Magnetron sputtering Si interlayer: a protocol to prepare solid phase microextraction coatings on metal-based fiber

Use of metal fibers in solid phase microextraction (SPME) can overcome the fragility drawback of conventional fused-silica ones. However, the surface modification of metal substrates is rather difficult, which largely prevents many mature traditional techniques, such as sol-gel and chemical bonding, being used in fabrication of SPME coating on metal-based fibers. This study demonstrates a protocol to resolve this problem by magnetron sputtering a firm Si interlayer on stainless steel fiber. The Si interlayer was easily modified active group, and attached with a multiwalled carbon nanotubes (MWCNTs) coating using the reported approach. The as-prepared MWCNTs/Si/stainless steel wire fiber not only preserved the excellent SPME behaviors of MWCNTs coatings, but also exhibited a number of advantages including high rigidity, long service life, and good stability at high temperature, in acid and alkali solutions. This new surface modification technique might provide a versatile approach to prepare sorbent coatings on unconfined substrates using traditional methods.     

Polypyrrole/graphene composite-coated fiber for the solid-phase microextraction of phenols

A polypyrrole (Ppy)/graphene (G) composite was developed and applied as a novel coating for use in solid-phase microextraction (SPME) coupled with gas chromatography (GC). The Ppy/G-coated fiber was prepared by electrochemically polymerizing pyrrole and G on a stainless-steel wire. The extraction efficiency of Ppy/G-coated fiber for five phenols was the highest compared with the fibers coated with either Ppy or Ppy/graphene oxide (GO) using the same method preparation. Significantly, compared with various commercial fibers, the extraction efficiency of Ppy/G-coated fiber is better than or comparable to 85 μm CAR/PDMS fiber (best extraction efficiency of phenol, o-cresol, and m-cresol in commercial fibers) and 85 μm polyacrylate (PA) fiber (best extraction efficiency of 2,4-dichlorophenol and p-bromophenol in commercial fibers). The effects of extraction and desorption parameters such as extraction time, stirring rate, and desorption temperature and time on the extraction/desorption efficiency were investigated and optimized. The calibration curves were linear from 10 to 1000 μg/L for o-cresol, m-cresol, p-bromophenol, and 2,4-dichlorophenol, and from 50 to 1000 μg/L for phenol. The detection limits were within the range 0.34-3.4 μg/L. The single fiber and fiber-to-fiber reproducibilities were <8.3 (n=7) and 13.3% (n=4), respectively. The recovery of the phenols spiked in natural water samples at 200 μg/L ranged from 74.1 to 103.9% and the relative standard deviations were <3.7%.     

Highly porous silica-polyaniline nanocomposite as a novel solid-phase microextraction fiber coating

A highly porous fiber-coated SBA-15/polyaniline material was prepared for solid-phase microextraction (SPME). The SBA-15/polyaniline nanocomposite was synthesized via chemical polymerization. The prepared SBA-15/polyaniline particles were analyzed by scanning electron microscopy analysis. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography-mass spectrometry (GC-MS). In optimum conditions (extraction temperature 60°C, extraction time 40 min, ionic strength 20%, stirring rate: 500 rpm, desorption temperature 260°C, desorption time 2 min), the repeatability for one fiber (n=3), expressed as relative standard deviation (RSD%), was between 5.3 and 8.6% for the test compounds. For deionized water, spiked with selected PAHs, the detection limits for the studied compounds were between 2 and 20 pg/mL.     

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%.     

Polymeric ionic liquid modified stainless steel wire as a novel fiber for solid‐phase microextraction

A polymeric ionic liquid modified stainless steel wire for solid‐phase microextraction was reported. Mercaptopropyl‐functionalized stainless steel wire that was formed by co‐condensation of tetramethoxysilane and 3‐mercaptopropyltrimethoxysilane via a sol‐gel process, which is followed by in situ surface radical chain‐transfer polymerization of 1‐vinyl‐3‐octylimidazolium hexafluorophosphate to result in polymeric ionic liquid modified stainless steel wire. The fiber surface was characterized by field emission scanning electron microscope equipped with energy dispersive X‐ray analysis. Coupled with GC, extraction performance of the fiber was tested with phenols and polycyclic aromatic hydrocarbons as model analytes. Effects of extraction and desorption conditions were investigated systematically in our work. RSDs for single‐fiber repeatability and fiber‐to‐fiber reproducibility were less than 7.34 and 16.82%, respectively. The calibration curves were linear in a wide range for all analytes and the detection limits were in the range of 10–60 ng L^?1. Two real water samples from the Yellow River and local waterworks were applied to test the as‐established solid‐phase microextraction–GC method with the recoveries of samples spiked at 10 μg L^?1 ranged from 83.35 to 119.24%. The fiber not only exhibited excellent extraction efficiency, but also very good rigidity, stability and durability.     

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.     

Electrodeposited polyaniline as a fiber coating for solid-phase microextraction of organochlorine pesticides from water

The study on the performance of polyaniline as a fiber coating for solid-phase microextraction (SPME) purposes has been reported. Polyaniline coatings were directly electrodeposited on the surface of a stainless steel wire and applied for the extraction of some organochlorine pesticides (OCPs) from water samples. Analyses were performed using GC-electron capture detection (GC-ECD). The results obtained show that polyaniline fiber coating is suitable for the successful extraction of organochlorine compounds. This behavior is most probably due to the porous surface structure of polyaniline film, which provides large surface areas and allowed for high extraction efficiency. Experimental parameters such as adsorption and desorption conditions were studied and optimized. The optimized method has an acceptable linearity, with a concentration range of 1-5000 ng/L. Single fiber repeatability and fiber-to-fiber reproducibility were less than 12 and 17%, respectively. High environmental resistance and lower cost are among the advantages of polyaniline fibers over commercially available SPME fibers. The developed method was applied to the analysis of real water samples from Yangtse River and Tianmu Lake.     

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.     

Three dimensional phytic acid-induced graphene as a solid-phase microextraction fiber coating and its analytical applications for nerolidol in tea

Three dimensional phytic acid-induced graphene coating was prepared by hydrothermal synthesis and fabricated on a stainless-steel wire as a solid phase microextraction (SPME) coating. Compared with the commercial 100 μm PDMS and 85 μm CAR/PDMS fibers, the home-made SPME fiber exhibited excellent extraction efficiency for the analysis of nerolidol in tea samples.     

Graphene oxide bonded fused-silica fiber for solid-phase microextraction-gas chromatography of polycyclic aromatic hydrocarbons in water

A novel chemically bonded graphene oxide/fused-silica fiber was prepared and applied in solid-phase microextraction of six polycyclic aromatic hydrocarbons from water samples coupled with gas chromatography. It exhibited high extraction efficiency and excellent stability. Effects of extraction time, extraction temperature, ionic strength, stirring rate and desorption conditions were investigated and optimized in our work. Detection limits to the six polycyclic aromatic hydrocarbons were less than 0.08 μg/L, and their calibration curves were all linear (R(2)≥0.9954) in the range from 0.05 to 200 μg/L. Single fiber repeatability and fiber-to-fiber reproducibility were less than 6.13 and 15.87%, respectively. This novel fiber was then utilized to analyze two real water samples from the Yellow River and local waterworks, and the recoveries of samples spiked at 1 and 10 μg/L ranged from 84.48 to 118.24%. Compared with other coating materials, this graphene oxide-coated fiber showed many advantages: wide linear range, low detection limit, and good stability in acid, alkali, organic solutions and at high temperature.     

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.     

Enhancing extraction rate in solid-phase microextraction by using nano-structured polyaniline coating

The decrement of equilibrium extraction time without losing extraction efficiency in solid-phase microextraction (SPME) was achieved using nano-structured coating. Polyaniline (PANI) was used as an extraction phase for the comparison of extraction capacity and equilibrium extraction time of nano- and micro-structured coatings. Polychlorinated biphenyls (PCBs) were used as model compounds to examine the extraction properties of nano- and micro-structured coatings. The results revealed that nano-structured PANI coating showed higher extraction rate and shorter desorption time than micro-structured coating, because of the larger surface area. In order to evaluate the extraction capability of prepared nano-structured PANI coating, headspace-SPME method was used for the determination of PCBs in sediment samples by GC-electron capture detector. The proposed method was validated using the certified reference material.     

Au nanoparticles as a novel coating for solid-phase microextraction

A novel solid-phase microextraction fiber based on a stainless steel wire coated with Au nanoparticles was prepared and has been applied, coupled with gas chromatography, to the extraction of aromatic hydrophobic organic chemical pollutants in rainwater and soil extract. The solid-phase microextraction fiber exhibited excellent extraction efficiency and selectivity. Effects of extraction time, extraction temperature, ionic strength, stirring rate and desorption conditions were investigated and optimized. Single fiber repeatability and fiber-to-fiber reproducibility were less than 7.90% and 26.40%, respectively. The calibration curves were linear in a wide range for all analytes. Correlation coefficients ranged from 0.9941 to 0.9993. The as-established SPME-GC method was used successfully to two real natural samples. Recovery of analytes spiked at 10 μg L(-1) and 100 μg L(-1) ranged from 78.4% to 119.9% and the relative standard deviations were less than 11.3%.     

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.     

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.     

Periodic mesoporous organosilica with ionic liquid framework as a novel fiber coating for headspace solid-phase microextraction of polycyclic aromatic hydrocarbons

Periodic mesoporous organosilica based on alkylimidazolium ionic liquid (PMO-IL) was prepared and used as a highly porous fiber coating material for solid-phase microextraction (SPME). The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography–mass spectrometry (GC–MS). A one at-the-time optimization strategy was applied for optimizing the important extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate, and desorption temperature and time. In optimum conditions, the repeatability for one fiber (n = 3), expressed as relative standard deviation (R.S.D.%), was between 4.3% and 9.7% for the test compounds. The detection limits for the studied compounds were between 4 and 9 pg mL⁻¹. The developed method offers the advantage of being simple to use, with shorter analysis time, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis.     

Tailor‐made ion‐imprinted polymer based on functionalized graphene oxide for the preconcentration and determination of trace copper in food samples

A tailor‐made Cu(II) ion‐imprinted polymer based on large‐surface‐area graphene oxide sheets has been synthesized for the preconcentration and determination of trace copper from food samples by solid‐phase extraction. Attributed to the ultrahigh surface area and hydrophilicity of graphene oxide, the Cu(II) ion‐imprinted polymer prepared by the surface ion‐imprinting technique exhibited a high binding capacity and a fast adsorption rate under the optimized experimental conditions. In the static adsorption experiments, the maximum adsorption capacity of Cu(II) ion‐imprinted polymer is 109.38 mg/g at 25°C, which is much higher than that of the nonimprinted polymer (32.12 mg/g). Meanwhile, the adsorption is very rapid and equilibrium is reached after approximately 30 min. The adsorption mechanism is found to follow Langmuir adsorption model and the pseudo‐second‐order adsorption process. The Cu(II) ion‐imprinted polymer was used for extracting and detecting Cu(II) in food samples combined with graphite flame atomic adsorption spectrometry with high recoveries in the range of 97.6–103.3%. The relative standard deviation and limit of detection of the method were evaluated as 1.2% and 0.37 μg/L, respectively. The results showed that the novel absorbent can be utilized as an effective material for the selective enrichment and determination of Cu(II) from food samples.     

Preparation of single-walled carbon nanotube fiber coating for solid-phase microextraction of organochlorine pesticides in lake water and wastewater

The feasibility of single-walled carbon nanotubes (SWCNTs) as adsorbents for solid-phase microextraction was investigated by using organochlorine pesticides (OCPs) as model compounds. SWCNTs were attached onto a stainless steel wire through organic binder. Potential factors affecting the extraction efficiency were optimized, including extraction time, extraction temperature, desorption time, desorption temperature, and salinity. The developed method has a linear range of 2-800 ng/L for most analytes, with coefficients of correlation ranging from 0.9911 to 0.9996, LODs ranged from 0.19 to 3.77 ng/L (S/N = 3), and RSDs in the range of 3.5-13.9% (n = 5). Compared with the commercial PDMS fiber, the SWCNT fiber has better thermal stability (over 350 degrees C) and longer life span (over 150 times). The developed method was applied to determine trace OCPs in lake water and wastewater samples with external standard calibration. Results showed that OCP contamination was very low in these samples, and HCHs were detected in almost all water samples while DDT concentrations were almost under detection limits in these samples. Recoveries obtained at 20 ng/L spiking level were in the range of 88.4-111% for OCPs in lake water. For wastewater samples, however, the recoveries were satisfactory for HCHs (63.6-97.1%) but relatively low for DDTs (44.7-116%) due to the high content of organic matter in wastewater.     

A sol-gel-based amino functionalized fiber for immersed solid-phase microextraction of organophosphorus pesticides from environmental samples

A method based on immersed solid-phase microextraction (SPME) and gas chromatography mass spectrometry detection (GC-MS) for the determination of organophosphorous pesticides (OPPs) in aqueous samples was developed. A sol-gel based coating fiber was prepared using 3-(trimethoxysilylpropyl) amine as precursor. The synthesized fiber was prepared in a way to impart polar moiety into the coating network and would be more suitable for extracting polar and semi-polar organic pollutants. Important parameters influencing the extraction process were optimized and an extraction time of 40 min at 30 °C gave maximum peak area, when NaCl (20% w/v) was added to the aqueous sample. The linearity for disulfoton, phorate and sulfotep was in the concentration range of 0.01 to 5 ng mL^− 1 and for parathion and O,O,O-triethylthiphosphate was in the range of 0.01 to 50 ng mL^− 1. Limits of detection ranged from 1 ng L^− 1, for parathion, to 0.05 ng L^− 1, for disulfoton using time-scheduled selected ion monitoring (SIM) mode, and the RSD% values were all below 10.5% at the 1 ng mL^− 1 level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 80 to 115%.