Comparison of ASE and SFE with Soxhlet, Sonication, and Methanolic Saponification Extractions for the Determination of Organic Micropollutants in Marine Particulate Matter

The methods of accelerated solvent extraction (ASE) and supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons, and chlorinated hydrocarbons from marine samples were investigated. The results of extractions of a certified sediment and four samples of suspended particulate matter (SPM) were compared to classical Soxhlet (SOX), ultrasonication (USE), and methanolic saponification extraction (MSE) methods. The recovery data, including precision and systematic deviations of each method, were evaluated statistically. It was found that recoveries and precision of ASE and SFE compared well with the other methods investigated. Using SFE, the average recoveries of PAHs in three different samples ranged from 96 to 105%, for ASE the recoveries were in the range of 97-108% compared to the reference methods. Compared to the certified values of sediment HS-6, the average recoveries of SFE and ASE were 87 and 88%, most compounds being within the limits of confidence. Also, for alkanes the average recoveries by SFE and ASE were equal to the results obtained by SOX, USE, and MSE. In the case of SFE, the recoveries were in the range 93-115%, and ASE achieved recoveries of 94-107% as compared to the other methods. For ASE and SFE, the influence of water on the extraction efficiency was examined. While the natural water content of the SPM sample (56 wt %) led to insufficient recoveries in ASE and SFE, quantitative extractions were achieved in SFE after addition of anhydrous sodium sulfate to the sample. Finally, ASE was applied to SPM-loaded filter candles whereby a mixture of n-hexane/acetone as extraction solvent allowed the simultaneous determination of PAHs, alkanes, and chlorinated hydrocarbons.     

Supercritical fluid extraction and accelerated solvent extraction of dioxins from high- and low-carbon fly ash

This study investigates the replacement of Soxhlet extraction by supercritical fluid extraction (SFE) or accelerated solvent extraction (ASE) for the removal of dioxins from municipal waste incinerator fly ash. SFE is very matrix dependent; higher percent recoveries versus Soxhlet extraction can be obtained for low-carbon-level fly ash, but only a few percent of dioxins can be extracted from high-carbon-level fly ash. The addition of large quantities of toluene in the extraction cell prior to extraction of high-carbon fly ash improves the recovery of the lowest chlorinated dioxins (approximately 90%), but a maximum of 20% of the octachlorodibenzo-p-dioxins can be extracted. Since large quantities of toluene are needed to improve the recoveries, ASE with toluene was tested. Recoveries similar to Soxhlet extraction can be obtained in 2 h at 80 degrees C. Increasing the temperature to 150 degrees C increases the extraction rate and yields recoveries of approximately 110-160% compared to 48-h Soxhlet extraction for all congeners for both low- and high-carbon fly ashes. These results question the choice of Soxhlet extraction as a reference method for dioxin determination.     

SFE plus C18 lipid cleanup method for selective extraction and GC/MS quantitation of polycyclic aromatic hydrocarbons in biological tissues

Lipid material represents a potential interference for determination of nonpolar compounds (e.g., polycyclic aromatic hydrocarbons) in biological tissue samples. This study reports the development of a selective extraction method using supercritical CO2 that allows the GC/MS quantitation of PAHs in the presence of a substantial lipid background. Selective extraction of PAHs relies upon addition of C18 adsorbent beads to the initial sample slurry. The dried mixture, including C18 adsorbent, is placed in the supercritical fluid extraction (SFE) chamber. During the SFE process, lipids are preferentially retained on the C18 beads. This "SFE plus C18" procedure was developed by first optimizing SFE conditions (100 degrees C, 350 bar) for recovery of PAH standards. PAHs containing added model lipid compounds (stearic acid and cholesterol) were then subjected to SFE plus C18 treatment followed by GC/MS analysis. Using this approach, a recovery of 94-100% of PAHs was obtained while only 9-17% of the lipid material present was coextracted from the same test sample. The developed method is demonstrated to permit efficient recovery and detection of PAHs spiked into crab tissue, a matrix with a high lipid content.     

Collection efficiency of various solid-phase traps for off-line supercritical fluid extraction.

Solid-phase extraction tubes were evaluated as traps for off-line supercritical fluid extraction. Normal- and reversed-phase traps were studied with hydrocarbons, phenols, and a "test mixture" in order to determine the trapping efficiency. These traps were then used for the extraction of PCBs from river sediment. Polyethylene frits were also investigated for their use as solid-phase traps in SFE.     

Extraction of petroleum hydrocarbons from soil using supercritical argon

The use of supercritical argon is described for the extraction of petroleum hydrocarbons from soil samples. Argon is an attractive solvent because it is inexpensive and inert. Additionally, it has a clear spectral window in the infrared region which makes it useful for on-line (i.e., directly coupled) experiments. Spiking studies conducted with gasoline, no. 1 fuel oil, and no. 5 fuel oil on sand, loam, and clay show that component recovery rates for argon supercritical fluid extraction (SFE) generally increase with increasing pressure and/or temperature. The highest recovery rates (and recoveries) were obtained for Ar SFE at 500 atm and 150 °C. Under these conditions, the components of the gasoline and no. 1 fuel oil spikes could be recovered in as little as 12 min. However, the no. 5 fuel oil components could not be quantitatively removed from the loam and clay matrixes even for extraction times as long as 100 min. We also show in this work that Ar SFE performs similarly to CO(2) SFE for petroleum hydrocarbon contamination in real-world soil samples under moderate pressure and temperature conditions. Specifically, Ar SFE and CO(2) SFE have similar recoveries and reproducibilities, but Ar SFE requires a slightly longer extraction time.     

Comparison of extraction techniques, including supercritical fluid, high-pressure solvent, and soxhlet, for organophosphorus hydraulic fluids from soil

The efficiencies of three extraction techniques for removal of nonpesticidal organophosphates from soil were determined. Traditional Soxhlet extraction was compared to supercritical fluid extraction (SFE) and a low solvent volume flow through technique referred to here as high-pressure solvent extraction (HPSE). SFE, optimized by varying parameters of temperature, pressure, and methanol polarity modifier, showed at least 90% efficiency in the extraction of OPs from both spiked and native soils. HPSE experiments showed efficient and consistent recoveries over a range of temperatures up to 200 °C and pressures up to 170 atm. Recovery of TCP from spiked soils with HPSE depends on the system variables of temperature and pressure, which dictate density and flow rate. HPSE provided extraction efficiencies comparable to those obtained with Soxhlet extraction and SFE but with substantial savings of time and cost.     

Summarizing the effectiveness of supercritical fluid extraction of polycyclic aromatic hydrocarbons from natural matrix environmental samples

A summary of the supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs) from four natural matrix Standard Reference Materials (SRMs) is presented. The work involved the investigation of the effects of extraction fluid [carbon dioxide (CO(2)), chlorodifluoromethane (R22), and 1,1,1,2-tetrafluoroethane (HFC134a)], fluid modifier (dichloromethane and aniline), temperature (60, 150, and 200 °C) and added water on the SFE recoveries of PAHs compared to certified results from Soxhlet extractions. For SRM 1649a (Urban Dust/Organics), R22 yielded excellent recoveries (>90% of certified concentrations) of all PAHs measured, while results for the same SRM using HFC134a as the fluid were typically <80% of the certified concentrations for most of the PAHs measured. For SRM 1941a and 1944, both aquatic sediments with similar physical and chemical compositions, extractions of the wet materials with dichloromethane-modified CO(2) (10%, v/v) yielded quantitative recoveries of all PAHs for SRM 1944 but an obvious trend of lower recoveries for higher molecular weight PAHs (≥228 amu) for SRM 1941a. Results of SFEs of SRM 1650 (Diesel Particulate Matter) showed that this material is the most refractory of the SRMs investigated in this study, with recoveries of indeno[1,2,3-cd]pyrene and benzo[ghi]perylene at <20% of the Soxhlet results.     

Na(4)EDTA-Assisted Sub-/Supercritical Fluid Extraction Procedure for Quantitative Recovery of Polar Analytes in Soil

Supercritical carbon dioxide (SC-CO(2)) is effective in extracting nonpolar and slightly polar chemicals from soils. However, pure SC-CO(2) is unsatisfactory for recovering polar chemicals in soils. A simple supercritical fluid extraction (SFE) procedure was developed to quantitatively recover polar and nonpolar chemicals from soils. The polar chemicals tested were aromatic acids and phenols. The nonpolar and slightly polar chemicals used as model compounds were common pesticides and environmental pollutants such as polycyclic aromatic hydrocarbons. The procedure required pretreatment of the samples with 15% water (g/g), 5% (ethylenedinitrilo)tetraacetic acid tetrasodium salt (Na(4)EDTA) (g/g), and 50% methanol (mL/g) prior to extractions using SC-CO(2) at 60 °C and 34.5 MPa. Recoveries ranged from 90 to 106% for the aromatic acids using the Na(4)EDTA-assisted SFE compared with only 7-63% recoveries of the corresponding chemicals when no Na(4)EDTA was used. The method quantitatively extracted 2,4-D and its close analogues aged in the soil for 2-30 days. The Na(4)EDTA-assisted SFE was also adequate for extracting phenolic analytes including picric acid and pentachlorophenol with recoveries from 85 to 104%. Na(4)EDTA is a good enhancer for extraction of the 29 analytes representing a wide range of polarity from the soil using SC-CO(2). The method is valuable for the analysis of parent pollutants and transformed products, particularly oxygen-borne metabolites in the environment.     

Extraction of chromated copper arsenate from wood wastes using green solvent supercritical carbon dioxide

To provide a green method to remove chromated copper arsenate (CCA) in the wood before its dumping, incineration, reuse or disposal, extraction of CCA from wood wastes using supercritical carbon dioxide (ScCO(2)) containing an organophosphorus reagent, Cyanex 302, was investigated. The majority of copper metal was removed using Cyanex 302 in supercritical fluid extraction (SFE). The order of extraction efficiency was found to be Cu>As>Cr. Factors that affected SFE efficiencies, such as matrices, oxidation state of metal species [Cr(III), Cr(VI), As(III), and As(V)], and SFE pressure, were studied. Using this in situ chelation/SFE technique to remove leachable metals from the CCA-treated wood was found to significantly reduce the risk of leaching metals into the environment during storage, or waste disposal.     

High extraction efficiency for POPs in real contaminated soil samples using accelerated solvent extraction

Systematic investigations were performed to study the dependence of the extraction efficiency of persistent organic pollutants (POPs), including chlorobenzenes, HCH isomers, DDX, PCB congeners, and PAHs, on the accelerated solvent extraction (ASE) operating variables solvent and temperature. Mixed soil samples from two locations with considerable differences in soil properties and contamination in the Leipzig-Halle region (Germany) were used. The objective was to optimize ASE for the extraction of POPs from real soil samples and to improve on the results achieved with Soxhlet extraction (SOX). Solvents with differing polarities were tested. Quadruple and triple determinations were performed on the two soils, respectively, between 20 and 180 degrees C in 20 degrees C steps. All the results were compared with those obtained by SOX, as well as, in some cases during preliminary studies, by ultrasonic extraction (USE). In ASE, the optimum conditions proved to be two extraction steps at 80 and 140 degrees C (average RSD 10.7%) with three static cycles (extraction time 35 min) using toluene as solvent and at a pressure of 15 MPa. Owing to the superior analyte/matrix separation by ASE, in many cases for real soil samples analytical values better by up to 1 order of magnitude or even more were obtained compared to SOX results.     

Simultaneous determination of 4-nonylphenol and bisphenol A in sewage sludge

An analytical method has been developed for simultaneous extraction and determination of two estrogenic active agents, 4-nonylphenol (4-NP) and bisphenol A (BPA), in activated sewage sludge and anaerobically stabilized sewage sludge. Both compounds were determined by GC/MS in freeze-dried sewage sludge samples that had been spiked with these compounds in order to indicate different contamination levels. Extractive steam distillation, Soxhlet extraction, supercritical fluid extraction (SFE), and accelerated solvent extraction (ASE) were applied, and the results were compared. ASE under use of ethyl acetate/formic acid and an extraction temperature of 170 degrees C provided the most efficient extraction procedure for simultaneous extraction and the only reliable extraction results. Analyses of the phenolic compounds were performed by capillary column gas chromatography/mass spectrometry (GC/MS), operating in selected ion monitoring (SIM) mode after an aluminum oxide column-cleanup step prior to acetylation. The observed recovery rates under optimized conditions-ASE with ethyl acetate/formic acid-for 4-NP in spiked activated sewage sludge samples (spiking levels: 51, 88, or 554 microg/g on dry weight basis (dwb)) were 90, 107, or 101%. BPA (spiking levels: 50, 87, or 474 microg/g dwb) was found with recovery rates of 70, 105, or 101%, respectively. For anaerobically stabilized sewage sludge, recoveries for 4-NP (spiking levels: 40, 66, or 196 microg/g dwb) were 97, 95, or 101% and 90, 95, or 101% for BPA (spiking levels: 41, 67, or 474 microg/g dwb), respectively.     

Polychlorinated biphenyl (PCB) recovery from spiked organic matrix using accelerated solvent extraction (ASE) and Soxhlet extraction

The recovery of five PCB congeners from PCB spiked organic matrices was studied using Accelerated solvent extraction (ASE) and Soxhlet extraction (SE). The chromatogram of ASE extract was found to be relatively clean and similar to that of SE extract. ASE extraction efficiency was dependent on the operation temperature and sample size loading. ASE showed extraction efficiency comparable or slightly higher to that of SE for the PCB spiked organic matrix. PCB recovery from spiked matrix was dependent on the type and molecular weight of congener, and nature of matrix. For some selected PCB congeners, ortho-substitution did influence the PCB recovery from graphite matrix.     

Supercritical fluid extraction and gas chromatography/mass spectrometry for the analysis of tobacco-specific nitrosamines in cigarettes

A method for measuring four tobacco-specific nitrosamines (TSNAs), an important group of compounds in tobacco products, was developed. These compounds were extracted using supercritical fluid extraction (SFE) and purified by a sodium hydroxide wash of the ethyl acetate eluting solvent and solid-phase extraction. Quantitation was performed using gas chromatography/mass spectrometry (GC/MS). Spiking experiments were carried out to determine the recovery, precision, and limits of detection of this method. The detection limits were 0.04 microgram per sample for N'-nitrosonornicotine and N'-nitrosoanatabine and 0.02 microgram for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N'-nitrosoanabasine. This method was used to measure TSNAs in various brands of cigarette tobacco with excellent reproducibility. The variation of TSNA levels among the cigarettes of different packs and types was significantly smaller than that among different brands. Comparable TSNA levels were obtained with SFE and liquid extraction methods. Signal-to-noise levels were similar for GC/MS and GC/thermal energy analysis when low-level tobacco samples were analyzed.     

超声强化超临界流体萃取装置的设计及应用

设计了适用于超临界状态下的超声波强化装置，以薏仁及海藻为提取物，采用超声强化超临界流体萃取过程的工艺流程，分别提取CLSO、CLSE及EPA、DHA。实验结果表明，本强化装置降低了超临界流体萃取系统的压力、萃取温度，减少了夹带剂用量、超临界流体流量和萃取时间，萃取效率明显提高：EPA、DHA分别提高了15.09％、15.96％；CLSO、CLSE分别提高了12.2％、10.53％。提取物经GC-MS分析表明，超声强化不改变提取物质的成分与组成。     

加速溶剂萃取-GC-MS法检测食品接触材料——纸、纸板、木材和木制品中的6种氯酚类物质残留

建立了检测食品接触材料——纸、纸板、木材和木制品中含氯酚(CPs)残留量的气相色谱-质谱(GC-MS)分析方法。采用加速溶剂萃取(ASE)法为样品前处理手段,优化了萃取溶剂、萃取温度、静态萃取时间、冲洗体积和萃取循环次数等实验参数。优化结果为:以二氯甲烷为萃取溶剂,萃取温度为150℃,静态萃取时间为10 min,冲洗体积为(占萃取罐体积的)60%,萃取循环次数为1次。结果表明:6种CPs在0.05～2.0μg/mL质量浓度范围内具有良好的线性关系(R>0.99);平均回收率在86.8%～108.8%之间(n=6);相对标准偏差(RSD)为1.8%～14.2%(n=6);方法的检测限为0.01 mg/kg。研究表明该方法高效、简便、快捷、灵敏、准确可靠,可用于实际样品的CPs残留量的监测。     

Enhanced detection of nitroaromatic explosive vapors combining solid-phase extraction-air sampling,supercritical fluid extraction,and large-volume injection-GC

A complete method for sampling and analyzing of energetic compounds in the atmosphere is described. The method consists of the hyphenation of several techniques: active air sampling using a solid-phase extraction cartridge to collect the analytes, extraction of the sorbed analytes by toluene/methyl tert-butyl ether modified supercritical fluid extraction (SFE), and analysis of the extract by large-volume injection GC-nitrogen/phosphorus detection. The GC system is equipped with a loop-type injection interface with an early solvent vapor exit, a utilizing concurrent solvent evaporation technique. Chemometric approaches, based on a Plackett-Burman screening design and a central composite design for response surface modeling, were used to determine the optimum SFE conditions. The relative standard deviations of the optimized method were determined to be 4.3 to 7.7%, giving raise to method detection limits ranging from 0.06 to 0.36 ng in the sampling cartridge, equivalent to 6.2-36.4 pg/L in the atmosphere, standard sampling volume 10 L. The analytical method was applied to characterize headspace composition above military grade trinitrotoluene (TNT). Results confirm that 2,4-dinitrotoluene (DNT) and 1,3-dinitrobenzene (DNB) constitute the largest vapor flux, but TNT, 2,6-DNT, and trinitrobenzene TNB were also consistently detected in all the samples.     

Hot water extraction with in situ wet oxidation: PAHs removal from soil

We are reporting the results of a small-scale batch extraction with and without in situ wet oxidation of soils polluted with polycyclic aromatic hydrocarbons (PAHs) using subcritical water (liquid water at high temperatures and pressures but below the critical point as the removal agent). Two types of soil; one spiked with four PAHs, and an aged sample were used. Experiments were carried out in a 300 ml volume reactor in the batch mode. In each experiment, the reactor was filled with 45-50 g of soil and 200-220 ml of double distilled water. For extraction without oxidation, the reactor was pressurized with nitrogen, while for those with the oxidation, an oxidizing agent (air, oxygen or hydrogen peroxide) was used.The extraction only experiments were carried out at 230, 250 and 270 degrees C for spiked soil samples, and at 250 degrees C for aged soil samples, while all of the combined extraction and oxidation experiments were carried out at 250 degrees C. Removal of PAHs from spiked soil in extraction-only experiments was from 79 to 99+% depending on the molecular weight of the PAH. This was in the range of 99.1% to excess of 99.99% for the combined extraction and oxidation. While 28-100% of extracted PAHs can be found in water phase in case of extraction alone, this reduces to a maximum of 10% if the extraction is combined with oxidation. With aged soil similar or comparable results were obtained. Based on these results, extraction with hot water, if combined with oxidation, would probably reduce the cost of post treatment for the water and can be used as a feasible alternative technique for remediation of contaminated soils and sediments.     

Supercritical fluid extraction in modern radiochemistry

The possibility of using supercritical fluid extraction (SFE) of radionuclides for spent nuclear fuel reprocessing and for decontamination of various environmental objects is considered. Subcritical and supercritical media (CO₂ and Freons) containing various organic ligands can be used for extractive recovery of actinides and other radionuclides from diverse matrices, including oxides of these elements. SFE is also suitable for recovery of actinides and their separation from fission products, and also for decontamination of various surfaces. In the process, the volume of secondary radioactive aqueous and toxic organic wastes, which are formed in large amounts in the existing processes and give rise to long-term environmental problems, is reduced to a minimum.     

Design for on-line coupling of supercritical fluid extraction with liquid chromatography: quantitative analysis of polynuclear aromatic hydrocarbons in a solid matrix

Supercritical fluid extraction (SFE) was directly coupled with high-performance liquid chromatography (LC) via the simplest interface--only one six-port injection valve. By using water to eliminate decompressed CO2 gas in the solid-phase octadecylsilica trap, high extraction recovery (> or = 95%) of polynuclear aromatic hydrocarbons (PAHs) from a sand matrix was achieved under optimized conditions. The volume of rinse water had little influence on the recovery, due to the very low solubility of PAHs in water and the sorption properties of the C-18 trap. Different amounts of sand matrix with a fixed mass of analytes have also been tested. No decrease in recovery was found when the matrix (sand) increased from 1 to 10 g. Methanol and acetone were used as a CO2 modifier to enhance the extraction efficiency. Finally, PAHs in naturally contaminated soil were successfully extracted and quantitatively determined by this hyphenated system. Compared to the EPA method (Soxhlet extraction following by GC/MS), on-line SFE-LC gave precise results in a much shorter time.     

Determination of Pentachlorophenol and Its Oil Solvent in Wood Pole Samples by SFE and GC with Postcolumn Flow Splitting for Simultaneous Detection of the Species

An alternative approach is described for the measurement of pentachlorophenol (PCP) and its oil solvent in wood samples by supercritical fluid extraction (SFE) and gas chromatography (GC). The determination is achieved over a single chromatographic run using postcolumn flow splitting for simultaneous ECD/FID detection of the SFE extracted species. First, PCP and oil components are quantitatively extracted from a 0.3-g wood sample using 10% MeOH/CO(2) supercritical fluid at 0.65 g/mL and 120 °C. An aliquot of the SFE solution is then mixed with 10 mL of a buffered aqueous phase at pH 9.4. After PCP is acetylated by the addition of 500 μL of acetic anhydride, it is followed by its extraction with 2.00 mL of hexane along with oil. Then, 0.5 μL of supernatant organic phase is injected into the GC for a selective and simultaneous determination of the species. The method has a linear response over 3 orders of magnitude for both species with a linear regression correlation coefficient higher than 0.98 (95% confidence limit) and an absolute detection limit of 60 ng of PCP and 80 μg of oil per 0.1-g wood sample. The precision (relative standard deviation) is 4% for PCP and 1% for oil as established for a typical average concentration sample. The accuracy of the SFE GC-ECD/FID combined technique for PCP and oil was assessed by analyzing wood samples collected from newly and in-service PCP/oil-impregnated red pine poles.