Pressurised liquid extraction of polycyclic aromatic hydrocarbons from gas and particulate phases of atmospheric samples

Pressurised liquid extraction (PLE) was applied to determine the atmospheric levels of 16 polycyclic aromatic hydrocarbons (PAHs) in the gas and particulate phases. The method involved high‐volume air sampling with quartz fibre filters (QFFs) and polyurethane foam (PUF) plugs and analytes were subsequently extracted from the samples by PLE, and determined with GC‐MS. We optimised the PLE conditions for the solvent, the number of cycles and extraction temperature. Recoveries were higher than 90% for most compounds. Method LODs and LOQs were between 0.001 and 0.02 ng/m³ and between 0.01 and 0.05 ng/m³. Air samples were taken from a site in the region of Tarragona in Catalonia, Spain, where one of the largest petrochemical complexes in southern Europe is located. The total concentration of PAHs were from 6.7 to 27.66 ng/m³, with predominant levels of PAHs appearing in the gas phase (48–81%), and an average level of benzo[a]pyrene, the most carcinogenic PAH, of 0.86 ng/m³.     

Pressurised solvent extraction of nitrated derivatives of polycyclic aromatic hydrocarbons from roadside dust

An analytical method based upon the pressurised solvent extraction and gas chromatography and mass spectrometry (GC-MS) for analysis of nitrated derivatives of polycyclic aromatic hydrocarbons (nitro-PAHs) in roadside dust has been developed. Five nitro-PAHs (1-nitronaphthalene, 1-nitropyrene, 9-nitroanthracene, 2-nitrofluorene, 6-nitrochrysene) were chosen for this study because of their variable physical properties and effect on human health. Experiments with spiked inert matrix were used for the best extraction conditions finding. Different extraction conditions (temperature, pressure, solvents and duration of extraction cycle) were examined. The highest recoveries were observed at the extraction pressure of 14?MPa, temperature of 100°C and two cycles of 5?min extraction time, when dichloromethane was used as an extraction solvent. These conditions were applied to the extraction of nitro-PAHs from roadside dust. After extraction the nitro-PAHs fraction was isolated by the silica gel column chromatography. The GC-MS detector was used for analyses of the extracts. Recoveries of nitro-PAHs after extraction from roadside dust ranged from 60% for 9-nitroanthracene to 108% for 6-nitrochrysene.     

Fluidized-bed extraction of polycyclic aromatic hydrocarbons from contaminated soil samples

Summary Due to the carcinogenity and ubiquity of polycyclic aromatic hydrocarbons in the environment they are of ongoing interest to analytical chemistry. In this study, a comparison of the classic Soxhlet extraction and, fluidized-bed extraction, has been conducted. The extraction of polycyclic aromatic hydrocarbons by this technique has been optimized considering as experimental variables the variation of the number of extraction cycles and the holding time after reaching the heating temperature by means of a surface response design. The significance of the operational parameters of the fluidized-bed extraction on the performance characteristics has been investigated. For the determination of the analytes a selective clean-up of the extracts followed by a fast gas chromatography method with mass spectrometric detection was used, resulting in low limits of detection (0.2 pg μL⁻¹). The accuracy of the complete analytical method was established by extraction and analysis of reference materials.     

Pressurised fluid extraction of polycyclic aromatic hydrocarbons and their polar oxidation products from atmospheric particles

An effective method utilising pressurised fluid extraction (PFE) to simultaneously extract polycyclic aromatic hydrocarbons (PAHs) and their polar oxidation products from atmospheric particulate matter (PM) is presented. The PFE method is advantageous over the traditional Soxhlet extraction due to its lower solvent consumption (9 mL compared to 90 mL) and shorter extraction time (15 min versus 18 h). Seventy compounds including PAHs and polar PAH oxidation products containing carbonyl (oxy-PAHs), hydroxyl (hydroxy-PAHs), and carboxylic acid (carboxy-PAHs) groups were targeted in the extraction of two different PM matrices: wood smoke (WS) and diesel exhaust (DE) PM. The PFE method was optimised and then compared to Soxhlet extraction for both PM matrices. The overall amounts of PAHs and their derivatives extracted from WS PM were slightly higher for the optimised PFE method (1849 ± 21 and 1863 ± 25 µg g^?1 with dichloromethane (DCM) and methanol (MeOH), respectively) than those obtained with Soxhlet extraction (1726 ± 33 and 1769 ± 22 µg g^?1 with DCM and MeOH, respectively). For DE PM (standard reference material (SRM) 2975) the overall amounts extracted by both methods were similar (average of 165 ± 6 µg g^?1), agreeing with previously published values. The detailed evaluation of extraction efficiencies for WS PM showed similar amounts for unfunctionalised PAHs (1100 µg g^?1) for both methods and solvents. For DE PM the mass yields for PAHs using PFE with DCM (62 ± 1 µg g^?1) were the highest and nearly 20% higher than those obtained with MeOH (53 ± 2 µg g^?1). The total mass yields of carboxy and hydroxy-PAHs from WS PM were also similar (412 ± 18 and 407 ± 11 µg g^?1) for PFE and Soxhlet with MeOH, and higher than when DCM was used (371 ± 5 and 379 ± 12 µg g^?1 for PFE and Soxhlet, respectively). For both matrices, the PFE yields for oxy-PAHs were higher than those obtained with Soxhlet.     

Cooling/heating-assisted headspace solid-phase microextraction of polycyclic aromatic hydrocarbons from contaminated soils

A simple, low-cost, and effective cooling/heating-assisted headspace solid-phase microextraction (CHA–HS–SPME) device, capable of direct cooling the fiber to low temperatures and simultaneous heating the sample matrix to high temperatures, was fabricated and evaluated. It was able to cool down the commercial and handmade fibers for the effective tapping of volatile and semi-volatile species in the headspace of complex solid matrices, with minimal manipulation compared with conventional SPME. The CHA–HS–SPME system can create large temperature gaps (up to 200 °C) between the fiber and the sample matrix, because the cooling process is directly applied onto the fiber.     

Ultrasound-assisted pressurized solvent extraction for aliphatic and polycyclic aromatic hydrocarbons from soils

In the present work the efficiency of extraction of aliphatic diesel range organics (DROs) and polycyclic aromatic hydrocarbons (PAHs) from soil was assessed by using dynamic modes of pressurized solvent extraction (PSE), and ultrasound-assisted pressurized solvent extraction (US-PSE). Optimization studies were carried out using a blank soil (Non-Polluted Soil#1, CLN-1, RTC) and a real soil which was previously spiked with the analyte mixture and aged for 90 days. A laboratory-made manifold with controlled temperature and pressure was used to carry out the leaching processes. The extraction cell was inserted into an oven for PSE and into an ultrasound bath for US-PSE. The following variables were studied in each case, keeping the pressure at about 1800 psi: extraction temperature, time of static and dynamic extraction and solvent flow rate. In addition, the time of ultrasound application was also studied in US-PSE. For PSE with dichloromethane (DCM) the recoveries were about 90-95% for both the families of analytes, using extraction times of 20 min. Analyte extraction was quantitative by using US-PSE with DCM for 10 min. In all cases, after the extraction process, the analytes were determined by GC-MS. Application of the method to a natural contaminated sample suggests that either the extraction time used in US-PSE should be increased to 20 min or the solvent (DCM) should be replaced by a mixture of DCM:acetone (1:1), to reach comparability with Soxhlet extraction.     

Static pressurised liquid extraction of nitrated polycyclic aromatic hydrocarbons from soils with on-line filtration-preconcentration prior to gas chromatography-mass spectrometry detection

Nitrated polycyclic aromatic hydrocarbons have been extracted from both spiked and natural contaminated soils by using static pressurised liquid extraction. The variables governing the extraction (namely, pressure, extraction time, temperature and number of static extraction cycles) have been optimised using the experimental design methodology. A laboratory-made pressurised liquid extractor has been used allowing its coupling to a filtration-preconcentration system through a flow injection interface, thus providing a partially automated approach. Gas chromatography with MS-MS ion preparation mode has been used for individual separation-identification/quantification providing both high selectivity (no interferences were observed) and sensitivity (detection limits of low pg). The comparison of the proposed approach with the reference EPA Method 3540 has shown that both methods provide similar efficiencies but with dramatic saving of time by the former (30 min vs. 24 h). The use of water as leaching agent avoids the use of organic solvents, thus providing an environmentally friendly method.     

Ultrasonic micellar extraction of polycyclic aromatic hydrocarbons from marine sediments

In this present study the extraction of polycyclic aromatic hydrocarbons (PAHs) from marine sediments with a micellar medium of Polyoxyethylene 10 lauryl ether by an ultrasound-assisted method has been studied. Factorial design experiments were used in order to optimize the extraction parameters: extraction time, surfactant concentration and surfactant volume:amount of sediment relationship. The results suggest that surfactant concentration is statistically the most significant factor. The analysis of extracts has been carried out by HPLC with UV detection. Fortified sediments gave an average recovery between 86.7 and 106.6%, with relative standard deviation of 2.02-6.83% for PAHs with a ring number higher than three.     

Heat capacities of liquid polycyclic aromatic hydrocarbons

Liquid heat capacities of 14 aromatic hydrocarbons were measured using a DSC calorimeter. Measurements were performed in the temperature range 100 K above the melting temperature of each hydrocarbon. The lowest and highest temperatures considered were respectively 303 and 692 K. Experimental results were correlated using Benson's group contribution approach. The group parameters determined allow the experimental results to be represented to within 2%.     

Extraction of polycyclic aromatic hydrocarbons from smoked fish using pressurized liquid extraction with integrated fat removal

Quantification of polycyclic aromatic hydrocarbons (PAHs) in smoked fish products often requires multiple clean-up steps to remove fat and other compounds that may interfere with the chemical analysis. We present a novel pressurized liquid extraction (PLE) method that integrates exhaustive extraction with fat retention in one single analytical step. The PLE parameters: type of fat retainer, flush volume, solvent composition, fat-to-fat retainer ratio (FFR), and the dimensions of the extraction cells were the most important factors for obtaining fat-free extracts with high recoveries of PAHs. A 100 mL extraction cell filled with 18 g activated silica gel, dichloromethane:hexane (15:85, v/v) as extraction solvent, FFR of 0.025 and 100% flush volume was the best analytical setup for integrated extraction and fat retention.The one-step procedure provided a more rapid and cost-efficient alternative with minimization of waste generation compared to the standard reference method that is based on a multi-step procedure. Furthermore, the analytical quality of the two methods are comparable, while the new integrated approach for extraction and cleanup is less prone to analytical errors (random and systematic) because of fewer analytical steps.     

Microwave assisted extraction of polycyclic aromatic hydrocarbons from atmospheric particulate samples

For several years, microwave assisted extraction (MAE) was applied to extract organic compounds such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, etc., from soils, sediments and standard reference materials. Very few authors applied this methodology for the extraction of PAHs from atmospheric particulate matter. In the present study, MAE of polycyclic aromatic hydrocarbons with hexane/acetone (1:1) from real atmospheric particulate samples was investigated and the effect of microwave energy and irradiation time studied. The yields of extracted compounds obtained by microwave irradiation were compared with those obtained using traditional Soxhlet extraction. MAE was evaluated using spiked real atmospheric particulate samples and two standard reference materials. Analytical determinations of PAHs were carried out by high performance liquid chromatography (HPLC) with ultraviolet and fluorescence detection. The best recoveries were achieved with a microwave energy of 400 W and an irradiation time of 20 min.     

Effect of moisture on the extraction efficiency of polycyclic aromatic hydrocarbons from soils under atmospheric pressure by focused microwave-assisted extraction

The performance of a large commercial chromatographic column was investigated using a short pulse of a tracer and an extension of the reverse-flow technique. This technique permits separate determination of the unavoidable irreversible microscopic processes and the reversible effects of flow maldistribution, and allows for the separation of flow maldistribution in the flow distributors from flow maldistribution inside the packed bed. This analysis was performed on a 0.44 m Millipore IsoPak column using Cellufine GC 700, cellulosic-based media with an average particle diameter of 75 microm, for the stationary phase. The column efficiency was quantified by analysis of the effluent curve from a short pulse of a 5% aqueous acetone tracer. The study examined behavior of beds of different lengths (10-24 cm) and beds packed from different slurry concentrations (10-75% v/v). The slurry-packed columns were very uniform, and no significant macroscopic flow maldistribution was observed inside the column. The observed bed plate heights conformed to the predictions of available one-dimensional continuum models. Dispersion in the flow distributors was significant, corresponding to 15-25% of the intracolumn dispersion when the full 24 cm available bed length was used and a proportionally larger increase for shorter bed lengths. Thus, the headers are shown to produce a significant increase in the observed plate height.     

Ultrasonication extraction coupled with magnetic solid-phase clean-up for the determination of polycyclic aromatic hydrocarbons in soils by high-performance liquid chromatography

C18-functionalized magnetic microspheres synthesized in a three-stage system and characterized by Fourier transform infrared (FTIR) spectroscopy and SEM were applied for clean-up and enrichment of polycyclic aromatic hydrocarbons (PAHs) in soil samples combined with ultrasonication extraction. Magnetic solid-phase extraction (MSPE) parameters, such as elution solvents, amounts of sorbents, enrichment time and organic modifier, were optimized together with ultrasonication time and extraction solvents. Under the optimal conditions, the developed method provided spiked recoveries of 63.2-92.8% with RSDs of less than 6.4% and limits of detection were 0.5-1.0 ng/g. This new method provides several advantages, such as high extraction efficiency, convenient extraction procedure and short analysis times. Finally, the method was successfully applied to the determination of polycyclic aromatic hydrocarbons in soil samples.     

Pressurized fluid extraction of polycyclic aromatic hydrocarbons using silanized extraction vessels

We have investigated the extraction efficiency of a pressurized fluid extraction system using an Ottawa sand matrix, soils and a certified reference material (HS-6) spiked with the 16 polycyclic aromatic hydrocarbon (PAHs) associated with method EPA 8100. Acceptable recoveries were achieved for all PAHs using a nominal sand concentration of 2.0 μg.g^-1. However, similar experiments that were conducted at a concentration of 0.20 μg.g^-1 afforded poor recoveries and poor reproducibility for the six-ring PAHs indeno(1,2,3-cd)pyrene, dibenz(a)anthracene, and benzo(ghi)perylene. These were not adequately addressed by the use of indeno(1,2,3-cd)pyrene-d12 and benzo(g,h,i)perylene-d12 surrogates. Silanization of vessels using dichlorodimethylsilane adequately passivates the system but is only required for the high surface area retention frits. Replicate analyses at concentrations of 200 and 20 ng.g^-1 demonstrated that detection limits in the low ppb range (ng.g^-1) are achieved for Ottawa sand, dry soil and soil with moisture contents up to a mass fraction of 30 %. Such performance is consistent with the analytical requirements of the Canadian Sediment Quality Guidelines. Improved analyte recoveries were also observed for the certified reference material HS-6 which were further improved by increasing extraction temperatures from 100 to 150 °C.

Miniaturised pressurised liquid extraction of polycyclic aromatic hydrocarbons from soil and sediment with subsequent large-volume injection-gas chromatography

Analyte extraction is the main limitation when developing at-line, or on-line, procedures for the preparation of (semi)solid environmental samples. Pressurised liquid extraction (PLE) is an analyte- and matrix-independent technique which provides cleaner extracts than the time-consuming classical procedures. In the study, the practicality of miniaturised PLE performed in a stainless-steel cell, and combined with subsequent large-volume injection (LVI)-GC-MS was studied. As an example, the new system was applied to the determination of polycyclic aromatic hydrocarbons (PAHs) in soils and a sediment. Variables affecting the PLE efficiency, such as pressure and temperature of the extraction solvent and total solvent volume, were studied. Toluene was selected as extraction solvent and a total solvent volume of 100 microl was used for the 10 min static-dynamic PLE of 50-mg samples. Additional clean-up or filtration of the sample extracts was not required. Detection limits using LVI-GC-MS were below 9 ng/g soil for the 13 PAHs more volatile than indeno[1,2,3-cd]pyrene in real soil samples and the repeatability of the complete PLE plus LVI-GC-MS method for the analysis of the endogenous PAH was better than 15%. Comparison of PLE and Soxhlet or liquid-partitioning extraction results for the analysis of non-spiked samples showed that the efficiency of PLE is the same or better than for the other two extraction methods assayed.     

Measurement of high-molecular-weight polycyclic aromatic hydrocarbons in soils by particle beam high-performance liquid chromatography-mass spectrometry

Polycyclic aromatic hydrocarbons (PAHs) comprise a class of potentially hazardous com- pounds of concern to the U.S. EPA. The application of particle-beam (PB) liquid chromatography-mass spectrometry (LC-MS) to the measurement of high-molecular-weight PAHs was investigated. Instrument performance was evaluated for 16 PAHs in the molecular weight range 300–450 u. The PAHs were separated by reverse-phase high-performance liquid chromatography via a polymeric octadecylsilica (C-18) packing and gradient elution with methanol-tetrahydrofuran. On-column instrument detection limits, as measured by selected ion monitoring on the singly charged molecular ion of each PAH, were found to be 0.15–0.60 ng for PAHs with molecular weights up to 352 u and 2–4 ng for PAHs with molecular weights greater than 352 u. Instrument response was generally linear for PAHs with molecular weights 300–352 u and generally nonlinear for PAHs with molecular weights greater than 352 u. The PB electron impact mass spectra of the PAHs were found to vary with the ion distribution ratio of the singly charged molecular ion to the doubly charged molecular ion, dependent on molecular weight, ion source temperature, and concentration. Analysis by PB LC-MS was applied to extracts of PAH-spiked soil and a PAH-contaminated soil from the Pacific Northwest. Target analyte concentrations in the PAH-contaminated soil ranged from 0.85 to 84 µg/g. Quantitative estimates for nontarget PAHs also were determined. Analysis of a second soil extract from a hazardous waste site in the northeast part of the United States displayed isomeric patterns of high-molecular-weight PAHs similar to those of the Pacific Northwest extract.     

Direct automatic screening of soils for polycyclic aromatic hydrocarbons based on microwave-assisted extraction/fluorescence detection and on-line liquid chromatographic confirmation

An integrated screening-confirmation system for PAHs in soils is presented. The sample screening configuration comprises on-line microwave-assisted extraction of the selected pollutants, followed by continuous preconcentration and sample clean-up on RP-C18. Those samples for which the total concentration is close to or above the threshold limit established (10 microg/g) are subjected to liquid chromatographic separation for confirmation. An evaluation of the qualitative data obtained was also carried out, by calculating the unreliability zone as well as the false positive and false negative rates. The whole method (extraction/determination/confirmation) was validated using industrial soil and harbour sediment certified reference materials (IRMM, European Commission CRM 524 and CRM 535). Application to the screening of solid environmental samples with subsequent confirmation of the results is also presented.     

Dynamic extraction in rotating coiled columns, a new approach to direct recovery of polycyclic aromatic hydrocarbons from soils

A new approach to the direct recovery of polycyclic aromatic hydrocarbons (PAHs) from environmental solid samples has been proposed. It has been shown that rotating coiled columns (RCCs) earlier used mainly in countercurrent chromatography can be successfully applied to the fast continuous-flow extraction of PAHs from soils. A particulate solid sample was retained in the rotating column as the stationary phase under the action of centrifugal forces while a mixture of organic solvents (acetone-cyclohexane, 1:1, v/v) was continuously pumped through. The separation procedure requires less than half an hour, complete automation being possible. No clean-up step is needed before the subsequent HPLC- analysis of extracts. Besides, the dynamic multistage extraction performed in the rotating column at room temperature and normal pressure may have nearly the same efficiency as accelerated batch solvent extraction repeated three times at 150 degrees C and 14 MPa. Contents of PAHs in extracts obtained by using both methods are in good agreement with the certified data on the PAHs concentrations in the soil samples. The use of appropriate "mild" solvents for the dynamic extraction in rotating columns may be very perspective for the simulation of naturally occurring processes and determination of environmentally-relevant forms of PAHs and other pollutants in environmental solids. A particular emphasis could be placed on time-resolved (kinetic) studies of the mobilization of toxicants in soil systems.