Synthesis of hydrophilic sorbents from N‐vinylimidazole/divinylbenzene and the evaluation of their sorption properties in the solid‐phase extraction of polar compounds

This article reports the synthesis of N‐vinylimidazole/divinylbenzene resins by suspension polymerization. Several polymerization conditions were tested to achieve a quantitative incorporation of the N‐vinylimidazole monomer into the final polymer while a high specific surface area was maintained. The retention properties of several copolymers with different nitrogen contents were evaluated with the solid‐phase extraction of polar compounds from water samples, and the best results were obtained for a polymer containing 6.3% N with a surface area of 627 m² g^?1. The sorption properties of the resins were compared to those of styrene–divinylbenzene and other copolymers containing nitrogen, and the results were best for the new sorbents with N‐vinylimidazole as the polar monomer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2019–2025, 2004     

Preparation and characterization of highly polar polymeric sorbents from styrene–divinylbenzene and vinylpyridine–divinylbenzene for the solid‐phase extraction of polar organic pollutants

This article explores the synthesis of styrene–divinylbenzene resins with different surface areas and the influence of these surface areas on their performance in the solid‐phase extraction of polar compounds from water samples. As expected, increasing the surface areas increases the retention capability of polar compounds. To improve the retention properties, we have used 4‐vinylpyridine instead of styrene in the polymerization and evaluated the influence of the sorbent polarity and surface area on the retention properties. We have found that a compromise is required between the percentage of 4‐vinylpyridine, which increases the polarity of the sorbent, and the percentage of divinylbenzene, which increases the surface area. In the solid‐phase extraction of polar compounds, the results are best for a polymer containing 2.14% N and having a surface area of 710 m²/g. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1927–1933, 2003     

Hypercrosslinked particles for the extraction of sweeteners using dispersive solid‐phase extraction from environmental samples

This work presents a new extraction material, namely, Q‐100, based on hypercrosslinked magnetic particles, which was tested in dispersive solid‐phase extraction for a group of sweeteners from environmental samples. The hypercrosslinked Q‐100 magnetic particles had the advantage of suitable pore size distribution and high surface area, and showed good retention behavior toward sweeteners. Different dispersive solid‐phase extraction parameters such as amount of magnetic particles or extraction time were optimized. Under optimum conditions, Q‐100 showed suitable apparent recovery, ranging in the case of river water sample from 21 to 88% for all the sweeteners, except for alitame (12%). The validated method based on dispersive solid‐phase extraction using Q‐100 followed by liquid chromatography with tandem mass spectrometry provided good linearity and limits of quantification between 0.01 and 0.1 μg/L. The method was applied to analyze samples from river water and effluent wastewater, and four sweeteners (acesulfame, saccharin, cyclamate, and sucralose) were found in both types of sample.     

Application of micro‐solid‐phase extraction for the on‐site extraction of heterocyclic aromatic amines in seawater

An efficient on‐site extraction technique to determine carcinogenic heterocyclic aromatic amines in seawater has been reported. A micro‐solid‐phase extraction device placed inside a portable battery‐operated pump was used for the on‐site extraction of seawater samples. Before on‐site applications, parameters that influence the extraction efficiency (extraction time, type of sorbent materials, suitable desorption solvent, desorption time, and sample volume) were investigated and optimized in the laboratory. The developed method was then used for the on‐site sampling of heterocyclic aromatic amines determination in seawater samples close to distillation plant. Once the on‐site extraction completed, the small extraction device with the analytes was brought back to the laboratory for analysis using high‐performance liquid chromatography with fluorescence detection. Based on the optimized conditions, the calibration curves were linear over the concentration range of 0.05–20 μg/L with correlation coefficients up to 0.996. The limits of detection were 0.004–0.026 μg/L, and the reproducibility values were between 1.3 and 7.5%. To evaluate the extraction efficiency, a comparison was made with conventional solid‐phase extraction and it was applied to various fortified real seawater samples. The average relative recoveries obtained from the spiked seawater samples varied in the range 79.9–95.2%.     

Synthesis and application of a novel solid‐phase extraction adsorbent for multiresidue analysis of insecticides in water

A new solid‐phase adsorbent was synthesized for the simultaneous enrichment of multiple classes of trace insecticides (neonicotinoids, organophosphates, fiproles, and organochlorines) in water. The adsorbent was spherical with a diameter, surface area, average pore volume, and pore size of approximately 5 μm, 341 m²/g, 0.092 m³/g, and 2.22 nm, respectively. Extraction conditions were optimized, including water pH and the type and volume of the rinsing and eluting solvents. After extraction, target insecticides were analyzed by gas chromatography with mass spectrometry and high‐performance liquid chromatography with tandem mass spectrometry. The recovery of neonicotinoids ranged from 63.0 to 124%, except for clothianidin (40.1–52.9%). Recoveries of organophosphates, fiproles, and organochlorines were in the ranges of 37.0–102, 64.0–101, and 42.0–69.3%, respectively. Relative standard deviations were <20% except for profenofos (5.1–30%) and method detection limits were 1.8–12.7 ng/L, suggesting that the precision and accuracy of the developed method were viable. At environmentally relevant concentrations, the new adsorbent achieved comparable recoveries of target insecticides to hydrophilic–lipophilic balance adsorbent while providing an additional advantage by further reducing matrix effects. Field water samples from the Pearl River in Guangzhou, China were analyzed, and the frequent detection of neonicotinoids raises concerns about their aquatic risk.     

Molecularly imprinted microspheres for the anticancer drug aminoglutethimide: Synthesis,characterization, and solid‐phase extraction applications in human urine samples

Molecularly imprinted microspheres (MIMs) for the anticancer drug aminoglutethimide (AG) were synthesized by aqueous suspension polymerization. The expected size and diameter of MIMs are controlled easily by changing one of the surfactant types, ratio of organic‐to‐water phase or stirring rate during polymerization. The obtained MIMs exhibit specific affinity toward AG with imprinting factor of 3.11 evaluated with a chromatographic model. The resultant MIMs were used as the SPE materials for the extraction of AG from human urine. A molecularly imprinted SPE (MISPE) method coupled with HPLC has been developed for the extraction and detection of AG in urine. Our results showed that most impurities from urine can be removed effectively after a washing step and the AG has been enriched effectively after MISPE operation with the recovery of >90% (n = 3). The developed MISPE–HPLC method could be used for enrichment and detection of AG in human urine.     

Analysis of microcystins using high‐performance liquid chromatography and magnetic solid‐phase extraction with silica‐coated magnetite with cetylpyridinium chloride

Microcystins (MCs), produced by freshwater cyanobacteria, can be serious water pollutants, so it is important to monitor their concentration in drinking water. We have developed a method for rapid and accurate determination of microcystin levels in environmental water, using magnetic solid‐phase extraction and high‐performance liquid chromatography with UV detection. The magnetic composite material, which was combined with cetylpyridinium chloride, was prepared by hydrothermal synthesis. The optimal extraction of microcystins in water sample was achieved by optimizing the amount of adsorbent, time of adsorption, ratio of eluting solvent, and volume of eluent. Under the optimal conditions, the limit of detection of MC‐LR was 0.001 μg/L, and the limit of quantification was 0.0028 μg/L. The limit of detection of MC‐RR was 0.001 μg/L, and the limit of quantification was 0.003 μg/L. These values are far lower than those established by the International Health Organization for the maximum concentration of microcystins in drinking water. The magnetic solid‐phase extraction adsorbent used in this method has the advantages of simple preparation, low price, and easy solid–liquid separation, and it can be used for the rapid and sensitive monitoring of trace microcystins in environmental water samples.     

Determination of ultraviolet filter compounds in environmental water samples using membrane‐protected micro‐solid‐phase extraction

A method based on membrane‐protected micro‐solid‐phase extraction coupled with gas chromatography and mass spectrometry was developed for the determination of six ultraviolet filter compounds in various aqueous media. Multiwalled carbon nanotubes as the sorbent were encapsulated in a sealed polypropylene membrane packet and immersed in the sample to extract the analytes, and then dichloromethane was used for desorption purpose. The method was sensitive enough for quantitative analysis of the target analytes, with limits of quantification between 0.01 and 0.06 μg/L, and produced a linear response (R² > 0.991) over the calibration range (0.05–6 μg/L). The obtained reproducibility was practically suitable with relative standard deviation values of less than 14% in pure water (spiked at 0.20/μg L) and less than 15% in real samples. The optimized method was applied for the analysis of real water samples with varying matrix complexity: tap, river, and dam water; geothermal spa; and sewage treatment plant effluent. Various levels and patterns of contamination were observed in the examined samples, while the sample from spa was the most contaminated, regarding the target analytes. Matrix spikes and matrix spike replicates were also analyzed to validate the technique for analysis of real aqueous samples, and satisfactory results were achieved.     

Preconcentration of indapamide from human urine using molecularly imprinted solid‐phase extraction

A simple, sensitive, and selective molecularly imprinted solid‐phase extraction and spectrophotometric method has been developed for the clean‐up and preconcentration of indapamide from human urine. Molecularly imprinted polymers were prepared by a non‐covalent imprinting approach using indapamide as a template molecule, 2‐(trifluoromethyl) acrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, N,N‐azobisisobutyronitrile as a thermal initiator and acetonitrile as a porogenic solvent. A non‐imprinted polymer was also prepared in the same way, but in the absence of template. Molecularly imprinted polymer and non‐imprinted polymer sorbents were dry‐packed into solid‐phase extraction cartridges. Eluates from cartridges were analyzed using a spectrophotometer for the determination of indapamide by referring to the calibration curve in the range 0.14–1.50 μg/mL. Preconcentration factor, limit of detection, and limit of quantification were 16.30, 0.025 μg/mL, and 0.075 μg/mL, respectively. A relatively high imprinting factor (9.3) was also achieved and recovery values for the indapamide spiked into human urine were in the range of 80.1–81.2%. In addition, relatively low within‐day (0.17–0.42%) and between‐day (1.1–1.4%) precision values were obtained as well. The proposed molecularly imprinted solid‐phase extraction and spectrophotometric method was successfully applied to selective extraction, preconcentration, and determination of indapamide from human urine samples.     

Extraction of phenolic compounds from water samples by dispersive micro‐solid‐phase extraction

In this article, the use of magnetically separable sorbent polyaniline/silica‐coated nickel nanoparticles is evaluated under a dispersive micro‐solid‐phase extraction approach for the extraction of phenolic compounds from water samples. The sorbent was prepared by in situ chemical polymerization of aniline on the surface of silica‐modified nickel nanoparticles and was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, X‐ray powder diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectrometry, and vibrating sample magnetometry. Effective variables such as amount of sorbent (milligrams), pH and ionic strength of sample solution, volume of eluent solvent (microliters), vortex, and ultrasonic times (minutes) were investigated by fractional factorial design. The significant variables optimized by a Box–Behnken design were combined by a desirability function. Under the optimized conditions, the calibration graphs of analytes were linear in a concentration range of 0.02–100 μg/mL, and with correlation coefficients more than 0.999. The limits of detection and quantification were in the ranges of 10–23 and 33–77 μg/L, respectively. This procedure was successfully employed in the determination of target analytes in spiked water samples; the relative mean recoveries ranged from 96 to 105%.     

Selective determination of alkylmercury compounds in solid matrices after subcritical water extraction,followed by solid‐phase microextraction and GC–MS

A method for the extraction and determination of methylmercury (MeHg) in solid matrices is presented. Combining the advantages of two extraction techniques—subcritical water extraction (subWE) and solid‐phase microextraction (SPME)—selective separation of MeHg from soils is possible. The procedure is based on extraction with subcritical water without using organic solvents, followed by in situ aqueous‐phase derivatization with sodium tetraethylborate and headspace SPME with a silica fiber coated with poly(dimethylsiloxane). The optimization of the extraction parameters is described. The identification and quantification of the extracted alkylmercury compounds from spiked soil samples is performed by GC–MS after thermal desorption. Copyright © 2000 John Wiley & Sons, Ltd.     

Two‐dimensional solid‐phase extraction strategy for the selective enrichment of aminoglycosides in milk

An orthogonal two‐dimensional solid‐phase extraction strategy was established for the selective enrichment of three aminoglycosides including spectinomycin, streptomycin, and dihydrostreptomycin in milk. A reversed‐phase liquid chromatography material (C₁₈) and a weak cation‐exchange material (TGA) were integrated in a single solid‐phase extraction cartridge. The feasibility of two‐dimensional clean‐up procedure that experienced two‐step adsorption, two‐step rinsing, and two‐step elution was systematically investigated. Based on the orthogonality of reversed‐phase and weak cation‐exchange procedures, the two‐dimensional solid‐phase extraction strategy could minimize the interference from the hydrophobic matrix existing in traditional reversed‐phase solid‐phase extraction. In addition, high ionic strength in the extracts could be effectively removed before the second dimension of weak cation‐exchange solid‐phase extraction. Combined with liquid chromatography and tandem mass spectrometry, the optimized procedure was validated according to the European Union Commission directive 2002/657/EC. A good performance was achieved in terms of linearity, recovery, precision, decision limit, and detection capability in milk. Finally, the optimized two‐dimensional clean‐up procedure incorporated with liquid chromatography and tandem mass spectrometry was successfully applied to the rapid monitoring of aminoglycoside residues in milk.     

Magnetic solid‐phase extraction of tobacco‐specific N‐nitrosamines using magnetic graphene composite as sorbent

Tobacco‐specific N‐nitrosamines are carcinogenic components in mainstream cigarette smoke. To explore tobacco‐specific N‐nitrosamine release levels in cigarettes, a magnetic solid‐phase extraction procedure using magnetic graphene composite as sorbent for fast enrichment of tobacco‐specific N‐nitrosamine was developed. Under optimal conditions, a tobacco‐specific N‐nitrosamine determination method was successfully proposed by combining magnetic solid‐phase extraction procedure and high‐performance liquid chromatography coupled with tandem mass spectrometry. The method's limit of detection for tobacco‐specific N‐nitrosamines in mainstream cigarette smoke ranged from 0.018 to 0.057 ng/cigarette. Good linearities were obtained with correlation coefficients above 0.9992. The accuracies of tobacco‐specific N‐nitrosamines in a spiked mainstream cigarette smoke sample were from 89.3 to 109.4%, with a relative standard deviation of less than 11.2%. The proposed method has the merits of rapidity and high sensitivity. Finally, the method was successfully applied to tobacco‐specific N‐nitrosamine analysis in real samples.     

Urinary l‐kynurenine quantification and selective extraction through a molecularly imprinted solid‐phase extraction device

l ‐Kynurenine is an endogenous metabolite generated by the catabolic pathway of l ‐tryptophan and it could be a potential biomarker to test the efficacy of several checkpoint inhibitors that have already reached the clinical trials in the antitumor therapy. Thus, a molecularly imprinted polymer specific for the recognition of this metabolite was synthesized and used as innovative system in solid‐phase extraction technique for the specific extraction and quantification of l ‐kynurenine in human urine. The off‐line system was firstly tested on l ‐kynurenine standard solutions, allowing recoveries up to 97.7% (relative standard deviation = 2.2%) and then applied to fortified and deproteinated human urine samples, where a recovery of 84.1% (relative standard deviation = 3.1%) was obtained. The method was validated and it revealed a good linearity in the range of 0.157–20 μg/mL (r² = 0.9992). The optimized procedure demonstrated a good feasibility on biological samples, allowing a ready quantification of l ‐kynurenine in the human urine, where the metabolite was found at a very low concentration (0.80 μg/mL). The extraction system developed could attract attention of pharmaceutical industries for l ‐kynurenine production as potential drug in the treatment of autoimmune disorders through its extraction and purification from biological matrixes.     

Multiresidue pesticides analysis in soils using modified QuEChERS with disposable pipette extraction and dispersive solid‐phase extraction

QuEChERS original method was modified into a new version for pesticides determination in soils. The QuEChERS method is based on liquid–liquid portioning with ACN and was followed by cleanup step using dispersive SPE and disposable pipette tips. Gas chromatographic separation with MS detection was carried out for pesticides quantification. The method was validated using recovery experiments for 36 multiclass pesticides. Mean reco‐veries of pesticides at each of the four spiking levels between 10–300 μg/kg of soil ranged from 70–120% for 26 pesticides with RSD values less than 15%. The method achieved low limit of detection less than 7.6 μg/kg. Matrix effects were observed for 13 pesticides. Matrix effects were compensated by using matrix‐matched calibration. The method was applied successfully using d‐SPE or DPX in the analysis of the pesticides in soils from organic farming and integrated pest management.     

Synthesis of a graphene‐based nanocomposite for the dispersive solid‐phase extraction of vancomycin from biological samples

The approach of this work was to study the capability of graphene‐based materials in the field of biological sample preparation. A polypyrrole/graphene composite was synthesized and characterized. The potential of the nanocomposite was investigated as a sorbent in dispersive solid‐phase extraction followed by high‐performance liquid chromatography with UV detection for vancomycin as a model drug. The effect of different parameters influencing extraction efficiency such as sample pH and sample volume, ionic strength, extraction time, type, and volume of desorption solvent and desorption time were investigated. A comparison study was also conducted between polypyrrole/graphene and some different novel and classic sorbents. Under optimized conditions, the calibration curve for vancomycin showed linearity in the range of 0.05–10 μg/mL. In addition, limits of detection, and quantification were 0.003 and 0.01 μg/mL, respectively. The intraday and interday relative standard deviations at a concentration of 0.05 μg/mL (n = 3) were 1.6 and 2.1%, respectively. Furthermore, the proposed method was successfully applied for the determination of vancomycin in plasma and urine samples. The relative recoveries indicated the feasibility of graphene‐based sorbents in biological sample analysis.     

Selective solid‐phase extraction using a molecularly imprinted polymer for the analysis of patulin in apple‐based foods

The aim of this work was to evaluate the use of a molecularly imprinted polymer as a selective solid‐phase extraction sorbent for the clean‐up and pre‐concentration of patulin from apple‐based food products. Ultra high pressure liquid chromatography coupled to ultraviolet absorbance detection was used for the analysis of patulin. The molecularly imprinted polymer was applied, for the first time, to the determination of patulin in apple juice, puree and jam samples spiked within the maximum levels specified by the European Commission No. 1881/2006. High recoveries (>77%) were obtained. The method was validated and found to be linear in the range 2–100 μg/kg with correlation coefficients greater than 0.965 and repeatability relative standard deviation below 11% in all cases. Compared with dispersive solid‐phase extraction (QuEChERS method) and octadecyl sorbent, the molecularly imprinted polymer showed higher recoveries and selectivity for patulin. The application of Affinisep molecularly imprinted polymer as a selective sorbent material for detection of patulin fulfilled the method performance criteria required by the Commission Regulation No. 401/2006, demonstrating the suitability of the technique for the control of patulin at low ppb levels in different apple‐based foods such as juice, puree and jam samples.     

Sulfonated poly(styrene‐divinylbenzene) modified with amines and the application for pipette‐tip solid‐phase extraction of carbendazim in apples

Sulfonated poly(styrene‐divinylbenzene) modified with five kinds of amine functional groups was applied to the determination of carbendazim in apple samples with a pipette‐tip solid‐phase extraction method. The structures of the polymers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Five different modifications of the solid‐phase extraction sorbent based on sulfonated poly(styrene‐divinylbenzene) were tested under static and pipette‐tip solid‐phase extraction conditions. The polymer modified with p‐methoxyaniline showed the best recognition capacity and adsorption amount for carbendazim. Under the optimum conditions, 3.00 mg of the adsorbent, 1.00 mL of ethyl acetate as washing solvent, and 1.00 mL of ammonia/acetonitrile (5:95, v/v) as elution solvent were used in the pretreatment procedure of apple samples. The calibration graphs of carbendazim in methanol were linear over 5.00–200.00 μg/mL, and the limits of detection and quantification were 0.01 and 0.03 μg/mL, respectively. The method recoveries of carbendazim were in the range of 91.31–98.13% with associated intraday relative standard deviations of 0.76–2.13% and interday relative standard deviations of 1.10–1.85%. Sulfonated poly(styrene‐divinylbenzene) modified with p‐methoxyaniline showed satisfactory results (recovery: 97.96%) and potential for the rapid purification of carbendazim in apple samples combined with the pipette‐tip solid‐phase extraction.     

Synthesis,characterization and solid‐phase extraction properties of novel bis(diazo‐azomethine) ligands supported on mesoporous silica

The novel mesoporous silica‐supported bis(diazo‐azomethine) compounds have been synthesized and characterized successively. In the first step, 1,3‐phenylenedimethanamine and 4,4′‐diaminodiphenylmethane were diazotized, and the obtained bis(diazonium) cations were coupled with 2,4‐dihydroxybenzaldehyde. The synthesized bis(diazo‐carbonyl) compounds, 5,5′‐((1,3‐phenylenebis(methylene))bis(diazene‐2,1‐diyl))bis(2,4‐dihydroxybenzaldehyde) (A1) and 5,5′‐((methylenebis(4,1‐phenylene))bis(diazene‐2,1‐diyl))bis(2,4‐dihydroxybenzaldehyde) (A2) were chemically supported on amino‐modified silica‐gel (as L1 and L2). Elemental analysis, liquid chromatography‐mass spectroscopy, liquid‐phase NMR (¹H and ¹³C) and solid‐phase NMR (CP‐MAS ²⁹Si and ¹³C), FT‐IR, TG/DTA, scanning electron microscopy and energy‐dispersive X‐ray spectroscopy techniques were used for characterizations of all the synthesized compounds. The syringe and batch techniques were applied for the solid‐phase extraction properties of Pb(II), Cu(II), Cd(II) and Cr(III) ions using an inductively coupled plasma‐atomic emission spectroscopy instrument. The recoveries of Pb(II), Cu(II), Cd(II) and Cr(III) ions have been achieved to 95–99% with the (RSDs) of ± 2–3% in optimum conditions.     

Synthesis of molecularly imprinted polymer adsorbents for solid‐phase extraction of strobilurin fungicides from agricultural products

Molecularly imprinted polymers for strobilurin fungicides were prepared by precipitation polymerization employing azoxystrobin as template molecular together with methacrylic acid monomer and trimethylolpropane triacrylate cross‐linker. Morphological characterization showed molecularly imprinted polymers were uniform spherical particles with about 0.2 μm in diameter, while the morphologies of nonimprinted polymers were irregular bulk. The equilibrium binding and selective experiments proved that molecularly imprinted polymers possessed a higher affinity toward four fungicides compared to nonimprinted polymers and heterogeneous binding sites were found in the molecularly imprinted polymers. Molecularly imprinted solid‐phase extraction conditions, including sample loading solvents, selective washing, and elution solvents, were carefully optimized. The developed method showed good recoveries (70.0–114.0%) with relative standard deviations in range of 1.0–9.8% (n  =  3) for samples (cucumber and peach) spiked at three different levels (10, 50, and 100 μg/ kg). The detection limit (signal/noise = 3) ranged from 0.01 to 0.08 μg/kg. The results demonstrated good potential use of this convenient and highly efficient method for determining trace strobilurin fungicides in agricultural products.