Separation Of Polycyclic Aromatic Hydrocarbons Research Articles

Exploring ionic liquids for the extraction separation of aromatic hydrocarbons from diesel via multiple interaction analyses coupled with experimental evaluation

The separation of aromatic hydrocarbons from petroleum fractions is of great significance for both the quality upgrading of products and value-added utilization of aromatic compounds. However, the separation of polycyclic aromatic hydrocarbons (PAHs) and their derivatives from diesel remains challenging because of their lower solubility and selectivity as compared to the monocyclic aromatic compounds. In this work, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TF2N]) was screened from 320 ionic liquid (IL) candidates through solvent capacity predication using COSMO-RS method. Liquid-liquid equilibrium experiments were carried out using a series of tetralin/n-decane mixtures with different tetralin concentrations to evaluate the extraction performance of several solvents. The results indicate that [EMIM][TF2N] has high selectivity up to 95.73 for tetralin over n-decane, which is 4.5 and 3.9 times higher than that of dimethyl sulfoxide and sulfolane. During five regeneration cycles, the [EMIM][TF2N] exhibits consistent extraction performance and nearly complete recovery. Molecular polarity index (MPI) analysis indicates that tetralin has larger dissolving affinity to solvents as compared to n-decane. Combined analyses of interaction energy, energy decomposition, and visualization of weak interaction reveal that the crucial role of weak hydrogen bond in dominating the complex solvent–solute interactions. Compared to n-decane, tetralin shows a stronger interaction with the solvents due to the existence of C-H···π and hydrogen bond interactions. The great difference in interaction energy between {[EMIM]+ + tetralin} and {[EMIM]+ + n-decane}, therefore, endows [EMIM][TF2N] with high selectivity for tetralin. Given the dominant role of cation, a IL, [CN1 = C2SCCS2(CC = C)C1][TF2N] having both high selectivity and high solvent capacity was subsequently explored using the cation generation method based on the SeqVAE model. Furthermore, present study proposes a strategy for the design of ILs for separation and other specific application circumstances.

Extraction and Separation of Polycyclic Aromatic Hydrocarbons from Catalytic Cracking Diesel

Extraction and Separation of Polycyclic Aromatic Hydrocarbons from Catalytic Cracking Diesel

Preparation of rosin-based polymer microspheres as a stationary phase in high-performance liquid chromatography to separate polycyclic aromatic hydrocarbons and alkaloids

AbstractAcrylpimaric acid ethylene glycol acrylate was used as the cross-linking agent to prepare rosin-based polymer microspheres through membrane emulsification–microsuspension polymerization. The prepared microspheres were used as the stationary phase in high-performance liquid chromatography for the separation of polycyclic aromatic hydrocarbons (PAHs) and two analogues of alkaloids. Five PAHs (benzene, naphthalene, fluorene, pyrene, and benzo(e)pyrene) were well separated in the rosin-based polymer column with the resolution (Rs) of 6.088 ± 0.006, 5.759 ± 0.017, 7.019 ± 0.020, and 8.584 ± 0.063. A linear relationship was observed for the carbon numbers of PAHs and lnK as obtained with the equation of ln k = 0.22nc – 2.45, R2 = 0.996 . The rosin-based polymer columns were also employed to separate theophylline–caffeine and camptothecin–10-hydroxy-camptothecin, and the good results were obtained with the Rs of 4.617 ± 0.005 and 2.245 ± 0.049, respectively.

Incorporation of metal-organic framework amino-modified MIL-101 into glycidyl methacrylate monoliths for nano LC separation.

Metal-organic frameworks consisting of amino-modified MIL-101(M: Cr, Al, and Fe) crystals have been synthesized and subsequently incorporated to glycidyl methacrylate monoliths to develop novel stationary phases for nano-liquid chromatography. Two incorporation approaches of these materials in monoliths were explored. The metal-organic framework materials were firstly attached to the pore surface through reaction of epoxy groups present in the parent glycidyl methacrylate-based monolith. Alternatively, NH2 -MIL-101(M) were admixed in the polymerization mixture. Using short time UV-initiated polymerization, monolithic beds with homogenously dispersed metal-organic frameworks were obtained. The chromatographic performance of embedded UV-initiated composites was demonstrated with separations of polycyclic aromatic hydrocarbons and non-steroidal anti-inflammatory drugs as test solutes. In particular, the incorporation of the NH2 -MIL-101(Al) into the organic polymer monoliths led to an increase in the retention of all the analytes compared to the parent monolith. The hybrid monolithic columns also exhibited satisfactory run-to-run and column-to-column reproducibility.

Polycyclic Aromatic Hydrocarbons Separation from Oil-Contaminated Soil Using Supercritical and Subcritical Water

Polycyclic Aromatic Hydrocarbons Separation from Oil-Contaminated Soil Using Supercritical and Subcritical Water

Dispersive Solid Phase Extraction Headspace Sampling in Gas ChromatographyMass Spectrometric Analysis of Volatiles: Application to Separation of Polycyclic Aromatic Hydrocarbons

For the first time, dispersive solid phase extraction combined with headspace sampling was introduced and applied to separation and pre-concentration of polycyclic aromatic hydrocarbons (PAHs) as representative of volatile and semi-volatile compounds, from aqueous solutions and sediments using multiwall carbon nanotubes (MWCNTs). After adsorption, PAHs were desorbed thermally from the surface of MWCNTs using a gas chromatography mass spectrometry (GC-MS) CombiPAL headspace device or a homemade thermal desorption system. Pre-concentration was maximized through optimization of solution pH, sorbent amount, and extraction time as well as desorption time and temperature of PAHs. The calibration curves were linear in the range 0.005-30 ng mL-1 for 13 PAHs at optimum conditions, with the coefficients of determination (R2) above 0.992, and detection limit in the range of 0.0021 to 0.0045 ng mL-1. Reproducibility for all PAHs was between 1.6 and 4.2%. Method recoveries were in the range of 94.0-102% for threeReferences spiked levels (1, 10, 20 ng mL-1). The methodology is even better if the selective or specific magnetic sorbent is used.

Polyaniline-dicationic ionic liquid coated with magnetic nanoparticles composite for magnetic solid phase extraction of polycyclic aromatic hydrocarbons in environmental samples

In this present study, magnetic nanoparticles (MNPs) nanocomposites modified with polyaniline (PANI) coated newly synthesised dicationic ionic liquid (DICAT) forming MNP-PANI-DICAT were successfully synthesised as new generation material for magnetic solid phase extraction (MSPE). MNP-PANI-DICAT was characterised by FT-IR NMR, CHN, BET, SEM, TEM, and VSM techniques and the results were compared with MNP-PANI and native MNP. This new material was applied as a magnetic adsorbent for the pre-concentration and separation of polycyclic aromatic hydrocarbons (PAHs) due to the π–π interaction between polyaniline shell and dicationic ionic liquid (DICAT) with PAHs compounds. Under the optimal conditions, the proposed method was evaluated and applied for the analysis of PAHs in environmental samples using gas chromatography-mass spectrometry (GC-MS). The validation method showed good linearity (0.005–500µgL−1) with the coefficient of determination (R2) > 0.999. The limits of detection (LOD) and quantification (LOQ) of the developed method (MNP-PANI-DICAT-MSPE) were in the range of 0.0008–0.2086µgL−1 and 0.0024–0.6320µgL−1, respectively. The enrichment factor (EF) of PAHs on MNP-PANI-DICAT-MSPE were in the range of 7.546–29.632. The extraction recoveries of natural water, sludge, and soil samples were ranged from 80.2% to 111.9% with relative standard deviation (RSD) less than 5.6%. The newly synthesised MNP-PANI-DICAT possess good sensitivity, reusability, and fast extraction of PAHs under the MSPE procedure in various environmental samples.

Selectivity differences of coordination compound stationary phases for polyaromatic hydrocarbons and polar analytes in gas and liquid phases

A precursor solution to the metal–organic framework (MOF), Cd(1,4,7,10-tetrakis(4-carboxybenzyl)-1,4,7,10-tetraazacyclododecane), was aged in a surface-functionalised 250μm-diameter capillary, to generate a film containing the constituents of the bulk phase crystalline material. EDX analysis revealed a higher ratio of ligand elements (C, N and O) to Cd in the capillary coated phase compared to that achieved from bulk synthesis in a vial. Separation performance of the coated capillary for gas chromatography (GC) was compared to the performance of the original MOF crystals packed in tips for liquid elution chromatography (LEC) towards the separation of polycyclic aromatic hydrocarbons (PAHs) and small probe analytes with different properties. This study showed that different retention mechanisms were observed for the same set of analytes in gas and liquid phases. Independently of the trend of vapour pressure difference, the GC result showed less specific size selective retention, but with stronger retention towards larger PAHs. A linear solvation energy relationship correlation further revealed enhanced retention contributions (positive stationary phase descriptor values) by cavity formation/dispersion interactions and H-bonding with acid functionality of the probe analytes in both GC and LEC (though stronger in LEC), whilst H-bonding with basic functional groups slightly increased retention in GC; retention was strengthened by dipole–dipole/dipole–induced dipole interactions only in LEC.

Determination of PAHs by ultra fast liquid chromatography using a core-shell technology – Application to their determination after using biochar as adsorbent

The C18 column (250mm×4.6mm) packed with 5μm core-shell particles was used in an effort to optimize the separation of 8 polycyclic aromatic hydrocarbons under very low pressure values (44–52bars), low temperature (16°C) and in 13min. Chromatogram and peaks of each polycyclic aromatic hydrocarbon studied, obtained using an ultra fast liquid chromatography fitted with this column and equipped with a diode array detector, were compared with those obtained using two other traditional C18 columns, packed with fully porous 5μm particles, usually used in our laboratory and specifically designed for the separation of polycyclic aromatic hydrocarbons. Thinnest peaks, highest sensitivity and efficiency are the main results related to the core-shell technology of the recent Kinetex column compared to more common C18 columns due to the bed uniformity and packing quality of the recent core-shell column. On the other hand, reduced retention time was highlighted for each polycyclic aromatic hydrocarbon using the column packed with core-shell particles resulting from the lower surface area of these particles compared to the totally porous particles of the both other columns used. Limits of detection and quantification, linearity range and repeatability were determined for the method developed with the core-shell column. A practical application was realized by evaluating the sorption capacity of the 8 polycyclic aromatic hydrocarbons studied in mixture using a biochar made from woody plants. To this end, the biochar was mixed with aqueous solution spiked with the mixture of polycyclic aromatic hydrocarbons and a kinetic study of their sorption was conducted. Sorption percentage was higher than 89% for each polycyclic aromatic hydrocarbon studied showing that the studied biochar could be good and low cost alternative products for the sorption of this type of pollutants.

The synthesis of weak acidic type hybrid monolith via thiol-ene click chemistry and its application in hydrophilic interaction chromatography.

In this work, a porous structure and good permeability monolithic column was polymerized in UV transparent fused-silica capillaries via photo-initiated thiol-ene click polymerization of 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (TMTVS), pentaerythritol tetra(3-mercaptopropionate)(PETMP), itaconic acid, respectively, in the presence of porogenic solvents (tetrahydrofuranand methanol) and an initiator (2,2-dimethoxy-2-phenylacetophenone) (DMPA) within 30 min. The physical properties of this monolith were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and nitrogen adsorption/desorption measurements. For an overall evaluation of the monolith in chromatographic application, separations of polycyclic aromatic hydrocarbons (PAHs), phenols, amides and bases were carried out. The column efficiency of this monolith could be as high as 112 560 N/m. It also possesses a potential application in fabrication of monoliths with high efficiency for c-LC. In addition, the resulting monolithic column demonstrated the potential use in analysis of environment waters.

Polymer-modified fibrous mesoporous silica nanoparticles as coating material for open-tubular capillary electrochromatography

A novel fibrous mesoporous silica nanoparticles (fSiO2) stationary phase grafted with polymer (Poly (2-(dimethylamino) ethyl methacrylate) (PDMAEMA) was developed for open tubular capillary electrochromatography (OT-CEC). The preparation procedure included synthesizing fSiO2 through biphase stratification approach, removing the surfactants, silanization and in situ graft polymerization with monomers via atom transfer radical polymerization (ATRP). Subsequently, PDMAEMA-modified mesoporous silica nanoparticles (P-fSiO2)/ethanol solution was immobilized onto the inner surface of the pretreated capillary and functionalized with octadecylsilane to fabricate the open-tubular column. Separation of polycyclic aromatic hydrocarbons (PAHs) and proteins were carried out to evaluate the performance of the column in CEC. The run-to-run, day-to-day and column-to-column reproducibility in terms retention time of naphthalene was 1.9%, 2.2%, and 3.7%, respectively. The effects of solvent concentration and pH on the separation were evaluated. The method was also used for the separation of real bio-sample, egg white proteins.

Incorporation of zeolitic imidazolate framework (ZIF-8)-derived nanoporous carbons in methacrylate polymeric monoliths for capillary electrochromatography

A series of metal organic frameworks-derived nanoporous carbons originating from zeolitic imidazolate framework-8 (ZIF-8) crystals as precursors have been prepared via varying the preparation conditions. The ZIF-8-derived carbons were subsequently admixed in the methacrylate monomers containing polymerization mixtures and polymerized to obtain monolithic columns for capillary electrochromatography (CEC). The effect of particle size and content of the ZIF-8-derived carbon materials in the polymerization mixture on the performance of the hybrid monolithic columns was investigated in detail. The resulting composites were characterized using scanning electron microscopy. Using short time UV-initiated polymerization, monolithic beds with homogenously dispersed ZIF-8-derived carbons were obtained. The chromatographic performance of these composites was demonstrated with separations of polycyclic aromatic hydrocarbons and non-steroidal anti-inflammatory drugs as test solutes. The incorporation of the ZIF-8-derived carbons into the organic polymer monoliths led to an increase in the retention of all the analytes compared to the parent monolith. Finally, the hybrid monolithic columns exhibited satisfactory run-to-run and batch-to-batch reproducibility.

Separation of polycyclic aromatic hydrocarbons from rhamnolipid solution by activated carbon adsorption

Separating hydrophobic organic contaminants from a surfactant solution facilitates the reuse of surfactants and reduces waste disposal costs. This study presented an investigation of selective adsorption of hydrophobic organic compounds in rhamnolipid solution by activated carbon as a means of recovering biosurfactants. Three polycyclic aromatic hydrocarbons (PAHs) were used as examples of hydrophobic organic compounds, along with rhamnolipid as biosurfactants. PAH solubility in the micelles increased linearly with increasing concentrations of rhamnolipid. Batch adsorption experiments on containing rhamnolipid and PAH solutions were performed using activated carbon. The adsorption behavior of rhamnolipid and PAH fitted the Freundlich isotherm model and pseudo-second-order kinetics model well. The selectivity value for PAH removal from the surfactant solution decreased with decreasing PAH hydrophobicity and increased with decreasing surfactant concentration. The sorption process was divided into four steps, and sorption schematics were proposed to elucidate the mechanism of sorption. Micelle adsorption was followed by surface solubilization. The findings demonstrate that activated carbon adsorption is an effective method for recovering biosurfactants.

Silica-Based Phenyl and Octyl Bifunctional Imidazolium as a New Mixed-Mode Stationary Phase for Reversed-Phase and Anion-Exchange Chromatography

In this study, octylbenzimidazolium-modified silica (BeImC8-Sil) was prepared by covalent attachment of 1-octylbenzimidazole to γ-chloropropyl silica. The synthesized materials were characterized by the elemental analysis, IR spectrum, and thermogravimetric analysis. Due to the introduction of phenyl and octyl groups on the quaternary imidazolium, the developed BeImC8-Sil column can function via both reversed-phase and anion-exchange retention mechanisms. The chromatographic properties of the synthesized material were investigated by the separations of polycyclic aromatic hydrocarbons, mono-substituted derivatives of benzene, anilines, and phenols, revealing the existence of multiple interactions, including hydrogen bonding, π–π stacking, electrostatic forces, and hydrophobic interactions in reversed-phase mode; inorganic and organic anions were also separated mainly through anion-exchange interaction. The proposed BeImC8-Sil is a promising mixed-mode stationary phase for the separation of complex samples in high-performance liquid chromatography.

Rapid separation of non-polar and weakly polar analytes with metal-organic framework MAF-5 coated capillary column

Metal-organic frameworks (MOFs) have attracted widespread attention due to their unique characters such as high surface area, high thermal and chemical stability, diverse structure topology and tunable pore size. The study first exploited a porous metal organic framework MAF-5 ([Zn[(eim)2], Heim=2-ethylimidazole) as stationary phase for gas chromatography by a novel dynamic coating method. The column efficiency of the 184 silicone@MAF-5 capillary column was up to 9045 platesm−1 for benzene. The column is very promising for the rapid separation of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs). And the column showed good reproducibility, retention time, peak area, high resolution, and a wide linear range. The determined thermodynamic parameters and chromatographic retention of all probe molecules on the 184 silicone@MAF-5 column showed the separation of analytes is a complex balance of thermodynamic and kinetic factors.

Molecular imprinted membrane based on molecular imprinted nanoparticles polymer for separation of polycyclic aromatic hydrocarbons

Molecular imprinted membrane based on molecular imprinted nanoparticles polymer for separation of polycyclic aromatic hydrocarbons

Repeatability of Octadecyl Methacrylate-Based Monolithic Columns for Capillary Electrochromatography

Octadecyl methacrylate-based monolithic capillary columns were prepared using octadecyl methacrylate as the monomer, ethylene dimethacrylate as the cross-linking agent, 2-acryloylamido-2-methylpropanesulfonic acid as the ionizable monomer, responsible for a negatively charged stationary phase surface and able to support a cathodic electrosmotic flow, and amyl alcohol and 1,4-butanediol as porogenic solvents. The repeatability of the morphological aspect of the monolithic material was evaluated by scanning electron microscopy (SEM). The uniformity along the same monolithic bed was also investigated by SEM. Replicate determinations of surface area and pore volume were also performed and compared. The repeatability of the obtained electrochromatographic efficiencies for separations of alkylbenzenes using the stationary phases prepared was also evaluated. A column that had a plate height of 31 μm was tested for separation of polycyclic aromatic hydrocarbons. Even though minimal possible variation of experimental parameters was maintained, it was not possible to reproduce the stationary phases of the monolithic columns, since the relative standard deviation for the efficiencies obtained on columns prepared from the same polymerization mixture composition was 62%. The lack of repeatability for the efficiency is thought to be a result of limited homogeneity of the monolithic globular structures along the length of the majority of the prepared columns. The poor precision of preparation was justified by the copolymerization reaction that occurs in the presence of 2, 2′-azobisisobutyronitrile as the initiator agent, whose decomposition starts at the moment that this is added to the reaction mixture.

Facile construction of macroporous hybrid monoliths via thiol-methacrylate Michael addition click reaction for capillary liquid chromatography

A facile approach based on thiol-methacrylate Michael addition click reaction was developed for construction of porous hybrid monolithic materials. Three hybrid monoliths were prepared via thiol-methacrylate click polymerization by using methacrylate-polyhedral oligomeric silsesquioxane (POSS) (cage mixture, n=8, 10, 12, POSS-MA) and three multi-thiol crosslinkers, 1,6-hexanedithiol (HDT), trimethylolpropane tris(3-mercaptopropionate) (TPTM) and pentaerythritol tetrakis(3-mercaptopropionate) (PTM), respectively, in the presence of porogenic solvents (n-propanol and PEG 200) and a catalyst (dimethylphenylphosphine, DMPP). The obtained monoliths possessed high thermal and chemical stabilities. Besides, they all exhibited high column efficiencies and excellent separation abilities in capillary liquid chromatography (cLC). The highest column efficiency could reach ca. 195,000N/m for butylbenzene on the monolith prepared with POSS-MA and TPTM (monolith POSS-TPTM) in reversed-phase (RP) mode at 0.64mm/s. Good chromatographic performance were all achieved in the separations of polycyclic aromatic hydrocarbons (PAHs), phenols, anilines, EPA 610 as well as bovine serum albumin (BSA) digest. The high column efficiencies in the range of 51,400–117,000N/m (achieved on the monolith POSS-PTM in RP mode) convincingly demonstrated the high separation abilities of these thiol-methacrylate based hybrid monoliths. All the results demonstrated the feasibility of the phosphines catalyzed thiol-methacrylate Michael addition click reaction in fabrication of monolithic columns with high efficiency for cLC applications.

New reversed-phase/anion-exchange/hydrophilic interaction mixed-mode stationary phase based on dendritic polymer-modified porous silica

A novel dendritic polymer-modified silica (DPS) stationary phase was prepared by a divergent synthesis scheme starting from propylamine on silica by consecutive amine-epoxy reactions with 1,4-butanedioldiglycidyl ether and aniline. Both elemental analysis and infrared spectra data shows the successful growth of dendritic polymer on silica particles. The carbon and nitrogen contents increased with an increasing number of reaction cycles and achieved 25.2% and 2.1% (w/w) after 11 reaction cycles. The combination of a phenyl ring with a quaternary ammonium, or a tertiary amine at the branch point along with embedded polar functionalities (including ether and hydroxyl groups) in the branch, generated hydrophobic, electrostatic, as well as hydrophilic interactive domains. Depending on solute structure and mobile phase composition, the DPS stationary phase provided multiple retention mechanisms, including reversed phase (RP), anion-exchange (AEX), and hydrophilic interactions. The RP capability achieved separation of polycyclic aromatic hydrocarbons. Basic, neutral and acidic molecules were well separated under RP/AEX mixed mode. Effective separation of small polar compounds (such as nucleobases and nucleosides) was also obtained under hydrophilic interaction liquid chromatography (HILIC) mode.

Comparison of monolithic capillary electrochromatography and micellar electrokinetic chromatography for the separation of polycyclic aromatic hydrocarbons

Atmospheric pollution of anthropic origin is recognized as a major risk factor for health, in particular for respiratory and cardio-vascular systems. Among these pollutants, polycyclic aromatic hydrocarbons (PAHs) are placed on the list of US Environmental Protection Agency (EPA) as 'priority' pollutants and four of them are assigned as potential carcinogens by The International Agency for Research on Cancer (IARC). In the present work two capillary techniques-micellar electrokinetic chromatography (MEKC) and monolithic capillary electrochromatography (CEC)-were compared for the separation of eleven PAHs. Both techniques compared in the present work are fully compatible with every standard apparatus of capillary electrophoresis. For MEKC, enhancement of selectivity and decrease of the separation window of eleven PAHs were obtained with methanol:borate 25 mM (20/80, v/v) running buffer containing 10 mM of hydroxypropylated γ-cyclodextrins with low SDS content (25 mM). In case of CEC, two acrylate-based monolithic stationary phases (MSPs) were evaluated for their application in the separation of eleven PAHs. The best MSP based on butyl acrylate was compared with MEKC in terms of sample capacity, PAHs elution order, LOQ, efficiency and effect of pH. Influence of the hydrophobicity of mobile phase on the PAHs elution order was also studied.