Coated Solid-phase Microextraction Fiber Research Articles

Screening of volatiles from explosive initiators and plastic-bonded explosives (PBX) using headspace solid-phase microextraction coupled with gas chromatography - mass spectrometry (SPME/GC-MS).

The detection of explosives and explosive devices based on the volatile compounds they emit is a long-standing tool for law enforcement and physical security. Toward that end, solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) has become a crucial analytical tool for the identification of volatiles emitted by explosives. Previous SPME studies have identified many volatile compounds emitted by common explosive formulations that serve as the main charge in explosive devices. However, limited research has been conducted on initiators like fuses, detonating cords, and boosters. In this study, a variety of SPME fiber coatings (i.e., polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), divinylbenzene/carboxin/polydimethylsiloxane (DVB/CAR/PDMS), and carboxin/polydimethylsiloxane (CAR/PDMS)) were employed for the extraction and analysis of volatiles from Composition C-4 (cyclohexanone, 2-ethyl-1-hexanol, and 2,3-dimethyl-2,3-dinitrobutane (DMNB)) and Red Dot double-base smokeless powder (nitroglycerine, phenylamine). The results revealed that a PDMS/DVB fiber was optimal. Then, an assortment of explosive items (i.e., detonation cord, safety fuse, slip-on booster, and shape charge) were analyzed with a PDMS/DVB fiber. A variety of volatile compounds were identified, including plasticizers (tributyl acetyl citrate, N-butylbenzenesulfonamide), taggants (DMNB), and degradation products (2-ethyl-1-hexanol).

Preparation of black phosphorus nanosheets/ zeolitic imidazolate framework nanocomposite for high-performance solid-phase microextraction of organophosphorus pesticides

Design and preparation of new fiber coatings for solid-phase microextraction (SPME) is of significance to the sample preparation techniques. Herein, a facile strategy has been developed for the integration of the black phosphorus (BP) nanosheets with metal-organic framework (ZIF-8) to generate a BP/ZIF-8 nanocomposite. For the first time, the newly-synthesized BP/ZIF-8 nanocomposite was adopted as the SPME fiber coating for the extraction of organophosphorus pesticides (OPPs). Under the optimized conditions, the BP/ZIF-8 based SPME method gained acceptable linearity (0.04-20 µg L−1), low limits of detection (0.012-0.051 µg L−1) and good repeatability (3.2-8.1%). Coupled with gas chromatography-mass spectrometric detection, the developed SPME method was successfully used for the preconcentration of OPPs from environmental waters with the method recoveries from 92.0%-103.8%. This method offers a good alternative for the analysis of trace OPPs in environmental water samples.

Aniline-Naphthylamine Copolymer as the Solid Phase Microextraction (SPME) Fiber Coating for the Determination of Chlorobenzenes by Gas Chromatography – Mass Spectrometry (GC-MS)

A new solid phase microextraction fiber coating based on aniline-naphthylamine copolymer was prepared using an electrochemical approach on a wire as a robust substrate. The aniline polymer, naphthylamine polymer, and diverse ratio of the aniline-naphthylamine copolymer were synthesized and subsequently characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The results demonstrate that the aniline-naphthylamine copolymer has high porosity and a non-uniform structure compared to the unmodified polymers. The method was employed for the determination of chlorobenzenes (CBs) as model compounds for determination from water samples. The significant parameters of the sorbent morphology and extraction processes, including the type of polymer, the concentration of polymer, the electrochemical time and applied voltage, the extraction time and temperatures, and the concentration of salts, were optimized. The developed approach is sensitive, rapid, and provides suitable detection limits between 0.8 and 1.5 ng L−1. Moreover, the limit of quantification was 3–5 ng L−1 with an equilibrium time of 25 min. The linearity of the method was between 5 and 1500 ng L−1 with the correlation coefficient R2 exceeding 0.9997. The repeatability of the method was evaluated at 40 ng L−1 and relative standard deviation values were from 4 to 8% were obtained. Lastly, the developed protocol was employed to analyze natural water samples with recovery values from 96 to 101%, illustrating the absence of matrix effects.

Application of the NU-1000 coated SPME fiber on analysis of trace organochlorine pesticides in water

Herein, a novel solid-phase microextraction (SPME) fiber based on the NU-1000 sorbent was developed for direct immersion extraction of organochlorine pesticides (OCPs) in water samples. As a kind of metal-organic framework, the NU-1000 possessed the mesoporous channels which were beneficial for the mass transfer of target analytes. Extraction equilibrium was achieved rapidly with the optimal extraction time of 30 min. The NU-1000 coated fiber with a high specific surface area showed better extraction efficiencies than commercial fibers (65 μm PDMS/DVB or 85 μm PA) towards OCPs, with the enrichment factors of the NU-1000 coated fiber 2–20 times higher than the latter. NU-1000 coated fiber showed higher extraction efficiencies toward polycyclic aromatic hydrocarbons (PAHs) than OCPs and nitrobenzenes. This indicated that π-π interaction and CH-π interaction between pollutants and aromatic groups of the NU-1000 contributed to the high extraction efficiencies. Under the optimal conditions (extraction at 40 °C for 30 min and desorption at 260 °C for 6 min), the NU-1000 coated fiber coupled with gas chromatography-mass spectrometry (GC-MS) exhibited satisfied analytical performance on analysis of OCPs, with a wide linear range (0.1–2000 ng L−1), low limits of detections (LODs, 0.011–0.058 ng L−1), and good reproducibility and repeatability. The established method has been successfully applied to the determination of OCPs in surface water with good sensitivity and recoveries, which proved the great promise of the NU-1000 on the extraction of organic pollutants with conjugated groups.

ZIF-8/h-BN coated solid-phase microextraction fiber via physical coating technology and sol-gel technology for the determination of nitro polycyclic aromatic hydrocarbons from water samples

As an emerging pollutant, nitro polycyclic aromatic hydrocarbons (NPAHs) exist widely in the environment, and some of them are potential carcinogens and mutagens. Solid phase microextraction (SPME) is a valuable technique to determine trace level pollutants and the advancements in its fiber preparation are boosting its performance multifold. In our study, zeolite imidazolate framework-8/hexagonal boron nitride (ZIF-8/h-BN) coating material was synthesized successfully and used to prepare SPME fibers by physical coating technology (PCT) and sol–gel technology (SGT) for analyzing 15 NPAHs in environmental water samples. Box-Behnken design was employed to optimize the key factors of SPME condition, such as the time and temperature during extraction and desorption events. The optimized extraction temperature, desorption time and desorption temperature were 45 ℃, 4.5 min, and 265 ℃, respectively, for both coating techniques (PGT and SGT). The extraction time (37 min) of SGT was shorter than that of PCT (50 min) due to the thickness of coating fiber. Under the optimized SPME conditions, the method based on ZIF-8/h-BN-coated fiber and gas chromatography-mass spectrometry achieved a wide linearity (5–5000 ng L−1). The PCT fiber-based method showed lower detection limits (0.3–11.1 ng L−1), which is suitable for surface water, such as tap water and lake water. SGT fiber-based method showed better repeatability (<11.6%) and fiber-to-fiber precision (<13.2%), which is suitable for complex matrices like wastewater. The recoveries obtained by spiking 15 NPAHs at various concentrations for all three kinds of real water samples (70.3–107.0%) was found much suitable than any other methods for field application. Therefore, ZIF-8/h-BN coated fiber prepared by PCT and SGT exhibits a great potential for use in trace NPAHs analysis.

Development of Ldh/Pegs Nanocomposite Materials as Solid Phase Microextraction Fiber Coatings for the Determination of Pesticides in Cucumber and Tomato Samples

Development of Ldh/Pegs Nanocomposite Materials as Solid Phase Microextraction Fiber Coatings for the Determination of Pesticides in Cucumber and Tomato Samples

Novel solid-phase microextraction fiber coatings: A review.

The materials used for the fabrication of solid-phase microextraction fiber coatings in the past five years are summarized in the current review, including carbon, metal-organic frameworks, covalent organic frameworks, aerogel, polymer, ionic liquids/poly (ionic liquids), metal oxides, and natural materials. The preparation approaches of different coatings, such as sol-gel technique, in-situ growth, electrodeposition, and glue methods, are briefly reviewed together with the evolution of the supporting substrates. In addition, the limitations of the current coatings and the future development directions of solid-phase microextraction are presented.

Electrochemical In Situ Fabrication of Titanium Dioxide Nanotubes on a Titanium Wire as a Fiber Coating for Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons

A novel titanium dioxide nanotube (TiO2NTS) coated fiber for solid-phase microextraction (SPME) was prepared by in situ anodization of titanium wire in electrolyte containing ethylene glycol and ammonium fluoride (NH4F). The effects of different electrolyte solutions (NH4F and ethylene glycol) and oxidation voltages on the formation and size of TiO2NTs was studied. It was obtained from the experiment that TiO2NTs arrays were arranged with a wall thickness of 25 nm and the diameter of 100 nm pores in ethylene glycol and water (v/v, 1:1) containing NH4F of 0.5% (w/v) with a voltage of 20 V at 25 °C for 30 min. The TiO2NTs were used as solid-phase microextraction fiber coatings coupled with high-performance liquid chromatography (HPLC) in sensitive determination of polycyclic aromatic hydrocarbons (PAHs) in spiked real samples water. Under the optimized SPME conditions, the calibration curve has good linearity in the range of 0.20–500 μg·L−1, and the correlation coefficient (R2) is between 0.9980 and 0.9991. Relative standard deviations (RSDs) of 3.5–4.7% (n = 5) for single fiber repeatability and of 5.2% to 7.9% for fiber-to-fiber reproducibility (n = 3) was obtained. The limits of detection (LOD) (S/N = 3) and limits of quantification (LOQ) (S/N = 10) of PAHs were 0.03–0.05 µg·L−1 and 0.12–0.18 µg·L−1. The developed method was applied to the preconcentration and determination of trace PAHs in spiked real samples of water with good recoveries from 78.6% to 119% and RSDs from 4.3 to 8.9%, respectively.

Polystyrene-based nanospheres with controllable microstructures for exceptional solid phase microextraction of organic pollutants

Systematic investigation on the adsorption performance of polystyrene-based nanospheres towards persistent organic pollutants (POPs) is of great importance to the design of high-capacity adsorbent and the toxicological risk assessment of nano plastic. In this study, a series of polystyrene-based nanospheres with controllable microstructures, have been constructed successfully as model adsorbents, by the strategies of emulsion polymerization, hyper-crosslinking and direct carbonization. In the form of Solid phase microextraction (SPME) coatings, the impacts of microstructures on the adsorption performance of constructed nanospheres have been highlighted, by employing benzene series, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) as target adsorbates. Moreover, it is surprisingly found that the grafted F atoms make PS demonstrate better enrichment effects towards PCBs than the Cl atoms, mainly due to stronger sigma (σ)-hole interactions between F atoms and PCBs. In consideration of the most outstanding performance, the F-functionalized nanospheres (xFFNs)-coated SPME fiber is employed for the enrichment of PCBs from water samples, and the enrichment factors range from 1500 to 10030. After coupling the xFFNs-coated fiber with gas chromatography-mass spectrometry (GC-MS), highly sensitive analytical method is developed with detection limits of 0.08–0.89 ng L−1, realizing precise quantifications of trace PCBs in treated sewage samples.

Ketoenamine Covalent Organic Framework Coating for Efficient Solid-Phase Microextraction of Trace Organochlorine Pesticides.

Fiber coating is a key part of solid-phase microextraction (SPME) technology, and it determines the selectivity, sensitivity, and reproducibility of the analytical method. A ketoenamine covalent organic framework called Tp-Azo-COF with rich electronegative N atoms was prepared as an SPME coating in this work. The Tp-Azo-COF coating had a large surface area of 1218 m2 g-1 and good thermal and chemical stability, and it was applied for the extraction of organochlorine pesticides (OCPs). According to quantum chemistry calculations, the adsorption affinity of the Tp-Azo-COF coating for five OCPs was primarily affected by the halogen bond and hydrophobicity interaction. The extraction efficiencies of the Tp-Azo-COF coating for five OCPs were higher than those of three commercial SPME fiber coatings, and the enrichment factors ranged from 1061 to 3693. When combined with gas chromatography-tandem mass spectrometry, a wide linear range (0.1-1000 ng L-1), low limits of detection (0.002-0.08 ng L-1), and good fiber-to-fiber accuracy (4.3-10.9%) were achieved under optimal conditions. Moreover, the applicability of the developed method was evaluated by analyzing four samples (milk, green tea, tap water, and well water), and the recoveries were in the range of 83.4-101.6%, with relative standard deviations <8.6%. This research extends the application of the stabilized ketoenamine COF as a sample enrichment probe for OCP analysis.

Fabrication of montmorillonite/ionic liquid composite coated solid-phase microextraction fibers for determination of phenolic compounds in fruit juices by gas chromatography and liquid chromatography

Novel montmorillonite composites including ionic liquid were prepared and utilized as coating materials for solid phase microextraction fibers. Ionic liquids containing amino terminated imidazolium cations with methyl and benzyl groups and hydrophobic anions (bis(trifluoromethylsulfonyl)imide) and hydrophilic anions (bromide and tetrafluoroborate) were intercalated to KSF-montmorillonite using stainless steel wire as support by using the layer-by-layer technique. After optimization of experimental conditions, solid phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (SPME-GC/MS) after derivatization by silylation and high performance liquid chromatography/diode array detector (SPME-HPLC/DAD) were developed for the determination of 16 phenolic compounds. The developed SPME-GC/MS method had wider linearity and lower limit of detection than the developed SPME-HPLC/DAD method with similar repeatability (for 5 runs, less than 4.2 %) for a single fiber. The percentage of the variance between two different fibers was less than 6.0 % in both methods. The developed SPME methods were applied successfully to fresh fruit juices and the relative recoveries and the repeatabilities from spiked fruit juice samples were satisfactorily achieved. The results obtained with both chromatographic methods were in good agreement with each other.

Validation and expanded uncertainty determination of pesticides in water; and their survey on paddy rice irrigation water from Argentina

A solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry method was validated for the simultaneous determination of penconazole, cyproconazole, epoxiconazole, deltamethrin, azoxystrobin and kresoxim-methyl in paddy rice irrigation water. Different SPME fiber coatings and pH values were tested. Polydimethylsiloxane (PDMS) and pH 7 were chosen to optimize extraction. All pesticides presented a recovery percentage between 90.5 and 104.2%; and detection and quantification limits were 0.03 and 0.05 µg/kg for azoxystrobin and cyproconazole, 0.02 and 0.05 µg/kg for deltametrhin and epoxiconazole, 0.02 and 0.03 µg/kg for kresoxim-methyl, and 0.01 and 0.02 µg/kg for penconazole. The expanded uncertainty was estimated for all pesticides showing results lower than 20%. A total of 100 paddy rice irrigation water samples, collected in different rice fields from Argentina, were evaluated. The study showed that 86 of them presented residues. The concentrations exceeded the values that were set by European legislation and the frequencies were higher than 86% so the agricultural practices should be revised.

Preparation of hydrophilic molecularly imprinted solid‐phase microextraction fiber for the selective removal and extraction of trace tetracyclines residues in animal derived foods

The present work reported a novel hydrophilic and selective solid-phase microextraction fiber by improved multiple co-polymerization method immobilization of tetracycline molecularly imprinted polymer on a stainless steel wire and directly coupled with high-performance liquid chromatography for sensitive determination of trace tetracyclines residues in animal derived foods. The developed molecularly imprinted polymer coated solid-phase microextraction fibers were characterized through scanning electron microscopy, Fourier transfer infrared spectroscopy, thermogravimetric analysis, and adsorption experiments, the fiber with cross-linked and porous structure was observed and high thermal and chemical stability. The maximum adsorption capacity of this fiber with good selectivity reached 2.35µg/mg in aqueous matrices, and showed good repeatability (relative standard deviation≤6.6%, n=5) and satisfying reproducibility between fiber to fiber (relative standard deviation ≤7.8%, n=5). Under the optimized solid-phase microextraction conditions, satisfactory linearity (5-1000µg/L) and detection limits (0.38-0.72µg/kg, S/N=3) for all the tetracyclines were obtained. The practicality of this method was proved by adding tetracycline, oxytetracycline at three levels to milk, chicken, and fish samples with good recoveries of 77.3-104.4%.

Design and optimization of the VA-TV-SPME method for ultrasensitive determination of the PAHs in polluted water

This paper describes how a novel and reliable alternative approach was developed for conventional solid-phase microextraction (SPME) sampling by total-vaporization of a sample under vacuum conditions. SPME sampling consists two stages of the equilibrium process, which take place between the sample/headspace and the headspace/fiber coating. In the total-vaporization SPME (TV-SPME) strategy, the first stage is omitted and analytes are directly partitioned between the headspace and fiber coating. In this research, the TV-SPME strategy was implemented by the extraction of PAHs from aqueous media, using a polydimethylsiloxane (PDMS) coated SPME fiber. The most important variables were investigated and optimized. Optimal conditions were obtained at an extraction temperature of 55 °C, a vaporization time of 25 min, and a sample volume of 100 μL. To achieve higher sensitivities in shorter times, the TV-SPME setup was coupled with the VA-SPME system, which resulted in a much lower extraction temperature and time, in comparison with the conventional TV-SPME method. Under optimal experimental conditions, the calibration curves were linear across the area of 0.015–2 μg mL−1 (R2 > 0.996). The limits of detection (LODs) were obtained in the range of 0.3–5 ng mL−1, and the relative standard deviations (RSDs, n = 6) were 6.1–7.5%. The developed vacuum-assisted total-vaporization SPME (VA-TV-SPME) technique, was coupled with GC-FID and successfully utilized for the determination of polycyclic aromatic hydrocarbons (PAHs) in river water samples. The data obtained was statistically in accordance with that achieved employing a validated approved method.

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.

Graphitic carbon nitride derivative with large mesopores as sorbent for solid-phase microextraction of polycyclic aromatic hydrocarbons

Although an efficient and stable fiber coating is essential for the development of the solid-phase microextraction (SPME) technique, it remains a challenging prospect. We report herein the construction of graphitic carbon nitride derivative (g–C3N4–d) nanosheets having a large surface area, large mesopores (3.15 and 36.6 nm), and abundant adsorption sites, and the application of coating g–C3N4–d on an SPME fiber. The coated SPME fiber combined with gas chromatography-mass spectrometry (GC-MS) was used for the determination of polycyclic aromatic hydrocarbons (PAHs). The coating contained large mesopores that accommodated large target molecules and promoted molecular diffusion inside the coating sorbent. The coating demonstrated significant extraction capability toward PAHs because of multiple interactions, including hydrophobic and strong π–π interactions. Under optimal conditions, the limits of detection for PAHs were achieved within the range of 0.01–0.10 ng L−1. The method developed to detect eight PAHs in six river water samples from different cities, and the recoveries were ranging from 83.3 to 103.0%. The g–C3N4–d nanosheet-coated fiber was sufficiently stable to be recycled more than 200 times without obvious loss of extraction capacity. This study describes the development of a novel SPME adsorbent having excellent analytical properties.

Effect of Ethanol on the Adsorption of Volatile Sulfur Compounds on Solid Phase Micro-Extraction Fiber Coatings and the Implication for Analysis in Wine

Complications in the analysis of volatile sulfur compounds (VSC) in wine using solid-phase microextraction (SPME) arise from sample variability. Constituents of the wine matrix, including ethanol, affect the volatility and adsorption of sulfur volatiles on SPME fiber coatings (Carboxen- polydimethylsiloxane(PDMS); DVB-Carboxen-PDMS and DVB-PDMS), which can impact sensitivity and accuracy. Here, several common wine sulfur volatiles, including hydrogen sulfide (H2S), methanethiol (MeSH), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), diethyl disulfide (DEDS), methyl thioacetate (MeSOAc), and ethyl thioacetate (EtSOAc) are analyzed, using SPME followed by gas chromatography (GC), using a system equipped with a pulsed-flame photometric detection (PFPD) system, at various ethanol concentrations in a synthetic wine matrix. Ethyl methyl sulfide (EMS), diethyl sulfide (DES), methyl isopropyl sulfide (MIS), ethyl isopropyl sulfide (EIS), and diisopropyl disulfide (DIDS) are evaluated as internal standards. The absorption of volatile compounds on the SPME fiber is greatly affected by ethanol. All compounds exhibit a stark decrease in detectability with the addition of ethanol, especially between 0.0 and 0.5% v/v. However, the ratio of interested sulfur compounds to the internal standard becomes more stable when the total alcohol concentration exceeds 2%. EMS was found to best resemble DMS. EIS and DES were found to best resemble DMDS, MeSOAc, and EtSOAc. DIDS was found to best resemble DEDS, DMTS, H2S, and MeSH.

Chemical bonding of oxygenated carbon nitride nanosheets onto stainless steel fiber for solid-phase microextraction of phthalic acid esters

In this work, oxygenated carbon nitride nanosheets (OCNNSs) were first introduced to the field of analytic chemistry for solid-phase microextraction (SPME). The rich hydroxyl and carboxyl contents of OCNNSs provided abundant adsorption sites. The coated stainless steel fibers, synthesized by the layer-by-layer chemical bonding method, had good chemical stability (in organic solvents), long life (durability ≥ 150 cycles), and good reproducibility (RSDs ≤ 9.2%). This novel OCNNSs-coated fiber was used for SPME with gas chromatography-mass spectrometry (GC-MS) for the analysis of phthalic acid esters (PAEs) in three types of food products (seafood, samshu, and instant noodles). Under optimal conditions, the limits of detection (LODs) for the PAEs ranged from 0.1 to 10.0 pg mL−1, and recovery was in the range of 80.0–118.1%. These novel coated SPME fibers displayed excellent separation and enrichment properties, which suggest a pretreatment application for analysis of PAEs.

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%.

Electrospun Polyethylene Terephthalate/Graphene Nanocomposite as a New Solid-Phase Microextraction Fiber Coating for Enhanced Determination of Organochlorine Compounds

A new unbreakable solid-phase microextraction fiber coating based on polyethylene terephthalate/graphene nanocomposite was developed. The nanocomposite coatings were prepared by an electrospinning technique using a polyethylene terephthalate (PET) polymer solution containing the dispersed graphene on the outer surface of a stainless-steel rod. The applicability of polyethylene terephthalate/graphene nanocomposite coatings was examined by extraction of organochlorine compounds (OCs) including heptachlor epoxide, aldrin, γ-HCH, and β-HCH from aqueous samples in headspace mode. Influential parameters on extraction efficiency such as polymer concentration, the weight ratio of components, the electrospinning time, time and temperature of extraction, the salt concentration, and desorption condition were investigated. Eventually, the developed method was validated by gas chromatography micro electron capture detector (GC-µECD). At the optimum conditions, the intra-day relative standard deviations for the determination of chloro compounds in distilled water spiked at the levels of 400, 800, and 1500 ng L− 1 were 1.9–7.3% (n = 3), the limit of detection is between 5 and 30 ng L− 1, and the calibration plots cover the 100 to 5000 ng L− 1 range. Inter-day precision values obtained for three replicates measured on different days were in the range of 2.6–9.5% at concentration levels of 400, 800, and 1500 ng L− 1. The method was applied to the analysis of (spiked) water samples and relative recoveries were found to range from 81 to 106%.