Determination of polycyclic aromatic hydrocarbons by solid-phase microextraction coupled to HPLC using a fiber with mesoporous silica coating

A novel SPME-HPLC method was developed for the determination of trace amounts of polycyclic aromatic hydrocarbons (PAHs). It was found that the SPME device with C₈H₁₇-SBA-15 (C ₈-SBA-15) mesoporous silica coating had high extraction efficiency, sufficient chemical and hydrothermal stability and good reversibility. The determination conditions for environmental pollutants like PAHs including extraction and desorption time, extraction temperature, ionic strength and stirring rate were optimized. Under optimized experimental conditions, results with good accuracy (with a recovery of 97.5–101.7%), precision (with a standard deviation of 0.15–1.07%) and low detection limit (LOD, 0.05–0.25 μg/L) were obtained, suggesting the SPME devices using chemical modified SBA-15 as coating material are promising in preconcentration, separation and determination of interested analytes in the future.     

Carbon nanotubes functionalized mesoporous silica for in‐tube solid‐phase microextraction of polycyclic aromatic hydrocarbons

A mesoporous silica was functionalized by carbon nanotubes to enhance the extraction performance. The mesoporous material was coated on stainless steel wires, and three wires were inserted inside of a polyetheretherketone tube for in‐tube solid‐phase microextraction. The tube was coupled to high‐performance liquid chromatography with diode array detection to obtain online analytical system, then its extraction performance was evaluated using eight polycyclic aromatic hydrocarbons as the targets. In order to good sensitivity and accuracy, four conditions were optimized such as sampling volume, sampling rate, methanol content in the sample, and desorption time. Under the optimum conditions, an online analytical method was established and exhibited low limits of detection from 0.005 to 0.050 µg/L, wide linear range of 0.016‐20.00 µg/L with acceptable correlation coefficients in 0.9921‐0.9999, as well as large enrichment factors in the range of 311‐2412. The method was successfully applied to determine trace polycyclic aromatic hydrocarbons in some real water samples including, two kinds of bottled water, tap water, and river water, a few polycyclic aromatic hydrocarbons were detected but none quantified in these samples.     

Nitrated polycyclic aromatic hydrocarbons in the environment: formation, occurrences and analysis

A review is presented on the formation and occurrence in the atmosphere of nitrated polycyclic aromatic hydrocarbons. Some analytical methodologies (covering various matrices) are also considered.     

苯基修饰二氧化硅纳米片纤维的制备及其对多环芳烃的固相微萃取

采用水热处理和溶胶-凝胶法在镍钛合金（NiTi）纤维表面组装了二氧化硅纳米片（SiO₂NFs）,成功制备了新型SiO₂纤维涂层,并用苯基三氯硅烷进行了自组装表面修饰,得到了可用于固相微萃取（SPME）的NiO/TiO₂@SiO₂NFs-Ph纤维。将制备的SPME纤维与高效液相色谱联用,通过对典型芳香化合物的分析评价了所制备纤维的萃取性能。该纤维对多环芳烃（PAHs）具有较高的萃取率和良好的萃取选择性。实验优化了pH值、搅拌速率、萃取温度、萃取时间和离子强度对PAHs萃取率的影响。在优化条件下,5种PAHs在各自的范围内呈良好的线性关系,相关系数（r）大于0.999,检出限为0.013~0.108 μg/L。使用单根纤维对含有50 μg/L PAHs的加标水样进行萃取,其含量的日内及日间RSD分别为4.1%~5.9%和4.8%~6.8%。实际环境水样中5种PAHs在10 μg/L和30 μg/L加标水平下的加标回收率分别为90.8%~105.7%和93.6%~103.1%。该法制备的NiO/TiO₂@SiO₂NFs-Ph纤维稳定性高、制备重现性好,适用于环境水样中目标PAHs的富集和测定。     

A polymer monolith incorporating stellate mesoporous silica nanospheres for use in capillary electrochromatography and solid phase microextraction of polycyclic aromatic hydrocarbons and organic small molecules

An inorganic-organic hybrid monolith incorporated with stellated mesoporous silica nanoparticles (SMSNs) was prepared. Using binary solvents, deep eutectic solvents and room temperature ionic liquids, an SMSN-incorporated poly(butyl methacrylate-co-ethylene glycol dimethacrylate) monolith demonstrated uniform structure with good column permeability. A systematic investigation of preparation parameter was performed, including SMSN content, crosslinking monomer content, and the component of binary solvent. The optimized monoliths were characterized by field emission scanning electron microscopy, transmission electron microscopy, area scanning energy dispersive spectrometry, and nitrogen adsorption. Column performance was tested by separating four groups of analytes (alkylbenzenes, anilines, naphthalenes and phenols) by capillary electrochromatography (CEC). Baseline separation of all analytes was obtained with column efficiencies of up to 266,000 plates m^?1. The performance of the resulting monolith was further investigated in detail by separating mixtures of polycyclic aromatic hydrocarbons (PAHs), nonsteroidal antiinflammatory drugs (NSAIDs), and hydroxybenzoic acid isomers. Compared with the corresponding SMSN-free monolith, the CEC performance was improved by about six times. Successful extraction of PAHs and quinolones (QNs) were also performed using this capillary. Improved extraction efficiency (20.2%) for complex samples, lake water, was also found when the material was applied to solid phase microextraction of fluoranthene.

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Graphical abstract A poly(butyl methacrylate-co-ethylene glycol dimethacrylate) monolith incorporated with stellated mesoporous silica nanoparticles was prepared. It demonstrated column efficiency up to 266,000 plates m^?1 in capillary electrochromatography and ability as solid phase microextraction for organic small molecules with good column permeability.

     

Solubility and partitioning studies with polycyclic aromatic hydrocarbons using an optimized SPME procedure

In order to determine the water solubilitiy (S _W) and octanol/water partition coefficient (K _OW) of polycyclic aromatic hydrocarbons, we have optimized the direct solid-phase microextraction (SPME) of selected compounds (fluoranthene (FLU), phenanthrene (PHE), pyrene (PYR), benz[a]anthracene (BaA), benz[a]pyrene (BaP), and coronene) from the matrices water and octanol-saturated water. By the use of a 100 μm polydimethylsiloxane fibre and magnetic stirring of the sample with glass-coated mini-impellers in combination with gas chromatography we obtained limits of determination (GC-MS) comparable to standard HPLC procedures. Only coronene could not be quantified. The determined S _W of FLU agree with reference data; for B[a]P we have obtained a 2 to 3 times higher value than described in recent literature. The obtained K _OW values are close to reference data for both single components. For a mixture of FLU, PHE, PYR, and B[a]A the measured K _OW values are 0.2–0.3 log units below tabulated values for the single components. Received: 22 July 1998 / Revised: 28 October 1998 / Accepted: 1 November 1998     

Solubility and partitioning studies with polycyclic aromatic hydrocarbons using an optimized SPME procedure

In order to determine the water solubilitiy (S _W) and octanol/water partition coefficient (K _OW) of polycyclic aromatic hydrocarbons, we have optimized the direct solid-phase microextraction (SPME) of selected compounds (fluoranthene (FLU), phenanthrene (PHE), pyrene (PYR), benz[a]anthracene (BaA), benz[a]pyrene (BaP), and coronene) from the matrices water and octanol-saturated water. By the use of a 100 μm polydimethylsiloxane fibre and magnetic stirring of the sample with glass-coated mini-impellers in combination with gas chromatography we obtained limits of determination (GC-MS) comparable to standard HPLC procedures. Only coronene could not be quantified. The determined S _W of FLU agree with reference data; for B[a]P we have obtained a 2 to 3 times higher value than described in recent literature. The obtained K _OW values are close to reference data for both single components. For a mixture of FLU, PHE, PYR, and B[a]A the measured K _OW values are 0.2–0.3 log units below tabulated values for the single components. Received: 22 July 1998 / Revised: 28 October 1998 / Accepted: 1 November 1998     

Bamboo charcoal as adsorbent for SPE coupled with monolithic column-HPLC for rapid determination of 16 polycyclic aromatic hydrocarbons in water samples

The coupling of solid-phase extraction (SPE) using bamboo charcoal (BC) as an adsorbent with a monolithic column-high performance liquid chromatography (MC-HPLC) method was developed for the high-efficiency enrichment and rapid determination of 16 polycyclic aromatic hydrocarbons (PAHs) in water. Key influence factors, such as the type and the volume of the elution solvent, and the flow rate and the volume of the sample loading, were optimized to obtain a high SPE recovery and extraction efficiency. BC as an SPE adsorbent presented a high extraction efficiency due to its large specific surface area and high adsorption capacity; MC as an HPLC column accelerated the separation within 8 min because of its high porosity, fast mass transfer, and low-pressure resistance. The calibration curves for the PAHs extracted were linear in the range of 0.2-15 μg/L, with the correlation coefficients (r(2)) between 0.9970-0.9999. This method attained good precisions (relative standard deviation, RSD) from 3.5 to 10.9% for the standard PAHs I aqueous solutions at 5 μg/L; the method recoveries ranged in 52.6-121.6% for real spiked river water samples with 0.4 and 4 μg/L. The limits of detection (LODs, S/N = 3) of the method were determined from 11 and 87 ng/L. The developed method was demonstrated to be applicable for the rapid and sensitive determination of 16 PAHs in real environmental water samples.     

Separation of polycyclic aromatic hydrocarbons with a C60 bonded silica phase in microcolumn liquid chromatography

A chemically bonded C₆₀ silica phase was synthesized as a stationary phase for liquid chromatography (LC) and its retention behavior evaluated for various polycyclic aromatic hydrocarbons (PAHs) using microcolumn LC. The results indicate that the C₆₀ bonded phase offers selectivity different from that of octadecylsilica (ODS) bonded phases in the separation of isomeric PAHs. With the C₆₀ phase, PAH molecules having a partial structure similar to that of the C₆₀ molecule, e.g. triphenylene and perylene, were retained longer than with ordinary ODS stationary phases. The results also show that good correlation exists between the retention data with this C₆₀ bonded phase and with C₆₀ itself as the stationary phase.     

Spontaneous formation and characterization of silica mesoporous crystal spheres with reverse multiply twinned polyhedral hollows

A crystal is an object with translational symmetry. Basic research into and production of new materials necessitates the preparation of crystals of a particular morphology and with well-defined crystal defects. In this work, we found novel silica mesoporous crystal spheres with polyhedral hollows (icosahedral, such as those observed for proteins of virus capsids, decahedral, Wulff polyhedral, etc.) formed by the reverse multiply twinned bicontinuous double diamond mesostructure. Vesicles with a low-curvature lamellar structure were first formed by the self-assembly of amphiphilic carboxylic acid molecules in the presence of a nonionic surfactant and then underwent a structural transformation process that gave a reverse multiply twinned mesoporous shell while maintaining the hollow shape. These polyhedral hollow crystals showed an enhanced contrast of backscattering signatures relative to the incident acoustic signals and thus could be used as a potential contrast agent in medical ultrasonography with drug loadings in the mesopores.     

Fluorescence optosensor using an artificial neural network for screening of polycyclic aromatic hydrocarbons

This paper presents an optosensor for screening of four polycyclic aromatic hydrocarbons: anthracene (ANT), benzo[a]pyrene (BaP), fluoranthene (FLT), and benzo[b]fluoranthene (Bbf) using a photomultiplier device with an artificial neural network as transducer. The optosensor is based on the on-line immobilization on a non-ionic resin (Amberlite XAD-4) solid support in a continuous flow. The determination was performed in 15 mM H₂PO₄⁻/HPO₄²⁻ buffer solution at pH 7 and 25% of 1,4-dioxane. Feed forward neural networks (multiplayer perceptron) have been trained to quantify the considered Polycyclic aromatic hydrocarbons (PAHs) in mixtures under optimal conditions. The optosensor proposed was also applied satisfactorily to the determination of the considered PAHs in water samples in presence of the other 12 EPA–PAHs.     

Determination of aromatic and polycyclic aromatic hydrocarbons in gasoline using programmed temperature vaporization-gas chromatography-mass spectrometry

A sensitive method is presented for the fast analysis of three aromatic and six polycyclic aromatic hydrocarbons (biphenyl, 3-methylbiphenyl, 4-methylbiphenyl, fluorene, phenanthrene, fluoranthene, pyrene, 1,2-benz(a)anthracene and chrysene) in gasoline samples. The applicability of a GC device equipped with a programmable temperature vaporizer (PTV) and an MS detector is explored. Additionally, a modular accelerated column heater (MACH) was used to control the temperature of the capillary gas chromatography column. This module can be heated and cooled very rapidly, making total analysis cycle times very short. The proposed method does not require any previous analyte extraction and preconcentration step, as in most methods described to date. Sample preparation is reduced to simply diluting the gasoline samples in methanol. This reduces the experimental errors associated with this step of the analytical process. By using sampling injection in the solvent vent mode, and through choice of a suitable temperature, the lightest major components of the gasoline were removed. Moreover, use of a liner packed with Tenax-TA allowed the compounds of interest to be retained during the process. This working strategy could be extended to other groups of compounds through the choice of different venting temperatures. In this way, a large part of the gasoline components are eliminated, the life of the liner is prolonged, and it is possible to inject sample volumes that will not saturate the chromatographic column. The limits of detection ranged from 0.61 microg/L (pyrene) to 6.1 microg/L (biphenyl), and precision (measured as the relative standard deviation) was equal to or lower than 7.3%. The method was applied to the determination of analytes in gasoline samples and the results obtained can be considered highly satisfactory.     

Structure-retention studies on the inclusion complex formation of some polycyclic aromatic hydrocarbons with β-cyclodextrin

Summary The retention behaviour of a group of polycyclic aromatic hydrocarbons having nearly equal ionization potentials but different molecular polarizability values was investigated using reversed-phase HPLC. Methanol-water binary systems containing -cyclodextrin were applied as the mobile phase. The relationships between the capacity factors, molecular polarizabilities and the shape parameter of solute molecules are discussed.     

Low temperature mechanism for the formation of polycyclic aromatic hydrocarbons from the pyrolysis of cellulose

The formation of polycyclic aromatic hydrocarbons (PAHs) from the pyrolysis of cellulose over the temperature range of 300–650 °C has been investigated. Detectable amounts (microgram per gram) of 2–4 ring PAHs were observed at and above 400 °C. Benzo[a]pyrene and benz[a]anthracene were observed at and above 500 °C. Changing the gas phase residence time from 2 to 18 s and the sample size from 200 to 500 mg did not significantly affect the yields of PAHs formed over this low temperature range. The addition of oxygen to the carrier gas stream significantly reduced the yields of PAHs. The pathway to PAH formation in the 300–650 °C temperature range is believed to proceed via the carbonization process where the solid residue undergoes a chemical transformation and rearrangement to give a more condensed polycyclic aromatic structure. The evolution profiles of PAHs from the solid residue suggests that smaller 2–3 ring PAHs evolve first and pass through a maximum at a slightly lower temperature than the larger 4–5 ring PAHs. The yields of PAHs obtained from the pyrolysis of d-glucose and sucrose are comparable to those obtained from cellulose.     

Modeling formation of molecules in the interstellar medium by radical reactions with polycyclic aromatic hydrocarbons

Adsorptions of CH°₂, CH°₃, NH°₂, and OH° radicals and molecule formation on a partially hydrogenated surface of a polycyclic aromatic hydrocarbon (PAH) (C₂₄H₂₇⁺) were modeled. It was found that radical adsorptions are feasible with important modifications of surface bond strengths and bond distances. Adsorbed hydrogen may diffuse due to adsorbate‐surface interactions. Formations of CH₄, NH₃, H₂O, CH₃NH₂, and CH₃OH were studied by Eley‐Rideal (ER) and Langmuir‐Hishelwood (LH) mechanisms. Potential energetic surfaces were performed for both mechanisms and the ER presents lower reaction energy barriers than the LH one, in all cases. Parametric quantum program (CATIVIC) was employed and comparisons with DFT results were performed. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem 110:2560–2572, 2010     

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.     

Determination of polycyclic aromatic hydrocarbons in sediment using solid-phase microextraction with gas chromatography-mass spectrometry

Manual solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) is applied for the determination of polycyclic aromatic hydrocarbons (PAHs) from natural matrix through a distilled water medium. Seven of the 16 PAH standards (naphthalene, acenaphthene, fluorene, anthracene, fluoranthene, pyrene, benzo[a]anthracene) are spiked on a marine muddy sediment. The samples, containing PAHs in the range of 10-20 ppm, are then aged at room temperature more than 10 days before analysis. The influence of the matrix, SPME adsorption time, pH, salt content, and SPME adsorption temperature are investigated. The reproducibility of the technique is less than 13% (RDS) for the first 6 considered PAHs and 28% (RDS) for benzo(a)anthracene with a fiber containing a 100-micron poly dimethylsiloxane coating. Linearity extended in the range of 5-50 picograms for PAHs direct injection, 5-70 picograms for PAHs in water, and 1-170 picograms for PAHs in sediment. The detection limit is estimated less than 1 microgram/kg of dry sample for the first 6 considered PAHs in sediment and 1.5 micrograms/kg of dry sample for benzo(a)anthracene using the selected ion monitoring mode in GC-MS. The recoveries of the considered PAHs are evaluated.     

Hydrophobic interaction electrokinetic chromatography for the separation of polycyclic aromatic hydrocarbons using non-aqueous matrices

Capillary electrophoresis methodology is developed to provide a rapid, inexpensive and robust technique for screening polycyclic aromatic hydrocarbons (PAHs) in water using additive complexation. A series of conventional RPLC ion-pairing agents are investigated in three different totally non-aqueous separation solvents, and the relative role of hydrophobic interaction versus electrostatic association is evaluated. Methanol is found to provide optimal selectivity when coupled with the tetrahexylammonium cation providing total analysis times of approximately 15 min for the analysis of thirteen 2-7-ring PAH pollutants. Solid-phase microextraction is demonstrated to be an effective sample preparation technique for extraction/preconcentration of PAHs from water into methanol run buffer prior to injection.