Magnetic solid-phase extraction of triclosan using core-shell Fe3O4@MIL-100 magnetic nanoparticles, and its determination by HPLC with UV detection

Computer-Aided Prediction, Synthesis, and Characterization of Magnetic Molecularly Imprinted Polymers for the Extraction and Determination of Tolfenpyrad in Lettuce

Tolfenpyrad, a pyrazolamide insecticide, can be effectively used against pests resistant to carbamate and organophosphate insecticides. In this study, a molecular imprinted polymer using tolfenpyrad as a template molecule was synthesized. The type of functional monomer and the ratio of functional monomer to template were predicted by density function theory. Magnetic molecularly imprinted polymers (MMIPs) were synthesized using 2-vinylpyridine as a functional monomer in the presence of ethylene magnetite nanoparticles at a monomer/tolfenpyrad ratio of 7:1. The successful synthesis of MMIPs is confirmed by the results of the characterization analysis by scanning electron microscopy, nitrogen adsorption-desorption isotherms, Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analyzer, and vibrational sample magnetometers. A pseudo-second-order kinetic model fit the adsorption of tolfenpyrad, and the kinetic data are in good agreement with the Freundlich isothermal model. The adsorption capacity of the polymer to the target analyte was 7.20 mg/g, indicating an excellent selective extraction capability. In addition, the adsorption capacity of the MMIPs is not significantly lost after several reuses. The MMIPs showed great analytical performance in tolfenpyrad-spiked lettuce samples, with acceptable accuracy (intra- and inter-day recoveries of 90.5-98.8%) and precision (intra- and inter-day relative standard deviations of 1.4-5.2%).

Use of Nanomaterial-Based (Micro)Extraction Techniques for the Determination of Cosmetic-Related Compounds

The high consumer demand for cosmetic products has caused the authorities and the industry to require rigorous analytical controls to assure their safety and efficacy. Thus, the determination of prohibited compounds that could be present at trace level due to unintended causes is increasingly important. Furthermore, some cosmetic ingredients can be percutaneously absorbed, further metabolized and eventually excreted or bioaccumulated. Either the parent compound and/or their metabolites can cause adverse health effects even at trace level. Moreover, due to the increasing use of cosmetics, some of their ingredients have reached the environment, where they are accumulated causing harmful effects in the flora and fauna at trace levels. To this regard, the development of sensitive analytical methods to determine these cosmetic-related compounds either for cosmetic control, for percutaneous absorption studies or for environmental surveillance monitoring is of high interest. In this sense, (micro)extraction techniques based on nanomaterials as extraction phase have attracted attention during the last years, since they allow to reach the desired selectivity. The aim of this review is to provide a compilation of those nanomaterial-based (micro)extraction techniques for the determination of cosmetic-related compounds in cosmetic, biological and/or environmental samples spanning from the first attempt in 2010 to the present.

Electrode modified with graphene quantum dots supported in chitosan for electrochemical methods and non-linear deconvolution of spectra for spectrometric methods: approaches for simultaneous determination of triclosan and methylparaben

Two analytical methods were developed using electrochemical and spectrometric techniques for the simultaneous determination of endocrine disruptors triclosan and methylparaben in the monitoring of personal care products. For the electroanalytical analyses, a sensitive electrode based on graphene quantum dots supported in chitosan was employed. Under optimized conditions and a working potential of typically + 0.60 V for triclosan and + 0.81 V (vs. Ag/AgCl) for methylparaben, the calibration plots obtained by differential pulse voltammetry were linear in the range 0.10 to 10.0 μmol L^-1. The detection limits were 0.03 and 0.04 μmol L^-1 for triclosan and methylparaben, respectively. For the spectrometric method, UV/VIS spectrometry was used with a mathematical processing of non-linear deconvolution. This processing was used to solve the problem of overlapping absorption bands of triclosan (282 nm) and methylparaben (257 nm), which enabled simultaneous determination. The calibration plots by UV/VIS spectrometry were linear in the range 1.0 to 14.0 μmol L^-1 with detection limits of 0.42 and 0.37 μmol L^-1, respectively, for triclosan and methylparaben. Similar results obtained from the calibration plots of individual analytes suggest that the methods can be applied for individual or simultaneous determination of these species. Both methods were employed in the analysis of five samples of personal care products: toothpaste, antiseptic soap, antiseptic deodorant, shampoo, and a bath kit (soap and shampoo). The statistical tests indicated that there were no significant differences regarding the accuracy and precision of the data provided by the two methods described herein. Graphical abstract Schematic representation for simultaneous determination of triclosan and methylparaben: electrochemical method employing an electrode modified with graphene quantum dots supported in chitosan and spectrometric method applying a non-linear deconvolution of spectrum.

One-step synthesized magnetic MIL-101(Cr) for effective extraction of triazine herbicides from rice prior to determination by liquid chromatography-tandem mass spectrometry

The magnetic metal-organic framework MIL-101(Cr) material-based solid-phase extraction method coupled with high-performance liquid chromatography and tandem mass spectrometry was applied to extract seven triazine herbicides in rices. Fe₃ O₄ /MIL-101(Cr) was synthesized using reduction-precipitation method, in which steps including pre-synthesis and modification of Fe₃ O₄ nanoparticles were by-passed. Various parameters including extraction solvent type and volume, ultrasonic extraction time, amount of Fe₃ O₄ /MIL-101(Cr) microspheres, adsorption time, desorption volume and time were investigated. Under optimal conditions, the proposed method had the limit of detection (S/N = 3) and the limit of quantification (S/N = 10) of 1.08-18.10 and 3.60-60.20 pg/g, respectively. Relative standard deviations calculated for all herbicides with concentrations of 2 and 20 ng/g were in the range of 0.5 to 13% (n = 3). In addition, at the two above-mentioned concentrations, the method achieved relative recoveries percentages of 79.3 to 116.7% when applied to determine the triazine herbicides in real samples spiked. This rapid, green, non-polluting, pre-concentrated extraction method was successfully developed and applied to analyze herbicides in rice samples.

Rapid in situ microwave synthesis of Fe3O4@MIL-100(Fe) for aqueous diclofenac sodium removal through integrated adsorption and photodegradation

Metal-Organic Frameworks (MOFs) are efficient adsorbent and catalyst, however, the prepare of MOFs can be extremely time consuming. The rapid in situ microwave synthesis process offers the possibility of MOFs to a large-scale application. In this study, Fe₃O₄@MIL-100(Fe) was rapidly prepared via microwave in 30 min using Fe₃O₄ as metal precursor and applied as the adsorbent and photocatalyst to remove diclofenac sodium (DCF) from water. Fe₃O₄@MIL-100(Fe) exhibited an excellent adsorption effect to DCF with the maximum adsorption capacities of 400 mg/L. The presence of H₂O₂ could promote the removal of DCF during photocatalytic process. Approximately 99.4% of the DCF was removed in Fe₃O₄@MIL-100(Fe)/vis/H₂O₂ system via adsorption removal and consequent photocatalytic degradation. The high efficiency was attributed to the large BET surface area (1244.62 m²/g) and abundant iron metal sites (Fe(III) and Fe(II)) of Fe₃O₄@MIL-100(Fe). The adsorptive, photocatalytic property of Fe₃O₄@MIL-100(Fe) and the Fenton-like reaction were the main mechanisms for DCF removal. TOC analyzer was served to assess the mineralization of solutions treated by Fe₃O₄@MIL-100(Fe)/vis/H₂O₂ in 12 h. High elimination of TOC (87.8%) was observed during the DCF mineralization process. In addition, the major products were illuminated using HPLC-Q-TOF-MS and DCF degradation pathways were also proposed.

Controllable Synthesis of SERS-Active Magnetic Metal-Organic Framework-Based Nanocatalysts and Their Application in Photoinduced Enhanced Catalytic Oxidation

Fabrication of multifunctional nanocatalysts with surface-enhanced Raman scattering (SERS) activity is of vital importance for monitoring catalytic courses in situ and studying the reaction mechanisms. Herein, SERS-active magnetic metal-organic framework (MOF)-based nanocatalysts were successfully prepared via a three-step method, including a solvothermal reaction, an Au seed-induced growth process, and a low-temperature cycling self-assembly technique. The as-synthesized magnetic MOF-based nanocatalysts not only exhibit outstanding peroxidase-like activity, but can also be applied as a SERS substrate. Owing to these features, they can be used for monitoring in situ catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H₂O₂ via a SERS technique, and the concentration of H₂O₂ was determined. Owing to the intrinsic character of the Fe-based MOF material (MIL-100(Fe)), a novel photoinduced enhanced catalytic oxidation effect was demonstrated, in which the catalytic oxidation of TMB and o-phenylenediamine was accelerated. This study provides a versatile approach for the fabrication of functional MOF-based nanocomposites as a promising SERS substrate with a unique photoinduced enhanced peroxidase-like activity for potential applications in ultrasensitive monitoring, biomedical treatment, and environmental evaluation.

Speciation analysis of Tl(I) and Tl(III) after magnetic solid phase extraction using a magnetite nanoparticle composite modified with aminodibenzo-18-crown-6 functionalized MIL-101(Cr)

The authors describe a magnetic metal-organic framework nanocomposite consisting of aminodibenzo-18-crown-6 magnetite nanoparticles and MIL-101(Cr). It was employed to the speciation analysis of Tl(I) and Tl(III) ions. The sorbent is capable of selectively extracting Tl(I) while Tl(III) remains in solution. The total amount of thallium was then determined by reducing Tl(III) to Tl(I) by hydroxylamine hydrochloride and also extracting it. The extraction parameters were optimized by employing design of experiments methodology. Thallium was quantified by ET-AAS. Under optimized conditions, the detection limit is as low as 1.5 ng L^-1, the quantification limit is 5.0 ng L^-1, the linear range extends from 5 to 400 ng L^-1, and the relative standard deviation is <12% (for n = 5 at levels of 5, 50 and 250 ng L^-1). The recoveries of real samples analysis were in the range of 90-106%. The method was successfully applied to the analysis of a certified reference material (NIST SRM 1643d water sample) and to various real water samples. Graphical abstract A novel metal-organic framework nanocomposite consisting of aminodibenzo-18-crwon-6 magnetite nanoparticles (Fe₃O₄@ADB18C6) and MIL-101(Cr) was synthesized, characterized and employed to speciation analysis of Tl(I) and Tl(III).

Magnetic framework composite as sorbent for magnetic solid phase extraction coupled with high performance liquid chromatography for simultaneous extraction and determination of tricyclic antidepressants

In this study, magnetic framework composites (MFCs) (Fe₃O₄@TMU-10) microspheres were successfully fabricated and applied as an effective sorbent for preconcentration of the two model tricyclic antidepressants (TCAs) amitriptyline and imipramine from biological samples. MFCs were fabricated by a step-by-step assembly, novel, simple and efficient strategy. The shell thickness of the Metal-organic frameworks (MOFs) could also be easily controlled by tuning the number of assembly cycles. By coupling magnetic solid-phase extraction (MSPE) with high-performance liquid chromatography with UV detector (HPLC-UV), a simple, reliable, fast, sensitive and cost-effective method for simultaneous determination of TCAs was developed. Under optimal conditions, the preconcentration factors and relative recoveries of the studied compounds were obtained in the range of 43-50 and 90.5-99.0% respectively. The calibration curves were obtained in the range of 5-800 μg L^-1 with reasonable linearity (R² > 0.9904) and the limits of detection (LODs) ranged between 2 and 4 μg L^-1 (based on S/N = 3). The relative standard deviations of intra- and inter-day tests ranged from 3.1 to 4.6% and from 4.3 to 5.2%, respectively. The results demonstrate that Fe₃O₄@TMU-10 core-shell magnetic microspheres combine advantages of MOFs and magnetic nanoparticles, and are the promising sorbents for rapid and efficient extraction of target analytes from urine and plasma complex biological samples.

Magnetic solid phase extraction using Fe3O4@SiO2@C8 nanoparticles performed in a narrow-bore tube followed by dispersive liquid–liquid microextraction for extraction and preconcentration of nine pesticides

In the present work, a new magnetic solid phase extraction method performed in a narrow-bore tube using synthesized Fe₃O₄@SiO₂@C₈ magnetic nanoparticles has been developed.

Vortex assisted-supramolecular solvent based microextraction coupled with spectrophotometric determination of triclosan in environmental water samples

A simple, fast and environmental friendly vortex assisted-supramolecular solvent based microextraction (VA-SSME) method was developed for the preconcetration of triclosan in wastewater prior to UV spectrophotometric determination. To achieve maximum sensitivity and accuracy for the target analyte, the experimental parameters affecting the VA-SSME procedure were optimized using response surface methodology (RSM). Under optimised conditions, the correlation coefficient (R2) and recoveries were 0.9994 and 100.31-118.5%, respectively. The intra-day (repeatability) and inter-day (reproducibility) precisions expressed in terms of relative standard deviation (RSD) were 2-4% and 5.2%, respectively. The preconcentration factor and limits of detection (LOD) and quantification (LOQ) were found to be 90, 0.28 μg L−1 and 0.92 μg L−1, respectively. The developed VA-SSME/UV method was applied for the determination of triclosan in real samples collected over a period of three months. The analytical results obtained showed that triclosan was frequently detected in influent wastewater samples but was not detected in effluent samples.

Recent advances in metal-organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF- or COF-based solid-phase extraction (SPE), solid-phase microextraction (SPME), gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.

Facile Synthesis of Magnetic Covalent Organic Framework with Three-Dimensional Bouquet-Like Structure for Enhanced Extraction of Organic Targets

A facile strategy for the fabrication of novel bouquet-shaped magnetic porous nanocomposite via grafting a covalent organic framework (COF, TpPa-1) onto the surface-modified Fe₃O₄ nanoparticles (Fe₃O₄ NPs) was reported. The magnetic TpPa-1 (a COF synthesized from 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa-1)) contains clusters of core-shell magnetic nanoparticles and interconnected porous TpPa-1 nanofibers. Thus, it possesses larger specific surface area, higher porosity, and supermagnetism, making it an ideal sorbent for enrichment of trace analytes. Its performance was evaluated by the magnetic solid-phase extraction (MSPE) of trace polycyclic aromatic hydrocarbons (PAHs) from environmental samples prior to high-performance liquid chromatographic analysis. The results indicated that the magnetic TpPa-1 possessed superior enrichment capacity of such organic compounds.