Gas chromatographic-mass spectrometric determination of polycyclic aromatic hydrocarbons formed during the pyrolysis of phenylalanine

The formation of polycyclic aromatic hydrocarbons (PAHs) during pyrolysis process of phenylalanine had been studied. Ten PAHs, including fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[k]fluoranthene, benzo[e]pyrene, and benzo[a]pyrene were analyzed by gas chromatography-mass spectrometry using selective ion monitoring mode. This technique offers the capability to analyze trace amounts of PAHs in phenylalanine pyrolyzates. The pyrolysis was carried out in a micro-furnace with quartz furnace liner. The injection was conducted with glass pelletizer syringe to avoid metal contamination. Qualitative results were obtained at 900 degrees C and quantitative analysis of 10 PAHs was done for 700 and 900 degrees C.     

The effect of acid treatment on the pyrolysis behavior of sewage sludges

One sewage sludge (SLA) from Ávila region (Spain) was selected and used as raw material in order to study the influence of acid treatment on the pyrolysis behavior of sewage sludges. SLA was heat treated with acid solutions at pH 1 and pH 2 leading to SLA-1 and SLA-2, respectively. Characterization of samples has showed that acid treatment leads to metals removal and modifications in the organic matter composition of sewage sludge. Pyrolysis of three samples showed that SLA and SLA-1 have a similar pyrolysis behavior whereas SLA-2 shows a slightly extended temperature interval for pyrolysis, beginning at lower temperature and finishing at higher temperatures.     

Characterization of polychlorinated aromatic hydrocarbons by reversed-phase liquid chromatography with ultraviolet absorbance and mass spectrometric detection

Ten polychlorinated aromatic hydrocarbons (PCAHs), perchlorobenzene (I), perchlorobiphenyl (II), perchlorobenzo[f]inden-1-one (III), perchloronaphthalene (IV), perchloropenta[def]phenanthren-4-one (V), 6H-1,2,4,5,7,8,9,10,11-nonachlorobenzo[cd]pyrene-3-one (VI), perchloroacenaphthylene (VII), 6-(p-tolyl)-6H-1,2,3,4,5,7,8,9,10,11-decachlorobenzo[cd]pyrene (VIII), perchlorofluoranthene (IX) and 6-(p-tolyl)-6H-1,11-dihydroxy-2,3,4,5,7,8,9,10-octachlorobenzo[cd]pyrene (X) have been separated with reversed-phase liquid chromatography (RPLC) by using two gradient eluents (toluene/methanol and cyclohexane/methanol), and were detected by ultraviolet (UV) and mass spectrometry (MS). The separation and detection of half of these ten compounds, which are of extremely high molecular weights, is an improvement over the chromatographic analysis of PCAHs. When the procedure was applied to the analysis of PCAHs of the products from the combustion of chlorobenzene and carbon tetrachloride, I, II, IV, VIII and X could be detected.     

Fluidised bed pyrolysis of Moroccan oil shales using the hamburg pyrolysis process

In the present work, the pyrolysis of the Moroccan Timahdit oil shale was studied, using a fluidised bed process. Four experiments were carried out at different temperatures between 520 and 630 °C. By mass balance could be shown that in relation to the kerogen content up to 60 wt.% of oil and 25 wt.% of gas are obtained. These are 40% higher yields compared with the Fischer assay. It was shown that the carbon in the residue, which is much lower (only 12 wt.%) than in the Fischer assay (26 wt.%), explains this difference.     

Kinetic models based in biomass components for the combustion and pyrolysis of sewage sludge and its compost

In the present work, pyrolysis and combustion of the sewage sludge (fresh and composted) have been simulated using five fractions: low stability organic compounds, hemicellulose, cellulose, lignin-plastic, and inorganic compounds. Thermal behavior and kinetic parameters (pre-exponential factor and apparent activation energy) of the main components of the sludge are similar to those reported for hemicellulose, cellulose, and lignin present in lignocellulosic biomass. Comparing non-isothermal thermogravimetric analysis data obtained from fresh and composted sewage sludge, it is possible to measure the efficiency of the composting process. Most of the biodegradable matter is volatized in a temperature range from 150 °C to 400 °C. Non-biodegradable organic matter volatilizes between 400 °C and 550 °C. In both, fresh and composted sludges, oxygen presence increases the mass loss rate at any temperature, but differences between pyrolysis and combustion are focused in two clearly defined ranges. At low temperature (200–350 °C), mass loss is related with a volatilization process. At higher temperature (350–550 °C), mass loss is due to slow char oxidation (oxidative pyrolysis).     

Development of an improved analytical method for the determination of carcinogenic polycyclic aromatic hydrocarbons in transformer oil

Polynuclear aromatic hydrocarbons (PAHs) are natural constituents of transformer oils and are essential in prolonging transformer in-service lifetime. Issues concerning PAH carcinogenicity demand methods that provide qualitative and quantitative information on the PAH composition of new and in-service oils to allow informed operational decisions to be made. However, current analytical methods focus on PAH fingerprinting, as opposed to quantitative analysis and are also cumbersome, relying on the use of large (>100 ml) volumes of organic solvents, some of which are hazardous. This paper reports a method for the improved quantification of carcinogenic PAHs in transformer oils that is both simple and repeatable. The method uses commercially available solid-phase extraction columns and millilitre volumes of relatively non-hazardous solvents. Extraction efficiencies of > or =74% were obtained for the Environmental Protection Agency priority PAHs. The method has potential for automation and high-throughput analysis and thus is of interest to industries that use transformer oils.     

Sample preparation of sewage sludge and soil samples for the determination of polycyclic aromatic hydrocarbons based on one-pot microwave-assisted saponification and extraction

A microwave-assisted sample preparation (MASP) procedure was developed for the analysis of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge and soil samples. The procedure involved the simultaneous microwave-assisted extraction of PAHs with n-hexane and the hydrolysis of samples with methanolic potassium hydroxide. Because of the complex nature of the samples, the extracts were submitted to further cleaning with silica and Florisil solid-phase extraction cartridges connected in series. Naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3-cd]pyrene, were considered in the study. Quantification limits obtained for all of these compounds (between 0.4 and 14.8 μg kg⁻¹ dry mass) were well below of the limits recommended in the USA and EU. Overall recovery values ranged from 60 to 100%, with most losses being due to evaporation in the solvent exchange stages of the procedure, although excellent extraction recoveries were obtained. Validation of the accuracy was carried out with BCR-088 (sewage sludge) and BCR-524 (contaminated industrial soil) reference materials.     

应用TGA-FTIR研究不同来源污泥的燃烧和热解特性

在空气气氛下，利用热重分析方法研究了三种不同来源的污泥燃烧特性。探讨水处理工艺和污泥处理工艺对污泥中有机物的分布影响和燃烧特性影响。研究发现，污水厌氧工艺和污泥厌氧工艺均导致结构复杂、燃烧温度高的有机物生成。在氮气气氛下利用热重红外联用技术，对比研究了同种污泥的热解和燃烧特性，污泥热解主要发生有机物裂解成小分子和小分子的挥发，氧气的存在加速了污泥的裂解。污泥热解温度200℃～500℃，主要气体H2O、CO2、CO以及甲烷等烃类，CO2在高温750℃还存在一个析出峰，由于无机碳酸盐的分解。     

Elution of organic solutes from different polarity sorbents using subcritical water

The intermolecular interactions between organic solutes and sorbent matrices under subcritical water conditions have been investigated at a pressure of 50 bar and temperatures ranging from 50 to 250°C. Both polar and nonpolar organics (chlorophenols, amines, n-alkanes, and polycyclic aromatic hydrocarbons) and five different sorbent matrices (glass beads, alumina, Florisil, silica-bonded C₁₈, and polymeric XAD-4 resins) were used. From the same matrix, the polar solutes always eluted at lower temperatures, while the moderately polar and nonpolar solutes only eluted at higher temperatures. Similar to matrix effects previously observed using supercritical carbon dioxide, the sorbent type greatly influenced the elution efficiency under subcritical water conditions. Lower temperatures are sufficient to elute a particular solute from glass beads, alumina, and Florisil, but higher temperatures (less polar water) are needed to elute the same solute from silica-bonded C₁₈. The highest temperatures were required to elute aromatic organics from XAD-4. These matrix effects demonstrate that, while low temperature water can break inert or dipole interactions between solutes and glass beads, alumina, and Florisil, higher temperature water is required to interrupt the van der Waals attractions between solutes and silica-bonded C₁₈, and even higher temperatures needed to overcome the π-electron interactions between aromatic solutes and XAD-4.     

Micellar microwave-assisted extraction combined with solid-phase microextraction for the determination of polycyclic aromatic hydrocarbons in a certified marine sediment

A method for the determination of polycyclic aromatic hydrocarbons (PAHs) in marine sediments using microwave-assisted extraction with a micellar medium combined with solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) has been developed. Two kinds of SPME fibers (100 μm polydimethylsiloxane and 85 μm polyacrylate) and different micellar media were compared for the extraction efficiency of the 16 EPA priority PAHs. The polyacrylate fiber with a micellar medium of polyoxyethylene-10-laurylether provides the highest extraction efficiency. The method is remarkable for presenting lower equilibrium times and considerably higher reproducibilities than the obtained in aqueous medium. The LODs obtained ranged between 0.28 ng/ml for fluorene and 7.66 ng/ml for indeno[1,2,3-cd]pyrene. The method has been applied to the determination of PAHs in a certified marine sediment (SRM 1941a), obtaining recoveries between 58.6 and 111.5% for three- to five-ring PAHs with precision close to or lower than the certified values.     

Simultaneous thermogravimetric-mass spectrometric study on the co-combustion of coal and sewage sludges

To combust coal together with a small percentage (<10%) of sewage sludge may be an option for the management of these wastes. Combustion of two different sewage sludge, one semianthracite coal and several sludges-coal blends (containing different dried mass% of each of the two sewage sludges) were studied by simultaneous TG/MS dynamic runs carried out at 5°C min^–1 in the temperature range 100–800°C. No interactions have been observed between coal and sludge during the blends combustion. Neither the combustion process, neither the studied emissions have changed appreciably for the mass% of sludge in the blends considered in this work.     

Study on the pyrolysis of Moroccan oil shale with poly (ethylene terephthalate)

Investigations into the pyrolytic behaviours of oil shale, poly (ethylene terephthalate) (PET) and their mixture have been conducted using a thermogravimetric analyzer. Experiments were carried out dynamically by increasing the temperature from 298 to 1273 K with heating rates of 2 to 100 K/min under a nitrogen atmosphere. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. The maximum degradation temperature of each component in the mixture was higher than those the individual components; thus an increase in thermal stability was expected. The kinetic processing of thermogravimetric data was carried out using Flynn-Wall-Ozawa (FWO) method.     

Development of a matrix solid-phase dispersion method for the determination of polycyclic aromatic hydrocarbons in sewage sludge samples

A new, single-step extraction and purification method based on matrix solid-phase dispersion (MSPD) was developed to determine 17 polycyclic aromatic hydrocarbons (PAHs) in sewage sludge samples. The MSPD method consists of sample homogenisation, exhaustive extraction and clean-up by a single process. The different operational parameters of the method, such as the type of dispersant, type and amount of additives, clean-up co-sorbent and extractive solvent were evaluated. Reversed-phase (C18) and polymeric (Oasis HLB and Oasis MAX) materials, as well as normal phase sorbents (Florisil, silica, neutral alumina) and an inert support (sand) were tested to assess the sorbents effect on the yield and selectivity of the MSPD process. Analysis of extracts was performed by high performance liquid chromatography (HPLC) coupled with fluorescence detection.Quantification limits obtained for all of these considered compounds (between 0.0001 and 0.005 μg g⁻¹ dry mass) were well below of the limits recommended in the EU. The extraction yields for the different compounds obtained by MSPD ranged from 76.3% to 103.6%. On the other hand, the extraction efficiency of the optimised method is compared with that achieved by microwave-assisted extraction and the method was applied to the analysis of real sewage sludge samples. A certified reference material (sewage sludge (BCR 088)) and a reference material (sewage sludge (RTC-CNS312-04)) were used to validate the proposed method.     

A new method for the routine analysis of LAS and PAH in sewage sludge by simultaneous sonication-assisted extraction prior to liquid chromatographic determination

Linear alkylbenzene sulphonates (LAS) and polycyclic aromatics hydrocarbons (PAH) are organic pollutants in sewage sludge which will have to be monitored in the European Union according to the third draft of a future sludge directive. In the present work, an analytical method for the simultaneous extraction of 4 LAS homologues and 16 PAH congeners in sludge from wastewater treatment plants is proposed to improve the routine analysis of these compounds in sludge samples. The method involves sonication assisted extraction, clean-up and preconcentration by solid phase extraction, and determination by high-performance liquid chromatography with ultraviolet diode array (UV-DAD) and fluorescence (FLD) detectors. Average recoveries were 87% for LAS and 76% for PAH, with relative standard deviations below 13%. Limits of quantification of LAS and PAH were in the range from 13 to 56 mg kg⁻¹ and from 80 to 650 μg kg⁻¹, respectively, when using UV-DAD. Limits of quantification of LAS and PAH were in the range 5-18 mg kg⁻¹ and from 1 to 150 μg kg⁻¹, respectively, when using FLD. The applicability of the proposed method was evaluated by the determination of these compounds in sludge from wastewater treatment plants in Seville (South Spain).     

Fluorescence study of the solubilization of benzo[a]pyrene: application to its detection in coal washing waters

The solubilization of benzo[a]pyrene by organic solvents (dioxane, toluene and dichloromethane) and a surfactant (Triton X-100) was investigated. These media were successfully used for the determination of benzo[a]pyrene using fluorescence detection, with excellent limits of detection and large linear analytical ranges. Benzo[a]pyrene was detected in coal washing waters using liquid chromatography with fluorescence detection. The stability of this compound in dioxane was also examined.     

Low temperature conversion (LTC) of castor seeds—A study of the oil fraction (pyrolysis oil)

The low temperature conversion (LTC) process applied to a castor seed sample at 380 °C produced pyrolysis oil (50%, w/w), pyrolytic char (29%, w/w), water (13%, w/w) and gas (8%, w/w) fractions. The oil fraction was subjected to analysis of by FTIR, ¹H NMR, ¹³C NMR, GCMS and physical–chemical analysis such as sulfur content, distillation, density, flash-point, kinematic viscosity, Ramsbottom carbon residue, ash content, corrosivity to copper, water content and sediment, cold filter plugging point, and gross calorific value.     

Development of a sample preparation procedure of sewage sludge samples for the determination of polycyclic aromatic hydrocarbons based on selective pressurized liquid extraction

An automated, simple and sensitive method based on selective pressurized liquid extraction (SPLE) was developed for the analysis of polycyclic aromatic hydrocarbons in sewage sludge samples. The new sample preparation procedure consists of on-line clean-up by inclusion of sorbents in the extraction cell, and combines elevated temperatures and pressures with liquid solvents to achieve fast and efficient removal of target analytes from complex sewage sludge matrices. The effects of various operational parameters (e.g. sample pretreatment, extraction solvent, temperature, pressure, static time, etc.) on the performance of SPLE procedure were carefully investigated, obtaining the best results when SPLE conditions were fixed at 140 °C, 1500 psi, static time of 5 min and n-hexane as extraction solvent. A new programmed temperature vaporization–gas chromatography–tandem mass spectrometry method based on large volume injection (PTV–LVI–GC–MS/MS) was also developed and analytical determinations were performed by high performance liquid chromatography coupled with fluorescence detection and GC–MS/MS. The extraction yields for the different compounds obtained by SPLE ranged from 84.8% to 106.6%. Quantification limits obtained for all of these studied compounds (between 0.0001 and 0.005 μg g⁻¹, dry mass) were well below the regulatory limits for all compounds considered. To test the accuracy of the SPLE technique, the optimized methodology was applied to the analysis of a certified reference material (sewage sludge (BCR088)) and a reference material (sewage sludge (RTC-CNS312-04)), with excellent results.     

Investigations on the chromatographic behavior of hybrid reversed-phase materials containing electron donor-acceptor systems. I. Contribution of sulfur-aromatic interactions

The influence of sulfur-aromatic interactions on the chromatographic separation behavior of hybrid RP phases, containing thiol-groups and/or embedded sulfide-groups (S-RP) has been investigated. To allow a precise outline of this new interaction mode, a wide variety of S-RP phases with different alkyl chain length, with and without residual thiol-groups and silanol-endcapping were prepared and tested in comparison to some conventional monomerical as well as polymerical n-alkyl type RP phases. The solute test sets employed in this study comprised the classical chromatographic column tests from Engelhardt and Tanaka as well as test assemblies containing polycyclic aromatic hydrocarbons, stilbene-based cis/trans isomers and functional isomers of benzene. In general, a pronounced strong planar recognition ability as well as a strong increase in the retention for aromatic compounds have been noticed. It was furthermore found that not only the sulfur atom incorporated into the alkyl chain, but also the residual thiol-groups of the 3-propylthiol silica backbone contribute to the overall retention behavior of these novel S-RP type phases.     

Analysis of nitrated polycyclic aromatic hydrocarbons by glass capillary gas chromatography using different detectors

Glass capillary gas chromatography has been investigated as a method for the analysis of nitrated polycyclic aromatic hydrocarbons (nitro-PAH) using both splitless and on-column injection techniques. The nitro-PAH showed good chromatographic performance and thermal stability under the GC conditions used. Retention times and response factors of several nitro-PAH were compared to those of conventional PAH. Simultaneous flame ionization and thermionic nitrogen selective detection was used to facilitate identification of nitro-PAH in complex samples. The feasibility of the method is demonstrated on two samples of commercial carbon black. Besides 1-nitropyrene several isomeric dinitropyrenes have been identified.     

Isobaric (vapour + liquid) equilibria of binary systems containing butyl acetate for the separation of methoxy aromatic compounds (anisole and guaiacol) from biomass fast pyrolysis oil

Developing value-added chemicals from pyrolysis oil has been gaining increasing attention. Thus effective separation and purification of the pyrolysis oil are important and the phase equilibrium data are essential for the design and simulation of the processes. In this study, isobaric vapour–liquid equilibrium (VLE) for the two binary mixtures (butyl acetate + anisole) and (butyl acetate + guaiacol) have been determined at 101.33 kPa, a knowledge of which is essential for the separation of methoxy aromatic compounds (anisole and guaiacol) from biomass fast pyrolysis oil using butyl acetate as a solvent. All the experimental values were confirmed to be thermodynamically consistent using the van Ness method. The NRTL, UNIQUAC, and Wilson activity coefficient models were applied to regress the experimental values. The calculated results agreed well with the measured values. Furthermore, the results were calculated by the UNIFAC (Do) method (modified UNIFAC model) in which aromatic methoxyl is treated as a group (ACOCH₃). The new interaction parameter (ACOCH₃–CH₃COO) was obtained and proved to be reliable. Based on the preceding results, a feasible separation process for the ternary mixture (butyl acetate + anisole + guaiacol) has been designed to obtain the required products.