Polythiophene–Chitosan Magnetic Nanocomposite as a Novel Sorbent for Disperse Magnetic Solid Phase Extraction of Triazine Herbicides in Aquatic Media

In this paper, polythiophene/chitosan magnetic nanocomposite as a novel adsorbent is proposed for the preconcentration of triazines in aqueous samples prior to gas chromatography. The synthesized nanoparticles, magnetic chitosan and polythiophene–chitosan magnetic nanocomposite were characterized by scanning electron microscopy. The magnetic polythiophene–chitosan nanocomposite containing analytes could be removed from the sample solution by applying a permanent magnet. The major factors influencing the extraction efficiency including desorption conditions, nanocomposite components ratio, sorbent amount, extraction time, ionic strength and sample pH were optimized. The developed method proved to be rather convenient and offers sufficient sensitivity and good reproducibility. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) of the method under optimized conditions were 10–30 and 100 ng L⁻¹, respectively. Under the optimum conditions, good linearity was obtained within the range of 100–5000 ng L⁻¹ for all triazines with correlation coefficients >0.9994. The relative standard deviation at a concentration level of 150 ng L⁻¹ was 7–12 %. Furthermore, the method was successfully applied to the determination of triazines in real samples, where relative recovery percentages of 96–102 % were obtained. Compared with other methods, the current method is characterized by easy, fast separation and low detection limits.

     

Preparation and Evaluation of Uniform-Sized Sol–Gel Theophylline Imprinted Microspheres as Solid Phase Extraction Sorbent

A highly selective imprinted amino-functionalized silica gel microsphere was prepared by a simple molecular imprinting technique with a sol–gel process. Theophylline was used as template; 3-aminopropyltrimethoxysilane (APTMS) as functional monomer and tetraethylorthosilicate (TEOS) as reticulating agent. These theophylline imprinted silica microspheres were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron micrographs (SEM), thermogravimetric analysis (TGA), and high performance liquid chromatography (HPLC) in detail. The results showed that monodispersive APTMS-silica imprinted microspheres with size of 250 nm were synthesized successfully. Two kind of binding sites exist between the sol–gel imprinted microspheres and theophylline with K _D and Q _max for the higher affinity binding parameters was 1.89 μg/mL and 7.47 μg/mg dry polymers, and for the lower affinity binding sites were found to be 0.18 μg/mL and 3.47 μg/mg dry polymers, respectively. Packed in column, the imprinted microspheres were employed to extract theophylline from green tea successfully.     

Box–Behnken Experimental Design for the Synthesis of Magnetite–Polypyrrole Composite for the Magnetic Solid Phase Extraction of Non-steroidal Anti-inflammatory Drug Residues

A magnetite–polypyrrole composite adsorbent was synthesized and applied for the magnetic solid phase extraction of three non-steroidal anti-inflammatory drugs in aqueous solution and systematically investigated using Box–Behnken design. The synthesized composite adsorbent was characterized using Fourier-transform infrared spectroscopy, transmission electron microscopy, the Brunauer–Emmett–Teller method, vibrating sample magnetometry, and X-ray diffraction. The material was successfully modeled by Box–Behnken design (R²?=?0.94–0.98, p value: <0.001%) by monitoring the extraction efficiencies of naproxen, diclofenac sodium, and mefenamic acid. The analytes were determined using high-performance liquid chromatography with ultraviolet detection. The polymerization time was found to be the most significant factor, followed by amount of oxidant and monomer in the synthesis of the composite with a fixed Fe₃O₄ mass. Box–Behnken design was employed for the optimization of four parameters affecting the magnetic solid phase extraction: sample pH, salt addition, adsorption, and desorption time (R²?=?0.88–0.94). The optimized conditions for the procedure were validated, providing low detection limits (0.9–3.5?µg?L^?1) with good reproducibility (<7.16% relative standard deviation) and excellent recoveries (97.87–100.49%) for tap, river, and wastewater samples. The synthesized adsorbent demonstrated good adsorption efficiency for the simultaneous determination of the non-steroidal anti-inflammatory drug residues.     

Development of a Solid‐Phase Extraction‐Enzyme‐Linked Immunosorbent Assay Method with a New Sorbent of Multiwall Carbon Nanotube for the Determination of Estrone in Water

Abstract

A sensitive solid‐phase extraction‐enzyme‐linked immunosorbent assay (SPE‐ELISA) method was developed to analyze the estrone in environmental water. A new SPE sorbent of the multiwall carbon nanotube was tested and proved to have similar adsorbability for estrone comparing to the commercial C₁₈ SPE. A specific polyclonal antibody for estrone (A‐E1) and a broad‐spectrum antibody for estrone, estradiol and estriol (A‐E2) were produced. For A‐E1, the limit detection of estrone was 0.04 µg/l and for A‐E2 were 0.07, 0.04 and 0.2 µg/l of estrone, estradiol and estriol, respectively. Different river water samples were analyzed by ELISA and HPLC method.     

Determination of Herbicides in Corn Flour by Novel Extraction and Gas Chromatography–Mass Spectrometry

A simple and efficient procedure was developed to determine eight herbicides in corn flour by gas chromatography–mass spectrometry in selected ion-monitoring mode. Samples were prepared with a modified, quick, easy, rapid, effective, rugged, and safe procedure. The type and volume of extraction solvent, type and amount of adsorbent, and time of sonication were optimized. The protocol method was rigorously verified. The mean recoveries were from 85 to 108% at various fortification levels with relative standard deviations below 15% and limits of quantification from 4 to 48?ng g^?1. The method was used to determine herbicides in corn flour.     

Magnetic Solid Phase Extraction Based on Modified Magnetite Nanoparticles Coupled with Dispersive Liquid–Liquid Microextraction as an Efficient Method for Simultaneous Extraction of Hydrophobic and Hydrophilic Drugs

In this work, surfactant-coated Fe₃O₄@decanoic acid nanoparticles was synthesized as a viable nanosorbent for coextraction of drugs with different polarities (hydrophobic, hydrophilic). To reach desirable enrichment factors, efficient clean-up and low limits of detection (LODs), the method was combined with dispersive liquid–liquid microextraction (DLLME). The coupling of these extraction methods with GC-FID detection was applied to simultaneous extraction and quantification of venlafaxine (VLF) as a hydrophilic model drug and desipramine (DESI) and clomipramine (CLO) as hydrophobic model drugs in urine samples. The effect of sample pH, nanosorbent amount, sorption time, surfactant concentration, eluent type, eluent volume, salt content, elution time in magnetic solid phase extraction step and extraction solvent and its volume along with sample pH in DLLME step were optimized. Under the selected conditions, linearity was achieved within the range of 5–5000 µg L^?1. The LOD values were obtained in the range of 1.5–3.0 µg L^?1 for DESI, 1.2–2.5 µg L^?1 for VLF and 2.0–4.0 µg L^?1 for CLO, respectively. The percent of extraction recoveries and relative standard deviations (n?=?5) were in the range of 82.4–95.9 and 6.1 for DESI, 60.5–92.8 and 6.9 for VLF and 57.2–58.0 and 5.5 for CLO, respectively. Ultimately, the applicability of the new method was successfully confirmed by the extraction and quantification of DESI, VLF and CLO from human urine samples.     

Amine-Functionalized Metal–Organic Framework as a New Sorbent for Vortex-Assisted Dispersive Micro-Solid Phase Extraction of Phenol Residues in Water Samples Prior to HPLC Analysis: Experimental and Computational Studies

Metal–organic frameworks (MOFs) are a new class of hybrid inorganic–organic microporous crystalline materials, which possess unique properties such as high surface area, tunable pore size, and good thermal stability. These unique characteristics make MOFs interesting targets for sample pretreatment. In this work, MIL-53 material based on aluminum and containing amine functional groups (NH₂-MIL-53(Al)) was synthesized and applied as an efficient sorbent for development of vortex-assisted dispersive micro-solid phase extraction for eight United States Environmental Protection Agency’s priority phenols from aqueous samples prior to analysis by high-performance liquid chromatography with photodiode-array detection. A simple extraction process was designed. The parameters affecting the extraction efficiency, such as amount of sorbent, extraction time, type of desorption solvent and its volume were investigated. The good linearity in the concentration range of 0.0015–10.0000 μg mL^?1 with the coefficients of determination of greater than 0.9929, low limits of detection (0.0004–0.0133 μg mL^?1) and relative standard deviations of lower than 10% were obtained. The proposed method has been successfully applied to the determination of phenol compounds in different water sample matrices including treated water, waste water, river water, sea water, lake water, drinking water and tap water. In addition, computational simulation was performed to predict the adsorption ability of NH₂-MIL-53(Al) towards the studied phenolic compounds. The computational results were in agreement with the experimental studies and it has been proved that NH₂-MIL-53(Al) is promising for enrichment of phenolic pollutants.     

Comparison of Modifiers for Mercury Speciation in Water by Solid Phase Extraction and High Performance Liquid Chromatography–Atomic Fluorescence Spectrometry

Diethyldithiocarbamate and 2-mercaptoethanol modifiers were compared for the preconcentration of mercury species in water by C₁₈ solid phase extraction (SPE). The recovery values of mercury species were determined by high performance liquid chromatography–atomic fluorescence spectrometry. The eluent type, pH, chloride ion concentration, humic acid concentration, and storage time were evaluated to compare the preconcentration efficiency. L-cysteine was employed to elute the mercury compounds. Less eluent was needed for 2-mercaptoethanol modified SPE than for diethyldithiocarbamate modified SPE at an L-cysteine concentration of 0.12%. Diethyldithiocarbamate modified SPE could be used over a wider pH range and higher humic acid concentrations, whereas 2-mercaptoethanol modified SPE was less affected by the chloride concentration. Both modified SPE systems stored mercury species for 5 days, but diethyldithiocarbamate modified SPE could be stored longer. Diethyldithiocarbamate SPE provided limits of detections of 3.5, 2.5, and 4 ng · L^?1 and average recoveries of 90.78 ± 3.37%, 96.79 ± 5.12%, and 84.88 ± 5.37% for mercury(II), methylmercury, and ethylmercury, respectively. The relative standard deviation was less 6.5%. For 2-mercaptoethanol modified SPE, the limits of detection were 1.4, 1, and 1.6 ng · L^?1 and the recoveries were of 87.66 ± 8.45%, 86.70 ± 2.61%, and 91.31 ± 6.98% for mercury(II), methylmercury, and ethylmercury, respectively, with a relative standard deviation below 9.7%. Water should be characterized for its physical and chemical characteristics before mercury preconcentration to choose the most suitable method.     

Production of a Novel Material Based on a Collagen–Chitosan Composite and Ibuprofen in a Supercritical Medium

A novel material for biomedical applications was obtained from a collagen–chitosan composite and ibuprofen by a fluid process using supercritical carbon dioxide. The material was characterized by IR and X-ray photoelectron spectroscopy. The applicability of XPS analysis of biomaterials for quantification of loaded therapeutic agents is demonstrated.     

Pressurized Liquid Extraction Coupled with LC–ESI–MS–MS for the Determination of Herbicides Chlormequat and Mepiquat in Flours

This paper describes a new method for the rapid extraction and unequivocal confirmation of herbicides chlormequat and mepiquat in wheat flours and various flours utilized in infant foods. The highly automated extraction procedure is based on accelerated solvent extraction, followed by liquid chromatography-tandem mass spectrometry as a confirmatory analysis. Typical recoveries from flours and baby food samples ranged from 83 to 99% at a fortification level of 10 ppb, corresponding to the maximum residue limits established by the European Union; while relative standard deviations (RSD) were less than 10% for all samples. The limit of detection (signal-to-noise ratio = 3) of the method for the considered phenols in baby food samples are less than 0.1 μg g^?1. Traces of the selected herbicides have been detected in about 50% of baby foods, bought from different Roman supermarkets and butcher shops, applying the described methodology.     

β-Cyclodextrin-Cross-Linked Polymer as Solid Phase Extraction Material Coupled Graphite Furnace Atomic Absorption Spectrometry for Separation/Analysis of Trace Copper

Abstract

The β-cyclodextrin cross-linked polymer (β-CDCP) was synthesized by the reaction of β-cyclodextrin with epichlorohydrin in NaOH and characterized by fourier transform infrared spectroscopy and thermoanalysis. The β-CDCP as a solid phase extraction (SPE) material was used to preconcentrate/separate trace copper using l-(2-pyridylazo)-2-naphthol (PAN) as a complexing agent for Cu-(II)-PAN coupled with a graphite furnace atomic absorption spectrometry (GFAAS) for analysis. The optimized experiment conditions and adsorption capacity were investigated. The detection limit (DL) was 1.11 µg.L^?1 with RSD 4.27% (n = 5, c = 25.0 µg L^?1). The linear range is 6.25–31.25 µg L^?1. Moreover, the β-CDCP could be used repeatedly and offered better a recovery and estimation of trace copper. In order to verify the accuracy of the method, a certified reference water sample was analyzed and the results obtained were in agreement with the certified values. The recovery for copper was 103.6%. The proposed method was applied to the analysis of copper in lake water samples.     

Spectrofluorimetric Determination of Aflatoxin B1 in Winter Herbal Teas via Magnetic Solid Phase Extraction Method by using Metal–Organic Framework (MOF) Hybrid Structures Anchored with Magnetic Nanoparticles

MIL53(Al)-SiO₂@Fe₃O₄ composite was prepared by co-precipitation route with a typical Stöber synthetic process and ultrasonic-agitation, then subsequently utilized as a multi-component novel sorbent in solid-phase microextraction (SPME) of aflatoxin B1 in winter herbal teas. Microstructural properties of MIL53(Al)-SiO₂@Fe₃O₄ composite was characterized by using Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) methods, and Brunauer–Emmett–Teller (BET) surface area measurement. The MIL53(Al)-SiO₂@Fe₃O₄ composite was found to be a very effective sorbent in spectrofluorimetric determination of aflatoxin B1 (AFB1) in winter herbal teas via magnetic solid-phase extraction (SPE) route. The proposed method showed a wide linear range from 0.5 to 150 ng/ml, low limit of detection (LOD = 0.5 ng/ml), and an acceptable recovery values (70.7–96.5%) in real samples analysis. This study shows that the suggested method possesses an important potential to use for detecting AFB1 in quality control laboratories.     

Determination of Chlorophenols and Alkylphenols in Water and Juice by Solid Phase Derivative Extraction and Gas Chromatography–Mass Spectrometry

A solid phase derivative extraction method using acetic anhydride was developed for the determination of chlorophenols and alkylphenols in water and fruit juice by gas chromatography–mass spectrometry (GC–MS). The quantitative extraction was performed by passing 100 mL of sample prepared in 0.1 mol L^?1 sodium hydroxide through a column packed with 500 mg of a strong anion-exchange resin at a flow rate of 0.75 mL min^?1. The retained phenols were quantitatively derivatized in the column by the introduction of 0.25 mL of acetic anhydride. The derivatized phenols were eluted with 3.0 mL of hexane and the effluent was dried under nitrogen. The final volume was diluted to fifty microliters with hexane and analyzed by GC–MS. Under the optimum conditions, preconcentration factors of 2000, limits of detection between 0.005 and 1.796 µg L^?1, and relative standard deviations of 2.1% to 6.7% were obtained. The method was successfully applied to wastewater and fruit juice and the recoveries of phenols were between 76% and 111%.     

Determination of Cotinine in Urine by Molecularly Imprinted Polymer Solid Phase and Liquid–Liquid Extraction Coupled with Gas Chromatography

A comparison between molecularly imprinted solid phase extraction (MISPE) and liquid–liquid extraction (LLE) was performed for cotinine in human urine followed by gas chromatography analysis. The molecularly imprinted polymer (MIP) was synthesized via bulk methodology employing cotinine, methacrylic acid, and ethylene glycol dimethacrylate as template, functional monomer, and cross-linker, respectively. Both methods were validated with good precision and accuracy. The LLE method (limit of quantification = 10 nanograms per milliliter) was slightly more sensitive than the MISPE (limit of quantification = 15 nanograms per milliliter) procedure, but both methods were able to determine cotinine at typical concentrations in urine. An important advantage of the molecularly imprinted polymer approach was its ability to be reused up to at least 100 times. Other advantages of the MISPE include simple manipulation, low solvent consumption, and low worker exposure.     

Determination of Chlorophenols in Wastewater with Methyl Chloroformate Derivatization,Solid Phase Extraction,and Gas Chromatography–Mass Spectrometry

The determination of chlorophenols in wastewater with methyl chloroformate derivatization, solid phase extraction, and gas chromatography–mass spectrometry is reported. In order to employ this combined solid phase derivative extraction method, quantitative extraction was performed by the introduction of 100 mL of sample in 1.0 mol L^?1 sodium hydroxide into a column containing 500 mg of packed resin at a flow rate of 1.0 mL/min. The chlorophenols were retained and derivatized quantitatively in the column by the introduction of 0.25 mL of methyl chloroformate. The derivatized analytes were eluted with 5.0 mL of hexane before the effluent was dried under a stream of nitrogen. The dried solution was diluted to a volume of 50 µL with hexane followed by analysis by gas chromatography–mass spectrometry. The preconcentration parameters were optimized and under these conditions: limits of detection from 0.010 to 0.423 µg L^?1, a preconcentration factor of 2500, and precision values from 4.8 to 7.7% as the relative standard deviation were obtained. The method was employed for the analysis of water samples and the recoveries of the analytes were between 76 and 103%.     

Facile Regioselective Synthesis of a Novel Chitosan–Pexiganan Conjugate with Potential Interest for the Treatment of Infected Skin Lesions

A pexiganan–chitosan conjugate was designed to combine the exceptional bioadhesion and tissue-regenerating abilities of chitosan with the excellent antibiotic properties of pexiganan. We herein report our first results on the successful synthesis, including Fourier transform infrared (FT-IR) and amino acid analysis of such conjugate, which was prepared by regioselective covalent attachment of a Cys-containing pexiganan analog to the chitosan's amino groups. Further results from ongoing research will be reported.