Solid-phase Microextraction Fiber Research Articles

A porous aromatic framework as a versatile fiber coating for solid-phase microextraction of polar and nonpolar aromatic organic compounds

A porous aromatic framework (PAF) derived from triphenylamine (type PAF-41) was prepared and is shown to be a viable coating for fibrous solid-phase microextraction (SPME). PAF-41 can be easily synthesized and has a high surface area, a rich π-electron structure, and electron-rich nitrogen atoms in its framework. The PAF-41-coated fibrous SPME extractor was combined with a gas chromatographic separation and flame ionization detection. The method was applied to the quantitation of some aromatic organic compounds (AOCs), including polar amphetamine and methamphetamine and nonpolar ethylbenzene, o-, m- and p-xylenes, andstyrene. The method was optimized after which a linear response is found for the 10-500ng·mL-1 amphetamine and methamphetamine concentration ranges. The limits of detection are 1.0 and 0.5ng·mL-1; and relative standard deviations for six repeated extractions with a single fiber are 5.3 and 6.7%. The method was applied for the determination of amphetamine and methamphetamine in spiked urine samples without any pretreatment except for dilution with water. The PAF-41 modified fiber also was applied to the extraction of styrene, xylenes and ethylbenzene. The enrichment capacities of the extractor for these AOCs were superior to those of commercial SPME extractors. Graphical abstract (a) Schemetic of the PAF-41-coated solid-phase microextraction (SPME) fiber.(b) Scanning electron microscope images of the PAF-41fiber.

Rapid detection of pesticides in honey by solid-phase micro-extraction coupled with electrospray ionization mass spectrometry.

Detection of pesticide residues in food samples is important for safeguarding food quality and safety. Conventional approaches for detection of pesticides in food samples typically involve labour-intensive and time-consuming sample pretreatment and chromatographic separation. In this study, solid phase micro-extraction fibres were used to rapidly extract and enrich pesticides in honey, a popular agricultural product with complex matrix, and then directly coupled with electrospray ionization mass spectrometry for qualitative and quantitative analysis. Three pesticides, ie, atrazine, benalaxyl, and pirimicarb, were investigated using the technique and their analytical performances were evaluated. The limits of detection and limits of quantitation of all the three pesticides could fulfil the cut-off values of the international standard. Linear calibration curves were constructed with good R2 coefficients, and the accuracy and precision were in acceptable ranges for all the pesticides. The analysis time is much reduced, with only minimum sample preparation and no chromatographic separation involved. The technique is simple and easy to set up, and can be extended for analysis of other analytes and sample systems.

Sol–gel based metal-organic framework zeolite imidazolate framework-8 fibers for solid-phase microextraction of nitro polycyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons in water samples

In this study, three kinds of Zeolite imidazolate framework-8 (ZIF-8), synthesized by solvothermal, stirring and ball-milling method, were fabricated on the stainless steel wire via sol-gel technique. These fibers were used as solid phase microextraction (SPME) coating materials and applied for analyzing 16 polycyclic aromatic hydrocarbons (PAHs) and 11 nitro polycyclic aromatic hydrocarbons (NPAHs) in environmental water samples by gas chromatography-tandem mass spectrometry (GC–MS). The optimal pH, ionic strength, extraction time, extraction temperature, desorption temperature and desorption time were 6.0, without salt addition, 45 min, 35 °C, 260 °C and 5 min, respectively. The extraction mechanism of the ZIF-8 fiber might be the hydrophobicity, molecular penetration and π-π stacking interactions. Under the optimized conditions, the as-proposed fiber provides a wide linearity range from 10 to 20,000 ng L−1 and a low detection limit of 0.3–27.0 ng L−1 for PAHs and NPAHs analysis. The single fiber and fiber to fiber relative standard deviations were observed in the range of 3.0%–13.9% and 3.5%–12.3%, respectively. The method shows great potential in environmental analysis field.

Hybrid Organosilica Coatings for Solid Phase Microextraction: Highly Efficient Adsorbents for Determination of Trace Parabens

New hybrid organosilica coatings with different amount of alkyl functional groups on a quartz fiber for solid phase microextraction (SPME) have been obtained by the of sol–gel synthesis in the presence of polyethylene glycol (PEG). The structural-sorption properties of the synthesized silica coatings of various compositions have been studied. According to the thermogravimetric analysis, the main thermolysis of the adsorption coatings’ organic layer was observed at temperatures higher than 350°C. The effect of synthesis conditions on the thermal stability of the obtained PEG-based organosilica coating has been studied. It has been established that the textural characteristics of the produced coatings for SPME and their adsorption properties can be controlled using different PEG and silica precursors and the equivalence ratio in the reaction mixture. Good prospects of application of the fabricated coatings for SPME have been demonstrated in paraben extraction and concentration in aqueous solutions at 24°C and pH 3.0–5.5 with their subsequent gas chromatography determination. The suggested technique was characterized by good accuracy and reproducibility (RSD ≤ 2.3%). Comparative studies of the obtained hybrid organosilica coatings for SPME with a commercially available fiber with a bipolar polymer coating—divinylbenzene/carboxen/polydimethylsiloxane—have been conducted.

Space-Resolved Tissue Analysis by Solid-Phase Microextraction Coupled to High-Resolution Mass Spectrometry via Desorption Electrospray Ionization.

It is hard to overstate the tremendous utility of desorption electrospray ionization (DESI) and its various configurations for rapid and high-throughput analyses or spatially resolved imaging of heterogeneous systems. However, there have been few attempts to employ this technique in spatially resolved mode with solid substrates featuring extractive and analyte-enrichment properties. This study documents the development of a platform that combines solid-phase microextraction (SPME) with desorption electrospray ionization mass spectrometry (DESI-MS) for unidimensional investigation of the heterogeneous distribution of compounds in semisolid systems (i.e., depth profiling across the fiber axis), with the ultimate end of employing it for brain tissue analysis. To this end, a DESI interface and a custom holder accommodating SPME probes were built in house, with the latter contributing to reduction of mechanical sources of signal instability. The system was evaluated through the quantitative reconstruction of the laminar and radial concentration gradients of xenobiotics introduced in multilayer gel arrangements and surrogate brain tissue models. Good quantitative capability was achieved by employing a strategy that combined signal correction via preloading internal standard onto SPME fibers and signal integration in scan-by-scan mode. The proposed technique's suitability for characterizing more complex systems, such as rat brains ex vivo, was also evaluated. The proposed approach allows for fast and noninvasive probing of three-dimensional objects without the need for their slicing, and the space-resolved mode reduces the number of required probe insertions, allowing in vivo applications. We foresee suitability of this setup for examining the spatial patterns of local drug release in the brain and the extent of the resultant physiological responses.

Preparation and application of molecularly imprinted polymer solid-phase microextraction fiber for the selective analysis of auxins in tobacco.

As signal molecules, auxins play an important role in mediating plant growth. Due to serious interfering substances in plants, it is difficult to accurately detect auxins with traditional solid-phase extraction methods. To improve the selectivity of sample pretreatment, a novel molecularly imprinted polymer -coated solid-phase microextraction fiber, which could be coupled directly to high-performance liquid chromatography, was prepared with indole acetic acid as template molecule for the selective extraction of auxins. The factors influencing the polymer formation, such as polymerization solvent, cross-linker, and polymerization time, were investigated in detail to enhance the performance of indole acetic acid-molecularly imprinted polymer coating. The morphological and chemical stability of this molecularly imprinted polymer-coated fiber was characterized by scanning electron microscopy, infrared spectrometry, and thermal analysis. The extraction capacity of the molecularly imprinted polymer-coated solid-phase microextraction fiber was evaluated for the selective extraction of indole acetic acid and indole-3-pyruvic acid followed by high-performance liquid chromatography analysis. The linear range for indole acetic acid and indole-3-pyruvic acid was 1-100µg/L and their detection limit was 0.5µg/L. The method was applied to the simultaneous determination of two auxins in two kinds of tobacco (Nicotiana tabacum L and Nicotiana rustica L) samples, with recoveries range from 82.1 to 120.6%.

Triazine-based porous organic framework as adsorbent for solid-phase microextraction of some organochlorine pesticides

Triazine-based porous organic frameworks (POFs) were constructed through a Friedel-Crafts reaction of cyanuric chloride (CC) with triphenylamine (TPA) monomers. The obtained POFs (CC-TPAs) were explored as the solid-phase microextraction (SPME) fiber coatings for the extraction of the organochlorine pesticides (OCPs). It was found that the mesoporous volume of the CC-TPAs was the main factor for their SPME adsorption performance. The CC-TPA-based fiber was successfully used for the SPME of the OCPs from fruit samples (apple, peach and pear). With the help of gas chromatography-micro-electron capture detection, the CC-TPA-based SPME method showed high enrichment factors (146–456), low limits of detection (0.032–0.090 ng g−1), good linearity (0.11–20 ng g−1, r2 > 0.991) and satisfactory repeatability (relative standard deviations <10.5%) for the OCPs. The method recoveries for spiked OCPs at the concentrations of 0.5, 2.0 and 10.0 ng g-1 in fruit samples were in the range of 86.0–114.0%, 83.5–116.5% and 81.1–118.6%, respectively. The CC-TPA coated fiber was stable enough for 100 extraction cycles without significant loss of the extraction efficiency.

Preconcentration and Determination Of Fluoxetine and Norfluoxetine in Biological and Water Samples with β-cyclodextrin Multi-walled Carbon Nanotubes as a Suitable Hollow Fiber Solid phase Microextraction Sorbent and High Performance Liquid Chromatography

‒A simple, selective and sensitive hollow fiber solid phase microextraction (SPME) combined with HPLC for the determination of fluoxetine (FLX) and norfluoxetine (NFLX) in human urine and real water samples has been developed and fully validated. Two solid phase microextraction sorbents, β-cyclodextrin functionalized multi-walled carbon nanotubes (βCD-MWCNTs) and acyl chloride functionalized MWCNTs, were synthesized and placed in the surface and pores of polypropylene hollow fiber by sol‒gel technique. In order to compare the analytical performance of βCD-MWCNTs as a new SPME sorbent with acyl chloride functionalized MWCNTs and MWCNTs, the hollow fiber device was directly immersed into the sample solution under a magnetic stirring. The βCD-MWCNTs are quite effective for extraction of fluoxetine and norfluoxetine. The extraction parameters such as pH of donor phase, donor phase volume, stirring rate, extraction time, type and volume of desorption solvent, and desorption time were thoroughly optimized. Under optimal conditions, the proposed method shows good linearity in the range of 1‒340 and 0.9‒360 ng/mL with a correlation coefficients of 0.9952 and 0.9967, low limits of detection of 0.4 and 0.3 ng/mL, and the high pre-concentration factors of 144 and 151 for determination of FLX and NFLX, respectively. Usage of proposed method for determination of FLX and NFLX in human urine and real water samples demonstrated a promising, simple, selective and sensitive sample preparation and determination method that can be applied in routine analysis.

Direct coupling of solid phase microextraction with electrospray ionization mass spectrometry: A Case study for detection of ketamine in urine

Electrospray ionization mass spectrometry (ESI-MS) is a commonly used technique for analysis of various samples. Solid phase microextraction (SPME) is a simple and efficient technique that combines both sampling and sample preparation into one consolidated step, preconcentrating extracted analytes for ultra-sensitive analysis. Historically, SPME has been coupled with chromatography-based techniques for sample separation prior to analysis, however more recently, the chromatographic step has been omitted, with the SPME device directly coupled with the mass spectrometer. In this study, direct coupling of SPME with ESI-MS was developed, and extensively validated to quantitate ketamine from human urine, employing a practical experimental workflow and no extensive hardware modification to the equipment. Among the different fibers evaluated, SPME device coated with C18/benzenesulfonic acid particles was selected for the analysis due to its good selectivity and signal response. Different approaches, including desorption spray, dripping, desorption ESI and nano-ESI were attempted for elution and ionization of the analytes extracted using the SPME fibers. The results showed that the desorption spray and nano-ESI methods offered better signal response and signal duration than the others that were evaluated. The analytical performance of the SPME-nano-ESI-MS setup was excellent, including limit of detection (LOD) of 0.027 ng/mL, limit of quantitation (LOQ) of 0.1 ng/mL, linear range of 0.1–500.0 ng/mL (R2 = 0.9995) and recoveries of 90.8–109.4% with RSD 3.4–10.6% for three validation points at 4.0, 40.0 and 400.0 ng/mL, far better than the performance of conventional methods. The results herein presented, demonstrated that the direct coupling of SPME fibers with ESI-MS-based systems allowed for the simple and ultra-sensitive determination of analytes from raw samples such as human urine.

Simultaneous Determination of Cocaine and Metabolites in Human Plasma Using Solid Phase Micro-Extraction Fiber Tips C18 and UPLC-MS/MS.

The determination of cocaine (COC) and its metabolites ecgonine methyl ester (EME), benzoylecgonine (BZE), norcocaine (NCOC) and cocaethylene (CE) in human plasma is relevant in clinical and forensic toxicology. An efficient extraction and clean-up of plasma specimens for the simultaneous determination of BZE along with COC and basic metabolites is challenging due to their widely different polarities and ionization characteristics. Recently, biocompatible SPME LC tips C18 became commercially available. We applied SPME LC tips C18 to the simultaneous extraction of COC, BZE, EME, NCOC, and CE by direct immersion of the fiber in plasma diluted with a buffer at pH 8.0. Analytes were desorbed from the fiber to methanol containing formic acid and injected into a UPLC-MS/MS system. The assay was linear from 5 to 500 ng mL-1. Precision assays presented CV% in the range of 2.22 to 10.54%, and accuracy was in the range of 93.4-108.1%. The assay requires minimal quantities of plasma and organic solvents, allowing multiple extractions in parallel. Biocompatible SPME is a promising alternative for preparing biological samples prior to drug measurement by UPLC-MS/MS.

Determination of quercetin using a molecularly imprinted polymer as solid-phase microextraction sorbent and high-performance liquid chromatography

A novel sorbent for solid-phase microextraction (SPME) based on molecularly imprinted polymers (MIPs) was developed to determine of quercetin by high-performance liquid chromatography -UV detection (HPLC-UV). Sol-gel process as a simple method was used to prepare the sorbent. The combination of MIP and SPME increased the selectivity and stability of the SPME fiber. First, stainless steel (SS) wires were modified and then MIPs synthesized through a sol-gel method using 3-aminopropyltriethoxysilane (APTES) as a functional monomer and tetraethyl orthosilicate (TEOS) as a cross link agent. The prepared MIP was characterized by field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). Influential parameters on extraction efficiency were investigated and optimized. The maximum extraction efficiency was obtained under the optimum conditions including: pH 4.5, extraction time 30 min, stirring rate 500 rpm, desorption time 20 min and MeOH/AcOH (9:1 V/V) as a desorption solvent. The proposed method was found to be linear for the concentration range from 0.05 to 100 μg mL−1 with R2 = 0.9998. The limit of detection (LOD) was 9.94 ng mL−1. Relative standard deviations (RSD) (n = 6) using a single fiber and between fibers were 2.3 and 5.0%, respectively. The proposed MIP-SPME fiber was successfully applied for selective determination of quercetin in tea and coffee samples.

Preparation of restricted access molecularly imprinted polymers based fiber for selective solid-phase microextraction of hesperetin and its metabolites in vivo

A novel restricted access molecularly imprinted polymers (RAMIPs) fiber was developed for solid-phase microextraction (SPME) of hesperetin and its metabolites in livers of live rats in vivo. Hesperetin as the template, N-isopropylacrylamide as the functional monomer, ethylene glycol dimethyl acrylate as the crosslinker, 2,2-azobisisobutyonnitrile as initiator and bovine serum albumin as the restricted access material were applied in the preparation process. Scanning electron microscopy and Fourier transform infrared spectroscopy were applied to characterize the polymers. The adsorption experiments indicated that RAMIPs-SPME fibers performed high selective recognition property to hesperetin. The selectivity experiment indicated that the adsorption capacity and selectivity of RAMIPs-SPME fibers to hesperetin was higher than that of quercetin, luteolin and baicalein. Macromolecules elimination test showed RAMIPs-SPME fibers could eliminate 94.80%–98.96% of macromolecules, which indicated that RAMIPs-SPME fibers can be used to extract analytes directly from complex biological samples. Furthermore, RAMIPs-SPME sampling combined to ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was applied to capture and identify hesperetin and its metabolites in rat livers in vivo. Finally, hesperetin-7-O-glucuronide, hesperetin-3′-O-glucuronide, eriodictyol and homoeriodictyol were identified as the metabolites of hesperetin. In comparison with the MIPs fibers, commercial PDMS and DVB fibers, RAMIPs-SPME fibers possessed better exclusion effect to macromolecules and higher selectivity to hesperetin and its metabolites. The results demonstrated that the prepared RAMIPs-SPME fiber were proven to be effective tool for the selective adsorption and enrichment of hesperetin and its metabolites from the complex biological fluids.

Braid solid-phase microextraction of polycyclic aromatic hydrocarbons by using fibers coated with silver-based nanomaterials in combination with HPLC with fluorometric detection.

Authors propose a novel braid support configuration for use in solid-phase microextraction (SPME) fibers. Two different braided supports (double and triple) were prepared and compared with the conventional single support configuration. Three kinds of silver-based nanomaterials that serve as coatings on these supports are described. They included silver dendrites, silver nanoparticles (AgNPs), and silver dendrites decorated with AgNPs (Ag-dendrites@AgNPs). They were prepared by electrodeposition, a layer-by-layer (LBL) method, and a hybrid strategy, respectively. Fibers were used in the direct-immersion (DI) mode of SPME. Five polycyclic aromatic hydrocarbons (PAHs) were studied as model analytes by DI-SPME when analyzing (spiked) underground waters. PAHs were further determined with high-performance liquid chromatography (HPLC) and fluorescence detection. The analytical performance of the fibers was compared to that of the commercial polydimethylsiloxane (PDMS) fiber of 100μm thickness. AgNPs obtained by LBL was the best coating and the double braid was the best support configuration. The configuration of the SPME support always played an important role independently on the coating material, being always beneficial the use of double-braids. Despite the low coatings volumes of the silver-based fibers compared to that of PDMS, the analytical features of the method were adequate. Figures of merit include: (a) limits of detection down to 20ng·L-1; (b) intra-day, inter-day, and inter-fiber precisions (expressed as RSDs) of <13%, <12%, and < 13%, respectively; and (c) adequate operational lifetime (>60 extractions). Graphical abstract Schematic presentation of braided solid-phase microextraction support configurations together with different silver-based nanomaterials as coatings.

Carbon and Tin-Based Polyacrylonitrile Hybrid Architecture Solid Phase Microextraction Fiber for the Detection and Quantification of Antibiotic Compounds in Aqueous Environmental Systems.

In this study, the detection and quantification of multiple classes of antibiotics in water matrices are proposed using a lab-made solid phase microextraction (SPME) fiber coupled with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The lab-made fiber was prepared using a graphene oxide (G), carbon nanotubes (C), and tin dioxide (T) composite, namely GCT, with polyacrylonitrile (PAN) as supporting material. The detected antibiotics were enrofloxacin, sulfathiazole, erythromycin, and trimethoprim. The custom-made fiber was found to be superior compared with a commercial C18 fiber. The excellent reproducibility and lower intra-fiber relative standard deviations (RSDs 1.8% to 6.8%) and inter-fiber RSDs (4.5% to 8.8%) made it an ideal candidate for the detection of traces of antibiotics in real environmental samples. The proposed validated method provides a satisfactory limit of detection and good linear ranges with higher (>0.99) coefficient of determination in the aqueous system. Application of the method was made in different real water systems such as river, pond and tap water using the standard spiking method. Excellent sensitivity, reproducibility, lower amount of sample detection and higher recovery was found in a real water sample. Therefore, the extraction method was successfully applied to the detection and quantification of multiple classes of antibiotics in different aqueous systems with satisfactory results.

Polymeric ionic liquid as a coating for monolithic solid-phase microextraction fiber: application in n-alkanes extraction from soil samples followed by gas chromatography

A new solid-phase microextraction (SPME) method was developed for extraction of 15 n-alkanes in soil samples. For this purpose, a new version of monolithic SPME fiber based on polymeric ionic liquids loaded on polyethersulfone monolithic substrate was presented. The quantitative analysis was carried out by GC-FID. The proposed fiber exhibits high thermal stability, reproducible extraction efficiency and long lifetimes. Analytical merits of the method, including correlation coefficients (0.9667–0.9987) and low detection limits (0.05–0.2 µg kg−1), made the proposed method suitable for the trace determination of n-alkanes in soil samples.

In situ self-transformation metal into metal-organic framework membrane for solid-phase microextraction of polycyclic aromatic hydrocarbons

In this work, a metal-organic framework (MOF) membrane coated copper wire (CW) was prepared as solid-phase microextraction (SPME) materials for extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The MOF based SPME fiber was fabricated by a facile and environment-friendly strategy, where the CW acted as both substrate and the copper ion source for MOF membrane growth. Characterization results confirmed that a uniform and dense HKUST-1 membrane was grown on the smooth surface of pristine CW. The effect of extraction parameters (i.e. extraction temperature, extraction time, desorption temperature, desorption time, and salt concentration) were fully optimized. Due to its large surface areas, the MOF membrane coated CW fiber showed good performance with great repeatability (2.6–14%, n = 5), low limits of detection (LODs, 0.12–9.9 ng L−1) and wide linear range (0.01–10 μg L−1). Moreover, the proposed method was proven to be highly effective for the determination of trace PAHs levels in real environmental water samples where the recoveries of PAHs were in the range of 80.8–114.1%, demonstrating that the as-prepared HKUST-1 membrane coated CW had great potential application in environmental water analysis.

Peanut shell-derived biochar materials for effective solid-phase microextraction of polycyclic aromatic hydrocarbons in environmental waters

In this contribution, low-cost and robust biochar material fabricated from waste peanut shells manifest highly-efficient adsorption capability and was prepared into a solid-phase microextraction fiber coating on the external surface of a stainless-steel wire. It was observed from scanning electron microscopy that, a homogeneity of cavities makes up the external surface of the coating, and Raman signals revealed that it contained graphite structures. Coupled with gas chromatography-mass spectrometry (GC-MS), headspace SPME (HS-SPME) based on the novel fiber was applied for the analysis of six polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. Under the selected optimum conditions in both extraction and desorption processes, satisfactory analytical performances were achieved, which included good intra-fiber repeatability (relative standard deviations, RSDs in the range from 6.93% to 10.86%, n = 6) and inter-fiber reproducibility (RSDs from 5.61% to 13.59%, n = 4), together with low limits of detection (LODs, 1.09–2.46 ng L−1) and limits of quantification (LOQs, 3.62–8.20 ng L−1), as well as a satisfactory linear range for the analysis of the target PAHs (10–2000 ng L−1). This established method also showed good reliability in the analysis of target PAHs in river water as well as pond water in the downtown area of Guangzhou, China, as the spiked recoveries were in the range from 81% to 116%.

Covalent immobilization of covalent organic framework on stainless steel wire for solid-phase microextraction GC-MS/MS determination of sixteen polycyclic aromatic hydrocarbons in grilled meat samples

Covalent organic framework TpBD was grafted on stainless steel wire with polydopamine as a linker. The fabricated TpBD bonded stainless steel wire was used as the solid-phase microextraction fiber to extract sixteen polycyclic aromatic hydrocarbons (PAHs) for subsequent GC-MS/MS determination in grilled meat samples. The developed method gave the limits of detection (S/N = 3) from 0.02 (pyrene)-1.66 (naphthalene) ng L−1 and enhancement factors from 1069 (naphthalene)-10879 (benz(a)anthracene). The relative standard deviations (RSDs) for intra-day and inter-day study are in the range of 2.6%–8.5% and 4.5%–9.4%, respectively. The fiber-to-fiber RSDs for three parallel prepared fibers were 5.3%–10.0%. One TpBD bonded fiber can stand at least 200 cycles without significant loss of extraction efficiency. The developed method was successfully applied for the determination of trace PAHs in grilled meat samples with recoveries from 85.1% to 102.8%.

Durable molybdenum oxide coated solid-phase microextraction fiber for highly selective and efficient extraction of polycyclic aromatic hydrocarbons in water.

A bonding method was developed for coating molybdenum oxides onto a steel wire substrate, which was used as a solid-phase microextraction fiber, was coupled with gas chromatography. Based on the characterization, it is found that the as-prepared molybdenum oxides material contained a nanobelt structure with a uniform size and good dispersibility. In addition, there were a large number of small protrusions on the surface of the nanobelts. These characteristics provided a large specific surface area for extraction. Molybdenum oxides exhibited a high extraction selectivity for polycyclic aromatic hydrocarbons owing to its moderate coordination. After the optimization of the factors, method detection limits of<1.25 μg/L were achieved, and the calibration curves were linear within the range of 2-600 μg/L. In addition, repeatability was demonstrated, and the relative standard deviation<6.4%. The molybdenum oxides coating had a high scratch resistance, which could effectively prevent coating wear and failure. Combined with the high thermal and chemical stability, the service life of the coating was improved and could be used 150 times without a significant reduction in the extraction performance. Finally, the as-prepared fiber had a comparable extraction capacity and higher partition coefficients that those of commercial polyacrylate fibers.

Corn-like stationary phase for solid phase microextraction prepared by electro-assisted deposition of sol-gel/silica nanoparticles composite

A novel solid phase microextraction (SPME) fiber was fabricated based on the electrophoretic and electrochemical deposition of silica nanoparticles and silicon alkoxides as sol-gel precursors. The surface of the Cu support was initially modified by a self-assembled monolayer (SAM) of (3-mercaptopropyl) trimethoxysilane (3MPTS). Then, the composite coating was electrodeposited on the modified substrate. The SEM images showed that porous and corn-like particles of composite were coated on the Cu wire substrate. The prepared composite was used as SPME fiber and applied to extract some halogenated benzenes from aqueous solution as model compounds. Parameters affecting the extraction efficiency such as extraction temperature, extraction time, and ionic strength were evaluated and optimized. Then, the extraction efficiency of the new fiber was evaluated by determining the limit of detection (LOD), linear dynamic range (LDR) and relative standard deviation (RSD). Using GC–MS determination of analytes it was found that LOD, LDR, and RSD of this method were between 0.1 and 0.6 μg L−1, 0.5–100 μg L−1 and less than 14.4%, respectively. The thermal stability of the fiber was investigated by thermogravimetric analysis, and finally, results show that each fiber is usable at 280 °C (3 min) for more than 80 times. Furthermore, the proposed fiber was successfully applied for quantification of halogenated benzenes in real water samples.