Adsorption/Thermal Desorption with Tenax-GC for the Collection and Analysis of Polycyclic Aromatic Hydrocarbons and Chlorinated Compounds

A system for the determination of polycyclic aromatic hydrocarbons(PAHs) and chlorinated compounds in air by means of adsorption/thermal desorption(ATD) with small bed volume (0.1 g) Tenax cartridges, followed by cryogenic trap in a U-shaped stainless steel tube with liquid nitrogen as an appropriate concentration method prior to capillary gas chromatography is described. Recoveries were determined for the complete ATD method. Desorption recoveries near 100% were found for a variety of chlorinated compounds and polycyclic aromatic hydrocarbons.     

Capillary column gas chromatography of environmental polycyclic aromatic compounds

The methodologies are described for isolating clean fractions of polycyclic aromatic compounds from diverse environmental samples such as air particulate matter, sediments, and fish tissue. The common step in all procedures is the separation of the polycyclic aromatic compound fraction into well-defined chemical classes by adsorption chromatography on an alumina column. These procedures greatly facilitate the detailed characterization of the polycyclic aromatic hydrocarbons, sulfur heterocycles, and nitrogen heterocycles by capillary column gas chromatography.     

Capillary Column Gas Chromatography of Environmental Polycyclic Aromatic Compounds

Abstract

The methodologies are described for isolating clean fractions of polycyclic aromatic compounds from diverse environmental samples such as air particulate matter, sediments, and fish tissue. The common step in all procedures is the separation of the polycyclic aromatic compound fraction into well-defined chemical classes by adsorption chromatography on an alumina column. These procedures greatly facilitate the detailed characterization of the polycyclic aromatic hydrocarbons, sulfur heterocycles, and nitrogen heterocycles by capillary column gas chromatography.     

Clean-up methods for polycyclic aromatic hydrocarbons analyses by capillary gas chromatography

Summary Comparative results of pre-treatment methods for the extracts of polycyclic aromatic hydrocarbons (PAHs) from airborne particulate matter for quantitative determination by gas chromatography (GC) are presented. The first method included liquid-liquid extraction and column liquid adsorption chromatography. In the second procedure the extract was fractionated by liquid-liquid chromatography and liquid adsorption chromatography. In the last procedure two different solid phase extraction (SPE) cartridges examined makes it possible to separate PAHs and remove paraffinic compounds which is very important for the quantitative GC analysis of the PAHs. Recoveries of PAH standards and some their derivatives were determined and the contents of 15 of the most important PAHs, were compared. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Analysis for polynuclear aromatic hydrocarbons in working atmospheres by computerized gas chromatography-mass spectrometry

Polynuclear aromatic hydrocarbons in particulate matter from working atmospheres have been analyzed by a glass capillary gas chromatography—mass spectrometer—computer system which has high separation efficiency and is capable of separating and identifying these complex mixtures. More than one hundred polynuclear aromatic hydrocarbons have been identified in samples from a coke plant and an aluminum smelter, including both pure polycyclic aromatic hydrocarbons and compounds where a CH-group is substituted with the hetero atoms oxygen, nitrogen, or sulfur. The occurrence of polynuclear aromatic hydrocarbons in working atmospheres is compared to that in ambient air and emissions from other sources.     

Application of capillary gas chromatography mass spectrometry/computer techniques to synoptic survey of organic material in bed sediment

A bed sediment sample taken from an area impacted by heavy industrial activity was analyzed for organic compounds of environmental significance. Extraction was effected on a Soxhlet apparatus using a freeze-dried sample. The Soxhlet extract was fractionated by silica gel micro-column adsorption chromatography. Separation and identification of the organic compounds was accomplished by capillary gas chromatography/mass spectrometry techniques. More than 50 compounds were identified; these include saturated hydrocarbons, olefins, aromatic hydrocarbons, alkylated polycyclic aromatic hydrocarbons, and oxygenated compounds such as aldehydes and ketones. The role of bed sediments as a source or sink for organic pollutants is discussed.     

Determination of polycyclic aromatic compounds in fish tissue

A method is presented for the analysis of polycyclic aromatic hydrocarbons (PAHs), polycyclic aromatic sulfur heterocycles (PASHs), and basic polycyclic aromatic nitrogen heterocycles (PANHs) in fish. The analytical procedure includes Soxhlet extraction of prepared fish tissue with methylene chloride followed by gel permeation chromatography (GPC) using Bio-beads SX-3. For PAHs/PASHs, further cleanup is performed using adsorption chromatography on Florisil (5% water deactivated) and elution with hexane. For basic PANHs further cleanup of the fish extracts after GPC is achieved using liquid-liquid partitioning with 6 M hydrochloric acid and chloroform and then basifying the aqueous phase and extracting it with chloroform. Analysis of fortified fish samples was performed using capillary gas chromatography with flame ionization detection and capillary gas chromatography-mass spectrometry. Good agreement was observed for both methods of analysis when applied to fish samples fortified with PAHs, PASHs and basic PANHs at 0.1 to 1 microgram/g, suggesting that the method is effective at removing interfering biogenic compounds prior to analysis. Average recovery of PAHs/PASHs from fortified fish tissue was 87% and 70% for fish tissue fortified at 0.24-1.1 and 0.024-0.11 microgram/g, respectively. Average recovery for basic PANHs was 97% for fish fortified at 1.2-1.4 micrograms/g.     

Rapid cleanup of natural organic extracts for the recovery of plyacyclic aromatic hydrocarbons by solid phase extraction

A rapid cleanup procedure has been tested and applied routinely in our laboratory to petroleum and sediment extracts for the recovery of polycyclic aromatic hydrocarbons. Solid-phase extractsion (SPE) on Florisil cartridges yields a fast and good recovery of neutral aromatic compounds which has been checked by normal-phase high performance liquid chromatographic (HPLC) analysis with UV-absorption detection.     

Influence of silicon defects on the adsorption of thiophene-like compounds on polycyclic aromatic hydrocarbons: a theoretical study using thiophene + coronene as the simplest model

Physisorption and chemisorption processes of thiophene on coronene and 2Si-coronene have been studied using density functional theory and MP2 methods. These systems have been chosen as the simplest models to describe the adsorption of thiophene-like compounds on polycyclic aromatic hydrocarbons (PAHs). The calculated data suggest that the presence of silicon atoms in PAHs could favor their interaction with thiophene and similar compounds. Small stabilization energies have been found for several physisorbed complexes. The thiophene chemisorption on coronene seems very unlikely to occur, while that on 2Si-coronene leads to addition products which are very stable, with respect to the isolated reactants. These chemisorption processes were found to be exoergic (DeltaG < 0) in the gas phase and in the nonpolar liquid phase. The results reported in this work suggest that silicon defects on extended polycyclic aromatic hydrocarbons, such as graphite, soot, and large-diameter carbon nanotubes, could make them useful in the removal processes of aromatic sulfur compounds from oil hydrocarbons.     

Magnetic graphene oxide as adsorbent for the determination of polycyclic aromatic hydrocarbon metabolites in human urine

Detection of monohydroxy polycyclic aromatic hydrocarbons metabolites in urine is an advisable and valid method to assess human environmental exposure to polycyclic aromatic hydrocarbons. In this work, novel Fe₃O₄/graphene oxide composites were prepared and their application in the magnetic solid‐phase extraction of monohydroxy polycyclic aromatic hydrocarbons in urine was investigated by coupling with liquid chromatography and mass spectrometry. In the hybrid material, superparamagnetic Fe₃O₄ nanoparticles provide fast separation to simplify the analytical process and graphene oxide provides a large functional surface for the adsorption. The prepared magnetic nanocomposites were characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometry. The experimental conditions were optimized systematically. Under the optimal conditions, the recoveries of these compounds were in the range of 98.3–125.2%, the relative standard deviations ranged between 6.8 and 15.5%, and the limits of detection were in the range of 0.01–0.15 ng/mL. The simple, quick, and affordable method was successfully used in the analysis of human urinary monohydroxy polycyclic aromatic hydrocarbons in two different cities. The results indicated that the monohydroxy polycyclic aromatic hydrocarbons level in human urine can provide useful information for environmental exposure to polycyclic aromatic hydrocarbons.     

Solvent-resistant sol-gel polydimethyldiphenylsiloxane coating for on-line hyphenation of capillary microextraction with high-performance liquid chromatography

A sol-gel polydimethyldiphenylsiloxane (PDMDPS) coating was developed for capillary microextraction on-line hyphenated with high-performance liquid chromatography (HPLC). This coating was created using methyltrimethoxysilane (MTMS) as the sol-gel precursor and di-hydroxy-terminated PDMDPS as the sol-gel active polymer. The methyl and phenyl groups on the sol-gel active polymer and the methyl groups on the sol-gel precursor ultimately turned into pendant groups providing the ability to extract non-polar analytes. A 40-cm segment of 0.25mm I.D. fused silica capillary containing the sol-gel PDMDPS coating was installed as an external sampling loop in an HPLC injection port. Aqueous samples containing polycyclic aromatic hydrocarbons (PAHs), aromatic compounds, ketones, and aldehydes were passed through this capillary wherein the analytes were extracted by the sol-gel coating. The extracted analytes were then transferred to the HPLC column using isocratic or gradient elution with an acetonitrile/water mobile phase. This capillary demonstrated excellent extraction capability for non-polar (e.g., polycyclic aromatic hydrocarbons and aromatic compounds) as well as moderately polar compounds, such as aromatic amines, ketones, and aldehydes. The test results indicate that PDMDPS can be successfully immobilized into a sol-gel network and that the resulting solvent-resistant sol-gel organic-inorganic hybrid coating can be effectively used for on-line hyphenation of capillary microextraction with high-performance liquid chromatography. The test results also indicate that the sol-gel PDMDPS coated capillary is resistant to high-temperature solvents, making it suitable for applications in high-temperature HPLC. To the best of our knowledge, this is the first report on the creation of a silica-based sol-gel PDMDPS coating used in capillary microextraction on-line hyphenated to HPLC.     

Identification of oxygenated polycyclic aromatic hydrocarbons in diesel particulate matter by capillary gas chromatography and capillary gas chromatography/mass spectrometry

Summary Using a two-step liquid chromatographic separation on normalphase cartridges, crude extracts of diesel particulate matter can be separated without time-consuming sample handling into special fractions which mainly contain slightly-polar oxygenated polycyclic aromatic hydrocarbons (oxy-PAH) and nitrated polycyclic aromatic hydrocarbons (nitro-PAH). Subsequent analysis was by fused-silica capillary gas chromatography on a SE54 column along with flame-ionisation (GC/FID) and positive-ion electron-impact mass spectrometric detection (GC/MS) respectively. A number of individual oxy-PAH belonging to four different chemical classes (ketones, quinones, anhydrides and aldehydes) and several individual nitro-PAH were characterized by their retention times and mass spectra. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Polytetrafluoroethylene‐jacketed stirrer modified with graphene oxide and polydopamine for the efficient extraction of polycyclic aromatic hydrocarbons

Steel stirrers jacketed with polytetrafluoroethylene can be regarded as an ideal substrate for stirrer bar sorptive extraction. However, it is still a great challenge to immobilize graphene onto a polytetrafluoroethylene stirrer due to the high chemical resistance of the surface of a polytetrafluoroethylene stirrer. We describe here a method to modify the surface of polytetrafluoroethylene stirrers with graphene. In this work, graphene was used as the sorbent due to its excellent adsorption capability for aromatic compounds, such as polycyclic aromatic compounds. Graphene was successfully immobilized onto polytetrafluoroethylene‐stirrer by a bio‐inspired polydopamine functionalization method. The graphene‐modified polytetrafluoroethylene‐stirrer shows good stability and tolerance to stirring, ultrasonication, strong acidic and basic solutions, and to organic solvents. The multilayer coating was characterized by scanning electronic microscopy and Fourier transform infrared spectroscopy. After the optimization of some experimental conditions, the graphene‐modified polytetrafluoroethylene stirrer was used for the stirrer bar sorptive extraction of polycyclic aromatic hydrocarbons, in which the binding between the polycyclic aromatic hydrocarbons and the graphene layer was mainly based on π–π stacking and hydrophobic interactions. The graphene‐modified polytetrafluoroethylene‐stirrer‐based stirrer bar sorptive extraction and high‐performance liquid chromatography method was developed for the determination of polycyclic aromatic hydrocarbons with great extraction efficiency, with enrichment factors from 18 to 62. The method has low limits of detection of 1–5 pg/mL, wide linear range (5–100 and 10–200 pg/mL), good linearity (R ≥ 0.9957) and good reproducibility (RSD ≤ 6.45%). The proposed method has been applied to determine polycyclic aromatic hydrocarbons in real dust samples. Good recoveries were obtained, ranging from 88.53 to 109.43%.     

Determination of Trace Amounts of Organic Pollutants in the Yellow River by Capillary Column Gas Chromatography-Mass Spectrometry

Abstract

The trace organic pollutants in the Yellow River enriched by a solvent extraction method were pre-separated into four different fractions of fatty hydrocarbons, polycyclic aromatic hydrocarbons, polar compounds and organic acids and were analyzed by the use of combined capillary column gas chromatography-mass spectrometry. Using the combined techniques of relative retention value, mass spectra and mass chromatogram, more than 60 organic pollutants were identified, among which 16 fatty hydrocarbons and 6 polycyclic aromatic hydrocarbons which were quantitatively analyzed. The concentration range of fatty hydrocarbon was 5–800 ng/l, and that of polycyclic aromatic hydrocarbon was 0-90ng/l.     

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

A 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.     

A silica-based monolithic column in capillary HPLC and CEC coupled with ESI-MS or electrospray-atmospheric-pressure laser ionization-MS

We describe the successful coupling of CEC and capillary HPLC with the recently developed atmospheric-pressure laser ionization (APLI) method. APLI is suitable for selectively and sensitively ionizing nonpolar aromatic compounds at ambient pressure for subsequent mass-selective detection. The polycyclic aromatic hydrocarbons used as analytes are first separated either by CEC on a silica-based monolithic column or by capillary HPLC. The eluent, along with a sheath flow, is volatilized by microelectrospray and then selectively ionized by excimer laser (KrF*) radiation via two-photon excitation. A QTOF-MS is used as mass-selective detector. This interface combination makes soft ionization of thermally labile nonpolar aromatic analytes possible.     

Optimization and determination of polycyclic aromatic hydrocarbons in biochar‐based fertilizers

The agronomic benefit of biochar has attracted widespread attention to biochar‐based fertilizers. However, the inevitable presence of polycyclic aromatic hydrocarbons in biochar is a matter of concern because of the health and ecological risks of these compounds. The strong adsorption of polycyclic aromatic hydrocarbons to biochar complicates their analysis and extraction from biochar‐based fertilizers. In this study, we optimized and validated a method for determining the 16 priority polycyclic aromatic hydrocarbons in biochar‐based fertilizers. Results showed that accelerated solvent extraction exhibited high extraction efficiency. Based on a Box–Behnken design with a triplicate central point, accelerated solvent extraction was used under the following optimal operational conditions: extraction temperature of 78°C, extraction time of 17 min, and two static cycles. The optimized method was validated by assessing the linearity of analysis, limit of detection, limit of quantification, recovery, and application to real samples. The results showed that the 16 polycyclic aromatic hydrocarbons exhibited good linearity, with a correlation coefficient of 0.996. The limits of detection varied between 0.001 (phenanthrene) and 0.021 mg/g (benzo[ghi]perylene), and the limits of quantification varied between 0.004 (phenanthrene) and 0.069 mg/g (benzo[ghi]perylene). The relative recoveries of the 16 polycyclic aromatic hydrocarbons were 70.26–102.99%.     

Application of sunflower stalk‐carbon nitride nanosheets as a green sorbent in the solid‐phase extraction of polycyclic aromatic hydrocarbons followed by high‐performance liquid chromatography

A green biocomposite of sunflower stalks and graphitic carbon nitride nanosheets has been applied as a solid‐phase extraction adsorbent for sample preparation of five polycyclic aromatic hydrocarbons in different solutions using high‐performance liquid chromatography with ultraviolet detection. Before the modification, sunflower stalks exhibited relatively low adsorption to the polycyclic aromatic hydrocarbons extraction. The modified sunflower stalks showed increased adsorption to the analytes extraction due to the increase in surface and existence of a π–π interaction between the analytes and graphitic carbon nitride nanosheets on the surface. Under the optimal conditions, the limits of detection and quantification for five polycyclic aromatic hydrocarbons compounds could reach 0.4–32 and 1.2–95 ng/L, respectively. The method accuracy was evaluated using recovery measurements in spiked real samples and good recoveries from 71 to 115% with relative standard deviations of <10% have been achieved. The developed method was successfully applied for polycyclic aromatic hydrocarbons determination in various samples—well water, tap water, soil, vegetable, and barbequed meat (kebab)—with analytes contents ranging from 0.065 to 13.3 μg/L. The prepared green composite as a new sorbent has some advantages including ease of preparation, low cost, and good reusability.     

Open tubular columns with mixed‐mode reversed‐phase and weak anion‐exchange stationary phase for capillary electrochromatography

Columns for open tubular capillary electrochromatography, coated with a mixed‐mode (RP/ion‐exchange) stationary phase, were prepared by using the sol–gel method. The synthetic procedure was optimized by changing the ratios of tetraethoxysilane, octyltriethoxysilane, and 3‐aminopropyltriethoxysilane in the initial sol. SEM studies reveal that a coating with about 400 nm thickness can be obtained. The inner surface properties of these capillaries were probed by measuring the EOF as a function of pH. The surface of this stationary phase contains octyl, amine, and residual silanol moieties; the amine and silanol groups determine the net charge on the inner surface of the capillary and can produce a switchable EOF (anodal/cathodal). The performances of the columns were evaluated by open tubular capillary electrochromatography using a wide range of compounds (polycyclic aromatic hydrocarbons, aromatic acids, and aromatic amines).     

酸催化及竞争吸附对CeY分子筛吸附脱硫性能的影响

采用液相离子交换(LPIE)法制备了CeY分子筛,并研究烯烃和芳烃对其吸附脱硫性能的影响. 利用固定床穿透曲线技术研究吸附剂的脱硫性能,结果表明：烯烃和芳烃的存在均导致吸附剂吸附硫容量减少,然而,烯烃的影响明显强于芳烃. 采用原位傅里叶变换红外(FTIR)光谱技术研究噻吩、环己烯和苯的吸附行为,结果发现：烯烃和芳烃降低吸附剂脱硫性能的实质分别为吸附剂表面酸性导致的酸催化反应和π-络合吸附的芳烃分子与硫化物分子的竞争吸附. 另外,烯烃的影响取决于吸附剂的表面酸性,尤其是强B酸(Brönsted 酸)中心.这是由于B酸中心会导致烯烃和噻吩发生质子化反应,且质子化物种易于进一步发生低聚反应. 生成的低聚物覆盖吸附活性中心导致吸附剂对其它噻吩分子的吸附能力降低.