Mian Wu

Electrochemical preparation of polyaniline-polypyrrole solid-phase microextraction coating and its application in the GC determination of several esters.

A novel polyaniline-polypyrrole (PANI-PPY) composite film coated stainless steel wire was prepared by cyclic voltammetry. Firstly, PANI was electrodeposited on a stainless steel wire from a solution containing 0.1 M aniline and 1M HNO3, after the PANI coating was dried in air PPY was electrodeposited on it from a solution containing 0.1 M pyrrole and 0.1 M p-methylbenzene sulfonic acid. The resulting PANI-PPY fiber showed reticulate structure and had large specific surface area. When it was used for the headspace solid-phase microextraction of several esters (i.e. methyl anthranilate, ethyl-o-aminobenzoate, dimethyl phthalate, methyl laurate, and diethyl phthalate), followed by gas chromatographic determination, it presented higher extraction capability in comparison with PPY and PANI coatings. Under the optimized conditions, the linear ranges were 0.07-300 μg L(-1) and the detection limits were 0.05-0.38 μg L(-1) for different esters. The PANI-PPY fiber also showed high durability, after being used for about 160 times its extraction capacity only changed a little. The proposed method was successfully applied to the determination of these esters in real samples and the recoveries were 90-102%.

In situ solvothermal growth of metal-organic framework-ionic liquid functionalized graphene nanocomposite for highly efficient enrichment of chloramphenicol and thiamphenicol.

Here we report a facile in situ solvothermal growth method for immobilization of metal-organic framework-ionic liquid functionalized graphene (MOF-5/ILG) composite on etched stainless steel wire. The X-ray diffraction spectra, scanning electron microscopy and transmission electron microscopy images showed that the metal organic framework possessed good crystal shape and its structure was not disturbed by the introduction of ILG. Moreover, the covalent bond established between the amino group of ILG and the carboxylic group of the metal organic framework improved the mechanical stability and structure uniformity of the microcrystals. The obtained material combined the favorable attributes of both metal-organic framework and ILG, having high surface area (820 m(2)/g) and good adsorption capability. Its adsorption properties were explored by preconcentrating chloramphenicol and thiamphenicol from aqueous solutions prior to gas chromatography-flame ionization detection. The MOF-5/ILG exhibited high enrichment capacity for the analytes as they could interact through π-π and H-bonding interaction. Under the optimum conditions, good linearity (correlation coefficients higher than 0.9981), low limits of detection (14.8-19.5 ng/L), and good precision (relative standard deviations less than 6.0% (n=5)) were achieved. The MOF-5/ILG composite displayed durable property. The method was applied to the determination of two antibiotics in milk, honey, urine and serum samples with acceptable relative recoveries of 82.3-103.2%.

Ionic liquid polymer functionalized carbon nanotubes-doped poly(3,4-ethylenedioxythiophene) for highly-efficient solid-phase microextraction of carbamate pesticides.

A poly(3,4-ethylenedioxythiophene)-ionic liquid polymer functionalized multiwalled carbon nanotubes (PEDOT-PIL/MWCNTs) composite solid-phase microextraction (SPME) coating was fabricated by electrodeposition. After being dipped in Nafion solution, a Nafion-modified coating was obtained. The outer layer Nafion played a crucial role in enhancing the durability and stability of the coating, thus it was robust enough for replicated extraction for at least 150 times without decrease of extraction performance. The Nafion-modified coating exhibited much higher sensitivity than commercial coatings for the direct extraction of carbamate pesticides in aqueous solutions, due to its strong hydrophobic effect and π-π affinity based enrichment. When it was used for the determination of carbamate pesticides in combination with gas chromatography-flame ionization detection, good linearity (correlation coefficients higher than 0.9981), low limits of detection (15.2-27.2 ng/L) and satisfactory precision (relative standard deviation <8.2%, n=5) were achieved. The developed method was applied to the analysis of four carbamate pesticides in apple and lettuce samples, and acceptable recoveries (i.e. 87.5-106.5%) were obtained for the standard addition.

Highly selective and effective solid phase microextraction of benzoic acid esters using ionic liquid functionalized multiwalled carbon nanotubes-doped polyaniline coating.

The present work reports the electrochemical fabrication of an ionic liquid functionalized multiwalled carbon nanotubes-polyaniline (MWCNT@IL/PANI) nanocomposite coating and its application in the headspace-solid phase microextraction (HS-SPME) and gas chromatography (GC) determination of benzoic acid esters (i.e., methyl benzoate, ethyl benzoate, propyl benzoate and butyl benzoate). The MWCNTs was firstly functionalized with amine-terminated IL (MWCNT@IL) through chemical reduction, and then was doped in PANI during the electropolymerization of aniline. The resulting coating was characterized by infrared spectroscopy, field emission scanning electron microscopy and thermo gravimetry. It showed net-like structure and had high thermal stability (up to 330°C). Furthermore, it presented high selectivity for the four benzoic acid esters and thus suited for their HS-SPME-GC determination. Results showed that under optimized extraction conditions, the detection limits were less than 6.1ngL(-1) (S/N=3) and the linear detection ranges were 0.012-50μgL(-1) (R≥0.9957) for these analytes. The relative standard deviations (RSDs) were lower than 6.4% for five successive measurements with one fiber, and the RSDs for fiber-to-fiber were 4.4-9.6% (n=5). The developed method was successfully applied to the determination of these benzoic acid esters in perfume samples.

Fabrication of poly(3,4-ethylenedioxythiophene)-ionic liquid functionalized graphene nanosheets composite coating for headspace solid-phase microextraction of benzene derivatives

A new poly(3,4-ethylenedioxythiophene)-ionic liquid (i.e. 1-hydroxyethyl-3-methyl imidazolium-bis[(trifluoromethyl)sulfonyl]imide) functionalized graphene nanosheets (PEDOT-IL/GNs) composite coating was electrodeposited on a stainless steel wire for headspace solid-phase microextraction. The coating showed porous folded and wrinkled structure and had large surface area due to the combined effect of PEDOT and IL/GNs. In addition, it displayed high thermal stability (up to 340 °C) and durable property (could be used for more than 200 times). The PEDOT-IL/GNs coating exhibited high affinity to benzene derivatives studied (i.e. toluene, 1,4-dimethylbenzene, 1,2-dimethylbenzene, 2-chlorotoluene, 1,3,5-trimethylbenzene and 1,4-dichlorobenzene) as they can interact through π-π and hydrophobic interactions. When they were extracted the enrichment factors ranged from 1901 (for 1,4-dichlorobenzene) to 3041 (for 1,4-dimethylbenzene). Coupled with gas chromatography-flame ionization detection, the benzene derivatives were extracted and determined. Wide linear ranges with 4 orders of magnitude (0.06-500 μg L(-1)) and low limits of detection (10.7-19.8 ng L(-1)) were achieved. The RSDs of chromatographic peak areas were <5.9% (n=5) and <7.5% (n=5) for single fiber and fiber-to-fiber, respectively. The method was applied to the determination of the benzene derivatives in real samples with acceptable recoveries from 82.3% to 108.3%.

A novel poly(3,4-ethylenedioxythiophene)-ionic liquid composite coating for the headspace solid-phase microextraction and gas chromatography determination of several alcohols in soft drinks.

A novel poly(3,4-ethylenedioxythiophene)-ionic liquid (i.e., 1-hydroxyethyl-3-methyl imidazolium-bis[(trifluoromethyl)sulfonyl]imide) composite film was electrodeposited on a Pt wire for headspace solid-phase microextraction. The film showed nodular structure and had large specific surface. In addition, it displayed high thermal stability (up to 300°C) and durable property (could be used for more than 200 times). Coupled with gas chromatography-flame ionization detection, the resulting fiber was applied to the headspace solid-phase microextraction and determination of several alcohols (i.e., linalool, nonanol, terpineol, geraniol, decanol and dodecanol). It presented higher extraction capability in comparison with the poly(3,4-ethylenedioxythiophene) and commercial polydimethylsiloxane/divinylbenzene fiber. Under the optimized conditions, the linear ranges exceeded three magnitudes with correlation coefficients above 0.9952 and the low limits of detection were 34.2-81.3ng L(-1). For different alcohols the repeatabilities (defined as RSD) were <5.8% and <7.8% for single fiber (n=5) and fiber-to-fiber (n=4), respectively. The proposed method was applied to the determination of these alcohols in real samples with acceptable recoveries from 81.1% to 106.6%.

High-Quality Metal–Organic Framework ZIF-8 Membrane Supported on Electrodeposited ZnO/2-methylimidazole Nanocomposite: Efficient Adsorbent for the Enrichment of Acidic Drugs

Metal–organic framework (MOF) membranes have received increasing attention as adsorbents, yet the defects in most membrane structures greatly thwart their capacity performance. In this work, we fabricated a novel ZnO/2-methylimidazole nanocomposite with multiple morphology by electrochemical method. The nanocomposite provided sufficient and strong anchorages for the zeolitic imidazolate frameworks-8 (ZIF-8) membrane. Thus, a crack-free and uniform MOF membrane with high performance was successfully obtained. In this case, 2-methylimidazole was believed to react with ZnO to form uniform ZIF nuclei, which induced and guided the growth of ZIF-8 membrane. The as-prepared ZIF-8 membrane had large surface area and good thermal stability. As expected, it displayed high adsorption capacity for acidic drugs (e.g., ibuprofen, ketoprofen and acetylsalicylic acid) as they could interact through hydrophobic, hydrogen bonding and π-π stacking interaction. Accordingly, by coupling with gas chromatography the ZIF-8 membrane was successfully applied to the real-time dynamic monitoring of ibuprofen in patient’s urine.

Ionic liquid polymer functionalized carbon nanotubes-coated polyaniline for the solid-phase microextraction of benzene derivatives

Multiwalled carbon nanotubes (MWCNTs) were non-covalently functionalized with poly(imidazolium ionic liquids) (PILs), and the resulting PIL/MWCNTs composite suspension was coated on electrodeposited polyaniline (PANI) film to fabricate a novel solid-phase microextraction coating (PANI-PIL/MWCNTs). The coating showed porous structure and had large specific surface area (231 m2 g−1, determined by the Brunauer–Emmett–Teller N2 adsorption method). Its adsorption properties were explored by preconcentrating benzene derivatives from water samples prior to gas chromatography-flame ionization detection. The results showed that the PANI-PIL/MWCNTs composite had high enrichment capacity for the analytes and high stability for repeatable use, due to the synergistic effect of PANI and PIL/MWCNTs. Hence, a detection method was developed for them, and good linearity (correlation coefficients higher than 0.9953), low limits of detection (17.7–32.6 ng L−1) and high precision (relative standard deviations less than 6.5% (n = 5)) were achieved. The method was applied to the determination of the benzene derivatives in real samples with recoveries of 84.0–106.9%.

Facile fabrication of ionic liquid doped polycarbazole coating for the headspace solid-phase microextraction of some environmental pollutants.

A novel polycarbazole (PCz)-ionic liquid (IL, i.e. 1-hydroxyethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [HOEMIm][NTf2]) composite coating (PCz-IL) was fabricated by electrodeposition. The IL could facilitate the electrodeposition of poor-conductive PCz and a more porous coating was obtained. The composite coating exhibited enhanced extraction capacity for some environmental pollutants (i.e. o-chlorotoluene, p-bromotoluene, o-nitrotoluene, m-nitrotoluene, p-nitrotoluene), as they could interact through π-π and hydrophobic interactions. Compared with [HOEMIm][NTf2] coated fiber, some other PCz-IL fibers (here IL=1-hydroxyethyl-3-methylimidazolium hexafluorophosphate and 1-methyl-3-octylimidazolium hexafluorophosphate) and commercial fibers (i.e. polydimethylsiloxane and polyacrylate), the PCz-IL fiber showed better performance. It was used for the determination of the environmental pollutants by coupling with gas chromatography, the limits of detection were 47.8-65.9 ng L(-1) under the optimized conditions and the linear ranges were 0.1-500 μg L(-1) with correlation coefficients above 0.9947 for different compounds. The relative standard deviations (RSDs) were 3.4-4.6% for five successive extractions with single fiber, and the RSDs for inter-fiber were 6.5-10.4% (n=5). The fiber was successfully applied to the detection of real samples and the recoveries for standards added were 88.6-108.8% with RSDs below 9.7%.

A Poly(ethylenglycol) Functionalized ZIF-8 Membrane Prepared by Coordination-Based Post-Synthetic Strategy for the Enhanced Adsorption of Phenolic Endocrine Disruptors from Water

Metal–organic framework (MOF) membranes have received increasing attention as adsorbents, yet single phase MOF membranes have certain limitations, which frustrate their capacity performance. In this work a MOF composite membrane was successfully prepared by a facile and green strategy through reasonable design. At first, a defect-free ZIF-8 membrane was fabricated on an ionic liquid modified pencil bar by a solvothermal method. Then, a novel poly(ethylenglycol) functionalized ZIF-8 composite membrane (ZIF-8/PEG-NH2) was prepared through a flexible coordination-based post-synthetic modification strategy. We found that reaction time and temperature were two crucial factors for successfully fabricating well-defined ZIF-8/PEG-NH2 membrane. Besides, the adsorption of phenolic endocrine disruptors (e.g., 4-nonylphenol) on original ZIF-8 membrane and ZIF-8/PEG-NH2 membrane was investigated, and the good adsorption selectivity of ZIF-8/PEG-NH2 membrane towards 4-nonylphenol was demonstrated, with high adsorption capacity and fast adsorption dynamics. Excitingly, such ZIF-8/PEG-NH2 membrane was successfully employed for the selective detection of 4-nonylphenol from environmental water samples, demonstrating its great application potential in environmental monitoring.