Polar Aromatic Amines Research Articles

Synthesis of stable and efficient amide-based covalent organic frameworks fiber coatings for the improved solid-phase microextraction of polar aromatic amines

BackgroundDeveloping facile and general functionalization strategies to improve the durability of covalent organic framework (COF) coatings and their affinity for polar targets is of great significance for solid-phase microextraction (SPME) technology. ResultsIn this work, a facile and general amidation strategy was developed for conversion from reversible (imine) to irreversible (amide) linkages in COF coatings. After the amidation, the durability of the obtained amide-linked covalent organic framework (Am-P-COF) coating was greatly improved, and the adsorption efficiency for polar aromatic amines (AAs) was also significantly increased. Moreover, this strategy is also applicable to the amidation of other two COF coatings, showing good general applicability. The obtained Am-P-COF coated fiber was used for SPME, and then coupled with gas chromatography tandem mass spectrometry (GC-MS/MS) to detect AAs. Under the optimal SPME conditions (extraction temperature: 50 °C, extraction time: 30 min, stirring rate: 600 rpm, pH: 8, NaCl concentration: 5.0 mg mL−1, desorption temperature: 290 °C and desorption time: 10 min), a detection method for trace AAs was established. The established method possess wide linear ranges (0.5–500.0 ng L−1), good correlation coefficients (0.9986–0.9993) and low detection limits (0.1–0.5 ng L−1). Moreover, the established method had also been successfully applied to detection of trace AAs in bottled tea beverage and plastic bags packed tea with satisfactory recoveries (83.5 %–116.8 %). Significance and noveltyThis research provides a facile and general pathway for increasing the durability of COF coatings and affinity to the polar AAs. The detection method based on the obtained fibers possesses high sensitivity, satisfactory reproducibility and good precision.

Efficient trap of polar aromatic amines in environmental waters by electroenhanced solid phase microextraction based on porous monolith doped with carboxylic carbon nanotubes

• A new adsorbent based on porous monolith doped with carboxylic carbon nanotubes. • Exertion of electric field during extraction period assisted the capture of polar AAs. • Extraction conditions were optimized and capture mechanism was deducted. • Practical applicability of suggested M@CCNs/EE-SPME-HPLC/DAD method was demonstrated. Efficient trap of polar aromatic amines (AAs) is challenging due to their high water-solubility. In this study, electroenhanced solid phase microextraction (EE-SPME) based on porous monolith doped with carboxylic carbon nanotubes (M@CCNs) was developed for the first time to efficiently capture AAs at trace levels in water samples. According to the chemical features of studied AAs, poly (1-vinyl-3-octylimidazolium tetrafluoroborate- co -divinylbenzene) monolith mingled with M@CCNs was fabricated on the surface of stainless steel wire and utilized as the extraction medium of EE-SPME. Results well evidenced that the introduction of carboxylic carbon nanotubes not only enhanced the surface area of monolith, but also introduced carboxyl group into the adsorbent. The implement of electric field during extraction process improved the trap performance, the extraction efficiencies increased by 36–48% compared with without application of electric field. The practicability and reliability of M@CCNs/EE-SPME was demonstrated by combining high-performance liquid chromatography with diode-array detector to quantify studied AAs in various water samples. The limits of detection and limits of quantification located at the ranges of 0.0013–0.012 μg/L and 0.0042–0.040 μg/L, respectively. The recoveries with different fortified concentrations were in the range of 83.1–118%. In addition, related extraction mechanism of M@CCNs/EE-SPME towards studied AAs was deduced.

Determination of polar aromatic amines using newly synthesized sol–gel titanium (IV) butoxide cyanopropyltriethoxysilane as solid phase extraction sorbent

A solid phase extraction (SPE) method has been developed using a newly synthesized titanium (IV) butoxide-cyanopropyltriethoxysilane (Ti-CNPrTEOS) sorbent for polar selective extraction of aromatic amines in river water sample. The effect of different parameters on the extraction recovery was studied using the SPE method. The applicability of the sorbents for the extraction of polar aromatic amines by the SPE was extensively studied and evaluated as a function of pH, conditioning solvent, sample loading volume, elution solvent and elution solvent volume. The optimum experimental conditions were sample at pH 7, dichloromethane as conditioning solvent, 10 mL sample loading volume and 5 mL of acetonitrile as the eluting solvent. Under the optimum conditions, the limit of detection (LOD) and limit of quantification (LOQ) for solid phase extraction using Ti-CNPrTEOS SPE sorbent (0.01-0.2; 0.03-0.61 µg L(-1)) were lower compared with those achieved using Si-CN SPE sorbent (0.25-1.50; 1.96-3.59 µg L(-1)) and C18 SPE sorbent (0.37-0.98; 1.87-2.87 µg L(-1)) with higher selectivity towards the extraction of polar aromatic amines. The optimized procedure was successfully applied for the solid phase extraction method of selected aromatic amines in river water, waste water and tap water samples prior to the gas chromatography-flame ionization detector separation.

Preparation of sorbent based on porous monolith incorporated with graphene oxide nanosheets for stir cake sorptive extraction of strongly polar aromatic amines

In this study, poly(ethylene glycol dimethacrylate/graphene oxide) (EDMA/GO) monolith was prepared by one-step in situ polymerization. The porous monolith was used for the first time as the sorbent of stir cake sorptive extraction (SCSE) for the preconcentration of strongly polar aromatic amines (AAs) from water samples. The effect of the content of EDMA and GO in the monolith on the extraction efficiencies was investigated in detail. The sorbent was characterized by elemental analysis, transmission electron microscopy, scanning electron microscopy and infrared spectroscopy. Analysis of polar AAs in environmental water samples by a combination of poly(EDMA/GO)-SCSE and HPLC with diode-array detection was selected as a paradigm for the practical application of the new sorbent. Under the optimal conditions, the limits of detection (S/N = 3.0) of the developed method for AAs ranged from 0.04 to 0.19 μg L−1. Good reproducibility of the method was obtained as intra- and inter-day precisions, the relative standard deviations (RSDs) were less than 4.0%. Finally, the proposed method was successfully applied to the determination of trace AAs in environmental water samples. The recoveries of AAs spiked in different matrices ranged from 74.2% to 105%, and RSDs of repeatability ranged from 1.6% to 9.6%.

Preparation and characterization of new sol–gel titanium(IV) butoxide–cyanopropyltriethoxysilane hybrid sorbent for extraction of polar aromatic amines

A new titanium(IV) butoxide-cyanopropyltriethoxysilane (Ti-CNPrTEOS) hybrid material was successfully synthesized for the use as sorbent for the extraction of polar aromatic amines. The sorbent was synthesized by hydrolysis and condensation of titanium(IV) butoxide and cyanopropyltriethoxysilane with the presence of hydrochloric acid as catalyst via sol–gel method. Several factors influencing the synthesized sorbent such as solvent selection, mol of water content, ratio of titanium(IV) butoxide and cyanopropyltriethoxysilane and aging temperature were investigated and optimized. The sorbents were characterized by fourier transform-infrared, field-emission scanning electron microscopy-energy, CHN elemental analysis and thermogravimetric analysis. The applicability of the sorbents for the extraction of polar aromatic amines by the batch sorption method was extensively studied and evaluated. Under the optimum synthesis conditions (tetrahydrofuran as solvent, 1.2 M of hydrochloric acid catalyst, 4 mol of water content with ratio of titanium(IV) butoxide and cyanopropylteriethoxysilane of 1:1 and aging temperature of 60 °C), the extraction showed high recovery towards the extraction of polar aromatic amines. The synthesized sorbent was successfully applied for the extraction of selected aromatic amines via batch sorption method in waste water samples prior to the gas chromatography-flame ionization detector separation. The synthesized sol–gel Ti-CNPrTEOS sorbent demonstrated the potential as an alternative extraction sorbent with higher selectivity towards polar aromatic amines.

Preparation of porous polymer monolithic column using functionalized graphene oxide as a functional crosslinker for high performance liquid chromatography separation of small molecules

A newly developed porous polymer monolith was prepared through copolymerization of 3-(trimethoxysilyl)propylmethacrylate modified graphene oxide with glycidyl methacrylate and ethylene dimethacrylate as a functional crosslinker, which was synthesized through silanization reaction of graphene oxide prepared by Hummers method with 3-(trimethoxysilyl)propylmethacrylate. The monolith was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, mercury intrusion porosimetry and nitrogen adsorption measurement. The monolith column was applied as the stationary phase of high performance liquid chromatography and its chromatographic performance was evaluated by separation of small molecules in the isocratic reversed-phase mode. The chromatograms of hydrophobic steroids and polar aromatic amines on the prepared monolith displayed the enhanced separation performance over those on the parent monolith. The reproducibility of the column was less than 3.5% in terms of relative standard deviation of retention time. The results demonstrate that copolymerization of functionalized graphene oxide into porous polymer monolith was an effective tool for chromatography separation enhancement of small molecules in an isocratic mode.

Sensitive determination of strongly polar aromatic amines in water samples by stir bar sorptive extraction based on poly(vinylimidazole-divinylbenzene) monolithic material and liquid chromatographic analysis

A simple and sensitive method for the determination of polar aromatic amines (PAAs) was developed using stir bar sorptive extraction (SBSE) coupling to high-performance liquid chromatography. A hydrophilic poly(vinylimidazole-divinylbenzene) (VIDB) monolithic material was prepared and acted as SBSE coating. The influences of polymerization conditions for VIDB on the extraction efficiency were investigated using aniline and 2,4-dinitroaniline as detected solutes. To achieve optimum extraction performance for PAAs, several parameters including extraction and desorption time, desorption solvent, ionic strength and pH value of sample matrix were investigated. The results showed that under the optimized experimental conditions, the method showed good sensitivity and excellent recoveries, as well as advantages such as linearity, simplicity, low cost and high feasibility. The extraction performance of present method to the target compounds also compared with commercial SBSE which using polydimethylsiloxane as coating and other SBSE which based on monolithic materials. Finally, the proposed method was successfully applied to the determination of PAAs in lake and sea waters, and excellent recoveries of spiked target compounds in real samples were obtained.

In situ derivatization/solid-phase microextraction: determination of polar aromatic amines.

A solid-phase microextraction GC/MS method for the trace determination of a wide variety of polar aromatic amines in aqueous samples was developed. Prior to extraction the analytes were derivatized directly in the aqueous solution by diazotation and subsequent iodination in a one-pot reaction. The derivatives were extracted by direct-SPME using a PDMS/DVB fiber and analyzed by GC/MS in the full-scan mode. By diazotation/iodination, the polarity of the analytes was significantly decreased and as a consequence extraction yields were dramatically improved. The derivatization proved to be suitable for strongly deactivated aromatic amines and even the very polar diamino compounds can efficiently be enriched after derivatization. We investigated 18 anilines comprising a wide range of functional groups, which could be determined simultaneously. The method was thoroughly validated, and the precision at a concentration of 0.5 microg/L was 3.8-11% relative standard deviation for nonnitrated analytes using aniline-d(5) as internal standard and 3.7-10% for nitroaromatic amines without internal standard. The in situ derivatization/SPME/GC/MS method was calibrated over the whole analytical procedure and was linear over 2 orders of magnitude. Using 10-mL samples, detection limits of 2-13 ng/L were achieved for 15 of the 18 analytes. For two aminodinitrotoluene isomers and a diaminonitrotoluene, detection limits ranged from 27 to 38 ng/L. By allowing quantification at the 0.1 microg/L level, analysis of all target compounds meets EU drinking water regulations. The method provides high sensitivity, robustness, and high sample throughput by automation. Finally, the method was applied to various real water samples and in wastewater from a former ammunition plant the contents of several aromatic amines were quantified.

Hydroxyfullerene as a novel coating for solid-phase microextraction fiber with sol-gel technology.

Hydroxyfullerene (fullerol) as a novel coating for solid-phase microextraction (SPME) fiber was first prepared by a sol-gel technology. The coating procedure involving sol solution composition and conditioning process was presented. A fullerene polysiloxane surface-bonded porous coating on the fused-silica fiber surface was obtained and confirmed by IR spectra and scanning electron microscopy. The coating has stable performance at high temperature (even to 360 degrees C) and solvents (organic and inorganic) because of the properties of fullerene and the chemical binding between the coating and the fiber surface. The extraction properties of the new coatings to less volatile organic compounds, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons and polar aromatic amines were investigated using headspace SPME coupled with GC-electron-capture detection and GC-flame ionization detection. In addition, compared with commercial SPME stationary phases, the new coatings showed higher sensitivity, faster velocities of mass transfer for aromatic compound, and possessed planarity molecular recognition for PCBs. Moreover, this fiber was firm, inexpensive, durable and can be prepared simply. The fiber-to-fiber reproducibility was very good.

Derivatization of aromatic amines for analysis in ammunition wastewater

A new derivatization method for aromatic amines is presented based on the bromination of the aromatic ring system in an acetic acid medium to yield bromo derivatives. The derivatization method is very simple to perform and overcomes several problems common in the analysis of polar aromatic amines. The derivatives are easy to extract with pentane and can be separated with gas chromatography. Due to the introduction of the electron withdrawing bromo substituents sensitive detection using an electron capture detector is possible. The method was used to investigate the contents of amino- and aminonitrotoluenes in water samples from the site of a former ammunition plant.

Hydrogen bonding of aromatic amines in hydroxylic solvents. Part 1. Absorption spectroscopy of substituted anilines and hydrogen bond‐induced rehybridization of trivalent nitrogen atoms.

AbstractThe longest wavelength absorption band of substituted anilines containing electron‐accepting groups is characterized as an intramolecular charge‐transfer (ICT) transition. Dual absorption peaks observed for the ICT transition of some para‐substituted anilines in a strongly hydrogen‐bonding solvent, hexafluoropropan‐2‐ol (HFP) can be attributed to two inequivalently hydrogen‐bonded species with differently hybridized aniline nitrogens in HFP. The hydrogen bond‐induced rehybridization causes appreciable changes in the ICT absorption spectra of highly polar aromatic amines. Rehybridization of aromatic amino nitrogens depends on the OH acidity in the solvent molecule and the basicity of the substituted anilines. The geometry of trivalent nitrogens in aryl amines is critically dependent upon the ionization potential of the amino group, the electron affinity of the electron‐accepting substituent and the substitution site of the electron‐withdrawing group with respect to the amino moiety.