Material For Solid-phase Microextraction Research Articles

Highly graphitized porous carbon/reduced graphene oxide for ultrahigh enrichment and ultrasensitive determination of polycyclic aromatic hydrocarbons

There is an urgent need to develop efficient and reliable coating materials for solid phase microextraction (SPME), in order to quantify and monitor pollutants in environmental waters. Herein, a highly graphitized porous carbon/reduced graphene oxide (PC/rGO) was successfully synthesized by pyrolysis of metal organic framework/graphene oxide precursors, and used as a SPME coating for ultrahigh enrichment of polycyclic aromatic hydrocarbons (PAHs) from water. The as-prepared PC/rGO exhibited high degree of graphitization, abundant number of micro/mesopores along with exceptional thermal stability, making it an ideal SPME coating material. The PC/rGO fiber offered an ultrahigh enrichment factor for PAHs (up to 126057), which could be attributed to the multiple interactions between the PC/rGO and PAHs, including hydrophobic and π-π interactions, partitioning, and mesopore filling effect. In the analysis of PAHs, the PC/rGO fiber showed a wide linearity (0.007–100 ng mL−1), low limits of detection (0.0005–0.005 ng mL−1), and good repeatability (RSDs <10.1%, n = 5) under optimized conditions. The established method was applicable for ultrasensitive determination of PAHs in different environmental waters and showed satisfactory recoveries. This study provides a novel way for constructing thermally stable SPME coating having efficient extraction performance.

Characterization of a hydrophilic-lipophilic balanced SPME material for enrichment of analytes with different polarities from aqueous samples

The choice of the extraction material is a critical step in solid-phase microextraction (SPME), especially the extraction of analytes which strongly differ in their polarity is challenging. This study is intended to give first insights into the headspace extraction of analytes with large differences in polarity by using a novel hydrophilic-lipophilic-balanced (HLB) SPME material with different particle sizes (5 µm, 5 + 30 µm, and 30 µm) in classical SPME, as well as SPME arrow format. The obtained results were compared to conventional and already established divinylbenzene carbon wide-range polydimethylsiloxane (DVB-CWR-PDMS) and PDMS SPME arrow fibers. The chosen model analytes toluene, indole, phenol, anisole, o-xylene, naphthalene, 2-heptanone, n-dodecane, and lindane are assigned to different substance classes with Kaw values ranging from -5.0–2.5 and Kow values from 1.5 to 7.5. The highest amount of the analytes was extracted by the HLB 5 + 30 µm arrow and the HLB 5 µm arrow, whereas the HLB SPME with a six times smaller phase volume compared to an SPME arrow, performed almost as well as the DVB-CWR-PDMS arrow. The 8-point calibration with the 5 + 30 µm HLB SPME arrow in the range of 5–70 µg L−1 of the analytes showed good linearity with R2 values ranging from 0.9765 to 0.9982, MDLs from 0.9 to 6.2 µg L−1 and RSDs from 2 to 31 %. For all of the observed analytes, the HLB material performed better than the conventional extraction materials and has great potential to replace the conventional extraction materials in many applications.

Melamine-participant hydrogen-bonded organic frameworks with strong hydrogen bonds and hierarchical micropores driving extraction of nitroaromatic compounds

Enrichment and detection of trace pollutants in the real matrix are essential for evaluating water quality. In this study, benefiting from the good affinities of 1,3,6,8-tetra(4-carboxylphenyl)pyrene) (H4TBAPy) with itself and melamine (MA) respectively, the composite hydrogen-bonded organic frameworks (HOFs, MA/PFC-1), PFC-1 self-assembled by 1,3,6,8-tetra(4-carboxylphenyl)pyrene), were successfully constructed by the mild strategy of solvent evaporation at room temperature. Through a series of characterizations, such as Fourier transform infrared spectra, X-ray diffraction, thermal gravimetric analyses, and N2 adsorption-desorption, etc., the MA/PFC-1 was confirmed to be a stable and excellent material. In addition, it possessed high surface area, hierarchical micropores, strong hydrogen bonds, and rich function groups containing N and O heteroatoms, since the newly introduced MA could be another hydrogen bonding motif, as well as increased the polarity of reaction solvent. These advantages make MA/PFC-1 be an ideal coating material for solid phase microextraction (SPME). Satisfactory enrichment factors for nitroaromatic compounds (NACs) were got by the MA/PFC-1 fiber under the optimized conditions obtained by the control variables (extraction time of 60 min, extraction temperature of 80 °C, desorption time of 6 min, desorption temperature of 260 °C, pH value of 7, and stirring speed of 250 rpm). MA/PFC-1 was further used to develop an analytical method for NACs based on head-space SPME coupled with gas chromatography‒mass spectrometry (GC‒MS). The developed method with low limits of detection (4.30–20.83 ng L−1) and good reproducibility (relative standard deviations <8.6%). The excellent performance allowed the successful application of the developed method in the determinations of trace NACs in real water samples with recoveries of 80.1%–119%. This study proposed a mild approach to synthesize composite HOFs via doping MA and developed an environmentally friendly method for the precise determinations of NACs in the environment.

Research progress on the application of derived porous carbon materials in solid-phase microextraction

固相微萃取是一种集采样、萃取、富集和进样于一体的样品前处理技术,其萃取效果与涂层材料密切相关。多孔碳材料具有比表面积大、多孔结构可控、活性位点多和化学稳定性好等优点,广泛应用于电池、超级电容器、催化、吸附和分离等领域,也是一种热门的用作固相微萃取探针的涂层材料。衍生多孔碳材料因种类丰富、可设计性强被广泛研究,研究主要集中在对衍生多孔碳材料的结构优化方面。但是衍生多孔碳材料在固相微萃取中的应用还存在如下问题:(1)共价有机框架衍生多孔碳材料的制备已取得较大进展,但将其应用于固相微萃取领域的研究仍较少;(2)有待进一步明确制备出的衍生多孔碳材料用作固相微萃取涂层表现出优异提取能力的机理;(3)有待进一步深入研究将衍生多孔碳材料用作固相微萃取涂层以实现对不同物理化学性质污染物的广谱高灵敏度分析。文章综述了近3年衍生多孔碳材料在固相微萃取中的应用研究,并展望了未来衍生多孔碳材料在固相微萃取中的研究前景。引用文献共56篇,主要来源于Elsevier。

Crystal violet-modified HKUST-1 framework with improved hydrostability as an efficient adsorbent for direct solid-phase microextraction.

Metal-organic frameworks (MOFs) have received extensive attention in adsorption applications owing to their high surface area. However, some MOFs do not perform well as the extraction medium when used under aqueous conditions. The low hydrostability of MOFs limits the practical application of these materials in solid-phase microextraction (SPME). Here, the fabrication of a water resistance SPME fiber coating is introduced based on the crystal violet (CV)-modified HKUST-1 framework on copper (Cu@HKUST-1@CV). The HKUST-1 was prepared by the in situ growth method, followed by post-synthetic modification of HKUST-1 with the CV layer. The preparation of the modified HKUST-1 was characterized by FESEM, XRD, FTIR, and DFT approaches. The prepared SPME coating was successfully employed for the quantification of anthracene (AN), as a model analyte, in water samples. The limit of detection was 0.8 ng mL-1. The developed method will open up a new door towards searching for promising materials in SPME applications.

Covalent organic framework-graphene oxide composite: A superior adsorption material for solid phase microextraction of bisphenol A

Novel materials with high adsorption and desorption efficiencies are significant for studying compounds at ultra-trace level. Herein, covalent organic framework-graphene oxide (COF-GO) composite materials are synthesized, and tested for solid phase microextraction (SPME) of bisphenol A (BPA) at ultra-trace level. With GO modified successively by 3-aminopropyltriethoxysilane, 1,3,5-triformylphloroglucinol (Tp), and different ratios of COF monomers (Tp and benzidine (BD)), the composites of TpBD-GO-n (n = 1–4) are synthesized. By coating the composites on a glass fiber, the extraction performances of the composites for BPA are tested with constant flow desorption ionization mass spectrometry (CFDI-MS). The extraction efficiency of the composite TpBD-GO-2 is 2.2 and 4.7 times higher than those of TpBD and GO, respectively. The chromatographic separation becomes a non-essential step for detection of BPA, the analysis time for each sample is reduced to 8 min. The limits of detection and quantification of MS for BPA analysis are improved to be 22.2 and 73.9 ng L−1. The linear range is extended to be 10.0 μg L−1 (R2 = 0.9990), and the relative standard deviations of one fiber (n = 11) and fiber-to-fiber (n = 8) are 4.3% and 5.6% (1 μg L−1), respectively. With this method, ultra-trace levels of BPA present in river water and sea water samples can be successfully detected and quantified. The results indicate that the TpBD-GO-n composites possess superior extraction performance, and their various applications could be expected.

In-tube solid-phase microextraction with a hybrid monolithic column for the preconcentration of ultra-trace metals prior to simultaneous determination by ICP-MS.

The preparation of an amino-functionalized hybrid monolithic column (TEOS-co-AEAPTES) via one-pot co-condensation of tetraethoxysilane (TEOS) and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane (AEAPTES) in a capillary is descibed. It was used as solid-phase microextraction (SPME) matrix followed by inductively coupled plasma-mass spectrometry (ICP-MS) for determination of trace metals. Under optimum conditions, the amino-functionalized SPME material can simultaneously retain Cu(II), Zn(II), Au(III), and Pb(II) with adsorption capacities of 148, 60, 81, and 64μgm-1, respectively. Subsequently, these four metal ions can be quantitatively eluted using 1molL-1 HNO3 containing 1% thiourea. The retention mechanism of Cu(II), Zn(II), Au(III), and Pb(II) on the amino-functionalized hybrid monolith was explained as the combination of electrostatic and coordination interactions. With a 10-fold enrichment factor, the calibration curves were established in the range 0.5-100μgL-1 with linear correlation coefficients above 0.9943 and the limits of quantitation were 0.05μgL-1 for four target analytes. The limits of detection were 0.006, 0.012, 0.004, and 0.007μgL-1 for Cu(II), Zn(II), Au(III), and Pb(II), respectively. The protocol was validated by analyzing Certified Reference Materials including standard sediment, soil, and nickel ore, and the results were in good agreement with their certified values. The relative standard deviations of the method were in the range 0.22-17.6%. The recoveries of the four metal ions in spiked samples were in the range 88.0-113.8%. Compared to direct ICP-MS determination, the proposed in-tube SPME procedure can effectively eliminate the interference from complex matrix, especially from those ores with very high content of main metal to improve the accuracy of analysis. Therefore the method is suitable for the simultaneous determination of ultra-trace Cu(II), Zn(II), Au(III), and Pb(II) in environmental and mineral samples. Graphical abstract The preparation of the TEOS-co-AEAPTES monolithic column and the SPME procedure of Cu(II), Zn(II), Au(III), and Pb(II).

Facile construction of superhydrophobic hybrids of metal-organic framework grown on nanosheet for high-performance extraction of benzene homologues

Encapsulating functional nanomaterials within the bulk of metal-organic frameworks (MOFs) offers the opportunity to construct high-performance hybrid coating materials for solid phase microextraction (SPME). In this work, we proposed the facile synthesis of a superhydrophobic MOF composite material (NSZIF-8Si) by growing ZIF-8 on MnxOy nanosheet (NS) and subsequently depositing short-chain polysiloxane on the surface of the composite. A novel SPME fiber was successfully prepared based on the NSZIF-8Si composite. The NSZIF-8Si fiber possessed outstanding thermal stability (up to 450 °C). In headspace SPME of BTEX, the home-made fiber exhibited extraction efficiencies much higher than the commercially available PDMS fiber. This phenomenon was due to the synergetic cooperation of the π-π stacking and the hydrophobic interactions between the NSZIF-8Si coating and the analyte molecules, as well as the increased aspect ratio of the MOF grown on the nanosheet. The established method achieved wide linearity (5–2000 ng L−1) and low LODs (0.02 ng L−1 to 0.21 ng L−1). Satisfactory recoveries were obtained in the analysis of real water samples collected from the Pearl River, indicative of the good reliability of the established method for real-scenario applications. This work might provide critical insights in constructing novel NS/MOF composite materials for the development of high-performance SPME fiber coatings.

Metal–Organic Frameworks as Key Materials for Solid-Phase Microextraction Devices—A Review

Metal–organic frameworks (MOFs) have attracted recently considerable attention in analytical sample preparation, particularly when used as novel sorbent materials in solid-phase microextraction (SPME). MOFs are highly ordered porous crystalline structures, full of cavities. They are formed by inorganic centers (metal ion atoms or metal clusters) and organic linkers connected by covalent coordination bonds. Depending on the ratio of such precursors and the synthetic conditions, the characteristics of the resulting MOF vary significantly, thus drifting into a countless number of interesting materials with unique properties. Among astonishing features of MOFs, their high chemical and thermal stability, easy tuneability, simple synthesis, and impressive surface area (which is the highest known), are the most attractive characteristics that makes them outstanding materials in SPME. This review offers an overview on the current state of the use of MOFs in different SPME configurations, in all cases covering extraction devices coated with (or incorporating) MOFs, with particular emphases in their preparation.

Melamine-formaldehyde aerogel functionalized with polydopamine as in-tube solid-phase microextraction coating for the determination of phthalate esters

To improve the extraction performance and stability of the melamine-formaldehyde (MF) aerogel, a melamine-formaldehyde aerogel functionalized with polydopamine (PDA/MF) has been prepared on the carbon fibers (CFs), and it was used as a solid-phase microextraction (SPME) material via packing into a polyetheretherketone (PEEK). The morphological structure of this SPME material was characterized by scanning electron microscope, and its performance was evaluated via coupled it with a high performance liquid chromatography (HPLC). The material exhibited good extraction performance for seven phthalate esters (PAEs). Compared with CFs and MF aerogel coated-CFs, PDA/MF aerogel coated-CFs have the best extraction efficiency for PAEs. Several influence factors were investigated in detail, including extraction volume, sampling flow rate, methanol content in sample and desorption time. Under the optimal conditions, an online in-tube SPME-HPLC analytical method was established with low limits of detection (LODs) (0.02–0.05 μg L−1) and limits of quantification (LOQs) (0.07–0.16 μg L−1), wide linear ranges (0.07–30 μg L−1) and superior correlation coefficients (0.9954–0.9986). The relative standard deviations (RSDs, n = 3) of the method were in the ranges of 1.0–4.9% (intra-day) and 1.6–7.3% (inter-day), respectively. RSDs of preparation repeatability among three tubes ranged from 6.6% to 12.1%. The analysis method was applied to the detection of seven PAEs from three real samples. The proposed extraction material had good durability and chemical stability, and it also exhibited a superior extraction performance than other SPME materials, including lower LODs, higher enrichment factors and shorter extraction time.

Melamine–formaldehyde aerogel coating for in-tube solid-phase microextraction

A melamine–formaldehyde (MF) aerogel coating was prepared on basalt fibers (BFs) for in-tube solid-phase microextraction (SPME). MF aerogel-coated BFs were placed in a polyetheretherketone tube to obtain the extraction tube. To build an in-tube SPME–high performance liquid chromatography (HPLC) online system, the extraction tube was connected with HPLC equipment by replacing the sample loop of a six-port valve. The extraction tube was evaluated using eight polycyclic aromatic hydrocarbons (PAHs) as model analytes. After the optimization of important factors, an online analysis method was established. Wide linear ranges (0.03–25 μg L−1, 0.06–30 μg L−1) and low detection limits (0.01, 0.02, and 0.05 μg L−1) were observed. High sensitivity resulted from large enrichment factors ranging from 2070 to 3246. To validate the analysis method, two real water samples were detected. Most of the analytes were not detected in tap water and rainwater, and relative recoveries spiked at 2 and 5 μg L−1 were in the range of 80%–117%. The extraction repeatability on one tube and the preparation repeatability among three tubes were also tested, and their RSDs (n = 3) were in the range of 0.77%–2.04% and 0.88%–9.17%, respectively. As a result of the high surface area of the MF aerogel and π-π interactions with PAHs, the MF aerogel coating exhibits a superior extraction performance than other SPME materials, including wider linear ranges, lower LODs and higher enrichment factors.

A novel analytical method for the determination of cadmium in sorrel and rocket plants at ultratrace levels: Magnetic chitosan hydrogels based solid phase microextraction-slotted quartz tube-flame atomic absorption spectrophotometry

A novel preconcentration method based on the magnetic chitosan hydrogels (MCH) was developed for trace level determination of cadmium in sorrel (Rumex acetosella) and rocket (Eruca sativa) as edible plants. Magnetic Fe3O4@chitosan composites were synthesized, characterized and used to obtain lower detection limits for cadmium by slotted quartz tube (SQT) - atomic absorption spectrophotometry (FAAS). The Box Behnken multivariate design was used to optimize the experimental variables. Under the optimum conditions, developed method provided 97.5 fold enhancements in detection power when compared to conventional FAAS. Proposed method also provided low detection and quantification limits (0.20 and 0.68 ng/mL, respectively), high precision with %RSD of 5.3 and high accuracy with recoveries ranged from 96.0–110.4% for Rumex acetosella and Eruca sativa matrices, respectively. The results demonstrated that magnetic chitosan hydrogels could be promising materials to be used as sorbent material in solid phase microextraction yielding simple, cost-effective and environmentally friendly preconcentration process.

A graphene oxide-based polymer composite coating for highly-efficient solid phase microextraction of phenols

Sensitivity and selectivity of the solid phase microextraction (SPME) in analysis are mostly determined by the coating material of the fiber used. Graphene oxide (GO) has attracted great attention because of its large specific surface area, rich oxygen functional groups, good dispersibility in aqueous solution and high reactivity. However, the low thermal stability of the functional groups limits the wide application of GO in SPME coating design. Highly cross-linked polyoxyethylene (POE) is a substrate widely used for composite material construction, which could significantly improve the thermal stability, water resistance as well as biocompatibility of the functional materials. In this study, we incorporated GO with highly cross-linked POE as a novel fiber coating material for SPME through the gluing approach. The obtained fiber possessed a wrinkled shape surface, which could increase the accessible surface area. In addition, the thermal and chemical stability of the fiber coating were also improved, rendering the fiber rigid enough for more than 100 repetitive extraction cycles. The performance of this developed SPME method for phenols was evaluated by headspace extraction of phenols in aqueous samples. Compared with three commercial fibers, the home-made fiber showed excellent extraction efficiencies towards phenols. Under the optimized conditions, it showed low detection limits (0.12–1.36 ng· L−1), good precision (<8.4%), good fiber-to-fiber repeatability (3.1%–8.1%), wide linear range (almost 5–1000 ng·L−1and correlation coefficients (R2) >99%), as well as good enrichment efficiencies (enrichment factors (EFs), 172–1752). Furthermore, the method was successfully applied in simultaneous analyses of five phenols for real water samples with satisfactory recoveries (81–113% for the Pearl River samples).

Combination of a graphene SERS substrate and magnetic solid phase micro-extraction used for the rapid detection of trace illegal additives.

Surface enhanced Raman scattering (SERS) is an ultra-sensitive spectroscopy technique, which can provide rich structural information for a great number of molecules, while solid phase micro-extraction (SPME) is an efficient method for sample pretreatment in analytical chemistry, particularly in a micro-system. In the present report, a silver-loaded and graphene-based magnetic composite (Fe3O4@GO@Ag) was fabricated for use as both a SERS-active substrate and SPME material. The π-π stacking and fluorescence quenching abilities of GO make the composite a perfect candidate for SERS in analyzing real-world samples. Therefore, through combining the magnetic nanoparticles with a SPME device, we have developed a pretreatment method named as disperse magnetic solid phase micro-extraction (Dis-MSPME). In comparison to traditional SPME, the proposed Dis-MSPME realized solid phase micro-extraction from a dispersive system and largely improved the extraction efficiency. Furthermore, by combining the advantages of both Dis-MSPME and SERS we have proposed a new detection method called Dis-MSPME-SERS. Finally, as an example, the illegal additive chloramphenicol (CAP) was successfully detected in aqueous solution with low LOQ and LOD values (1.0 × 10-8 and 1.0 × 10-10 M, respectively), which was finalized within 10 min based on the proposed Dis-MSPME-SERS method. Therefore, a simpler, more efficient and sensitive approach to realize enrichment, magnetic separation and detection, all-in-one, for the detection of illegal additives has been reported, which will be promising towards the detection of trace amounts of substance in micro-systems.

Poly(glycidyl methacrylate) nanoparticle-coated capillary with oriented antibody immobilization for immunoaffinity in-tube solid phase microextraction: Preparation and characterization

A combination between modification with nanoparticles (NP) and oriented antibody immobilization (OAI) on the inner face of capillary was for the first time developed for immunoaffinity in-tube solid-phase microextraction (SPME) to promise high antigen extraction capacity. β2-microglobin (β2MG) and cystatin C (Cys-C) were selected as model antigens. Poly(glycidyl methacrylate) (PGMA) NPs were chemically immobilized onto the capillary by a ring-opening reaction. Antibodies for β2MG and Cys-C were immobilized on the NPs through OAI. Scanning electron micrograph of the OAI capillary clearly showed that the PGMA NPs were coated onto the inner surface of capillary in a dense monolayer. In addition, random antibody immobilized (RAI) capillaries and OAI capillaries without NP were also prepared as controls. The extraction capacities of OAI capillaries were 2.02 and 2.18mgm−1 for β2MG and Cys-C, and were about 5 and 6 times as many as RAI capillaries and OAI capillaries without NP, respectively. The resultant capillaries were used as in-tube SPME materials to enrich β2MG and Cys-C for particle-enhanced turbidimetric immunoassay. When using 1.0mgL−1 standard solutions, the recoveries of OAI capillaries, RAI capillaries and OAI capillaries without NP were 103.6% and 96.8%, 48.5% and 31.5%, and 24.2% and 25.7% for β2MG and Cys-C, respectively. Furthermore, the method quantitation limit by OAI capillaries was 5 and 10 times lower than that by RAI capillaries and OAI capillaries without NP, respectively. This result indicated that the NP-coated capillaries with OAI are more suitable for using as immunoaffinity in-tube SPME materials than that with RAI.

Fabrication of porous ionic liquid polymer as solid-phase microextraction coating for analysis of organic acids by gas chromatography – mass spectrometry

A kind of porous ionic liquid polymer was designed as coating material for solid-phase microextraction (SPME) fibers to extract polar organic acids. The synthesized ionic liquids (1-vinyl-3-(4-vinyl-benzyl)imidazolium chloride) were polymerized in the presence of azobisisobutyronitrile (AIBN), and subsequently coated on stainless steel wires with physical adhesion. To guarantee the adhesion between coating and the surface of stainless steel wires, micro-wave induced plasma was applied to modify the stainless steel wires. The derivatives of extracted organic acids were analyzed by gas chromatography combined with mass spectrometry (GC-MS) with N-tert-Butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) as the derivatization reagent. Under the optimal condition, a calibration study was carried out to evaluate the performance of the SPME fibers. The calibration curves were linear (R2>0.99) in the range from 0.01μg/ml to 1μg/ml for six organic acids. Detection limits were detected down to 0.07ng/ml. To further validate the extraction efficiency of the fibers, experiments were conducted in comparison with commercial fibers. Lower LOD and LOQ values were obtained by the in-house fabricated fibers especially for polyatomic acids. Good repeatability (RSD≤16%) and fiber-to-fiber reproducibility (RSD≤20%) were obtained. The acceptable recovery of the spiked grape wine samples ranged from 78.19% to 98.11%. Additionally, long lifetime and good durability of the fibers have been demonstrated. The performance of the established SPME-GC-MS method for analysis of organic acids was shown to be greatly improved in comparison to the direct HPLC/CE method or other SPME materials as reported in the literature. In summary, a feasible and effective approach has been demonstrated to fabricate the in-house fabricated fibers based on porous ionic liquid polymers, which were proved to be advantageous and sensitive for extraction of polar organic acids. Simultaneously, application of the SPME derivatization GC-MS method for analysis of organic acids has been successfully verified as feasible and reliable.

Exploration 304 Stainless Steel Wire as Novel Sorbent Material for Determination of Polycyclic Aromatic Hydrocarbons in Water

The etched stainless steel wire was prepared and explored as sorbent material for solid-phase micro extraction (SPME) coupled with gas chromatography (GC) and flame ionization detection (FID) for the trace polycyclic aromatic hydrocarbons (PAHs) determination in water. This paper explored different factors that affected the extraction efficiency of etched stainless steel wire, including the extraction time, the thermal desorption time and the thermal desorption temperature. Under the optimal conditions, six kinds of analytes, including trace biphenyl, acenaphthylene, fluorene, phenanthrene, fluoranthene and pyrene were extracted by etched stainless wire with high concentration efficiency and separated by GC-FID. In view of the high selectivity of the etched stainless steel wires for PAHs, a new SPME method was developed with the detection limits of 0.05-0.53 μg/L. The precision for the six kinds of analytes ranged from 2.6% to 8.8%. The developed etched stainless steel wires were very stable, highly selective, and reproducible for the SPME of PAHs.

Preparation and Characterization of a Novel Solid-Phase Microextraction Material for Application to the Determination of Pesticides

ABSTRACTThe preparation and characterization of a novel solid-phase microextraction fiber is reported with application to the determination of pesticides in fruit juice. The fiber was fabricated by electrochemically coating a stainless steel wire with a thin polymeric film of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl) benzenamine. The procedure was initiated in 10 mL of acetonitrile containing 5.5 mg of monomer, 0.1 mol NaClO4, and 0.1 mol LiClO4 by cycling the potential between −0.5 and 1.2 V with a scan rate of 100 mV/sec. The morphology of the fiber surface was examined by scanning electron microscopy and its stability was characterized by thermal gravimetric analysis. The fiber was exposed to headspace extraction of bromopropylate, chlorpyrifos, lambda-cyhalothrin, penconazole, and procymidone prior to the analysis by gas chromatography with an electron capture detector. Operational parameters affecting the extraction efficiency, adsorption and desorption times and temperature, and stirring rate were screened using a Plackett-Burman Design. Emerging parameters were further optimized via Central Composite Design that were 20 min at 64°C for adsorption and 4.4 min at 250°C for desorption. Solution parameters were optimized to be 5.0 mL of sample in pH 2.0 Britton-Robinson buffer containing 0.1 mg/L NaCl to promote the volatilization of the analytes. The limits of detection were at the ng/mL level for the pesticides. The fiber was used as a selective and sensitive tool for the trace determination of these pesticides in grape juice.

Headspace solid phase microextraction of volatile aromatic hydrocarbons using a steel wire coated with an electrochemically prepared nanocomposite consisting of polypyrrole, carbon nanotubes, and titanium oxide

We have prepared a new material for solid-phase microextraction (SPME) of volatile aromatic hydrocarbons by electropolymerization of pyrrole, carbon nanotubes, and titanium oxide on the surface of a stainless steel wire. This fiber-like wire was used for the headspace solid-phase microextraction of mixtures of benzene, toluene, ethylbenzene, and o-xylene (BTEX), followed by their quantitation by GC with FID detection. The fiber is easily prepared, robust, thermally stable, and has good extraction efficiency. Under optimal conditions, the detection limits (at an SNR of 3) are in the range from 0.01 to 0.04 ng mL−1, and the limits of quantification (at an SNR of 10) are between 0.03 and 0.09 ng mL−1. The relative standard deviations (RSDs) for one fiber (i. e. the repeatability; for n = 5) range from 3.5 to 5.6 %, while the RSDs between fibers or from batch to batch (i.e. the reproducibility; for n = 3) are in the range from 5.9 to 8.1 %. The method was successfully applied to (spiked) real water samples, the relative recovery percentages being between 93.7 and 106.2 %.

Poly(3-alkylthiophenes): new sorption materials for solid phase microextraction of drugs isolated from human plasma

A novel sorbent in solid phase microextraction (SPME) method based on poly(3-alkylthiophenes) was used in the isolation of linezolid from human plasma samples following liquid chromatography determination. The effect of extraction time on the sorption capacity of the SPME process was studied and pointed at 10 min both for adsorption and desorption. Poly(3-methylthiophene) and poly(3-nonylthiophene) were applied for the extraction of linezolid from water solutions. In plasma samples, four coatings including polythiophene and poly(3-penthylthiophene) were investigated. With these measurements, correlation coefficients were calculated in the range from 0.9820 to 0.9995, and the relative standard deviations were below 15%. That allowed claiming that the synthesized and described materials can be successfully applied in the analysis of linezolid also from other matrices such as urine or blood.