Efficiency of Different Methods and Solvents for the Extraction of Polycyclic Aromatic Hydrocarbons from Soils

The efficiencies of supercritical fluid extraction (SFE), accelerated solvent extraction (ASE), Soxhlet, and ultrasonic extraction in the analysis of polycyclic aromatic hydrocarbons (PAHs) in soils were evaluated. Solvents with different polarity were used to extract the PAHs from two soils, one with high and one with low contamination level. ASE showed good results with all solvents almost independent of the solvent polarity and the best results with acetone-toluene (1 : 1). Ultrasonic extraction with acetone-toluene for the uncontaminated soil and acetone-ethanolamine for the highly contaminated also showed good recoveries. The time-consuming Soxhlet extraction with pentane or dichloromethane was less effective. The PAH recovery from SFE was related to the soil matrix or the contamination level. The best extraction conditions (CO 2 /10% pentane) are successful for the soil with a low contamination level and a high humic acid content whereas the extractions of the highly contaminated soil gave poor results irrespective of the solvent used.     

Sequential Automated Focused Microwave-Assisted Soxhlet Extraction of Compounds with Different Polarity from Marine Sediments Prior to Gas Chromatography Mass Spectrometry Detection

An extraction method based on the use of a focused microwave-assisted Soxhlet extractor with subsequent gas chromatography separation and mass spectrometry detection is proposed for the analysis of environmental pollutants from marine sediments collected at the outflow of an urban wastewater treatment plant to the sea. For the extraction of compounds with different polarity, sequential extraction with dichloromethane and water was performed on each sample. The experimental variables were optimized by the experimental design methodology for both the organic and aqueous extractant. The total time required for quantitative extraction of triclosan, bisphenol A, estrone, estradiol, oxyfluorofen and permethrin was 75 min, a short time as compared with the 24 h Soxhlet extraction (diethylstilbestrol, 4-octylphenol, procymidone and 2,7/2,8-dichlorodibenzo-p-dioxin isomer pair).Revised: 10 March and 18 April 2005     

An eco-friendly efficient extractor

A microscale solid-liquid Pyrex extractor is described. The extractor has a novel detachable extraction vessel (H) containing a filter paper cylinder (C) over the reservoir. A filter paper cylinder (C) is firmly placed in the socket (E) with a plug (G) on which the cylinder has been placed. The sample is directly weighed in the extraction vessel (H) and the vessel is clamped (F) to the body (B). Contents in the extraction reservoir (H) are stirred (I) with a magnetic stirrer (J) and heated sufficiently (e.g. at 84.8 °C in using water) by the solvent vapor (D). Easy filtration (C) and continuous outflow (D) of the filtrates out of the reservoir (H) keeps a stable boiling condition (K), rather than batchwise conditions operative in a Soxhlet; this results in rapid and exhaustive extraction. The present extractor (8.0 mL extraction reservoir (H) capacity) equipped with a 25 mL solvent flask (K) was applied to fat extraction from powdered peanut by using 18 mL of ether. The extraction was complete in 30-60 min depending on reflux rate; in contrast, extraction with a commercial micro-Soxhlet device (23.9 mL extraction reservoir capacity) equipped with a 25 mL flask by using 34 mL of the solvent was incomplete in 120 min. Unlike filter paper thimbles used in Soxhlet devices, filter paper cylinder (C) in the new extractor could be reused many times and results in significant savings of the filter paper cylinders. Small reservoir and flask capacities of the new extractor minimize the use of organic solvents. The present apparatus permits fast and efficient extraction, sharply reduces waste, minimizes solvent consumption, and thus should find wide use aiming at the Green Solutions to Global Problems.     

Determination of Four Pesticides in Soil by Homogeneous Ionic Liquid-based Microextraction Coupled with High-performance Liquid Chromatography

Homogeneous ionic liquid microextraction was developed for the simultaneceus extraction of dimethomorph, mefenacet, isoprothiolane and oxadiazon from soil. 1-Butyl-3-methylimidazolium tetrafluoroborate was used as extraction solvent, and ammonium hexafluorophosphate was used as ion-pairing agent. High-performance liquid chromatography(HPLC) was employed for separation and determination of the analytes. The calibration curves show good linear relationship(r>0.9988). The recoveries are between 74.2% and 97.9% with relative standard deviations(RSDs) lower than 5.97%. The present method is free of volatile organic solvents, and expenditures of sample, extraction time and solvent are lower, compared with ultrasonic and Soxhlet extraction. There was no obvious diffe- rence in the extraction recoveries of pesticides obtained by the three extraction methods.     

Direct ultrasonic agitation for rapid extraction of organic matter from airborne particulate

Direct ultrasonic extraction (DUE) is proposed as simple and rapid sample pretreatment method. This new approach is applied to the extraction of particulate organic matter (POM) from airborne particulate by using dichloromethane (DCM) or DCM/methanol (90/10, v/v) as extractant. The analytical determination was carried out by weighing the extractable POM on an electrobalance. Total recovery for POM could be obtained when the sample was extracted three times with 25–50 mL extractant each for about 5 min at 50 W ultrasonic power. In comparison with conventional Soxhlet extraction, less extraction time (total 15 min only) and solvent consumption(100 mL) were required by DUE. The efficiency of the DUE was similar or even higher than the routine Soxhlet method. Additionally, the new extractor is very simple and easy to use and can accelerate the extraction procedures of organic components from various solid samples.     

Direct ultrasonic agitation for rapid extraction of organic matter from airborne particulate

Direct ultrasonic extraction (DUE) is proposed as simple and rapid sample pretreatment method. This new approach is applied to the extraction of particulate organic matter (POM) from airborne particulate by using dichloromethane (DCM) or DCM/methanol (90/10, v/v) as extractant. The analytical determination was carried out by weighing the extractable POM on an electrobalance. Total recovery for POM could be obtained when the sample was extracted three times with 25-50 mL extractant each for about 5 min at 50 W ultrasonic power. In comparison with conventional Soxhlet extraction, less extraction time (total 15 min only) and solvent consumption (100 mL) were required by DUE. The efficiency of the DUE was similar or even higher than the routine Soxhlet method. Additionally, the new extractor is very simple and easy to use and can accelerate the extraction procedures of organic components from various solid samples.     

Extraction of polychlorinated biphenyls from soils by automated focused microwave-assisted Soxhlet extraction

The application of a new focused microwave-assisted Soxhlet extractor for the extraction of polychlorinated biphenyls from differently aged soils is here presented. The new extractor overcomes the disadvantages of previous devices based on the same principle and enables a fully automated extraction of two samples simultaneously. The variables affecting the extraction step (namely, power of irradiation, irradiation time, extractant volume, extractant composition and number of extraction cycles) have been optimized using experimental design methodology. The optimized method has also been applied to a certified reference material (CRM910-050 "real" contaminated soil) for quality assurance validation. Quantification of the target compounds has been performed by GC with ion-trap MS. The mass spectrometer was operated in the electron-ionization mode, with selected-ion monitoring at m/z 152, 186, 292, 326 and 498. The results obtained have demonstrated that this approach is as efficient as conventional Soxhlet but with a drastic reduction of both extraction time (70 min vs. 24 h for the "real" contaminated soil) and organic solvent disposal, as 75-80% of the extractant is recycled.     

Derivatization of Humic Compounds: An Analytical Approach for Bound Organic Residues

Abstract

Bound residues of pesticides and their metabolites are defined as being nonextractable with organic solvents, but partly extractable together with the humic matrix by NaOH or other solvents suitable to extract humic compounds. Recently, an improvement in humus extraction from soils was achieved upon derivatization of the organic matter with silylating reagents at room temperature. By this method 70–90% of the organic carbon or nitrogen either from soil or from humin became soluble in organic solvents. The extracts were analyzed by means of ¹³C NMR-spectroscopy. The spectra were well resolved with signal-separation of less than 1 ppm. The extracted humic compounds were of rather low molecular weight, ranging from 300 to 4000 to 6000 d or more.

¹⁴C-labeled residues of pesticides or other xenobiotics found to be nonextractable after exhaustive organic solvent extraction became readily dissolved along with most of the humic matrix using this derivatization procedure. Between 60–80% of ¹⁴C anilazine residues or of ¹⁴C-labeled chlorinated phenols or anilines originating from both previously solvent extracted soil samples or from humin became solubilized in organic solvents.     

The influence of organic sample solvents on the separation efficiency of basic compounds under strong cation exchange mode

This study investigated the influence of organic sample solvents on separation efficiency of basic compounds under strong cation exchange (SCX) mode. The mixtures of acidic aqueous solution and organic solvent such as acetonitrile, ethanol, methanol and dimethyl sulfoxide (DMSO) were tested as sample solvents. For later-eluting analytes, the increase of sample solvent elution strength was responsible for the decrease of separation efficiency. Thus, sample solvents with weak elution strength could provide high separation efficiencies. For earlier-eluting analytes, the retention of organic sample solvents was the main factor affecting separation efficiency. Weakly retained solvents could provide high separation efficiency. In addition, an optimized approach was proposed to reduce the effect of organic sample solvent, in which low ionic solvent was employed as initial mobile phase in the gradient. At last, the analysis of impurities in hydrophobic drug berberine was performed. The results showed that using acidic aqueous methanol as sample solvents could provide high separation efficiency and good resolution (R > 1.5).     

Development of a pressurized liquid extraction and clean-up procedure for the determination of alpha-endosulfan, beta-endosulfan and endosulfan sulfate in aged contaminated Ethiopian soils

Pressurized liquid extraction (PLE) was investigated for the extraction of two endosulfan isomers and their metabolite from two real contaminated soil samples. PLE for 3x10min at 100 degrees C was proven to be more exhaustive than Soxhlet extraction (SOX) in one soil sample. On the other soil sample investigated the method was found to be equally exhaustive as SOX. The use of hazardous organic solvents such as n-hexane, toluene, and diethyl ether has been avoided in PLE and clean-up. Instead less toxic solvents have been used both at the extraction step (acetone/n-heptane) and clean-up step (ethyl acetate/n-heptane). A column Florisil clean-up procedure that consumes relatively low solvent volumes has been optimized and applied to purify soil extracts. The developed analytical procedure was validated by applying it to a certified reference soil material (CRM811-050). A recovery of 103% total endosulfan residue was obtained versus certified values.     

A liquid–liquid extraction technique for phthalate esters with water-soluble organic solvents by adding inorganic salts

In the presence of inorganic salts, the mixture solution of some water-soluble organic solvents and water can form two clearly separated phases. One is the organic solvent rich phase, the other is the water rich phase. In the phase separation process, hydrophobic solutes dissolved in the mixture solution such as phthalate esters can be extracted into the organic solvent rich phase quantitatively. Based on this phase separation phenomenon, a liquid–liquid extraction technique of phthalate esters using water-soluble organic solvents as organic phases was developed. Several important parameters affecting the extraction efficiency including the kind and the amount of water-soluble organic solvents, the kind and the amount of inorganic salts and the pH of the sample solutions were carefully studied. This new extraction technique has been applied to the HPLC analysis for water lixivium of plastic wrapping film. Under the optimized conditions, detection limits of 1.5, 2.3, 1.0, 2.6, 1.3 and 3.0 ng mL⁻¹ were obtained for diethylphthalate, di-n-propylphthalate, di-iso-butylphthalate, dicyclohexylphthalate, di-n-octylphthalate and di-n-nonylphthalate ester respectively. The strongpoints of this new liquid–liquid extraction technique are the easy phase separation, rapid partition equilibrium, less toxicity and very good compatibility with subsequent HPLC determinations.     

Solvent Effects in Reversed Phase Liquid Chromatooraphy for High and Low Loadings of Octadecylsilane on Microparticle Silica. I

Abstract

The selectivity of two ODS bonded phase packings, one with a high carbon load, the other with a low carbon load, were investigated. Many organic solvent/water mobile phases were used with three sample mixtures of varying polarity. When the separations were normalized, trends in the solubility parameters of the various classes of organic solvents were noted. Analyzing the separation factors and considering possible mobile phase, solute, and bonded phase interactions furnished some insight into possible separation/selectivity mechanisms.     

Optimisation of pressurised liquid extraction for the determination of p,p′-DDT and p,p′-DDE in aged contaminated Ethiopian soils

The effectiveness of extracting p,p′-DDT and p,p′-DDE from aged contaminated soil samples by means of pressurized liquid extraction (PLE) was evaluated. Two soil samples, which were contaminated more than 10 years ago, were used in the investigation. The static extraction time was optimised and then validated against the total sum of target analytes obtained from multiple sequential extractions. The PLE results were also compared with Soxhlet extraction (SOX). PLE for 3×10 min at 100 °C was proven to be more exhaustive than SOX in the determination of p,p′-DDE from both soil samples. In the case of p,p′-DDT, PLE was found to be equally as exhaustive as SOX. Additionally, most of the previous PLE investigations used hazardous organic solvents such as n-hexane, toluene and dichloromethane mixed with acetone, whereas in this investigation the less toxic solvent combination n-heptane/acetone has been employed.     

Extraction of organic compounds with room temperature ionic liquids

Room temperature ionic liquids are novel solvents with a rather specific blend of physical and solution properties that makes them of interest for applications in separation science. They are good solvents for a wide range of compounds in which they behave as polar solvents. Their physical properties of note that distinguish them from conventional organic solvents are a negligible vapor pressure, high thermal stability, and relatively high viscosity. They can form biphasic systems with water or low polarity organic solvents and gases suitable for use in liquid–liquid and gas–liquid partition systems. An analysis of partition coefficients for varied compounds in these systems allows characterization of solvent selectivity using the solvation parameter model, which together with spectroscopic studies of solvent effects on probe substances, results in a detailed picture of solvent behavior. These studies indicate that the solution properties of ionic liquids are similar to those of polar organic solvents. Practical applications of ionic liquids in sample preparation include extractive distillation, aqueous biphasic systems, liquid–liquid extraction, liquid-phase microextraction, supported liquid membrane extraction, matrix solvents for headspace analysis, and micellar extraction. The specific advantages and limitations of ionic liquids in these studies is discussed with a view to defining future uses and the need not to neglect the identification of new room temperature ionic liquids with physical and solution properties tailored to the needs of specific sample preparation techniques. The defining feature of the special nature of ionic liquids is not their solution or physical properties viewed separately but their unique combinations when taken together compared with traditional organic solvents.     

Supercritical fluid extraction of polychlorinated biphenyls and pesticides from soil. Comparison with other extraction methods.

A comparison is made of supercritical fluid extraction (SFE) with two other techniques widely used for the extraction of polychlorinated biphenyls (PCBs) and organochlorine pesticides in soil. Extraction conditions for the SFE of PCBs and pesticides were first determined. An experimental approach was set up to determine the influence of different extraction parameters such as pressure, extraction time, static and dynamic extraction, restrictor type and collection solvent for off-line SFE. The use of carbon dioxide at 50 degrees C and 20 MPa, 10 min static followed by 20 min dynamic extraction with collection in iso-octane were been found to be the optimum conditions. Two types of soil, with a low and high content of organic carbon, respectively, spiked with 16 PCBs and organochlorine pesticides with a wide range of volatility and polarity at a level of 5 ng/g dry matter, were used as test materials. Conventional solvent extraction gives a good extraction yield for soil with a low content of organic carbon, but for peat soil the recoveries decrease dramatically to 30% for DDE, DDT and PCB 138 and 153. The recoveries with Soxhlet extraction are good, but an extra clean-up step before analysis is necessary. SFE gives good extraction yields for PCBs and organochlorine pesticides, varying between 85 and 105% with a reproducibility of 5% for each component for both types of soil. SFE is a fast, clean and reproducible method for the extraction of PCBs and organochlorine pesticides from these two soil matrices.     

茶叶中咖啡因的提取实验装置的改进与探索

"茶叶中咖啡因的提取"是有机化学实验的一个经典实验,本文对该实验所用的原索氏提取器进行改进,得到内通气集热式索氏提取器并用于实验教学。通过对照实验,对改进索氏提取器和原索氏提取器的提取效果进行比较。结果表明,改进装置具有原装置的功能和特点,且提取时间更短、提取温度和提取率更高,可在高校推广使用。     

Development and optimisation of a novel three‐way extraction technique based on a combination of Soxhlet extraction,membrane assisted solvent extraction and a molecularly imprinted polymer using sludge polycyclic aromatic hydrocarbons as model compounds

A novel technique that integrates extraction and clean‐up into a single step format is reported as part of the search for new sample preparation techniques in the analysis of persistent organic pollutants from complex samples. This was achieved by combining the extraction efficiency of the Soxhlet extractor, the selectivity of a size exclusion membrane and the specificity of a molecularly imprinted polymer for the extraction of polycyclic aromatic hydrocarbons from wastewater sludge followed by quantitation using gas chromatography with time‐of‐flight mass spectrometry. The approach is described as the Soxhlet extraction membrane‐assisted solvent extraction molecularly imprinted polymer technique. This technique was optimised for various parameters such as extraction solvent, reflux time and membrane acceptor phase. The applicability of the developed technique was optimised using a wastewater sludge certified reference material and then tested on real wastewater sludge samples. The method detection limits ranged from 0.14 to 12.86 ng/g with relative standard deviation values for the extraction of the 16 US‐EPA priority polycyclic aromatic hydrocarbons from wastewater sludge samples ranging from 0.78 to 18%. The extraction process was therefore reproducible and showed remarkable selectivity. The developed technique is a promising prospect that can be applied in the analysis of organic pollutants from complex solid samples.     

Extraction of polycyclic aromatic nitrogen heterocycles from spiked soil samples

Extraction recovery of 10 selected polycyclic aromatic nitrogen heterocycles (PANHs), quinoline, 2-methylquinoline, 6-methylquinoline, 8-methylquinoline, acridine, benzo[h]quinoline, phenantridine, indole, 2-methylindole, and carbazole from spiked soil samples was tested. Four different extraction techniques, pressurized solvent extraction (PSE), supercritical fluid extraction (SFE), Soxhlet warm extraction (SOXW) and standard Soxhlet extraction (SOX), were applied and compared. The RP-HPLC technique with a silica-based octadecyl stationary phase was used for recovery determination of individual PANHs. Supercritical fluid extraction has been found to be the most effective method for the extraction of selected PANHs from soil. PSE and SOXW methods offered similar results with slightly lower extraction recoveries compared with SFE. On the contrary, SOX is a time-consuming method with a low recovery of target analytes and is not suitable for the extraction of PANHs from soils.     

Supramolecular solvents in the extraction of organic compounds. A review

The increasing pressure to decrease organic solvent usage in laboratories is fostering the search for alternative solvents. The liquid-liquid phase separation of surfactants, induced by environmental conditions, viz. temperature, electrolytes, pH, etc., has been largely used in analytical extraction and concentration schemes. The surfactant-rich phase is a nano-structured liquid, recently named as supramolecular solvent, generated from the amphiphiles through a sequential self-assembly process occurring on two scales, molecular and nano. This review covers progress on both theoretical and practical aspects related to the use of supramolecular solvents in analytical extractions reported over the last decade. Advances allowing a better understanding of the mechanisms of solvent production and solvent structure are outlined. Emphasis is then placed on solvent composition and its consequences on extraction efficiency, concentration factors and suitability for solubilising analytes over a wide range of polarities. Recent developments in formats and strategies making supramolecular solvents compatible with chromatographic and electrophoretic techniques along with a variety of detection systems are discussed. Applications of supramolecular solvents to the extraction of organic compounds mainly in the biological, environmental and agrifood areas are critically reviewed and main future trends outlined.     

Extractions with superheated water

As the temperature of liquid water is raised under pressure, between 100 and 374 degrees C, the polarity decreases markedly and it can be used as an extraction solvent for a wide range of analytes. Most interest has been in its application for the determination of PAHs, PCBs, and pesticides from environmental samples, where it gives comparable results to Soxhlet extraction but more rapidly and without the use of significant volumes of organic solvents. Unlike SPE, n-alkanes are not extracted unless the pressure is reduced and steam is used. Other applications have included the extraction of essential oils from plant material where it preferentially extracts the economically more important oxygenated components compared to steam distillation. The aqueous extract has been concentrated in a number of different methods (solvent extraction, SPE, SPME, extraction disc) or the extraction can be linked on-line to LC or GC. In many cases the superheated water extraction is cleaner, faster and cheaper than the conventional extraction methods.