Solid-phase Microextraction Coatings Research Articles

Utilization of montmorillonite nanocomposite incorporated with natural biopolymers and benzyl functionalized dicationic imidazolium based ionic liquid coated fiber for solid-phase microextraction of organochlorine pesticides prior to GC/MS and GC/ECD

A novel montmorillonite clay (MMT) bionanocomposite modified with chitosan (CH), carboxymethyl cellulose (CMC), and benzylimidazolium based dicationic ionic liquid with tetraethylene glycol linker (DIL) was fabricated on stainless steel wire by in situ process. The MMT–CH–CMC-DIL coated solid-phase microextraction (SPME) fiber was examined for the determination of organochlorine pesticides (OCPs) in real samples by HS-SPME-GC method using mass spectrometry (MS) and electron capture detector (ECD). Under optimized conditions, the proposed method exhibited low limits of detection (0.5 ng L−1 with MS and 0.1 ng L−1 with ECD detection), good linearities (R2 = 0.9972–0.9993 with MS and 0.9987–0.9998 with ECD detection), favorable single-fiber repeatability, and fiber-to-fiber reproducibility (less than 8.2% and 9.9% for both types of detection) and high reusability around 125 cycles. Recovery studies were carried out for OCPs in tap water, green tea, and milk samples to verify the applicability of the developed SPME-GC method.

Preparation of Ti3 C2 Tx MXene based solid-phase microextraction coating for sensitive determination of polychlorinated biphenyls in environmental water samples.

In this study, a new Ti3 C2 Tx -coated fiber was synthesized and utilized as coatings for solid-phase microextraction of seven polychlorinated biphenyls. The as-produced multilayered Ti3 C2 Tx MXene was characterized by X-ray diffractometer, thermos-gravimetric analysis, scanning electron microscopy, and energy dispersive spectroscopy. It is noteworthy that the Ti3 C2 Tx showed some attractive features including unique 2D layered structures, large surface area, good hydrophilicity, and rich active recognition sites, endowing it has a high affinity towards the target polychlorinated biphenyls. Subsequently, the affecting parameters on the extraction efficiency of polychlorinated biphenyls were optimized. Under the optimal conditions, a novel method for the analysis of polychlorinated biphenyls in water samples was proposed. The Ti3 C2 Tx -coated fiber-based solid-phase microextraction method showed good linearity (r2 >0.9928), high enrichment factors (268-442), low limits of detection (0.06-0.15ng/L), and satisfactory repeatability (RSDs<7.5%) for the polychlorinated biphenyls. The excellent method recoveries were in the range of 90.0-98.4, 92.0-98.2, and 92.0-98.0% for river water, lake water, and tap water samples, respectively. These results suggested that the proposed Ti3 C2 Tx -coated fiber-based method represents a promising alternative for the analysis of polychlorinated biphenyls.

Synthesis of hypercrosslinked polymers for efficient solid-phase microextraction of polycyclic aromatic hydrocarbons and their derivatives followed by gas chromatography-mass spectrometry determination

Three novel hypercrosslinked polymers (HCPs) were synthesized via Friedel-Crafts reaction employing 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene as alkylating agent, and triphenylbenzene, tetraphenylethylene and p-quaterphenyl as the aromatic units, respectively. The prepared HCPs were applied as solid-phase microextraction coatings for direct immersion extraction of polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives in environmental water samples. The key factors affecting the extraction efficiency including extraction time, extraction temperature, stirring rate, ionic strength and desorption conditions, were carefully studied. Coupled with gas chromatography mass spectrometry analysis, a new method for determining PAHs and their derivatives was developed. Under the optimized conditions, the limits of detection (S/N=3) and limits of quantitation (the lowest concentration for quantification) of the method were in the range of 2.5-25.0 and 7.5-75.0 ng L−1, respectively. The recoveries of spiked samples were in the range of 73.1-118.3% with relative standard deviations less than 13.0%. The developed method was applied for the simultaneous determination of nine PAHs and their derivatives in environmental water samples, showing good accuracy and reliability.

Molecular Simulation-Aided Preparation of Molecularly Imprinted Polymeric Solid-Phase Microextraction Coatings for Kojic Acid Detection in Wheat Starch and Flour Samples

An effective method based on molecularly imprinted polymer solid-phase microextraction (MIP-SPME) to assess the risk of kojic acid (KA) in food was proposed in this work. KA is widely used in the food industry but may have potential hazards, such as carcinogenicity. Herein, theoretical simulation and UV–vis spectrum were applied to investigate the synthesis procedure of MIP. The molecular simulation was in marked contrast with the traditional complicated preparation optimization of MIP-SPME coating. The prepared MIP-SPME fiber coating was a mesoporous material with high porosity, the leading cause of better mass transfer of target analytes in complex media. Furthermore, a novel theoretical simulation method of annealing operation was used to obtain the hydrogen bond interaction force for every possible or even dominate action site in the template-monomer system. In addition, compared to the existing approaches of KA determination, this method exhibited ultralow limits of quantification (0.20 and 0.72 μg L−1); it was successfully used for the selective trace detection of KA in wheat flour and starch. The proposed MIP-SPME approach, as a strategy for the risk assessment of KA, is proven to have great stability, high sensitivity and reproducibility.

Solvent-Free Synthesis of Phenolic Hydroxyl Enriched Ordered Mesoporous Polymer as an Efficient Solid-Phase Microextraction Coating for the Determination of Trace Phenols in Food Samples

The determination of trace phenols in food samples is of great significance, but it is still very challenging due to the low concentration and complex matrix. A robust method was developed to determine trace phenols in food sample by combining headspace-solid phase microextraction (HS-SPME) with gas chromatography-mass spectrometry (GC-MS). The hydroxylated ordered mesoporous polymer (OMP-OH) synthesized by solvent-free strategy possessed ordered mesoporous structure and high specific surface area and was used as SPME fiber coating. Factors affecting the extraction efficiency were optimized, including extraction time, extraction temperature, pH value, salt effect, and desorption conditions. Under the optimal conditions, OMP-OH coating exhibited a high capability for the enrichment of phenols, which was 2~8 times that of commercial SPME coating. Moreover, the coating can be reused for more than 150 times without a significant change in performance. Linear ranges of this method were 0.5~10000 ng L−1, of which 5~10000 ng L−1 for 2-nitrophenol and 1~10000 ng L−1 for 2, 4-dichlorophenol. The limits of detection (LODs) for phenols in tomato and grape are 0.19~2.13 ng L−1 and 0.21~2.41 ng L−1, respectively. High enrichment factors (439~1851), good precision (RSD< 8.87%), and superior reproducibility (RSD< 10.0%) were obtained. Ultimately, the established method was successfully applied to quantify the phenols in real food samples, i.e., tomato and grape. The results demonstrated that the established method was very promising for the determination of trace phenols in food samples with complex matrix.

Hybrid ZIF-8-90 for Selective Solid-Phase Microextraction of Exhaled Breath from Gastric Cancer Patients.

Metal-organic frameworks (MOFs) are a new kind of microporous materials whose unique properties make them promising as coatings for solid phase microextraction (SPME). However, previous MOF coatings for SPME exclusively focus on single-linker MOFs, and the selective enrichment of polar or nonpolar targets depends on the polarity of linker on the surface of MOFs, which greatly limits the application of MOF coating for SPME in real samples. Here, we report a hybrid MOF-coated stainless steel fiber for SPME of biomarkers in exhaled breath from gastric cancer patients. Zeolitic imidazolate framework-8-90 (ZIF-8-90) possesses the aldehyde groups and methyl groups in the framework as a model MOF, and eight biomarkers (ethanol, acetone, hexanal, hexanol, nonane, isoprene, heptane, and decane) were used as the target analytes. The ZIF-8-90-coated fiber shows high enrichment efficiency for hydrophilic targets and hydrophobic targets, wide linearity (three orders of magnitude), and low detection limits (0.82-2.64 μg L-1). The ZIF-8-90-coated fiber exhibited higher enrichment performance for all the investigated analytes as a result of the synergy of methyl and aldehyde groups, the porous structure, and the suitable pore size of ZIF-8-90 (4-5 Å). The relative standard deviation (RSD) of six repetitions for extractions using the same ZIF-8-90-coated fiber ranged from 2.5 to 7.3%. The reproducibility between the three fibers prepared in parallel varied in the range of 4.8-12% (RSD). The fabricated ZIF-8-90-coated fiber lasted for at least 120 cycles of extraction/desorption/conditioning without an obvious reduction in extraction efficiency and precision. Finally, the developed ZIF-8-90-coated SPME fiber has been successfully used for the analysis of exhaled breath samples from gastric patients with satisfied recoveries (88-106%).

Construction of hypercrosslinked polymers for high-performance solid phase microextraction of phthalate esters from water samples

Design and synthesis of novel coatings for solid phase microextraction (SPME) is urgently needed for sample pretreatment. In this study, three hypercrosslinked polymers (HCPs) were constructed by the facile Friedel-Crafts alkylation reactions between tetraphenylethylene (TPE) and 1,4-bis(chloromethyl)benzene (BCMB), 4,4′-bis(chloromethyl)-1,1′-biphenyl (BCMBP), and cyanuric chloride (CC), respectively. The newly-synthesized HCPs were employed as SPME coatings for the extraction of phthalate esters (PAEs). Various parameters influencing the SPME efficiencies, including extraction time and temperature, ionic strength, stirring rate, desorption temperature and time were optimized. Under the optimal conditions, low limits of detection (0.003–0.033 μg L − 1), wide linearity (0.01–10 μg L − 1) and good repeatability (4.1–9.3%) were achieved. The HCPs-based SPME method was successfully applied for the determination of eight PAEs in environmental water and bottled water samples with recoveries from 75.3% to 116%. This method provides a good alternative for monitoring trace level of PAEs in water samples.

Assessment of solid phase microextraction as a sample preparation tool for untargeted analysis of brain tissue using liquid chromatography-mass spectrometry

This work presents an evaluation of solid-phase microextraction (SPME) SPME in combination with liquid chromatography-high resolution mass spectrometry (LC-HRMS) as an analytical approach for untargeted brain analysis. The study included a characterization of the metabolite coverage provided by C18, mixed-mode (MM, with benzene sulfonic acid and C18 functionalities), and hydrophilic lipophilic balanced (HLB) particles as sorbents in SPME coatings after extraction from cow brain homogenate at static conditions. The effects of desorption solvent, extraction time, and chromatographic modes on the metabolite features detected were investigated. Method precision and absolute matrix effects were also assessed. Among the main findings of this work, it was observed that all three tested coating chemistries were able to provide comparable brain tissue information. HLB provided higher responses for polar metabolites; however, as these fibers were prepared in-house, higher inter-fiber relative standard deviations were also observed. C18 and HLB coatings offered similar responses with respect to lipid-related features, whereas MM and C18 provided the best results in terms of method precision. Our results also showed that the use of methanol is essential for effective desorption of non-polar metabolites. Using a reversed-phase chromatographic method, an average of 800 and 1200 brain metabolite features detected in positive and negative modes, respectively, met inter-fibre RSD values below 30% (n=4) after removal of fibre and solvent artefacts from the associated datasets. For features detected using a lipidomics method, a total of 900 and 1800 features detected using C18 fibers in positive and negative mode, respectively, met the same criteria. In terms of absolute matrix effects, the majority of the model metabolites tested showed values between 80 and 120%, which are within the acceptable range. Overall, the findings of this work lay the foundation for further optimization of parameters for SPME-LC-HRMS methods suitable for in vivo and ex vivo brain (and other tissue) untargeted studies, and support the applicability of this approach for non-destructive tissue metabolomics.

ZIF-67 derived hollow nanomaterials as solid phase microextraction coatings for rapid capture of polycyclic aromatic hydrocarbons from water samples

Zeolitic imidazole framework-67 derived hollow nanomaterials were prepared by etching technique and used as solid-phase microextraction coating, which provided a new, effective and low-cost method for the rapid capture of PAHs from real samples.

In-situ solvothermal polymerization of metal-organic framework/carbon-nitrogen nanosheet-coated solid-phase microextraction fiber for highly sensitive detection of pesticide residues in black tea

Pyrethroids (PYs) and organochlorine pesticides (OCPs) are widely used to control pests and diseases in plants; however, they threaten human health. In this study, a metal-organic framework/carbon-nitrogen nanosheet composite nanomaterial (UiO-66/HOCN)-coated solid-phase microextraction (SPME) fiber was prepared by in-situ thermal polymerization. The prepared UiO-66/HOCN composite material was characterized by transmission electron microscopy, X-ray diffraction, nitrogen adsorption porosimetry, thermogravimetric analysis, and zeta potentiometry. The prepared UiO-66/HOCN composite-coated MSPE fiber was used for the enrichment and separation of OCPs and PYs, which showed good thermal and chemical stability as well as high extraction efficiency. Combined with gas chromatography-mass spectrometry (GC-MS), an efficient and sensitive method for the detection of trace levels of OCPs and PYs was developed. Under the optimal experimental conditions, wide linear ranges (0.1-800.0 ng/L), good linearity (≥ 0.9978), low limits of detection (0.03-0.30 ng/L), and acceptable repeatability (RSD ≤ 8.9%, n=3) were obtained. Typical black tea samples were analyzed by the developed method, and trace levels of aldrin (6.6 ng/g), α -endosulfan (54.7 ng/g), and bifenthrin (185.8 ng/g) were detected. The results demonstrate that the developed method has immense potential for the detection of pesticides in a complicated matrix.

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.

Corncob biochar as a coating for trace analysis of polycyclic aromatic hydrocarbons in water samples by online in-tube solid-phase microextraction coupled to high performance liquid chromatography

Biochar materials have been focused on enormous attention in the fields of capacitance, catalysis, adsorption due to its renewability, abundant in content and widespread distribution. In this work, corncob biochar materials were prepared under different carbonized temperature and characterized by scanning electron microscopy and Raman spectroscopy for surface morphology and graphitization degree. Then the materials were separately attached onto stainless steel wires as the coatings for solid-phase microextraction (SPME). Four wires with the same coating were placed into a polyetheretherketone tube to develop several extraction tubes. Coupled to high performance liquid chromatography (HPLC) with diode array detector (DAD), the tubes were evaluated using several polycyclic aromatic hydrocarbons (PAHs) as model analytes. According to the comparison of extraction efficiency, the best tube was selected. To achieve high sensitivity, both main extraction and desorption processes were optimized. Under the optimum conditions, an in-tube SPME-HPLC-DAD method for PAHs was established with low limits of detection (0.003–0.030 ng mL−1), wide linear ranges (0.010–15 ng mL−1, 0.017–15 ng mL−1, 0.033–15 ng mL−1 and 0.099–15 ng mL−1), high enrichment factors (1864–2615) and acceptable repeatability (relative standard deviations (RSDs, n = 3) less than 2.9% and 6.7% for intra-day and inter-day tests). Furthermore, the accuracy of the method was investigated via analyzing trace PAHs in real water samples and good recoveries (81.7%-116.8%) were obtained. In addition, the extraction tube exhibited satisfactory durability and chemical stability (RSDs ≤ 8.0%, n = 3) and acceptable reproducibility (RSD ≤ 7.8%, n = 3).

In-situ kinetic and thermodynamic study of 2,4-dichlorophenoxyacetic acid adsorption on molecularly imprinted polymer based solid-phase microextraction coatings

Solid-phase microextraction (SPME) is attracting increasing interest due to being promising, new and green sample-preparation technique. Despite the vast research on the SPME, little is known about adsorption kinetics and thermodynamics of SPME coating, which plays the key role in the extraction. In this paper, a blade type SPME coating was prepared on glass slide, and 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption on the coating were monitored by in-situ fiber-optic sensing. The effects of contact time, temperature (298-318 K) and initial concentration (20-150 mg/L) of 2,4-D on the adsorption properties of SPME coating were discussed. The results demonstrated that the pseudo-second-order model was most suitable for describing 2,4-D adsorption on the SPME coating. The thermodynamic parameters (ΔH, ΔS, ΔG) indicate that 2,4-D adsorption at low concentration by the SPME coating is exothermic and spontaneous process. Under the same conditions, the molecularly imprinted polymers (MIPs) coating have significantly higher adsorption capacity, and faster adsorption rate than the non-imprinted polymers (NIPs) SPME coating. This approach provides a tool for in-situ monitoring of adsorption kinetics and thermodynamics of SPME coating which requires fast measurement and small volume.

Sorbent coatings for solid-phase microextraction targeted towards the analysis of death-related polar analytes coupled to comprehensive two-dimensional gas chromatography: Comparison of zwitterionic polymeric ionic liquids versus commercial coatings

Decomposition of bodies generates several types of polar volatile organic compounds (VOCs), whose types, patterns and ratios change during the various stages of decomposition and, therefore, their determination has huge potential to provide useful information to disclose events related to the time of death, or body surrounding environment. As sample preparation is a mandatory key-point in a method development, this research aims to develop a simple, accurate and rapid approach to study death-related polar VOCs based on headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC × GC-ToFMS) analysis. The performance of zwitterionic PIL-based fibers (containing a [VIm+C9COO−] monomer and a [(VIm)2C122+]-2Br− crosslinker), tailored for polar compounds, was evaluated for a set of 19 analytes associated with the unique odour created by decomposing bodies, and it was compared to the commercially-available fibers: divinylbenzene/carboxen/poly(dimethylsiloxane) – DVB/CAR/PDMS, poly(dimethylsiloxane)/divinylbenzene – PDMS/DVB and polyacrylate (PA). Fibers with absorptive-type mechanism, such as PA and PIL, showed the best results in the balance of the parameters studied, being able to detect analytes at ng level and providing a profile representative of the headspace composition, thus they may represent a useful tool to respond to current challenges in forensic taphonomy. The reproducibility (with relative standard deviation lower than 18%, depending on the analyte) and relative recoveries (higher than 99.1%) were similar and acceptable for both fibers. The zwitterionic PIL, with ca. 4 times smaller film thickness than PA, still has potential to have the best performance, supported by the efforts to obtain thicker sorbent coatings.

Graphene Oxide-Ionic Liquid Used As Solid-Phase Microextraction Coating For Polyphenolic Compounds' Extraction And Determination With GC-MS After On-Fiber Derivatization In Wine

We describe the use of a home-made fiber coated by graphene oxide modified by an ionic liquid having methylimidazolium cation with an amino-functional group for the extraction of polyphenolic compounds (P.C.s). We then performed the determination by gas chromatography coupled with mass spectrometry after on-fiber derivatization. The authors optimized the main parameters influencing the extraction and derivatization processes. The on-fiber derivatization was employed within 15 min at 60 ºC using 20 µL of trimethylsilyl reagents. Under the optimized conditions, the calibration curves for 12 P.C.s were linear from 0.1 to 1000 µg/L, and the detection limits were between 0.02 and 0.1 µg/L. We determined the single fiber repeatability obtained for all calibration points and the fiber to fiber reproducibility for 100 µg/L to be &amp;lt; 14.82% and &amp;lt; 5.87%, respectively. The extraction efficacy of the home-made fiber due to high intermolecular and electrostatic attractions was much better than the commercial fibers. We successfully applied the method to the analysis of P.C.s in wine samples with the recoveries from 72.8 to 99.9%.

Polymeric ionic liquid sorbent coatings in headspace solid-phase microextraction: A green sample preparation technique for the determination of pesticides in soil

In this work, a green approach utilizing novel polymeric ionic liquid (PIL) coatings for headspace solid-phase microextraction (HS-SPME) of four current-use pesticides from soil samples was studied for the first time. Epoxiconazole, fluroxypyr, metribuzin, and oxyfluorfen were the target pesticides. Three PIL coatings containing 1-vinylbenzyl-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide (PIL1 and PIL2) and 1-vinyl-3-(10-hydroxydecyl)imidazolium bis[(trifluoromethyl)sulfonyl]imide (PIL3) monomers, and 1,12-di(3-vinylbenzylimidazolium)dodecane bis[(trifluoromethyl)sulfonyl]imide (PIL1) and 1,12-di(3-vinylbenzimidazolium)dodecane bis[(trifluoromethyl)sulfonyl]imide (PIL2 and PIL3) crosslinkers were employed in this study. The performance of these PIL coatings was evaluated and compared with commercial SPME coatings based on polydimethylsiloxane/divinylbenzene (PDMS/DVB) and polydimethylsiloxane (PDMS) at the different extraction temperatures (50–90 °C) and sampling times (15–60 min). HS-SPME at 90 °C for 60 min provided the highest sensitivity and adequate reproducibility for the majority of analytes. Despite having a lower thickness, PIL2 and PIL3 coatings provided similar extraction effectiveness of analytes, and 24–247% higher coating volume-normalized responses compared to the commercial PDMS/DVB coating. The use of the PIL1 sorbent coating resulted in excellent linearity (R2 = 0.995–0.999) and lower detection limits (0.06–0.4 ng g−1) for all analytes. The optimized method provides acceptable recoveries of spiked concentrations with better performance (84–112%) achieved with the PIL1 coating. Compared to other known methods for target pesticides in soil, the proposed method provides the highest compliance with the principles of green analytical chemistry evaluated using Analytical Eco-Scale and Green Analytical Procedure Index tools.

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%.

Solid-phase microextraction coatings based on the metal-organic framework ZIF-8: Ensuring stable and reusable fibers

Chemical vapor deposition of MOFs (MOF-CVD) has been used to coat solid-phase microextraction (SPME) fibers with ZIF-8, by exposing ZnO layers to the linker vapor (2-methylimidazole). This ZIF-8 coating has been used as a seed layer in a following solvothermal MOF growth step in order to increase the ZIF-8 thickness. The combined MOF-CVD and solvothermal growth of ZIF-8 on the fibers result in a thickness of ~3 μm, with adequate thermal stability, and mechanical integrity when tested with methanol and acetonitrile ultrasonic treatments. The fibers have been evaluated in direct immersion mode using gas chromatography and flame ionization detection (GC-FID), for a group of target analytes including three polycyclic aromatic hydrocarbons (PAHs) and five personal care products (PCPs). The optimized conditions of the SPME-GC-FID methods include low amount of aqueous sample (5 mL), stirring for 45 min at 35 °C, and desorption at 280 °C for 5 min. The method presents limits of detection down to 0.6 μg L−1; intra-day, inter-day and inter-batch relative standard deviation values lower than 16%, 19%, and 23%, respectively; and a lifetime higher than 70 cycles.

Zn (II)-imidazole derived metal azolate framework as an effective adsorbent for double coated solid-phase microextraction of sixteen polycyclic aromatic hydrocarbons

Zn (II)-imidazole derived metal azolate framework materials were synthesized via rapid solvent reaction and developed as an effective adsorbent for solid-phase microextraction of trace sixteen polycyclic aromatic hydrocarbons (PAHs) from real samples prior to their determination by HPLC. The adsorbent was characterized by Fourier transform infrared spectrometry, X-ray diffractometry, Scanning electron microscopy, Thermal gravimetric analysis and Nitrogen adsorption-desorption. An orthogonal array design (OAD) was carried out to evaluate the variables affecting extraction efficiency. Under the optimum conditions, the proposed method showed low limits of detection (LOD, 0.006–0.54 μg L−1), wide linear ranges (0.02–2000 μg L−1), and good repeatability (the relative standard deviation (RSD) is 0.11%–4.93% for single fiber and 0.42%–7.36% for fiber-to-fiber). The spiked recoveries at two levels of 20.0, 50.0 μg L−1 were in the range of 76.5%–112.0% with the RSDs less than 8.3%. Compared with commercial fibers and other reported methods, the homemade fiber displayed excellent extraction capacity. The MAF-6 coating was stable over 120 successive cycles of extraction/desorption without significant loss of extraction efficiency. The method was successfully applied for the determination of sixteen PAHs in real samples.

A simple strategy based on fibers coated with surfactant-functionalized multiwalled carbon nanotubes to improve the properties of solid-phase microextraction of phenols in aqueous solution

Methods and experimentsIn this study, a functionalized multiwalled carbon nanotube (MWCNT)-coated solid-phase microextraction (SPME) fiber was developed for concentrating analytes in aqueous samples. Sodium deoxycholate (NaDC) was used as a dispersing agent for non-covalent modification of MWCNTs. The coating showed porous structure and large adsorption capacity. To investigate the capability of this MWCNTs/NaDC SPME fiber, it was applied to the analysis of phenols in aqueous solution. After extraction, the analytes were desorbed in an acetonitrile–water solution and analyzed using high-performance liquid chromatography.ResultsThe MWCNTs/NaDC fiber exhibited good analytical performance, and fine preparation reproducibility was obtained with the relative standard deviations (RSDs) ranging from 4.9% to 10.2% (n = 6) in one batch, from 5.7% to 11.9% (n = 3) among different batches. Under the optimum extraction conditions, the detection limits were 0.15–0.30 ng/mL(S/N = 3), the linear detection ranges were 1–100 ng/mL (R2 ≥ 0.9997) for these analytes, and good recoveries (80.3–95.4%) were obtained for the spiked samples.ConclusionThis is a simple and accurate pretreatment method for the analysis of phenols in aqueous samples.