Polar Aromatic Compounds Research Articles

Preparation and chromatographic evaluation of 9-oxa-10-phosphophenanthrene 10-oxide bonded phenyl stationary phase and investigation of its retention mechanism through nuclear magnetic resonance spectroscopy

BackgroundIn reversed-phase liquid chromatography, the C18 alkyl bonded phase, as the primary stationary phase, is widely used in pharmaceutical and food analysis. The phenyl bonded phase often serves as a complementary choice to the C18 phase to enhance the separation performance of specific categories of compounds. However, both C18 and the currently available phenyl bonded phase chromatography columns show room for further optimization in improving the separation efficiency of specific compound classes, such as dihydroflavonoids. Additionally, the potential role and impact of introducing phosphorus groups into chromatographic stationary phases have not been fully explored, indicating a promising direction for research. ResultsIn the present work, we prepared a novel phenyl stationary phase by bonding 9-oxa-10-phosphaphenanthrene 10-oxide onto silica gel. The obtained material was characterized by scanning electron microscopy, fourier transforms infrared spectroscopy, and elemental analysis. The results show that 9-oxa-10-phosphaphenanthrene 10-oxide was successfully bonded on the silica surface with a load of 3.90 %. Further chromatographic characterization in high-performance liquid chromatography exhibited high column efficiency (40,792 plates m-1 for the determination of biphenyl) and good stability (RSD of 0.28 %∼5.38 %). Moreover, we made a detailed study of the column separation mechanism by nuclear magnetic resonance spectroscopy titration experiment. Comparing to commercial phenyl column, the proposed stationary phase showed shorter retention time and higher throughput. In addition, the stationary phase has a strong ability to separate multiple types of compounds, which provides a new strategy for the separation of complex samples, such as active ingredients in traditional Chinese medicine. SignificanceWe have developed a novel phenyl column and conducted a comprehensive examination of its chromatographic performance, demonstrating excellent separation capabilities and high efficiency for both nonpolar and moderately polar aromatic compounds. Additionally, we explored the impact of phosphorus-containing groups on the separation performance of chromatographic stationary phases.

Qualitative analysis of aromatic compounds via 1D TOCSY techniques

The aromatic compounds, including o-xylene, m-xylene, p-xylene, and ethylbenzene, primarily originate from the catalytic reforming of crude oil, and have a wide variety of applications. However, because of similar physical and chemical properties, these compounds are difficult to be identified by gas chromatography (GC) without standard samples. With the development of modern nuclear magnetic resonance (NMR) techniques, NMR has emerged as a powerful and efficient tool for the rapid analysis of complex and crude mixtures without purification. In this study, the parameters of one-dimensional (1D) total correlation spectroscopy (TOCSY) NMR techniques, including 1D selective gradient TOCSY and 1D chemical-shift-selective filtration (CSSF) with TOCSY, were optimized to obtain comprehensive molecular structure information. The results indicate that the overlapped signals in NMR spectra of nonpolar aromatic compounds (including o-xylene, m-xylene, p-xylene and ethylbenzene), polar aromatic compounds (benzyl alcohol, benzaldehyde, benzoic acid), and aromatic compounds with additional conjugated bonds (styrene) can be resolved in 1D TOCSY. More importantly, full molecular structures can be clearly distinguished by setting appropriate mixing time in 1D TOCSY. This approach simplifies the NMR spectra, provides structural information of entire molecules, and can be applied for the analysis of other structural isomers.

Polar Nitrated Aromatic Compounds in Urban Fine Particulate Matter: A Focus on Formation via an Aqueous-Phase Radical Mechanism.

Polar nitrated aromatic compounds (pNACs) are key ambient brown carbon chromophores; however, their formation mechanisms, especially in the aqueous phase, remain unclear. We developed an advanced technique for pNACs and measured 1764 compounds in atmospheric fine particulate matter sampled in urban Beijing, China. Molecular formulas were derived for 433 compounds, of which 17 were confirmed using reference standards. Potential novel species with up to four aromatic rings and a maximum of five functional groups were found. Higher concentrations were detected in the heating season, with a median of 82.6 ng m-3 for Σ17pNACs. Non-negative matrix factorization analysis indicated that primary emissions particularly coal combustion were dominant in the heating season. While in the non-heating season, aqueous-phase nitration could generate abundant pNACs with the carboxyl group, which was confirmed by their significant association with the aerosol liquid water content. Aqueous-phase formation of 3- and 5-nitrosalicylic acids instead of their isomer of 4-hydroxy-3-nitrobenzoic acid suggests the existence of an intermediate where the intramolecular hydrogen bond favors kinetics-controlled NO2• nitration. This study provides not only a promising technique for the pNAC measurement but also evidence for their atmospheric aqueous-phase formation, facilitating further evaluation of pNACs' climatic effects.

An Overview of Imidazole, Derivatives Ofimidazole and its Pharmacological Applications

In recent decades, many studies have been carried out on heterocycles, especially imidazole rings. The pharmacological properties such as antibacterial, antifungal, anticancer, antiviral and antidiabetic properties Apart from that, there are few side effects. The search for new biologically active imidazoles remains an area of interest An overview of medicinal chemistry. This white paper aims to collect and explain a wealth of information. Antibacterial profile of imidazole. Therefore, it can be used for future development to obtain new effective drug molecules. These heterocycles are important building blocks of functional molecules used in various fields. Used on a daily basis. Emphasis was placed on the bonds that form during the formation of imidazole. The usefulness of these methods is based on functional group compatibility. Processes around the ring and the resulting permutation patterns are described, including domain descriptions. Limitations, Reaction Mechanisms, and Future Challenges. The imidazole ring is part of several important natural products Products containing purines, histamine, histidine, nucleic acids. as polar and ionic Aromatic compounds that improve the pharmacokinetic properties of lead molecules Used as a remedy to optimize poorly proposed solubility and bioavailability parameters soluble lead molecule. Imidazole derivatives occupy a unique position in the art medicinal chemistry. Imidazole drugs have expanded the scope of eliminating various dispositions in clinics dose.

Tricyclic octaurea "Temples" for the recognition of polar molecules in water.

Two water-soluble tricyclic "Temple" macrocycles featuring pyrene roof/floor units and bis-urea spacers have been synthesised and studied as receptors for aromatic compounds in aqueous media. The tricycles show good selectivity for methylated purine alkaloids such as caffeine versus unsubstituted heterocycles such as adenine and indole. Binding is signalled by major changes in fluorescence, apparently due to the break-up of intramolecular excimers. The formation of excimers implies cavity collapse in the absence of guests explaining why, unlike an earlier relative, these receptors do not bind carbohydrates. Naphthalenediimides (NDIs) have also been studied as geometrically complementary guests, and indeed bind especially strongly (Ka > 107 M-1); this powerful and selective association suggests potential applications in supramolecular self-assembly.

Simultaneous Determination of 79 Polar and Non-Polar Polycyclic Aromatic Compounds in Airborne Particulate Matter by Gas Chromatography – Tandem Mass Spectrometry

Research on Polycyclic Aromatic Compounds (PACs) in the atmospheric environment has been mainly focused on the 16 EPA’s PAHs. Due to toxicological relevance and particular emission sources, there is a research need in broadening the scope of PACs analysis to include polar and semi-polar PACs in new analytical methods. Here, we describe a single GC-MS/MS method to simultaneously determine 79 polar, semi-polar and non-polar PACs. Temperature gradient and injection conditions were optimized. Optimal Multiple Reaction Monitoring (MRM) and pseudo-MRM mass transitions were searched to enhance the detection. PACs were extracted from particulate samples by Pressurized Liquid Extraction (PLE). The choice of the optimal extraction solvent was carefully evaluated. Instrumental LOQ were from 1 to 2 ng. The method was validated against linearity of the calibration, intra-day and inter-day variability, LOQ and recoveries. The analysis of a Diesel Particulate Matter Certified Reference Material enabled a firm method validation. The method was applied to PM10 samples from a residential parking lot. PACs total amount varied from 2.3 to 14 ng/m3. The most abundant PACs were phthalic anhydride, 1,8-naphthalic anhydride and benzo(b)fluoranthene. PAHs diagnostic ratios enabled the identification of fuel combustion and vehicular traffic as the main source of PACs.

Screening Method for 23 Alkaloids in Human Serum Using LC/MS/MS with a Pentafluorophenyl Column in Dynamic Multiple Reaction Monitoring Mode

Alkaloids are nitrogen-containing organic compounds, generally basic, and found in plants, fungi, and bacteria. Some alkaloids are used in medicine, but some compounds are highly toxic. Accidental ingestion, homicide, and suicide have occurred due to plants containing alkaloids. The identification of toxic components in biological samples is important for the diagnosis and/or treatment of poisoning cases in forensic and emergency medicine. Alkaloids have a wide variety of structures, such as isoquinoline alkaloid, indole alkaloid, tropane alkaloid, and diterpene alkaloid; therefore, there are few reports of simultaneous analysis methods. We have established a method for the simultaneous analysis of 23 alkaloids in human serum with a liquid chromatograph-tandem mass spectrometer (LC/MS/MS). A liquid-liquid extraction which was modified from the first step of the QuEChERS AOAC method was used for serum pretreatment. The separation of the compounds was performed using a pentafluorophenyl (PFP) column, CAPCELL CORE PFP (2.1 mm I.D. × 100 mm, 2.7 μm) in gradient mode. Mobile phase A consisted of 10 mM ammonium formate and 0.1% formic acid in ultrapure water, and mobile phase B was 10 mM ammonium formate and 0.1% formic acid in methanol. Simultaneous analysis was performed in dynamic multiple reaction monitoring mode. The separation of 23 alkaloids was satisfactory, as PFP columns exhibited different retention behaviors than alkyl phase columns. The PFP column effectively retained polar aromatic compounds; therefore, it was suitable for alkaloid analysis. The validated method was applied to a forensic case of aconite poisoning. The present method was useful in LC/MS/MS screening for 23 alkaloids in human serum.

Polar Aromatic Compounds in Soot from Premixed Flames of Kerosene, Synthetic Paraffinic Kerosene, and Kerosene–Synthetic Biofuels

Polar Aromatic Compounds (PAC) adsorbed on soot produced in laboratory premixed flames of fossil kerosene (Jet A-1), Synthetic Paraffinic Kerosene (SPK), and Jet A-1 - synthetic biofuels (2,5-dimethylfuran, methyloctanoate, diethylcarbonate and 1-butanol) were characterized for the first time in the aim of shedding light on the combustion mechanisms and evaluating the environmental impact of these synthetic biofuels. The following families of compounds were fractioned from the soot extracts and further their relative abundances estimated: (a) oxa-AHs (xanthenes, benzoxanthene, alcoxy-AHs, furan…); (b) aldehydes-AHs, (c) ketones-AHs; (d) quinones-AHs; (e) aromatic monocarboxylic acids; (f) aromatic hydroxy-acids; (g) aromatic dicarboxylic acids; (h) nitrated-AHs (including amines, acridines, cinnoline derivatives, carbazoles…); (i) nitro-AHs. The results obtained point out that overall, soot from Jet A-1 - biofuels premixed flames are richer in PAC than soot from pure Jet A-1 and SPK. Out of the fuels studied, Jet A-1 - 1-butanol produces the highest concentrations of nitro-AHs (namely nitro-benzaldehydes), of aldehydes-AH and hydroxy-AHs (including two isomers of hydroxy-benzaldehyde); whereas Jet A-1 - diethylcarbonate produces the highest concentrations of quinone-AHs (especially phenanthrene-quinones) and large concentrations of nitrated-AHs. On the other hand, soot from Jet A-1 - methyloctanoate is the richest one in mono aromatic and dicarboxylic acids, aromatic hydroxyacids, nitrated-AHs, and esters. Combustion of the Jet A-1 - 2,5-dimethylfuran mixture emits the highest concentrations of ketone-AHs, and oxa-AHs (namely, furan derivatives). We should remark that although the soot samples were obtained from pre-mixed flames, the lab conditions being far from the industrial conditions, particularly in terms of pressure; the chemistry going on should not be so different that our findings could not be extrapolated to industrial conditions.

Kinetic modeling of asphaltene nano-aggregates formation using dynamic light scattering technique

Asphaltene is known as a class of polar poly-nuclear aromatic compounds of crude oil which is extracted by its solubility difference in normal heptane and toluene. Precipitation of this hydrocarbon compound by changing in fluid thermodynamic conditions decelerates flow when passing through up-stream and down-stream processes. In order to understand the thermodynamics of the deposition phenomenon, one needs to pay attention to the kinetics of the aggregation of these nano-particles. In this study, the kinetics phenomenon of aggregation of asphaltene clots in toluene is investigated using dynamic light scattering (DLS) technique. The dynamic light scattering results for super dilute solutions showed that at high and low sonication time, the asphaltene is monomeric and polymeric forms, respectively. Moreover, the experiments revealed that the relationship between the amount of sonication energy given to the solutions and the particle size is logarithmic. The DLS spectra obtained from the lower-sonication solutions were decomposed to the four normal distributions using the deconvolution technique, indicating four different clusters in the solution. The ratio of the area of each normal distribution to the area of the spectrum indicates the fraction of the presence of each cluster in the solution. For the lower and the higher concentrations of the asphaltene solution, the percentage of nano-aggregates is between 8%-41% and 4%–51%, respectively. By assuming the asphaltene molecule to be on a coin-shaped plate and forming a π bond with a minimal coinage overlap, the coin model of asphaltene aggregation kinetics has been developed. The concentration of each nano-aggregates in equilibrium solution is calculated according to the fraction of its presence in the medium and the coin model. Then, these equilibrium concentrations are used to calculate the equilibrium reaction constants. The correlation coefficient between the reaction constants and the diffusion coefficients of the clots in the solutions for all reactions was found to be equal to 0.42. This same value indicates that this coefficient is independent of the concentration of asphaltene in the solution and is dependent on the nature of the solution.

Synthesis and chromatographic evaluation of poly(pentabromostyrene)-silica composite: A versatile stationary phase for separating both polar and non-polar aromatic compounds

Polymer-silica composite materials have been witnessed as one of the most promising chromatographic packing materials. The demands of novel stationary phases are always existing due to the requirements for the separation of special samples. In our present work, the novel poly(pentabromostyrene)-silica composite stationary phases were successfully prepared by surface initial free-radical polymerization. The polymer chains bonding on the surface of the poly(pentabromostyrene) contain plenty of phenyl moiety, which provide hydrophobic and π-π interactions between the stationary phase and analytes. Besides, the bromide atoms, existing in the polymer, provide extra polar interaction with polar or easily polarized analytes. Compared with the typical C18 stationary phase, the novel stationary phase showed special separation selectivity. Samples, including polycyclic aromatic hydrocarbons, phenols, anilines, amino acids, halogenated benzenes, acetophenone derivatives, benzene homologous compounds, were all well separated by the new stationary phase. Also, the great stability (0.13% ≤ RSDs ≤ 0.98%, n = 5) of packed columns and the good synthesis repeatability were demonstrated. Finally, the new columns were applied to the separation of fullerenes. The loading ratio reached 2.67% (36 mg of fullerenes was loaded onto the column packed with 1.35 g stationary phase), with high yield (86.3%) of high pure C60 (>95%). This novel stationary phase has a great potential to be a complementary to traditional C18 column and a special column for fullerenes separation.

Preparation and Evaluation of Methacrylate-based Reversed-phase Sorbents for Solid-phase Extraction of Polar Compounds

In solid-phase extraction (SPE), hydrophilic-lipophilic balance (HLB) type sorbents prepared by copolymerization with divinylbenzene (DVB) and polar monomers are widely used. The hydrophobicity of the HLB-type sorbents depends on DVB as the main component, and the extraction efficiency for polar compounds is enhanced by interaction with the polar groups introduced by polar monomers. On the other hand, high adsorption ability, due to the hydrophobicity of DVB, adversely affects the rapid elution of trapped compounds. In this study, the non-aromatic sorbents that has high adsorption ability for polar compounds, and can rapidly elute polar compounds including aromatic rings were developed. Porous polymer particles were prepared with trimethylolpropane trimethacrylate (TMPT), and the solid-phase extraction characteristics were evaluated. By optimizing the pore characteristics of TMPT-type sorbent, it was possible to effectively extract the nucleobases and nucleosides whose extraction efficiency was comparable to that of the commercial HLB-type sorbent. Furthermore, in order to improve the hydrophobicity of the TMPT-type sorbents, non-aromatic sorbents copolymerized with stearyl methacrylate (SMA) were prepared. However, the adsorption abilities of the TMPT-type sorbent could not be improved. The adsorption and desorption properties of the non-aromatic sorbents were evaluated using the TMPT-type sorbent. The aromatic polar compounds were able to be strongly sorbed to the TMPT-type sorbent, but they could be rapidly eluted by low concentration organic solvent as eluent. These results suggest that the TMPT-type sorbents are useful for a solid-phase extraction of the polar compounds and will solve the problem of the poor desorption in the HLB-type sorbents containing DVB.

The Impact of Salinity on the Interfacial Structuring of an Aromatic Acid at the Calcite/Brine Interface: An Atomistic View on Low Salinity Effect.

This study aims to elucidate the impact of salinity on the interactions governing the adsorption of polar aromatic oil compounds onto calcite. To this end, molecular dynamics simulations were employed to assess adsorption of a model polar organic molecule (deprotonated benzoic acid, benzoate) on the calcite surface in NaCl brines of different concentration levels, namely, deionized water (DW), low-salinity water (LS, 5000 ppm), and sea water (SW; 45,000 ppm). Calcite was found to be completely covered by several well-ordered water layers. The top hydration layer is very compact and prevents direct adsorption of benzoates onto the substrate. Instead, Na+ ions form a distinct positively charged layer by adhering on the calcite substrate through inner-sphere complexion mode. Cl- ions mostly lodge on top of the adsorbed sodium cations, forming a negatively charged layer. The distribution of ions at the calcite/brine interface thus exhibits the features of an electrical double layer, composed of a Stern-like positive layer followed by a negative one. The positive charged layer attracts benzoates toward the surface. As such, the sodium ions attached onto the calcite can act as adsorption sites to connect benzoates to the surface. By increasing the salinity, more Na+ ions adsorb onto the calcite surface, and the density of benzoate molecules at the interface is enhanced as a result of more Na+ bridging ions. The monotonic salinity-dependent adsorption of benzoate molecules on calcite offers a mechanism driving additional oil recovery upon injection of diluted brine into subsurface carbonate reservoirs.

A porous aromatic framework as a versatile fiber coating for solid-phase microextraction of polar and nonpolar aromatic organic compounds

A porous aromatic framework (PAF) derived from triphenylamine (type PAF-41) was prepared and is shown to be a viable coating for fibrous solid-phase microextraction (SPME). PAF-41 can be easily synthesized and has a high surface area, a rich π-electron structure, and electron-rich nitrogen atoms in its framework. The PAF-41-coated fibrous SPME extractor was combined with a gas chromatographic separation and flame ionization detection. The method was applied to the quantitation of some aromatic organic compounds (AOCs), including polar amphetamine and methamphetamine and nonpolar ethylbenzene, o-, m- and p-xylenes, andstyrene. The method was optimized after which a linear response is found for the 10-500ng·mL-1 amphetamine and methamphetamine concentration ranges. The limits of detection are 1.0 and 0.5ng·mL-1; and relative standard deviations for six repeated extractions with a single fiber are 5.3 and 6.7%. The method was applied for the determination of amphetamine and methamphetamine in spiked urine samples without any pretreatment except for dilution with water. The PAF-41 modified fiber also was applied to the extraction of styrene, xylenes and ethylbenzene. The enrichment capacities of the extractor for these AOCs were superior to those of commercial SPME extractors. Graphical abstract (a) Schemetic of the PAF-41-coated solid-phase microextraction (SPME) fiber.(b) Scanning electron microscope images of the PAF-41fiber.

Graphene quantum dots-functionalized C18 hydrophobic/hydrophilic stationary phase for high performance liquid chromatography

Graphene quantum dots (GQDs) were chosen as functional material to improve the separation performance of C18 column since GQDs could provide multiple interactions such as hydrophilic, π-π stacking and hydrogen bonding interactions. In this study, a novel octadecyl modified GQDs-bonded silica (C18/GQDs/SiO2) stationary phase was prepared and applied in reversed-phase and hydrophilic interaction liquid chromatography. This column showed satisfactory separation performance for both hydrophobic, polar and hydrophilic compounds including polycyclic aromatic hydrocarbons, alkylbenzenes, anilines, phenols, aromatic acids, alkaloids, nucleosides and nucleobases. Through investigating the impact of organic solvent content on retention, it was found this new stationary phase had typical characteristics of hydrophobic/hydrophilic chromatography. Compared with commercial C18 column, this column showed better separation performance for polar aromatic compounds because the introduction of GQDs provided more interactions such as π-π stacking, hydrophilic and hydrogen bonding interaction with analytes. To get an in-depth understanding of the retention mechanism, linear solvation energy relationship model was established for both C18/GQDs/SiO2 and C18 columns, theoretically calculated data indicated that C18/GQDs/SiO2 column had higher π-π stacking and hydrogen-bonding acceptance ability. C18/GQDs composite stationary phase equipped with hydrophobic/hydrophilic properties has great prospect in separation science.

Sugar Cane-Converted Graphene-like Material for the Superhigh Adsorption of Organic Pollutants from Water via Coassembly Mechanisms.

A sugar cane-converted graphene-like material (FZS900) was fabricated by carbonization and activation. The material exhibited abundant micropores, water-stable turbostratic single-layer graphene nanosheets, and a high BET-N2 surface area (2280 m2 g-1). The adsorption capacities of FZS900 toward naphthalene, phenanthrene, and 1-naphthol were 615.8, 431.2, and 2040 mg g-1, respectively, which are much higher than those of previously reported materials. The nonpolar aromatic molecules induced the turbostratic graphene nanosheets to agglomerate in an orderly manner, forming 2-11 graphene layer nanoloops, while polar aromatic compounds induced high dispersion or aggregation of the graphene nanosheets. This phase conversion of the nanosized materials after sorption occurred through coassembly of the aromatic molecules and the single-layer graphene nanosheets via large-area π-π interactions. An adsorption-induced partition mechanism was further proposed to explain the nanosize effect and nanoscale sorption sites observed. This study indicates that commonly available biomass can be converted to graphene-like material with superhigh sorption ability in order to remove pollutants from the environment via nanosize effects and a coassembly mechanism.

Hydroxyundecanethiol-Modified Steel Fibers for the Selective Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons from River and Wastewater

ABSTRACTA novel organic–inorganic composite-coated fiber was developed for selective solid-phase microextraction (SPME) by direct electrodeposition of zinc oxide microparticles on a pretreated stainless steel wire followed by self-assembly of hydroxyundecanethiol with zinc–sulfur bonds. The performance of the hydroxyundecyl-modified zinc oxide-coated steel fiber was then assessed for SPME of polar aromatic compounds coupled to high-performance liquid chromatography with ultraviolet detection. Excellent extraction and selectivity were obtained for polycyclic aromatic hydrocarbons. The extraction and desorption times, temperature, stirring rate, and ionic strength were optimized. The limits of detection were from 0.034 to 0.132 µg L−1. The relative standard deviations were from 3.4 to 4.9% for a single fiber and from 5.1 to 6.4% for multiple fibers. The recovery of polycyclic aromatic hydrocarbons in environmental water fortified at 5.0 and 50 µg L−1 was from 83.1 to 103% with relative standard deviations below 8.4%. This fiber was shown to withstand at least 200 extraction and desorption cycles. The method was used for the preconcentration and determination of polycyclic aromatic hydrocarbons in environmental water.

Chromatographic selectivity of poly(alkyl methacrylate-co-divinylbenzene) monolithic columns for polar aromatic compounds by pressure-driven capillary liquid chromatography

In this study, divinylbenzene (DVB) was used as the cross-linker to prepare alkyl methacrylate (AlMA) monoliths for incorporating π-π interactions between the aromatic analytes and AlMA-DVB monolithic stationary phases in capillary LC analysis. Various AlMA/DVB ratios were investigated to prepare a series of 30% AlMA-DVB monolithic stationary phases in fused-silica capillaries (250-μm i.d.). The physical properties (such as porosity, permeability, and column efficiency) of the synthesized AlMA-DVB monolithic columns were investigated for characterization. Isocratic elution of phenol derivatives was first employed to evaluate the suitability of the prepared AlMA-DVB columns for small molecule separation. The run-to-run (0.16–1.20%, RSD; n = 3) and column-to-column (0.26–2.95%, RSD; n = 3) repeatabilities on retention times were also examined using the selected AlMA-DVB monolithic columns. The π-π interactions between the aromatic ring and the DVB-based stationary phase offered better recognition on polar analytes with aromatic moieties, which resulted in better separation resolution of aromatic analytes on the AlMA-DVB monolithic columns. In order to demonstrate the capability of potential environmental and/or food safety applications, eight phenylurea herbicides with single benzene ring and seven sulfonamide antibiotics with polyaromatic moieties were analyzed using the selected AlMA-DVB monolithic columns.

A novel polar-modified post-cross-linked resin and its enhanced adsorption to salicylic acid: Equilibrium, kinetics and breakthrough studies

Improving the surface polarity is of significance for the post-cross-linked resins to enhance their adsorption to polar aromatic compounds. In the present study, we prepared a novel polar-modified post-cross-linked PDEpc_D by the Friedel–Crafts alkylation reaction and the amination reaction, the Brunauer–Emmett–Teller (BET) surface area and pore volume increased significantly after the Friedel–Crafts alkylation reaction and the surface polarity improved greatly after the amination reaction. Batch adsorption showed that PDEpc_D possessed a much enhanced adsorption to salicylic acid as compared the precursors PDE and PDEpc as well as the non-polar post-cross-linked PDVBpc. The equilibrium data was characterized by the Freundlich model, π–π stacking, hydrogen bonding and static interaction were the possible driving forces. The adsorption was a fast process and the kinetic data obeyed the micropore diffusion model. Column adsorption–desorption experiments suggested that PDEpc_D was a potential candidate for adsorptive removal of salicylic acid from aqueous solution.

Investigation of sorbate-induced plasticization of Pahokee peat by solid-state NMR spectroscopy

Sorbate-induced swelling and plasticization of sorbent have been linked to sorption hysteresis of organic compounds in the natural organic matter of isolated humic acids, soils, and coals. The above processes, which have important implications for the fate and bioavailability of organic and inorganic contaminants, are mostly based on macroscopic changes and require molecular-level confirmation. This study aimed to investigate the presence or absence of sorbate-induced plasticization of Pahokee peat soil as a function of different sorbates. The plasticization of Pahokee peat soil was studied upon sorption of different proton-free solutes including C6D6, CDCl3, CCl4, C2Cl4, CBr4, C6D5Cl, and C5D5N, covering apolar and polar aromatic and aliphatic compounds. The swelling and plasticization of Pahokee peat soil were verified at the molecular level by 1H wideline and two-dimensional wideline separation (2D WISE) NMR. The use of 1H wideline shapes is the traditional technique for studying molecular dynamics but hampered by the lack of spectral resolution, with one dimension displaying 13C chemical shifts and the second showing 1H wideline shapes, is capable of providing information on molecular dynamics of specific functional groups. Our results showed that the segments of Pahokee peat soil sorbed with C6D6, C2Cl4, and C5D5N became more mobile, but the changes due to the plasticization were small. Both C6D6 and C5D5N selectively increased the mobility of specific components, C6D6 of the nonpolar alkyl domains, and C5D5N of both the nonpolar alkyl domains and aromatic components. Some liquid solutes at high concentrations (2–5 wt%) are capable of slightly “softening” natural organic matter of a soil, and this provides support for the hypothesis that natural organic matter in Pahokee peat soil is in a glassy state that is subject to plasticization.

Correlation and prediction of adsorption capacity and affinity of aromatic compounds on carbon nanotubes

Adsorption of 22 nonpolar and polar aromatic compounds on 10 carbon nanotubes (CNTs) with various diameters, lengths and surface oxygen-containing group contents was investigated to develop predictive correlations for adsorption, using the isotherm fitting of Polanyi theory-based Dubinin-Ashtakhov (DA) model. Adsorption capacity of aromatic compounds on CNTs is negatively correlated with melting points of aromatic compounds, and surface oxygen-containing group contents and surface area ratios of mesopores to total pores of CNTs, but positively correlated with total surface area of CNTs. Adsorption affinity is positively correlated with solvatochromic parameters of aromatic compounds, independent of tube lengths and surface oxygen-containing group contents of CNTs, but negatively correlated with surface area ratios of mesopores to total pores of CNTs. The correlations of adsorption capacity and adsorption affinity with properties of both aromatic compounds and CNTs clearly have physical significance, can be used successfully with DA model to predict adsorption of aromatic compounds on CNTs from the well-known physiochemical properties of aromatic compounds (i.e., solvatochromic parameters, melting points) and CNTs (i.e., surface area and total acidic group contents), and thus can facilitate the environmental application of CNTs as sorbents and environmental risk assessment of both aromatic contaminants and CNTs.