Nanostructured‐silver‐coated polyetheretherketone tube for online in‐tube solid‐phase microextraction coupled with high‐performance liquid chromatography

Polyetheretherketone tube is a better substrate for in‐tube solid‐phase microextraction than fused‐silica capillary and metal tube because of its resistance to high pressure and good flexibility. It was modified with a nanostructured silver coating, and characterized by scanning electron microscopy and energy dispersive X‐ray spectroscopy. It was connected into high‐performance liquid chromatography equipment to build the online analysis system by replacing the sample loop of a six‐port injection valve. To get the highest extraction capacity, the preparation conditions of the coating was investigated. Important extraction conditions including length of tube, sample volume, and desorption time were optimized using eight polycyclic aromatic hydrocarbons as model analytes. The tube exhibits excellent extraction efficiency toward them, with enrichment factors from 52 to 363. The online analysis method provides good linearity (0.5–100 or 1.0–100 μg/L) and low detection limits (0.15–0.30 μg/L). It has been used to determine polycyclic aromatic hydrocarbons in water samples, with relative recoveries in the range of 92.3–120%. The tube showed highest extraction ability for polycyclic aromatic hydrocarbons, higher extraction ability for hydrophobic phthalates and anilines, and almost no extraction ability for low hydrophobic phenols, due to the possible extraction mechanism including hydrophobic and electron‐rich element‐metal interactions.     

Graphene oxide decorated with silver nanoparticles as a coating on a stainless‐steel fiber for solid‐phase microextraction

A novel graphene oxide decorated with silver nanoparticles coating on a stainless‐steel fiber for solid‐phase microextraction was prepared. Scanning electron microscopy and X‐ray photoelectron spectroscopy were used to characterize the coating surface and showed that silver nanoparticles were dispersed on the wrinkled graphene oxide surface. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined in the headspace solid‐phase microextraction mode. The extraction parameters including adsorption time, adsorption temperature, salt concentration, desorption time and desorption temperature were investigated. Under the optimized condition, wide linearity with low limits of detection from 2 to 10 ng/L was obtained. The relative standard deviations for single‐fiber repeatability and fiber‐to‐fiber reproducibility were less than 10.6 and 17.5%, respectively. The enrichment factors were from 1712.5 to 4503.7, showing the fiber has good extraction abilities. Moreover, the fiber exhibited a good stability and could be reused for more than 120 times. The established method was also applied for determination of polycyclic aromatic hydrocarbons in two real water samples and the recoveries of analytes ranged from 84.4–116.3% with relative standard deviations less than 16.2%.     

Mesoporous titanium oxide with high‐specific surface area as a coating for in‐tube solid‐phase microextraction combined with high‐performance liquid chromatography for the analysis of polycyclic aromatic hydrocarbons

Stainless‐steel wires coated with mesoporous titanium oxide were placed into a polyether ether ketone tube for in‐tube solid‐phase microextraction, and the coating sorbent was characterized by X‐ray diffraction and scanning electron microscopy. It was combined with high‐performance liquid chromatography to build an online system. Using eight polycyclic aromatic hydrocarbons as the analytes, some conditions including sample flow rate, sample volume, organic solvent content, and desorption time were investigated. Under optimum conditions, an online analysis method was established and provided good linearity (0.03–30 μg/L), low detection limits (0.01–0.10 μg/L), and high enrichment factors (77.6–678). The method was applied to determine target analytes in river water and water sample of coal ash, and the recoveries are in the range of 80.6–106.6 and 80.9–103.5%, respectively. Compared with estrogens and plasticizers, extraction coating shows better extraction efficiency for polycyclic aromatic hydrocarbons.     

Loading controlled magnetic carbon dots for microwave‐assisted solid‐phase extraction: Preparation,extraction evaluation and applications in environmental aqueous samples

An adsorbent of carbon dot@poly(glycidyl methacrylate)@Fe₃O₄ nanoparticles has been developed for the microwave‐assisted magnetic solid‐phase extraction of polycyclic aromatic hydrocarbons in environmental aqueous samples prior to high‐performance liquid chromatography with UV/visible spectroscopy detection. Poly(glycidyl methacrylate) was synthesized by atom transfer radical polymerization. The chain length and amount of carbon dots attached on them can be easily controlled through changing polymerization conditions, which contributes to tunable extraction performance. The successful fabrication of the nano‐adsorbent was confirmed by transmission electronic microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and vibrating sample magnetometry. The extraction performance of the adsorbent was evaluated by using polycyclic aromatic hydrocarbons as model analytes. The key factors influencing the extraction, such as microwave power, adsorption time, desorption time and desorption solvents were investigated in detail. Under the optimal conditions, the microwave‐assisted method afforded magnetic solid‐phase extraction with short extraction time, wide dynamic linear range (0.02–200 μg/L), good linearity (R² ≥ 98.57%) and low detection limits (20–90 ng/L) for model analytes. The adsorbent was successfully applied for analyzing polycyclic aromatic hydrocarbons in environmental aqueous samples and the recoveries were in the range of 86.0–124.2%. Thus, the proposed method is a promising candidate for fast and reliable preconcentration of trace polycyclic aromatic hydrocarbons in real water samples.     

A green extraction material — natural cotton fiber for in‐tube solid‐phase microextraction

Natural cotton fiber was applied as a green extraction material for in‐tube solid‐phase microextraction. Cotton fibers were characterized by scanning electron microscope. A bundle of cotton fibers (685 mg, 20 cm) was directly packed into a polyetheretherketone tube (i.d. 0.75 mm) to get the extraction device. It was connected into high performance liquid chromatography, building an online extraction and dectection system. Through the online analysis system, several polycyclic aromatic hydrocarbons were used as the targets to evaluate the extraction performace of the device. In order to get high extraction efficiency and sensitivity, the extraction and desorption conditions were optimized. Under the optimum conditions, the sensitive analysis method was established, and provided low limits of detection of 0.02 and 0.05 μg/L, good linearity ranges of 0.06–15 and 0.16–15 μg/L, as well as high enrichment factors of 176–1868. The method was applied to the online determination of trace polycyclic aromatic hydrocarbons in snow water and river water, and the relative recoveries corresponding to 2 and 5 μg/L were in the range of 80–116%. The repeatability of extraction and preparation of the device was investigated and the relative standard deviations (n = 3) were less than 3.6 and 5.2%.     

Inorganic–organic hybrid coating material for the online in‐tube solid‐phase microextraction of monohydroxy polycyclic aromatic hydrocarbons in urine

An inorganic–organic hybrid nanocomposite (zinc oxide/polypyrrole) that represents a novel kind of coating for in‐tube solid‐phase microextraction is reported. The composite coating was prepared by a facile electrochemical polymerization strategy on the inner surface of a stainless‐steel tube. Based on the coated tube, a novel online in‐tube solid‐phase microextraction with liquid chromatography and mass spectrometry method was developed and applied for the extraction of three monohydroxy polycyclic aromatic hydrocarbons in human urine. The coating displayed good extraction ability toward monohydroxy polycyclic aromatic hydrocarbons. In addition, long lifespan, excellent stability, and good compression resistance were also obtained for the coating. The experimental conditions affecting the extraction were optimized systematically. Under the optimal conditions, the limits of detection and quantification were in the range of 0.039–0.050 and 0.130–0.167 ng/mL, respectively. Good linearity (0.2–100 ng/mL) was obtained with correlation coefficients larger than 0.9967. The repeatability, expressed as relative standard deviation, ranged between 2.5% and 9.4%. The method offered the advantage of process simplicity, rapidity, automation, and sensitivity in the analysis of human urinary monohydroxy polycyclic aromatic hydrocarbons in two different cities of Hubei province. An acceptable recovery of monohydroxy polycyclic aromatic hydrocarbons (64–122%) represented the additional attractive features of the method in real urine analysis.     

Carbonized cotton fibers via a facile method for highly sensitive solid‐phase microextraction of polycyclic aromatic hydrocarbons

Cotton fiber is an environmentally friendly and natural material with a certain extraction capacity, while its enrichment ability is poor. In order to improve the extraction efficiency of cotton fibers, it was carbonized to form a layer of amorphous carbon as the sorbent by a simple carbonization method. Carbonized cotton fibers were filled into a polyetheretherketone tube for in‐tube solid‐phase microextraction. The carbonization time was investigated to obtain high extraction efficiency. Coupled to high‐performance liquid chromatography, the extraction tube was evaluated with polycyclic aromatic hydrocarbons, estrogens and phthalates, and it exhibited best extraction efficiency for polycyclic aromatic hydrocarbons. Under the optimum conditions, an online analysis method for several polycyclic aromatic hydrocarbons was established with large linear ranges (0.016–0.20 μg/L), low limits of detection (0.005–0.020 μg/L), and high enrichment factors (948–2874). Analysis method was successfully applied to the detection of targets in the real samples and shown satisfactory durability and chemical stability. Moreover, the relative recoveries ranged from 82 to 119.2%, which demonstrated the applicability of carbonized cotton fibers in sample preparation. Compared with other reported methods, the proposed method provided shorter extraction time, higher enrichment factors, comparable limits of detection, and recoveries.     

Silicon carbide nanomaterial as a coating for solid‐phase microextraction

Silicon carbide has excellent properties, such as corrosion resistance, high strength, oxidation resistance, high temperature, and so on. Based on these properties, silicon carbide was coated on stainless‐steel wire and used as a solid‐phase microextraction coating, and polycyclic aromatic hydrocarbons were employed as model analytes. Using gas chromatography, some important factors that affect the extraction efficiency were optimized one by one, and an analytical method was established. The analytical method showed wide linear ranges (0.1–30, 0.03–30, and 0.01–30 μg/L) with satisfactory correlation coefficients (0.9922–0.9966) and low detection limits (0.003–0.03 μg/L). To investigate the practical application of the method, rainwater and cigarette ash aqueous solution were collected as real samples for extraction and detection. The results indicate that silicon carbide has excellent application in the field of solid‐phase microextraction.     

Selective solid-phase microextraction of polycyclic aromatic hydrocarbons in water based on oriented phosphorus-containing titanium oxide nanofibers grown on titanium support prior to high-performance liquid chromatography with ultraviolet detection

A novel solid-phase microextraction coating of phosphorous-containing titanium oxide composite was developed using titanium fiber as a support and a titanium source by hydrothermal oxidation in a phosphoric acid solution containing hydrogen peroxide. The morphology of the fiber coatings was controlled by the conditions of the hydrothermal oxidation reaction. The oriented nanofiber coating was employed to extract several types of representative aromatic analytes. The experimental results demonstrated that the as-prepared fiber exhibited excellent extraction efficiency toward polycyclic aromatic hydrocarbons. Combined with high-performance liquid chromatography with ultraviolet detection, main extraction conditions were optimized, including pH, ionic strength, extraction temperature, stirring rate, extraction time and desorption time. The established method presented good linearity from 0.05 to 200 μg/L with limit of detection ranging from 0.012 to 0.126 μg/L. This convenient and green procedure was suitable for the selective extraction and determination of typical polycyclic aromatic hydrocarbons in environmental water samples. The relative recoveries of 85.8–112% were obtained for the determination of target polycyclic aromatic hydrocarbons in water samples spiked with 5.0 and 15.0 μg/L. Moreover, the as-prepared fiber showed at least 210 extraction/desorption cycles due to its high mechanical and chemical stability.     

Basalt fibers functionalized with gold nanoparticles for in‐tube solid‐phase microextraction

Basalt fibers were functionalized with gold nanoparticles and characterized by scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. An in‐tube solid‐phase microextraction device was developed by packing the functionalized basalt fibers in a polyether ether ketone tube. The device was connected into high performance liquid chromatography equipment with a diode array detector to build online enrichment and analysis system. Eight polycyclic aromatic hydrocarbons were used as model analytes, important factors including sampling rate, sampling volume, organic solvent content in sample, and desorption time were investigated. Linear range (0.01–20 μg/L), detection limits (0.003–0.015 μg/L), and enrichment factors (130–1628) were given by the online analysis method. Relative standard deviations (n = 5) of extraction repeatability on one tube and tube‐to‐tube repeatability were less than 5.2 and 14.7%, respectively. The analysis method was applied to detect polycyclic aromatic hydrocarbons in environmental water samples, and relative recoveries ranged from 87 to 128%.     

Simultaneous determination of 16 polycyclic aromatic hydrocarbons in reclaimed water using solid‐phase extraction followed by ultra‐performance convergence chromatography with photodiode array detection

A new fast and effective analysis method has been developed to simultaneously determine 16 polycyclic aromatic hydrocarbons in reclaimed water samples by ultra‐performance convergence chromatography with photodiode array detection and solid‐phase extraction. The parameters of ultra‐performance convergence chromatography on the separation behaviors and the crucial condition of solid‐phase extraction were investigated systematically. Under optimal conditions, the 16 polycyclic aromatic hydrocarbons could be separated within 4 min. The limits of detection and quantification were in the range of 0.4–4 and 1–10 μg/L in water, respectively. This approach has been applied to a real industrial wastewater treatment plant successfully. The results showed that polycyclic aromatic hydrocarbons were dramatically decreased after chemical treatment procedure, and the oxidation procedure was effective to remove trace polycyclic aromatic hydrocarbons.     

Polyaniline‐coated cigarette filters as a solid‐phase extraction sorbent for the extraction and enrichment of polycyclic aromatic hydrocarbon in water samples

Polyaniline coated cigarette filters were successfully synthesized and used as a solid‐phase extraction sorbent for the extraction and preconcentration of polycyclic aromatic hydrocarbons in water samples. The polyaniline helped to enhance the adsorption ability of polycyclic aromatic hydrocarbons on the sorbent through π–π interactions. The high porosity and large surface area of the cigarette filters helped to reduce backpressure and can be operated with high sample flow rate without loss of extraction efficiency. The developed sorbent was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The parameters that affected the extraction efficiencies, i.e. polymerization time, type of desorption solvent and its volume, sample flow rate, sample volume, sample pH, ionic strength, and organic modifier were investigated. Under the optimal conditions, the method was linear over the range of 0.5–10 μg/L and a detection limit of 0.5 ng/L. This simple, rapid, and cost‐effective method was successfully applied to the preconcentration of polycyclic aromatic hydrocarbons from water samples. The developed method provided a high enrichment factor with good extraction efficiency (85–98%) and a relative standard deviation <10%.     

An Ag2S@ZnS‐coated fiber for efficient,long‐life solid‐phase microextraction of polycyclic aromatic hydrocarbons in water

Although an efficient and stable fiber coating is essential for the development of solid‐phase microextraction technique, it remains a challenging prospect. Herein, an inorganic nanocomposite material Ag₂S@ZnS was prepared and used as a coating for fibers to detect polycyclic aromatic hydrocarbons in water samples in combination with a GC with flame ionization detector. Compared with a single ZnS material, the Ag₂S@ZnS composite shows many uneven nano‐protrusions on the surface of the microspheres. In conjunction with the relatively scattered microstructure of the coating and the effective anion‐π interaction formed between ZnS and the hydrocarbons, it has a large specific surface area, fast diffusion of the target molecule on its surface, and appropriate adsorption of the target molecules; therefore, it exhibits good extraction efficiency for the hydrocarbons. Under optimal conditions, the proposed analytical method exhibits superior performance with good linearity (0.01–500 µg/L) and low limits of detection (0.001–0.200 µg/L). Combined with high thermal, chemical, and mechanical stability, the service life of the coating was improved and could be used 200 times without a significant reduction in the extraction performance, and at least 2000 extraction–desorption cycles can be achieved. Satisfactory results were also obtained for the real samples.     

Development of a solid‐phase microextraction fiber by the chemical binding of graphene oxide on a silver‐coated stainless‐steel wire with an ionic liquid as the crosslinking agent

Graphene oxide was bonded onto a silver‐coated stainless‐steel wire using an ionic liquid as the crosslinking agent by a layer‐by‐layer strategy. The novel solid‐phase microextraction fiber was characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and Raman microscopy. A multilayer graphene oxide layer was closely coated onto the supporting substrate. The thickness of the coating was about 4 μm. Coupled with gas chromatography, the fiber was evaluated using five polycyclic aromatic hydrocarbons (fluorene, anthracene, fluoranthene, 1,2‐benzophenanthrene, and benzo(a)pyrene) as model analytes in direct‐immersion mode. The main conditions (extraction time, extraction temperature, ionic strength, and desorption time) were optimized by a factor‐by‐factor optimization. The as‐established method exhibited a wide linearity range (0.5–200 μg/L) and low limits of determination (0.05–0.10 μg/L). It was applied to analyze environmental water samples of rain and river water. Three kinds of the model analytes were quantified and the recoveries of samples spiked at 10 μg/L were in the range of 92.3–120 and 93.8–115%, respectively. The obtained results indicated the fiber was efficient for solid‐phase microextraction analysis.     

Synthesis of polydopamine‐functionalized magnetic graphene and carbon nanotubes hybrid nanocomposites as an adsorbent for the fast determination of 16 priority polycyclic aromatic hydrocarbons in aqueous samples

A novel adsorbent made of polydopamine‐functionalized magnetic graphene and carbon nanotubes hybrid nanocomposite was synthesized and applied to determine 16 priority polycyclic aromatic hydrocarbons by magnetic solid phase extraction in water samples. FTIR spectroscopy, transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy consistently indicate that the synthesized adsorbents are made of core–shell nanoparticles well dispersed on the surface of graphene and carbon nanotubes. The major factors affecting the extraction efficiency, including the pH value of samples, the amount of adsorbent, adsorption time and desorption time, type and volume of desorption solvent, were systematically optimized. Under the optimum extraction conditions, a linear response was obtained for polycyclic aromatic hydrocarbons between concentrations of 10 and 500 ng/L with the correlation coefficients ranging from 0.9958 to 0.9989, and the limits of detection (S/N = 3) were between 0.1 and 3.0 ng/L. Satisfactory results were also obtained when applying these magnetic graphene/carbon nanotubes/polydopamine hybrid nanocomposites to detect polycyclic aromatic hydrocarbons in several environmental aqueous samples.     

Determination of phthalate esters from environmental water samples by micro‐solid‐phase extraction using TiO2 nanotube arrays before high‐performance liquid chromatography

We describe a highly sensitive micro‐solid‐phase extraction method for the pre‐concentration of six phthalate esters utilizing a TiO₂ nanotube array coupled to high‐performance liquid chromatography with a variable‐wavelength ultraviolet visible detector. The selected phthalate esters included dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, bis(2‐ethylhexyl)phthalate and dioctyl phthalate. The factors that would affect the enrichment, such as desorption solvent, sample pH, salting‐out effect, extraction time and desorption time, were optimized. Under the optimum conditions, the linear range of the proposed method was 0.3–200 μg/L. The limits of detection were 0.04–0.2 μg/L (S/N = 3). The proposed method was successfully applied to the determination of six phthalate esters in water samples and satisfied spiked recoveries were achieved. These results indicated that the proposed method was appropriate for the determination of trace phthalate esters in environmental water samples.     

Development of a carbon‐nanoparticle‐coated stirrer for stir bar sorptive extraction by a simple carbon deposition in flame

Stir bar sorptive extraction is an environmentally friendly microextraction technique based on a stir bar with various sorbents. A commercial stirrer is a good support, but it has not been used in stir bar sorptive extraction due to difficult modification. A stirrer was modified with carbon nanoparticles by a simple carbon deposition process in flame and characterized by scanning electron microscopy and energy‐dispersive X‐ray spectrometry. A three‐dimensional porous coating was formed with carbon nanoparticles. In combination with high‐performance liquid chromatography, the stir bar was evaluated using five polycyclic aromatic hydrocarbons as model analytes. Conditions including extraction time and temperature, ionic strength, and desorption solvent were investigated by a factor‐by‐factor optimization method. The established method exhibited good linearity (0.01–10 μg/L) and low limits of quantification (0.01 μg/L). It was applied to detect model analytes in environmental water samples. No analyte was detected in river water, and five analytes were quantified in rain water. The recoveries of five analytes in two samples with spiked at 2 μg/L were in the range of 92.2–106% and 93.4–108%, respectively. The results indicated that the carbon nanoparticle‐coated stirrer was an efficient stir bar for extraction analysis of some polycyclic aromatic hydrocarbons.     

Cadmium sulfide nanoparticles as a novel coating for solid‐phase microextraction

CdS nanoparticles coated on a stainless‐steel wire for solid‐phase microextraction was prepared. Scanning electron microscopy showed that the CdS nanoparticles clustered together to form a porous structure and X‐ray diffraction confirmed that the CdS nanoparticles were the wurtzite phase. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined by the headspace method. The parameters of adsorption time, adsorption temperature, salt concentration, desorption time, and desorption temperature were investigated and optimized. For the method, wide linearity and low limits of detection from 5 to 15 ng/L were obtained. The relative standard deviations for single‐fiber repeatability and fiber‐to‐fiber reproducibility were less than 10.2 and 12.6%, respectively. The enrichment factors were from 1155.6 to 3905.4, showing the fiber has good extraction capacity for polycyclic aromatic hydrocarbons. Moreover, the fiber can be used more than 50 times, exhibiting good stability. The established method was also used to analyze the polycyclic aromatic hydrocarbons in two real samples, and the recoveries from 82.7 to 114.2% further proved the reliability of the method.     

Layer‐by‐layer self‐assembly of a novel covalent organic frameworks microextraction coating for analyzing polycyclic aromatic hydrocarbons from aqueous solutions via gas chromatography

In this study, a new covalent organic framework, consisting of tetra(4‐aminophenyl)porphyrin and tris(4‐formyl phenyl)amine, was layer‐by‐layer immobilized on stainless‐steel wire as a coating for microextraction. The fabrication process was easy and controllable under mild conditions. The as‐grown fiber was applied to extract polycyclic aromatic hydrocarbons in aqueous solution via head‐space solid‐phase microextraction. Furthermore, it was analyzed by gas chromatography with a flame ionization detector. A wide linear range (0.1–50 µg/L), low limits of detection (0.006–0.024 µg/L, signal‐to‐noise ratio = 3), good repeatability (intra‐fiber, n = 6, 3.1–8.50%), and reproducibility (fiber to fiber; n = 3, 5.79–9.98%), expressed as relative standard deviations, demonstrate the applicability of the newly developed coating. This new material was successfully utilized in real sample extraction with a satisfactory result. Potential parameters affecting the extraction efficiency, including extraction temperature and extraction time, salt concentration, agitation speed, sample volume, desorption temperature, and time, were also optimized and discussed.     

Carbonized silk fibers for in‐tube solid‐phase microextraction to detect polycyclic aromatic hydrocarbons in water samples

Silk fibers were carbonized to develop a biomass carbon material as an adsorbent for solid‐phase microextraction. The surface structure of the carbonized silk fibers was characterized by scanning electron microscopy, and the graphitization degree was determined by Raman spectrometry. After carbonization under high temperature, the orderliness and structural regularity of carbon atoms on silk fibers were promoted. Extraction tube packed with carbonized silk fibers was prepared for in‐tube solid‐phase microextraction. Coupled with high performance liquid chromatography, it exhibited good extraction performance for hydrophobic polycyclic aromatic hydrocarbons. Main parameters including sampling volume, sampling rate, methanol content in sample, and desorption time were systematically investigated. Under the optimum conditions, the analysis method was established and it exhibited wide linear range (0.016–20 μg/L) with good linearity (correlation coefficient ≥ 0.9947), low limits of detection (0.005–0.050 μg/L), and high enrichment factors (1189–2775). Relative standard deviations (n = 3) for intraday (≤3.3%) and interday (≤9.6%) tests indicated that the extraction material had satisfactory repeatability. Finally, the analytical method was successfully applied to detect trace polycyclic aromatic hydrocarbons in real water samples, demonstrating its satisfactory practicability.