Electrochemical preparation of zinc oxide/polypyrrole nanocomposite coating for the highly effective solid‐phase microextraction of phthalate esters

In this work, zinc oxide/polypyrrole nanocomposite coating was fabricated on stainless steel and evaluated as a novel headspace solid‐phase microextraction fiber coating for extraction of ultra‐trace amounts of environmental pollutants, namely, phthalate esters, in water samples. The fiber nanocomposite were prepared by a two‐step process including the electrochemical deposition of polypyrrole on the surface of stainless steel in the first step, and electrochemical deposition of zinc oxide nanosheets in the second step. Porous structure together with zinc oxide nanosheets with the average diameter of 30 nm were observed on the surface by using scanning electron microscopy. The effective parameters on extraction of phthalate esters (i.e., extraction temperature, extraction time, desorption temperature, desorption time, salt concentration, and stirring rate) were investigated and optimized by one‐variable‐at‐a‐time method. Under optimized conditions (extraction temperature, 90°C; extraction time, 40 min; desorption temperature, 270°C; desorption time, 5 min; salt concentration, 25% w/v; and stirring rate, 1000 rpm), the limits of detection were in the range of 0.05–0.8 μg/L, and the repeatability and fiber‐to‐fiber reproducibility were in the ranges of 6.1–7.3% and 8.7–10.2%, respectively.     

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.     

Application of magnetized MOF‐74 to phthalate esters extraction from Chinese liquor

In this study, magnetized MOF‐74 (Ni) was prepared using an ultrasound‐assisted synthesis method. This novel functional magnetic adsorbent was characterized using various techniques. Using the prepared material as adsorbents, a magnetic solid‐phase extraction method coupled with high‐performance liquid chromatography was proposed for determining four phthalate esters in Chinese liquor samples. The extraction parameters, including solution pH, adsorbent amount, extraction time, and eluent type and volume, were optimized. Under the optimized conditions, proposed method showed good linearity within the range of 1.53–200 μg/L for diphenyl phthalate, 2.03–200 μg/L for butyl benzyl phthalate, 7.02–200 μg/L for diamyl phthalate, and 6.03–200 μg/L for dicyclohexyl phthalate, with correlation coefficients > 0.9944, low limits of detection (0.46–2.10 μg/L, S/N = 3), and good extraction repeatability (relative standard deviations of 3.7%, n = 6). This method was successfully used to analyze phthalate esters in Chinese liquor samples with recoveries of 74.4–104.8%. Two phthalate esters were detected in two samples, both at concentrations that satisfied the Chinese national standard, indicating this method has practical application prospects. The extraction efficiency of this method was also compared with conventional solid‐phase extraction using commercial C₁₈ cartridges. The results demonstrated that the proposed magnetic solid‐phase extraction is a simple, time‐saving, efficient, and low‐cost method.     

A porous carbon derived from amino‐functionalized material of Institut Lavoisier as a solid‐phase microextraction fiber coating for the extraction of phthalate esters from tea

In this work, a porous carbon derived from amino‐functionalized material of Institut Lavoisier (C‐NH₂‐MIL‐125) was prepared and coated onto a stainless‐steel wire through sol–gel technique. The coated fiber was used for the solid‐phase microextraction of trace levels of phthalate esters (diallyl phthalate, di‐iso‐butyl ortho‐phthalate, di‐n‐butyl ortho‐phthalate, benzyl‐n‐butyl ortho‐phthalate, and bis(2‐ethylhexy) ortho‐phthalate) from tea beverage samples before gas chromatography with mass spectrometric analysis. Several experimental parameters that could influence the extraction efficiency such as extraction time, extraction temperature, sample pH, sample salinity, stirring rate, desorption temperature and desorption time, were investigated. Under the optimal conditions, the linearity existed in the range of 0.05–30.00 μg/L for green jasmine tea beverage samples, and 0.10–30.00 μg/L for honey jasmine tea beverage samples, with the correlation coefficients (r) ranging from 0.9939 to 0.9981. The limits of detection of the analytes for the method were 2.0–3.0 ng/L for green jasmine tea beverage sample, and 4.0–5.0 ng/L for honey jasmine tea beverage sample, depending on the compounds. The recoveries of the analytes for the spiked samples were in the range of 82.0–106.0%, and the precision, expressed as the relative standard deviations, was less than 11.1%.     

Palladium‐coated stainless‐steel wire as a solid‐phase microextraction fiber

A novel palladium solid‐phase microextraction coating was fabricated on a stainless‐steel wire by a simple in situ oxidation–reduction process. The palladium coating exhibited a rough microscaled surface and its thickness was about 2 μm. Preparation conditions (reaction time and concentration of palladium chloride and hydrochloric acid) were optimized in detail to achieve sufficient extraction efficiency. Extraction properties of the fiber were investigated by direct immersion solid‐phase microextraction of several polycyclic aromatic hydrocarbons and phthalate esters in aqueous samples. The extracted analytes were transferred into a gas chromatography system by thermal desorption. The effect of extraction and desorption conditions on extraction efficiency were investigated. Under the optimum conditions, good linearity was obtained and correlation coefficients between 0.9908 and 0.9990 were obtained. Limits of detection were 0.05–0.10 μg/L for polycyclic aromatic hydrocarbons and 0.3 μg/L for phthalate esters. Their recoveries for real aqueous samples were in the range from 97.1 to 121% and from 89.1 to 108%, respectively. The intra‐ and interday tests were also investigated with three different addition levels, and satisfactory results were also obtained.     

Zeolite/Fe3O4 as a new sorbent in magnetic solid‐phase extraction followed by gas chromatography for determining phthalates in aqueous samples

In the present study, for the first time, we successfully employed zeolite/Fe₃O₄ as a new magnetic nanoparticle sorbent in magnetic solid‐phase extraction for determining phthalates in aqueous samples. Gas chromatography with flame ionization detection was used to detect the target analytes as a powerful instrumental analysis. Affecting parameters in the extraction process, including the amount of adsorbent, adsorption and desorption time, and volume of desorption solvent, were optimized using a response surface methodology based on central composite design. Under the optimum conditions, the linear range for dibutyl phthalate and bis(2‐ethylhexyl phthalate) was varied in the interval of 10–1700 and 10–1200 μg/L, respectively. Limits of detection were 2.80 μg/L for dibutyl phthalate and 3.20 μg/L for bis(2‐ethylhexyl phthalate). The recovery value for the extraction of target analytes was between 97 and 111%. The repeatability and reproducibility of the new proposed method were obtained: 10–13% and 13–13.5%, respectively. The increased sensitivity in using the proposed method has been demonstrated. Compared with previous methods, the new proposed method is an accurate, rapid, and reliable sample‐pretreatment method.     

Polyethylene glycol/graphene oxide coated solid‐phase microextraction fiber for analysis of phenols and phthalate esters coupled with gas chromatography

A new polyethylene glycol/graphene oxide composite material bonded on the surface of a stainless‐steel wire was used for solid‐phase microextraction. The layer‐by‐layer structure increased the adsorption sites of the novel fiber, which could facilitate the extraction of trace compounds. The polyethylene glycol/graphene oxide was characterized by Fourier transform infrared spectroscopy and elemental analysis, which verified that polyethylene glycol was successfully grafted onto the surface of graphene oxide. The performance of the polyethylene glycol/graphene oxide coated fiber was investigated for phenols and phthalate esters coupled with gas chromatography with flame ionization detection under the optimal extraction and desorption conditions, and the proposed method exhibited an excellent extraction capacity and high thermal stability. Wide linear ranges were obtained for the analytes with good correlation coefficients in the range of 0.9966–0.9994, and the detection limits of model compounds ranged from 0.003 to 0.025 μg/L. Furthermore, the as‐prepared fiber was used to determine the model compounds in the water and soil samples and satisfactory results were obtained.     

Magnetic nanocomposite of self‐doped polyaniline–graphene as a novel sorbent for solid‐phase extraction

This work is the first study on the extraction efficiency of self‐doped polyaniline that is immobilized on the graphene‐modified magnetic nanoparticles. The new material was used as a sorbent for the magnetic solid‐phase extraction of methyl‐, propyl‐, and butylparabens. The use of graphene provides a high surface area and prevents aggregation of the nanoparticles. The self‐doped polyaniline also provides multifunctionality, high extraction capacity, and chemical stability even in the basic medium. The parabens were acetylated for determination by gas chromatography with flame ionization detection. The effects of monomer ratio, extraction solvent, sorbent amount, sample volume, desorption solvent volume, adsorption and desorption times, and sample ionic strength were optimized. Preconcentration factors obtained were from 190 to 310. The detection limits of the method were <2.8 μg/L. Linear ranges of the method were 5–2000 μg/L for propyl and butyl parabens, and 10–2000 μg/L for methyl paraben. The method was applied for the determination of the parabens in cosmetic products and extraction recoveries were 89–101% with RSDs ≤7.9%.     

Polydopamine‐coated cotton fibers as the adsorbent for in‐tube solid‐phase microextraction

Polydopamine was coated onto cotton fibers as the adsorbent to improve the extraction efficiency. Polydopamine‐coated cotton fibers were placed into a polyetheretherketone tube for in‐tube solid‐phase microextraction. To develop an online analysis system, the extraction tube was connected with high‐performance liquid chromatography. The tube was evaluated with five estrogenic analytes, and the extraction and desorption conditions were optimized to get high extraction efficiency. Under the optimum conditions, the enrichment factors of five analytes were 143–1745. An online analysis method was established, it had large linear ranges (0.10–40 and 0.16–40 μg/L), low limits of detection (0.03, 0.05 μg/L) and satisfactory repeatability (≤3.2%). The analysis method was applied to detect targets in the real samples like as hot water in new plastic cup and tap water. The relative recoveries spiked at 1 and 5 μg/L in these samples were investigated and the results were in the range of 83.7–109%.     

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%.     

Application of magnetic graphitic carbon nitride nanocomposites for the solid‐phase extraction of phthalate esters in water samples

Magnetic graphitic carbon nitride nanocomposites were successfully prepared in situ and used to develop a highly sensitive magnetic solid‐phase extraction method for the preconcentration of phthalate esters such as di‐n‐butyl phthalate, butyl phthalate, dihexyl phthalate, and di‐(2‐ethyl hexyl) phthalate from water. The adsorption and desorption of the phthalate esters on magnetic graphitic carbon nitride nanocomposites were investigated and the parameters affecting the partition of the phthalate esters, such as adsorption, desorption, recovery, were assessed. Under the optimized conditions, the proposed method showed excellent sensitivity with limits of detection (S/N = 3) in the range of 0.05–0.1 μg/L and precision in the range of 1.1–2.6% (n = 5). This method was successfully applied to the analysis of real water samples, and good spiked recoveries over the range of 79.4–99.4% were obtained. This research provides a possibility to apply this nanocomposite for adsorption, preconcentration, or even removal of various carbon‐based ring or hydrophobic pollutants.     

Cyclodextrin‐functionalized reduced graphene oxide as a fiber coating material for the solid‐phase microextraction of some volatile aromatic compounds

A novel solid phase microextraction fiber was prepared for the first time by using a sol–gel technique with hydroxypropyl‐β‐cyclodextrin‐functionalized reduced graphene oxide as the fiber coating material. The results verified that the β‐cyclodextrin was successfully grafted onto the surface of reduced graphene oxide and the coating possessed a uniform folded and wrinkled structure. The performance of the solid phase microextraction fiber was evaluated by using it to extract nine volatile aromatic compounds from water samples before determination with gas chromatography and flame ionization detection. Some important experimental parameters that could affect the extraction efficiency such as the extraction time, extraction temperature, desorption temperature, desorption time, the volume of water sample solution, stirring rate, as well as ionic strength were optimized. The new method was validated to be effective for the trace analysis of some volatile aromatic compounds, with the limits of detection ranging from 2.0 to 8.0 ng/L. Single fiber repeatability and fiber‐to‐fiber reproducibility were in the range of 2.5–9.4 and 5.4–12.9%, respectively. The developed method was successfully applied to the analysis of three different water samples, and the recoveries of the method were in the range from 77.9 to 113.6% at spiking levels of 10, 100, and 1000 ng/L, respectively.     

Coating of optical fiber with a smart thermosensitive polymer for the separation of phthalate esters by solid‐phase microextraction

A solid‐phase microextraction fiber was prepared by coating an optical fiber with a temperature‐sensitive polymer to determine phthalate esters. N‐Isopropylacrylamide and N,N′‐methylenebisacrylamide were used as the monomer and the cross linker, respectively. The fabricated fiber was characterized by FTIR spectroscopy, thermogravimetric analysis, and scanning electron microscopy. During extraction, important factors such as extraction time, pH, temperature, and ionic strength were optimized. The fabricated fiber, which is firm, inexpensive, stable, and efficient, is a vital material used in solid‐phase microextraction. Under optimum conditions, the calibration curve was linear and in the range of 1–20 μg/L (r² = 0.9747). The high extraction efficiency was obtained for phthalates with a detection limit of 0.12 μg/L. The fabricated fiber was successfully applied to the solid‐phase micro extraction of phthalates from water samples after its extraction, followed by gas chromatography with flame ionization detection.     

Multiple monolithic fiber solid‐phase microextraction based on a polymeric ionic liquid with high‐performance liquid chromatography for the determination of steroid sex hormones in water and urine

The development of a simple and sensitive analytical approach that combines multiple monolithic fiber solid‐phase microextraction with liquid desorption followed by high‐performance liquid chromatography with diode array detection is proposed for the determination of trace levels of seven steroid sex hormones (estriol, 17β‐estradiol, testosterone, ethinylestradiol, estrone, progesterone and mestranol) in water and urine matrices. To extract the target analytes effectively, multiple monolithic fiber solid‐phase microextraction based on a polymeric ionic liquid was used to concentrate hormones. Several key extraction parameters including desorption solvent, extraction and desorption time, pH value and ionic strength in sample matrix were investigated in detail. Under the optimal experimental conditions, the limits of detection were found to be in the range of 0.027–0.12 μg/L. The linear range was 0.10–200 μg/L for 17β‐estradiol, 0.25–200 μg/L estriol, ethinylestradiol and estrone, and 0.50–200 μg/L for the other hormones. Satisfactory linearities were achieved for analytes with the correlation coefficients above 0.99. Acceptable method reproducibility was achieved by evaluating the repeatability and intermediate precision with relative standard deviations of both less than 8%. The enrichment factors ranged from 54‐ to 74‐fold. Finally, the proposed method was successfully applied to the analysis of steroid sex hormones in environmental water samples and human urines with spiking recoveries ranged from 75.6 to 116%.     

Solid‐phase microextraction with a graphene‐composite‐coated fiber coupled with GC for the determination of some halogenated aromatic hydrocarbons in water samples

In this work, a graphene composite was coated onto etched stainless‐steel wire through a sol–gel technique and it was used as a solid‐phase microextraction (SPME) fiber. The prepared fiber was characterized by SEM, which revealed that the fiber had a highly porous structure. The application of the fiber was evaluated through the headspace SPME of five halogenated aromatic hydrocarbons (chlorobenzene, bromobenzene, 1,3‐dichlorobenzene, 1,2‐dichlorobenzene, and 1,2,4‐trichlorobenzene) in water samples followed by GC with flame ionization detection. The main factors influencing the extraction efficiency, including headspace volume, extraction time, extraction temperature, stirring rate, ionic strength of sample solution, and desorption conditions, were studied and optimized. Under the optimum conditions, the linearity of the method ranged from 2.5 to 800.0 μg/L for 1,2,4‐trichlorobenzene and from 2.5 to 500.0 μg/L for chlorobenzene, bromobenzene, 1,3‐dichlorobenzene, and 1,2‐dichlorobenzene, with the correlation coefficients (r) ranging from 0.9962 to 0.9980, respectively. The LODs (S/N = 3) of the method for the analytes were in the range between 0.5 and 1.0 μg/L. The recoveries of the method for the analytes obtained for the spiked water samples at 50.0 and 250.0 μg/L were from 76.0 to 104.0%.     

Solid‐phase microextraction of phthalate esters by a new coating based on a thermally stable polypyrrole/graphene oxide composite

A novel polypyrole/graphene oxide coating was made by the electrochemical polymerization of pyrrole in the presence of sodium dodecyl sulfate and graphene oxide on a platinum wire. The prepared fiber has shown a good thermal stability up to 300°C. The fiber was applied to the direct solid‐phase microextraction and gas chromatographic analysis of four phthalate esters. The effect of four parameters on gas chromatography peak area including extraction temperature, extraction time, injection temperature, and ionic strength were investigated. Under the optimized conditions, the detection limits were between 0.042 and 0.26 μg/L. The intraday and interday relative standard deviations obtained at 55 μg/L, using a single fiber, were 8.2–16% and 17.3–25.6%, respectively. The method was successfully applied to the analysis of phthalate esters in two real samples of boiling water in cheap disposable clear plastic drinking cups showing recoveries from 83 to 120%.     

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%.     

A novel silver-coated solid-phase microextraction metal fiber based on electroless plating technique

A novel silver-coated solid-phase microextraction fiber was prepared based on electroless plating technique. Good extraction performance of the fiber for model compounds including phthalate esters (dibutyl phthalate, dioctyl phthalate, dicyclohexyl phthalate and diallyl phthalate) and polycyclic aromatic hydrocarbons (naphthalene, fluorene, phenanthrene, fluoranthene) in aqueous solution was obtained. Under the optimized conditions (extraction temperature, extraction time, ionic strength and desorption temperature), the proposed SPME-GC method showed wide linear ranges with correlation coefficients (R²) ranging from 0.9745 to 0.9984. The limits of detection were at the range of 0.02 to 0.1 μg L⁻¹. Single fiber repeatability and fiber-to-fiber reproducibility as well as stability to acid, alkali and high temperature were studied and the results were all satisfactory. The method was applied successfully to the aqueous extracts of disposable paper cup and instant noodle barrel. Several kinds of analytes were detected and quantified.     

Preparation of monolithic fibers for the solid‐phase microextraction of chlorophenols in water samples

Monolithic fibers were synthesized and applied for the solid‐phase microextraction and determination of chlorophenols in environmental water samples by coupling with HPLC. The fibers were prepared by copolymerization of vinylimidazole and ethylene dimethacrylate as functional monomer and cross‐linker, respectively. The effect of the preparation conditions of monolithic fibers on the extraction efficiencies was investigated in detail. Several characteristic techniques, such as elemental analysis, infrared spectroscopy, mercury‐intrusion porosimetry, and SEM were used to characterize the monolithic material. The effect of the extraction parameters, including desorption solvent, extraction and desorption time, pH values, and ionic strength in sample matrix on the extraction performance was investigated thoroughly. Under the improved extraction conditions, the linear ranges of 2‐chlorophenol, 2,4‐dichlorophenol and pentachlorophenol were 1.0–200 μg/L and 2.0–200 μg/L for 2,4,6‐trichlorophenol. The detection limits (S/N = 3) were in the range of 0.16–0.45 μg/L, the RSDs for intraday and interday precisions were <7.0%. Finally, the proposed method was successfully used to detect different environmental water samples. The recoveries of spiked water samples were ranged from 90.0 to 115%. At the same time, satisfactory repeatability was achieved with RSDs < 9.0%.     

Application of a solid‐phase microextraction fiber coated with a graphene oxide‐poly(dimethylsiloxane) composite for the extraction of triazoles from water

A solid‐phase microextraction fiber was prepared by mixing graphene oxide and hydroxyl‐terminated polydimethylsiloxane together and then coating the mixture on the surface of etched stainless‐steel wire by sol–gel technology. After aging by heating, the graphene oxide‐polydimethylsiloxane composite coated fiber was used for the direct solid phase microextraction of triazole fungicides from water samples. The properties of the graphene oxide‐polydimethylsiloxane coating were characterized by transmission electron microscopy and thermogravimetric analysis. And the chemical stability of the coating was tested as well. Several important experimental parameters that could influence the extraction efficiency such as desorption temperature and time, extraction temperature and time, sample pH and stirring rate, were investigated and optimized. Under the optimized conditions, the limits of detection were in the range from 0.01 to 0.03 μg/L. The results indicated that the homemade fiber had the advantages of good thermal and chemical stability and high extraction efficiency, which was successfully applied to the analysis of triazoles in water samples.