacin, fleroxacin, ofloxacin, norfloxacin, pefloxacin, and lomefloxacin) were extracted by magnetic solid phase extraction with the magnetic adsorbent. High-performance liquid chromatography detects the entire adsorption and desorption process to further evaluate the optimal extraction and desorption conditions. Under the optimal chromatographic conditions, this method showed a low detection limit (0.05 to 0.20 μg/L), good linearity in the range of 0.5 to 200 μg/L, and the enrichment factor reaches 115.5-127.3. The spiked recovery of the fluoroquinolones in milk sample ranged from 90.4 to 101.2%.

Preparation of magnetic core-shell Fe3O4@polyaniline composite material and its application in adsorption and removal of tetrabromobisphenol A and decabromodiphenyl ether

Present study described a magnetic adsorption and removal method with prepared magnetic core-shell Fe₃O₄@polyaniline microspheres for the removal of two typical BFRs, tetrabromobisphenol-A (TBBPA) and decabromodiphenyl ether (BDE-209) from water samples. Magnetic core-shell Fe₃O₄@polyaniline microspheres were prepared by a hydrothermal and two step polymerization method with cheap iron salts and aniline, which were characterized with transmission electron microscopic (TEM) and scanning electron microscopy (SEM). The results showed that the Fe₃O₄@polyaniline microspheres earned a clear thickness shell of polyaniline (about 50 nm) and a saturation magnetization of 40.4 emu g^-1. The Magnetic core-shell Fe₃O₄@polyaniline exhibited excellent adsorption capability and removal rate to TBBPA and BDE 209. The adsorption of TBBPA and BDE 209 all followed pseudo-second order kinetics and agreed well to the Freundlich adsorption isotherms model. The negative Gibbs free energy change (ΔG⁰) and positive standard enthalpy change (ΔH⁰) for TBBPA and BDE-209 suggested that the adsorption was spontaneous and endothermic in nature. These results demonstrated that Fe₃O₄@PANI was a good adsorbent and would have a good application prospect in the removal of pollutants from environmental water.

Preparation and characterization of magnetic nanomaterial and its application for removal of polycyclic aromatic hydrocarbons

Fe₃O₄@polyaniline, a Fe₃O₄-based magnetic core-shell material, was synthesized and its morphology and microstructure were characterized with transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometry. Polyaniline was modified onto the surface of Fe₃O₄ nanoparticles by a self-assembly method based on a two-step oxidative polymerization method. The new materials exhibited good adsorption to polycyclic aromatic hydrocarbons such as fluoranthene, pyrene and benzo[a]pyrene from environmental water samples due to the high affinities of polyaromatic hydrocarbons to polyaniline via π-π and van der Waals interactions. The experimental results indicate that the adsorption of polyaromatic hydrocarbons follows pseudo-second order kinetics and the adsorption isotherms conform to a Langmuir isotherm model. The thermodynamic parameters for polyaromatic hydrocarbons indicate that the adsorption process is spontaneous and endothermic in nature, but adsorption occurs via non-covalent interactions. This study indicated that the Fe₃O₄@polyaniline hybrid core-shell structure was proved to be a good adsorbent for polyaromatic hydrocarbons while exhibiting simple preparation, easy separation, low cost, high reusability and great potential applicability for removal of polyaromatic hydrocarbons from water.

Fe3O4-based composite magnetic nanoparticles for volatile compound sorption in the gas phase: determination of selenium(iv)

On-line selenium separation based on hydride generation followed by sorption on magnetic nanoparticles.

An automated magnetic dispersive micro-solid phase extraction in a fluidized reactor for the determination of fluoroquinolones in baby food samples

An automated magnetic dispersive micro-solid phase extraction procedure in a fluidized reactor was developed for the determination of fluoroquinolone antimicrobial drugs (fleroxacin, norfloxacin and ofloxacin) in meat-based baby food samples. A stepwise injection system was successfully combined with afluidized reactorand applied for the magnetic dispersive micro-solid phase extraction procedure automation. The developed automated procedure involved injection of the sample solution into the fluidized reactor followed by the on-line separation of the analytes from the sample matrix based on fluidized beds strategy using magnetic nanoparticles, elution and determination of the analytes using a high performance liquid chromatography system with fluorescence detection. The floating of the magnetic nanoparticles in a liquid sample phase was accomplished by air-bubbling. In the developed method Zr-Fe-C magnetic nanoparticles were used as an efficient sorbent for the determination of fleroxacin, norfloxacin and ofloxacin. Under the optimal conditions, the calibration graphs were linear over the concentration ranges of 10-1000 μg L^-1 for fleroxacin (R² = 0.996), 5-1000 μg L^-1for norfloxacin (R² = 0.998) and ofloxacin (R² = 0.998). The limits of detection, calculated from the blank tests based on 3σ, were 3.0 μg L^-1forfleroxacin, 1.5 μg L^-1for norfloxacin and ofloxacin. The limits of quantification, calculated from the blank tests based on 10σ, were 10 μg L^-1 forfleroxacin, 5 μg L^-1for norfloxacin and ofloxacin. The method was applied for the determination of fluoroquinolonesin meat-based baby food samples and the results were compared with those obtained by the reference method. The recovery values for all analytes were within of 86-122% range.

Fabrication and characterisation of magnetic graphene oxide incorporated Fe3O4@polyaniline for the removal of bisphenol A, t-octyl-phenol, and α-naphthol from water

In this study, we fabricated a novel material composed of magnetic graphene oxide incorporated Fe₃O₄@polyaniline (Fe₃O₄@PANI-GO) using a modified Hummers' method, solvothermal, and two-step polymerisation method. The resulting products were characterised by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The results indicated that magnetic Fe₃O₄@PANI particles were successfully loaded onto the surface of the graphene oxide. Further Fe₃O₄@PANI-GO was investigated to remove bisphenol A(BPA), α-naphthol, and t-octyl-phenol (t-OP) from water samples by magnetic solid phase extraction. Under the optimal conditions, the Fe₃O₄@PANI-GO composite exhibited good adsorption capacity for t-OP, BPA, and α-naphthol, and the adsorption of these followed a pseudo-second-order kinetic model. Adsorption isotherms fit the Langmuir model, and the adsorption was an endothermic and spontaneous process. This work indicated that Fe₃O₄@PANI-GO earned great application prospect for removing phenolic contaminants from polluted water.

Magnetic graphene dispersive solid phase extraction combining high performance liquid chromatography for determination of fluoroquinolones in foods

In this study, a magnetic graphene-based dispersive solid phase extraction method was developed that was combined with high performance liquid chromatography to determine the residues of fluoroquinolone drugs in foods of animal origin. During the experiments, several parameters possible influencing the extraction performance were optimized (amount of magnetic graphene, sample pH, extraction time and elution solution). This extraction method showed high absorption capacities (>6800ng) and high enrichment factors (68-79-fold) for seven fluoroquinolones. Furthermore, this absorbent could be reused for at least 40 times. The limits of detection were in the range of 0.05-0.3ng/g, and the recoveries from the standards fortified blank samples (bovine milk, chicken muscle and egg) were in the range of 82.4-108.5%. Therefore, this method could be used as a simple and sensitive tool to determine the residues of fluoroquinolones in foods of animal origin.

Magnetic solid phase extraction using ionic liquid-coated core-shell magnetic nanoparticles followed by high-performance liquid chromatography for determination of Rhodamine B in food samples

Three hydrophobic ionic liquids (ILs) (1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6), 1-hexyl-3-methyl-imidazole hexafluoro-phosphate ([HMIM]PF6), and 1-octyl-3-methylimidazole hexafluorophosphate ([OMIM]PF6)) were used to coat Fe3O4@SiO2 nanoparticles (NPs) with core-shell structures to prepare magnetic solid phase extraction (MSPE) agents (Fe3O4@SiO2@IL). A novel method of MSPE coupled with high-performance liquid chromatography for the separation/analysis of Rhodamine B was then established. The results showed that Rhodamine B was adsorbed rapidly on Fe3O4@SiO2@[OMIM]PF6 and was released using ethanol. Under optimal conditions, the pre-concentration factor for the proposed method was 25. The linear range, limit of detection (LOD), correlation coefficient (R), and relative standard deviation (RSD) were found to be 0.50-150.00 μgL(-1), 0.08 μgL(-1), 0.9999, and 0.51% (n=3, c=10.00 μgL(-1)), respectively. The Fe3O4@SiO2 NPs could be re-used up to 10 times. The method was successfully applied to the determination of Rhodamine B in food samples.

Determination of hexanal and heptanal in human urine using magnetic solid phase extraction coupled with in-situ derivatization by high performance liquid chromatography

In this study, magnetic solid phase extraction coupled with in-situ derivatization (MSPE-ISD) was established for the determination of hexanal and heptanal in human urine. 2,4-Dinitrophenylhydrazine (DNPH) was used as the derivatization reagent that was adsorbed onto the surface of magnetite/silica/poly(methacrylic acid-co-ethylene glycol dimethacrylate) (Fe3O4/SiO2/P(MAA-co-EGDMA)). And then simultaneous extraction and derivatization of the aldehydes were performed on the DNPH-adsorbed Fe3O4/SiO2/P(MAA-co-EGDMA). The simple, rapid and sensitive determination of hexanal and heptanal can be accomplished within 9min. Under optimized conditions, the limits of detection (LODs) were 1.7 and 2.5nmol/L for hexanal and heptanal, respectively. The relative recoveries ranged from 72.8% to 91.4% with the intra- and inter-day relative standard deviations (RSDs) being less than 9.6%. Furthermore, the proposed method was successfully applied to determine endogenous hexanal and heptanal in human urine from healthy persons and lung cancer patients. The results showed the higher concentrations of hexanal and heptanal were observed in lung cancer patients compared to healthy controls. Thus, the developed MSPE-ISD method is suitable for the determination of aldehydes in urines.

Magnetic Solid Phase Extraction Applied to Food Analysis

Magnetic solid phase extraction has been used as pretreatment technique for the analysis of several compounds because of its advantages when it is compared with classic methods. This methodology is based on the use of magnetic solids as adsorbents for preconcentration of different analytes from complex matrices. Magnetic solid phase extraction minimizes the use of additional steps such as precipitation, centrifugation, and filtration which decreases the manipulation of the sample. In this review, we describe the main procedures used for synthesis, characterization, and application of this pretreatment technique which were applied in food analysis.

Dispersive micro-solid phase extraction based on self-assembling, ionic liquid-coated magnetic particles for the determination of clofentezine and chlorfenapyr in environmental water samples

Two ionic liquid-coated-Fe3O4 magnetic particles (IL-Fe3O4 MPs) were developed for use in two types of dispersive micro-solid phase extraction (D-μ-SPE) for the high-performance liquid chromatographic analysis of clofentezine and chlorfenapyr in environmental water samples. Self-assembling IL-Fe3O4 MPs were used in D-μ-SPE as adsorbents. Two D-μ-SPE extraction methods, namely, direct dispersive micro-solid phase extraction (d-D-μ-SPE) and in situ solvent formation-based dispersive micro-solid phase extraction (ISF-D-μ-SPE), were proposed, using [C8MIM][PF6] to extract analytes through two pathways. Lower IL doses were required in the extraction process compared with those in other IL-based methods. Fe3O4 MPs can also be recycled and reused after extraction and are thus environmentally friendly. These newly developed methods were demonstrated to be feasible for use in the quantitation of clofentezine and chlorfenapyr at trace levels, with lower limit of detection values ranging from 0.4 to 0.5 ng mL(-1) for d-D-μ-SPE and 0.4 ng mL(-1) for ISF-D-μ-SPE. Finally, relative standard deviations of less than 6.0% were obtained.

Microwave-assisted preparation of poly(ionic liquids)-modified magnetic nanoparticles for pesticide extraction

Novel poly(ionic liquids) were synthesized and immobilized on prepared magnetic nanoparticles, which were used to extract pesticides from fruit and vegetable samples by dispersive solid-phase extraction prior to high-performance liquid chromatography analysis. Compared with monomeric ionic liquids, poly(ionic liquids) have a larger effective contact area and higher viscosity, so they can achieve higher extraction efficiency and be used repeatedly without a decrease in analyte recovery. The immobilized poly(ionic liquids) were rapidly separated from the sample matrix, providing a simple approach for sample pretreatment. The nature and volume of the desorption solvent and amount of poly(ionic liquid)-modified magnetic material were optimized for the extraction process. Under optimum conditions, calibration curves were linear (R(2) > 0.9988) for pesticide concentrations in the range of 0.100-10.000 μg/L. The relative standard deviations for repeated determinations of the four analytes were 2.29-3.31%. The limits of detection and quantification were 0.29-0.88 and 0.97-2.93 μg/L, respectively. Our results demonstrate that the developed poly(ionic liquid)-modified material is an effective absorbent to extract pesticides from fruit and vegetable samples.