Carbon nanospheres as solid‐phase microextraction coating for the extraction of polycyclic aromatic hydrocarbons from water and soil samples

A solid‐phase microextraction with carbon nanospheres coated fiber coupled with gas chromatographic detection was established for the determination of eight polycyclic aromatic hydrocarbons (naphthalene, biphenyl, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene, and pyrene) in water and soil samples. The experimental parameters (extraction temperature, extraction time, stirring rate, headspace volume, salt content, and desorption temperature) which affect the extraction efficiency were studied. Under the optimized conditions, good linearity between the peak areas and the concentrations of the analytes was achieved in the concentration range of 0.5‐300 ng/mL for water samples, and in the concentration range of 6.0‐2700 ng/g for soil samples. The detection limits for the analytes were in the range of 0.12‐0.45 ng/mL for water samples, and in the range of 1.53‐2.70 ng/g for soil samples. The method recoveries of the polycyclic aromatic hydrocarbons for spiked water samples were 80.10‐120.1% with relative standard deviations less than 13.9%. The method recoveries of the analytes for spiked soil samples were 80.40‐119.6% with relative standard deviations less than 14.4%. The fiber was reused over 100 times without a significant loss of extraction efficiency.     

An in situ electrochemical fabrication of layer by layer graphenized graphite polyaniline as a stable solid‐phase microextraction fiber coating for trace environmental analysis

A layer by layer graphenized graphite/polyaniline coating was fabricated on commercial pencil lead substrate by an in situ facile, fast and efficient electrochemical procedure. The electrodeposited polyaniline film on surface‐confined graphene structure can integrate the advantages of the both layers and was used for solid‐phase microextraction. Effective experimental parameters in electrochemical production of graphene nanosheets and electropolymerization of aniline were optimized. The prepared fiber was used for extraction and determination of four polycyclic aromatic hydrocarbons: phenanthrene, anthracene, fluoranthene and pyrene in aqueous samples by high performance liquid chromatography. The fiber coating was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscopy. Under the optimized conditions, the coating provided good linear ranges (0.10–25 μg/L for phenanthrene, 0.05–12.5 μg/L for anthracene, 0.825–99 μg/L for fluoranthene and 0.625–75 μg/L for pyrene (R² = 0.999)) and limits of detection, 0.016 to 0.275 μg/L. The produced coating has several attractive features such as high stability, low cost and long operation time.     

Polypyrrole–montmorillonite nanocomposite as sorbent for solid‐phase microextraction of phenolic compounds in water

A fiber‐coated polypyrrole–montmorillonite nanocomposite was prepared for solid‐phase microextraction. The fiber coating can be prepared easily; it is mechanically stable and exhibits relatively high thermal stability. The prepared fiber was evaluated for the extraction of some phenolic compounds from aqueous sample solutions by gas chromatography–mass spectrometry. The effects of the extraction and desorption parameters including extraction time, extraction temperature, stirring rate, ionic strength, pH and desorption temperature and time have been studied. At optimum conditions, the repeatability for one fiber (n = 5), expressed as % relative standard deviation was between 6.5 and 7.8% for the phenolic compounds. The detection limits for the studied phenolic compounds were between 0.05–1.3 ng/mL. The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost, thermal stability of the fibers, and high relative recovery in comparison to conventional methods of analysis.     

Electrospun magnetic polybutylene terephthalate nanofibers for thin film microextraction

A thin film microextraction method using elecrospun magnetic polybutylene terephthalate nanofibers is developed and implemented to isolate some selected triazines. Due to the high mechanical stability of these nanofibers, they are repeatedly used under harsh magnetic stirring and ultrasonic conditions without any damage and structure degradation. The presence of magnetic nanoparticles within the nanofiber structure increases the extraction efficiency while the fibers could be collected by an external magnet. The synthesized nanocomposite showed strong affinity toward the selected analytes. Apart from the concentration of magnetic nanoparticles within the nanocomposite network, the effect of different parameters on the extraction and desorption processes including the sample pH, extraction time, sample volume, type of desorption solvent, solvent volume, and desorption time were optimized. Eventually, the detection limits were in the range of 0.02–0.05 ng/mL, while the limits of quantification were between 0.1 and 0.2 ng/mL. The linear dynamic range was 0.1–100 ng/mL, and the relative standard deviations were 4–9% (n =  3). The developed method was extended to the real water samples, and the relative recoveries were in the range of 86–103%, indicating that the prepared sorbent is suitable for extraction of triazines from environmental samples.     

Magnetic solid-phase extraction of organophosphorus pesticides from apple juice and environmental water samples using magnetic graphene oxide coated with poly(2-aminoterephthalic acid-co-aniline) nanocomposite as a sorbent

An effective magnetic solid-phase extraction method was proposed using magnetic graphene oxide coated with poly(2-aminoterephthalic acid-co-aniline) as a sorbent for preconcentration and extraction of organophosphorus pesticides from environmental water and apple juice samples, and determined using the gas chromatography-mass spectrometry analysis. To approve the successful synthesis of the magnetic nanocomposite, the prepared sorbent was characterized by field emission scanning electron microscopy, X-ray diffraction, vibrating sample magnetometer, and Fourier transforms infrared techniques. The main parameters affecting the extraction efficiency were considered and studied to afford an optimized procedure. Systematic method validation verified its suitable recoveries (89.4–107.3%), and precision (relative standard deviations < 6.8%). The method showed a wide linear dynamic range (0.04–700 ng/mL) with low limits of detection (0.01–0.06 ng/mL) and quantification (0.04–0.21 ng/mL). This method presented good potential and great sensitivity for the pesticides determination.     

Fabrication of boronate‐decorated polyhedral oligomeric silsesquioxanes grafted cotton fiber for the selective enrichment of nucleosides in urine

Various cotton fiber based boronate‐affinity adsorbents are recently developed for the sample pretreatment of cis‐diol‐containing biomolecules, but most do not have efficient capacity due to limited binding sites on the surface of cotton fibers. To increase the density of boronate groups on the surface of cotton fiber, polyhedral oligomeric silsesquioxanes were used to modify cotton fiber to provide plentiful reactive sites for subsequent functionalization with 4‐formylphenylboronic acid. The new adsorbent showed special recognition ability towards cis‐diols and high adsorption capacity (175 μg/g for catechol, 250 μg/g for dopamine, 400 μg/g for adenosine). The in‐pipette‐tip solid‐phase extraction was investigated under different conditions, including pH and ionic strength of solution, adsorbent amount, pipette times, washing solvent, and elution solvent. The in‐pipette‐tip solid‐phase extraction coupled with high‐performance liquid chromatography was used to analyze four nucleosides in urine samples. Under the optimal extraction conditions, the detection limits were determined to be between 5.1 and 6.1 ng/mL (S/N  =  3), and the linearity ranged from 20 to 500 ng/mL for these analytes. The accuracy of the analytical method was examined by studying the relative recoveries of analytes in real urine samples with recoveries varying from 83 to 104% (RSD = 3.9–10.2%, n = 3).     

微孔有机聚合物固相微萃取纤维的制备及在有机氯农药检测中的应用

利用1,3,6,8-四(4-醛基)芘和三聚氰胺为单体合成微孔有机聚合物(MOP),并将其固定在不锈钢丝上,制备成固相微萃取纤维涂层。将其用于顶空固相微萃取(HS-SPME),结合气相色谱-电子捕获检测手段,建立了对大米中有机氯农药的在线检测方法。实验考察了4种实验参数对富集能力的影响,得到了最优的实验条件:萃取温度80℃、萃取时间25 min、NaCl质量浓度200 g/L、解吸时间6 min。在此实验条件下,对有机氯农药的富集倍数达到115~318倍。方法在0.05~50μg/kg范围内具有良好的线性关系,检出限为2.4~11.3 ng/kg。同一纤维及不同纤维富集后测定结果的相对标准偏差范围分别为1.3%~13.1%和2.3%~13.6%。该方法简单、快速,可以实现对实际样品中有机氯农药的痕量分析。     

Application of a new fiber coating based on electrochemically reduced graphene oxide for the cold‐fiber headspace solid‐phase microextraction of tricyclic antidepressants

A new fiber based on the electrochemical reduction of graphene oxide was prepared on a copper wire for solid‐phase microextraction (SPME) applications. The prepared fiber was used for the SPME and gas chromatographic analysis of tricyclic antidepressants (TCADs), including amitriptyline, trimipramine, and clomipramine. The feasibility of direct‐immersion and headspace modes of SPME for the determination of TCADs was studied. The effects of four parameters including pH, salt content, extraction temperature with and without cooling the fiber, and extraction time were investigated. The comparison showed that headspace cold fiber SPME results in the best outcome for the extraction of TCADs. Under the optimized conditions of this mode, the calibration curves were linear between 2.0 and 500 ng/mL and the detection limits were between 0.30 and 0.53 ng/mL. The intraday and interday RSDs obtained at 20 ng/mL (n = 5), using a single fiber, were 5.5–9.0 and 7.5–9.8, respectively. The fiber to fiber repeatability (n = 4), expressed as the RSD, was between 12.8 and 13.2% at a 20 ng/mL concentration level. The method was successfully applied to the analysis of TCADs in plasma samples showing recoveries from 73 to 96%.     

A novel strategy to increase performance of solid‐phase microextraction fibers: Electrodeposition of sol‐gel films on highly porous substrate

In the present work, the effect of substrate porosity for preparation of solid‐phase microextraction (SPME) fibers was investigated. The fibers were prepared by electrodeposition of sol‐gel coatings using negative potentials on porous Cu wire and compared with previous reported technique for preparation of SPME fibers using positive potentials on smooth gold wire. Porous substrate was prepared by electrodeposition of a thin layer of Cu on a Cu wire. The extraction capability of prepared fibers was evaluated through extraction of some aromatic hydrocarbons from the headspace of aqueous samples. The effect of substrate porosity and some operating parameters on extraction efficiency was optimized. The results showed that extraction efficiency of SPME fibers highly depends on porosity of the substrate. The LOD ranged from 0.005 to 0.010 ng/mL and repeatability at the 1 ng/mL was below 12%. Electrodeposited films were characterized for their surface morphology and thermal stability using SEM and thermogravimetric analysis, respectively. SEM analysis revealed formation of porous substrate and subsequently porous coating on the wire surface and thermogravimetric analysis showed high thermal stability of the prepared fiber.     

Investigation of the continuous flow of the sample solution on the performance of electromembrane extraction: Comparison with conventional procedure

In this study, electromembrane extraction from a flowing sample solution, termed as continuous‐flow electromembrane extraction, was developed and compared with conventional procedures for the determination of four basic drugs in real samples. Experimental parameters affecting the extraction efficiency were further studied and optimized. Under optimum conditions, linearity of continuous‐flow procedure was within 8.0–500 ng/mL, while it was wider for conventional procedures (2.0–500 ng/mL). Moreover, repeatability (percentage relative standard deviation) was found to range between 5.6 and 10.4% (n  = 3) for the continuous‐flow procedure, with a better repeatability than that of conventional procedures (2.3–5.5% (n  = 3)). Also, for the continuous‐flow procedure, the estimated detection limit (signal‐to‐noise ratio = 3) was less than 2.4 ng/mL and extraction recoveries were within 8–10%, while the corresponding figures for conventional procedures were less than 0.6 ng/mL and 42–60%, respectively. Thus, the results showed that both continuous flow and conventional procedures were applicable for the extraction of model compounds. However, the conventional procedure was more convenient to use, and thus it was applied to determine sample drugs in real urine and wastewater samples.     

Improvement of solid‐phase microextraction efficiency by the application of a carbon‐nanotubes‐based ternary microextraction fiber composite

In this study, a novel technique is proposed for preparation of an efficient and unbreakable metal‐wire‐supported solid‐phase microextraction fiber. A sol–gel film was deposited on electrophoretically deposited carbon nanotubes on a stainless‐steel wire. The applicability of the fiber was evaluated through the extraction of some aromatic pollutants as model compounds from the headspace of aqueous samples in combination with gas chromatography and mass spectrometry. The parameters affecting the structure and extraction efficiency of the fiber (including the type of solvent, time, and potential for electrophoretic deposition) and the parameters affecting the extraction efficiency (such as coating type, salt content, extraction temperature, and time) were investigated. The results showed that the film thickness will be increased by increasing the potential and time duration. Finally, the characterization of the deposited film was accomplished by scanning electron microscopy and thermogravimetric analysis. After the optimization of the extraction parameters, the limit of detection of less than 20 pg/mL was achieved, and the calibration curves were all linear (r ² ≥ 0.9737), in the range from 50 to 500 pg/mL. The solid‐phase microextraction fiber has a high mechanical strength; good stability and long service life, making it potentially applicable in the extraction of trace polycyclic aromatic hydrocarbons from aqueous samples.     

Development of a simple and valid method for the trace determination of phthalate esters in human plasma using dispersive liquid–liquid microextraction coupled with gas chromatography–mass spectrometry

A new method was developed for the trace determination of phthalic acid esters in plasma using dispersive liquid–liquid microextraction and gas chromatography with mass spectrometry analysis. Plasma proteins were efficiently precipitated by trichloroacetic acid and then a mixture of chlorobenzene (as extraction solvent) and acetonitrile (as dispersive solvent) rapidly injected to clear supernatant using a syringe. After centrifuging, chlorobenzene sedimented at the bottom of the test tube. 1 μL of this sedimented phase was injected into the gas chromatograph for phthalic acid esters analysis. Different factors affecting the extraction performance, such as the type of extraction and dispersive solvent, their volume, extraction time, and the effects of salt addition were investigated and optimized. Under the optimum conditions, the enrichment factors and extraction recoveries were satisfactory and ranged between 820–1020 and 91–97%, respectively. The linear range was wide (50–1000 ng/mL) and limit of detection was very low (1.5–2.5 ng/mL for all analytes). The relative standard deviations for analysis of 1 μg/mL of the analytes were between 3.2–6.1%. Salt addition showed no significant effect on extraction recovery. Finally, the proposed method was successfully utilized for the extraction and determination of the phthalic acid esters in human plasma samples and satisfactory results were obtained.     

Magnetic solid‐phase extraction of polycyclic aromatic hydrocarbons in water samples by Fe3O4@polypyrrole/carbon nanotubes

A magnetic solid‐phase extraction method coupled with gas chromatography was proposed for the determination of polycyclic aromatic hydrocarbons in the environmental water samples. The magnetic adsorbent was prepared by incorporating Fe₃O₄ nanoparticles, multi‐walled carbon nanotubes, and polypyrrole. The main factors affecting the extraction efficiency including the amount of the sorbents, desorption conditions, extraction time, salt concentration, and sample solution pH were investigated and optimized. Under the optimum conditions, good linearity was obtained within the range of 0.03?100 ng/mL for all analytes, with correlation coefficients ranging from 0.9942 to 0.9973. The method detection limits (S/N = 3) were in the range of 0.01–0.04 ng/mL and the limits of quantification (S/N = 10) were 0.03–0.1 ng/mL. Repeatability of the method was assessed through five consecutive extractions of independently prepared solutions at concentrations of 0.1, 10, and 100 ng/mL of the compounds. The observed repeatability ranged 3.4–10.9% depending of the compound considered. The proposed method was successfully applied in the analysis of PAHs in environmental samples (tap, well, river, and wastewater). The recoveries of the method ranged between 93.4 and 99.0%. The procedure proved to be efficient and environmentally friendly.     

Ionic‐liquid‐mediated poly(dimethylsiloxane)‐ grafted carbon nanotube fiber prepared by the sol–gel technique for the head space solid‐phase microextraction of methyl tert‐butyl ether using GC

A headspace solid‐phase microextraction method was developed for the preconcentration and extraction of methyl tert‐butyl ether. An ionic‐liquid‐mediated multiwalled carbon nanotube–poly(dimethylsiloxane) hybrid coating, which was prepared by covalent functionalization of multiwalled carbon nanotubes with hydroxyl‐terminated poly(dimethylsiloxane) using the sol–gel technique, was used as solid‐phase microextraction adsorbent. This innovative fiber exhibited a highly porous surface structure, high thermal stability (at least 320°C) and long lifespan (over 210 uses). Potential factors affecting the extraction efficiency were optimized. Under the optimum conditions, the method LOD (S/N = 3) was 0.007 ng/mL and the LOQ (S/N = 10) was 0.03 ng/mL. The calibration curve was linear in the range of 0.03–200 ng/mL. The RSDs for one fiber (repeatability, n = 5) at three different concentrations (0.05, 1, and 150 ng/mL) were 5.1, 4.2, and 4.6% and for the fibers obtained from different batches (reproducibility, n = 3) were 6.5, 5.9, and 6.3%, respectively. The developed method was successfully applied to the determination of methyl tert‐butyl ether in different real water samples on three consecutive days. The relative recoveries for the spiked samples with 0.05, 1, and 150 ng/mL were between 94–104%.     

Molecularly imprinted polymer-sol-gel tablet toward micro-solid phase extraction: I. Determination of methadone in human plasma utilizing liquid chromatography–tandem mass spectrometry

In the present work molecularly imprinted sol-gel tablet (MIP-Tablet) was prepared. The MIP-sol-gel was prepared as a thin layer on polyethylene material in a tablet form. Methadone-d₉ was selected as the template and 3-(propylmethacrylate)-trimethoxysilane was used as precursor. MIP-Tablet was applied for micro-solid phase extraction (μ-SPE). The MIP-Tablet was used for the determination of methadone in human plasma samples utilizing liquid chromatography-tandem mass spectrometry; and each tablet could be used twenty times. The extraction time was 10 min while desorption time was 6 min. Factors affecting the extraction efficiency such as desorption solvents, sample pH, salt addition, extraction time, desorption time and adsorption capacity were investigated. The calibration curves were obtained within the range of 5–5000 ng/mL using methadone in human plasma samples. The coefficients of determination (r²) values were ≥0.999 for all runs and the extraction recovery was >80%. The accuracy values for quality control samples varied from +3.6 to +9.7% and the inter-day precision (RSD %) values were ranged from 5.0 to 8.0%. The limit of detection was 1.0 ng/mL and the lower limit of quantification was 5 ng/mL utilizing methadone in human plasma samples.     

Single-walled carbon nanotubes coated fibers for solid-phase microextraction and gas chromatography-mass spectrometric determination of pesticides in Tea samples

Using a single-walled carbon nanotubes (SWCNTs) as stationary phase of solid-phase microextraction (SPME) fibers, a simple, low cost and environmentally friendly method for extraction of 13 pesticides in Tea samples has been developed following gas chromatography-mass spectrometric determination. Potential factors affecting the extraction efficiency were investigated and optimized, including extraction and desorption time, extraction temperature, stirring rate, solution pH and ionic strength. Under optimized conditions, the linearity of the developed method was in the range of 0.125-25 ng/mL with correlation coefficients greater than 0.9928 and the limits of detections (LODs) were 0.027-0.23 ng/mL (S/N = 3). Meanwhile, the relative standard deviations (RSDs) for five successive measurements with single fiber, fiber-to-fiber, day-to-day were 2.3-13.0, 8.2-14.6 and 4.1-12.5%, respectively, indicating good reproducibility of the proposed method. The fiber had high extraction efficiency for studied pesticides in comparison with commercial poly(dimethylsiloxane) (PDMS) and polyacrylate (PA) fibers and could be used for more than 70 times without decrease of efficiency. The developed method was successfully applied for the analysis of real samples including green Tea, oolong Tea, white Tea, and flower Tea, and the recoveries of the pesticides spiked in these samples ranged from 75.1 to 118.4%. Chlorfenapyr and λ-cyhalothrin were found in the Tea samples bought randomly from local market. The results demonstrated that the developed SWCNTs-SPME method was a simple, efficient pretreatment and enrichment procedure for pesticides in complex matrices.     

Simple determination of some antidementia drugs in wastewater and human plasma samples by tandem dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography

In this work, a simple method, namely, tandem dispersive liquid–liquid microextraction, with a high sample clean‐up is applied for the rapid determination of the antidementia drugs rivastigmine and donepezil in wastewater and human plasma samples. This method, which is based on two consecutive dispersive microextractions, is performed in 7 min. In the method, using a fast back‐extraction step, the applicability of the dispersive microextraction methods in complicated matrixes is conveniently improved. This step can be performed in less than 2 min, and very simple tools are required for this purpose. To achieve the best extraction efficiency, optimization of the variables affecting the method was carried out. Under the optimized experimental conditions, the relative standard deviations for the method were in the range of 6.9–8.7%. The calibration curves were obtained in the range of 2–1100 ng/mL with good correlation coefficients, higher than 0.995, and the limits of detection ranged between 0.5 and 1.0 ng/mL.     

Fiber‐in‐tube solid‐phase microextraction of caffeine as a molecular tracer in wastewater by electrochemically deposited layered double hydroxide

Modified stainless‐steel wires with a layer of polyaniline conductive polymer were coated by electrochemical deposition with Zn/Al layered double hydroxide to make solid‐phase microextraction fibers. The coating layer was also electrochemically deposited on the inner surface of a stainless‐steel tube. Then, ten prepared fibers were put inside the inner coated tube to make a fiber‐in‐tube solid phase microextraction device. The device was applied for the extraction of caffeine (1,3,7‐trimethylxanthine) from domestic wastewater samples. Extraction conditions including extraction and desorption times, pH and ionic strength of the sample solution, and content of the organic desorption solvent were investigated and optimized. Under the optimized conditions, the fiber‐in‐tube solid phase microextraction exhibited excellent extraction efficiency toward caffeine. The precision of the method was evaluated. Average relative standard deviation of 5.7% (n = 6) for intraday analysis and 8.3% (n = 5) for interday analysis was obtained. The limits of detection and limits of quantification of the method (at signal to noise ratio of 3 and 10) were obtained as 0.14 and 0.37 ng/mL, respectively. The current study can provide new prospective applications of layered double hydroxide conductive polymer fiber coatings.     

Dispersive solid‐phase extraction for the determination of trace organochlorine pesticides in apple juices using reduced graphene oxide coated with ZnO nanocomposites as sorbent

In this work, reduced graphene oxide coated with ZnO nanocomposites was used as an efficient sorbent of dispersive solid‐phase extraction and successfully applied for the extraction of organochlorine pesticides from apple juice followed by gas chromatography with mass spectrometry. Several experimental parameters affecting the extraction efficiencies, including the amount of adsorbent, extraction time, and the pH of the sample solution, as well as the type and volume of eluent solvent, were investigated and optimized. Under the optimal experimental conditions, good linearity existed in the range of 1.0–200.0 ng/mL for all the analytes with the correlation coefficients (R ²) ranging from 0.9964 to 0.9994. The limits of detection of the method for the compounds were 0.011–0.053 ng/mL. Good reproducibilities were acquired with relative standard deviations below 8.7% for both intraday and interday precision. The recoveries of the method were in the range of 78.1–105.8% with relative standard deviations of 3.3–6.9%.     

Facile preparation of multifunctional carbon nanotube/magnetite/polyaniline nanocomposite offering a strong option for efficient solid‐phase microextraction coupled with GC–MS for the analysis of phenolic compounds

The aim of this study was to synthesize a highly efficient organic–inorganic nanocomposite. In this research, the carbon nanotube/magnetite/polyaniline nanocomposite was successfully prepared through a facile route. Monodisperse magnetite nanospheres were prepared through the coprecipitation route, and polyaniline nanolayer as a modified shell with a high surface area was synthesized by an in situ growth route and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, and energy‐dispersive X‐ray spectroscopy. The prepared nanocomposite was immobilized on a stainless‐steel wire for the fabrication of the solid‐phase microextraction fiber. The combination of headspace solid‐phase microextraction using carbon nanotube/magnetite/polyaniline nanocomposite fiber with gas chromatography and mass spectrometry can achieve a low limit of detection and can be applied to determine phenolic compounds in water samples. The effects of the extraction and desorption parameters including extraction temperature and time, ionic strength, stirring rate, pH, and desorption temperature and time have been studied. Under the optimum conditions, the dynamic linear range was 0.01–500 ng/mL and the limits of detection of phenol, 4‐chlorophenol, 2,6‐dichlorophenol, and 2,4,6‐trichlorophenol were the lowest (0.008 ng/mL) for three times. The coefficient of determination of all calibration curves was more than 0.990.