Pressurized liquid extraction in environmental analysis

A critical evaluation of recent literature utilizing pressurized liquid extraction (PLE) for environmental analysis is presented by compound class. Overall, the extraction efficiency of PLE, using the appropriate solvent, temperature and pressure for extraction, is similar to that of Soxhlet extraction. PLE has been used for some classes of compounds that are thermally labile (e.g., explosives) and may require acidic conditions for extraction (e.g., organometallic compounds). References to recent applications are presented emphasizing studies which utilize unspiked, natural matrices and studies that compare PLE to alternate extraction techniques.     

Current use of pressurised liquid extraction and subcritical water extraction in environmental analysis

This review updates our knowledge about pressurised liquid extraction (PLE) and subcritical water extraction (SWE), two sample preparation techniques which are increasingly used for the extraction of moderately and non-volatile organic pollutants from a variety of solid and semi-solid environmental matrices. Parameters influencing the extraction yield and selectivity are discussed. The results deriving from the analysis of several different classes of compounds in a variety of matrices are compared with a reference method, e.g., Soxhlet extraction. PLE and SWE are both promising techniques due to the short extraction times and low solvent consumption. In addition, SWE offers a wide range of polarities by changing the temperature and can easily provide class-selective extraction by temperature programming and/or the addition of modifier(s). This indicates that, even though many applications have already been reported, more can be expected.     

Comparison of different extraction techniques for the determination of chlorinated pesticides in animal feed

The performances of Soxhlet extraction, dive-in Soxhlet extraction, microwave-assisted extraction (MAE), accelerated solvent extraction (ASE), fluidized-bed extraction (FBE), and ultrasonic extraction (UE) for the analysis of organochlorine pesticides in animal feed have been investigated. ASE and MAE provided significantly better extraction efficiency than Soxhlet extraction. The concentrations were 126.7 and 114.8%, respectively, of the values obtained by classical Soxhlet extraction, whereas the results from FBE and dive-in Soxhlet were comparable with those from the standard Soxhlet procedure. The reproducibility of FBE was the best, with RSDs ranging from 0.3 to 3.9%. Under the investigated operation conditions UE was not efficient, with the recoveries of target compounds being about 50% less than Soxhlet. Additionally, the performances of Soxhlet, dive-in Soxhlet, MAE, ASE and FBE were validated by determination of the certified reference material BCR-115. The results from the extraction techniques were in good agreement with the certified values.     

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。     

Focused microwave aqueous extraction of chlorophenols from solid matrices and their analysis by chromatographic techniques

Open-vessel focused microwave (FMW) extraction with a purely aqueous carbonate solution was used for the extraction of chlorophenols from various solid matrices. After SPE on C18-bonded silica, the analytes were determined as such by LC-UV or, as their acetyl derivatives, by GC-ECD. The FMW aqueous extraction is efficient and rapid and no organic solvents are used. PCP was detected in several solid samples, with recoveries of 101-115% (RSD, 2-4%) relative to Soxhlet extraction. Similar recoveries were obtained for the other chlorophenols for spiked samples.     

Determination of nitrated polycyclic aromatic hydrocarbons and their precursors in biotic matrices

Analytical method for the determination of ultra-trace levels of nitro-PAHs in various biotic matrices has been developed. Soxhlet extraction and/or solvent extraction enhanced by sonication were used for isolation of target analytes; GPC followed by SPE were employed for purification of crude extracts. GC-MS/NCI technique was utilised for identification/quantitation of target analytes. Performance characteristics of implemented method were obtained through thorough in-house validation procedure. The main sources of uncertainties were critically evaluated, possible strategies of their elimination/minimisation were considered and consequently employed. Examination of real-life samples of various foodstuffs (complete human diet, mate tea, pumpkin seed oil, parsley, sausages) was performed in this study.     

土壤中有机氯农药残留分析用标准样品的制备

介绍了土壤中有机氯农药残留分析用标准样品的制备方法。土壤样品经风干、研磨、筛分、混匀后装瓶。样品经索氏提取、弗罗里硅土小柱净化后,采用气相色谱-质谱法对残留的有机氯农药进行测定。结果表明,采自沈阳地区的土壤中的有机氯农药含量分布较为均匀,是一种理想的环境标准样品候选物样品。该研究为土壤中有机氯农药残留分析用标准样品的研制奠定了基础。     

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.     

Dynamic microwave-assisted extraction

An apparatus for extraction of solid matrices has been constructed which utilizes a microwave technique for heating in a dynamic mode. During the extraction, fresh solvent is continuously pumped through the extraction cell, which is maintained at a slight overpressure in order to keep the solvent in a liquid state. The extraction efficiency, which can be easily monitored, has been investigated in a factorial design and validated for polycyclic aromatic hydrocarbons in a reference sediment sample (EC-1). Important parameters were found to be temperature and duration of extraction. Flow-rate had no significant first-order effect on the recovery, but interaction effects with flow-rate were found to be significant. The dynamic microwave-assisted extraction apparatus was demonstrated to yield recoveries equivalent to Soxhlet extraction, but in a much shorter time. Each extraction of EC-1 typically takes 40 min.     

On-line monitoring of Soxhlet extraction by chromatography and mass spectrometry to reveal temporal extract profiles

Soxhlet extraction is a popular sample preparation technique used in chemical analysis. It enables liberation of molecules embedded in complex matrices (for example, plant tissues, foodstuffs). In most protocols, samples are analyzed after the extraction process is complete. However, in order to optimize extraction conditions and enable comparisons between different types of extraction, it would be desirable to monitor it in real time. The main development of this work is the design and construction of the interface between Soxhlet extractor and GC–MS as well as ESI-MS system. The temporal extract profiles, obtained in the course of real-time GC–MS monitoring, have been fitted with mathematical functions to analyze extraction kinetics of different analytes. For example, the mass transfer coefficients of pinene, limonene and terpinene in lemon sample, estimated using the first-order kinetic model, are 0.540 h⁻¹, 0.507 h⁻¹ and 0.722 h⁻¹, respectively. On the other hand, the Peleg model provides the following extraction rates of pinene, limonene and terpinene: 0.370 nM h⁻¹, 0.216 nM h⁻¹ and 0.596 nM h⁻¹, respectively. The results suggest that both first-order kinetic and Peleg equations can be used to describe the progress of Soxhlet extraction. On-line monitoring of Soxhlet extraction reveals extractability of various analytes present in natural samples (plant tissue), and can potentially facilitate optimization of the extraction process.     

土壤中烃类污染物的超临界流体萃取

采用超临界流体萃取技术提取环境样品中的烃类污染物，以色谱－质谱联用仪测定了萃取物的化学成分，考察了影响萃取效率的主要因素。比传统的索氏萃取能更有效地从复杂环境样品中萃取分析物。     

含镧金属富勒烯不同溶剂的高温高压提取

将金属原子或离子置于以Ｃ６０、Ｃ８２为代表的富勒烯笼内形成金属富勒烯包合物是目前富勒烯研究的热点课题［１～３］．合成的金属富勒烯常伴随生成较难分离的空心富勒烯,传统的索氏提取法效率又较低,使得金属富勒烯的深入研究受到限制［１,２］．本文采用改进的高温...     

快速溶剂萃取柚皮中的黄酮类化合物

采用快速溶剂萃取法从柚子皮中提取出黄酮类化合物,考察了不同的提取溶剂、提取时间、提取温度、循环次数等提取条件下的提取效果,并与微波法、超声波法及索氏提取法进行了对比.结果表明,快速溶剂萃取法提取柚子皮中的黄酮类化合物,在提取溶剂用量、提取时间和提取效率等方面,均优于传统的提取方法,且自动化程度高,为进一步开发利用柚子皮的药用价值提供了参考.     

Comparison of techniques for the extraction of the anti-cancer drug camptothecin from Nothapodytes foetida

Extraction methods using stirring extraction, Soxhlet extraction, ultrasonic extraction and microwave-assisted extraction (MAE) were evaluated for the percentage extraction of camptothecin (CPT) and 9-methoxycamptothecin (9-Me-CPT) from Nothapodytes foetida. The extracts were analyzed by high performance liquid chromatography (HPLC). Methanol (90%, v/v) extracted high percentage extraction of CPT and 9-Me-CPT compared to ethanol (90%, v/v). The results shows that the percentage extraction of CPT and 9-Me-CPT from N. foetida by MAE was more efficient in short time followed by Soxhlet extraction, ultrasonic and stirring extraction methods. Maximum percentage extraction of CPT (2.67%, w/w) was obtained by MAE technique. MAE has need of 3 min, whereas ultrasonic extraction, Soxhlet extraction and stirring extraction techniques require 30, 120 and 30 min, respectively to leach higher percentage extraction of CPT and 9-Me-CPT. The times taken by the microwave extraction process was 40 times less than the Soxhlet extraction for percentage extraction of alkaloids. The present results show that the extraction efficiency and considerable saving of time by MAE was more competent than the other extraction techniques.     

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.     

Simultaneous extraction and determination of anionic surfactants in waters and sediments

A new method has been developed for the simultaneous determination of the most frequently used anionic surfactants - linear alkylbenzene sulfonates (LAS), alkyl ethoxysulfates (AES) and alkyl sulfates (AS) - in aqueous and sediment samples. Preconcentration and purification of water samples are carried out by means of solid-phase extraction (SPE). The efficiency of two different extraction methods for the analysis of sediments - Soxhlet extraction and pressurized liquid extraction (PLE) - has been compared. Identification and quantification of the target compounds is performed using a liquid chromatography - mass spectrometry (LC-MS) system equipped with an electrospray interface (ESI) in negative ion-mode. Homologue recoveries are 85-123% for SPE, 94-112% for Soxhlet extraction and 81-125% for PLE in the case of LAS, and 60-94% for SPE, 61-109% for Soxhlet extraction and 55-99% for PLE in the case of AES, whereas the limits of detection are 0.1-0.5 ngml(-1) in water and 1-5 ngg(-1) in sediment. This method has been applied to the determination of anionic surfactants in the Guadalete estuary (SW Spain), and LAS concentration levels from 538 to 1014 ngg(-1) in sediments and from 25.1 to 64.4 ngml(-1) in waters have been found. AES values from 168 to 536 ngg(-1) in sediments and from 4.5 to 11.9 ngml(-1) in waters are reported for the first time in European rivers.     

Determination of polybrominated diphenyl ethers in marine biological tissues using microwave-assisted extraction

Growing concern on the environmental impact of polybrominated diphenyl ethers (PBDEs) has created the need for rapid and quality assured analytical methods to quantify PBDEs in a spectrum of matrix types. This study presents the first validated method for the quantification of major PBDE congeners (47, 99 and 100) in marine biological tissues using microwave-assisted extraction (MAE). The recovery of polychlorinated biphenyls and various organochlorine pesticides has also been ascertained. Analytical accuracy, precision, limits of detection and cleanup efficiency were evaluated for PBDE congeners, and empirical data justifies the use of MAE for the extraction and analysis of PBDEs in biological matrices. MAE was also compared to Soxhlet extraction efficiency for PBDEs in the standard reference materials SRM2978 and SRM1588a and gave comparable results (<15% variation).     

Comparison of various extraction techniques for isolation and determination of isoflavonoids in plants

In the present paper, the following extraction techniques have been used for extracting isoflavonoids from the species Matricaria recutita, Rosmarinus officinalis, Foeniculum vulgare, and Agrimonia eupatoria L.: supercritical fluid extraction (SFE), pressurized fluid extraction, matrix solid phase dispersion, ultrasonic extraction in an ultrasonic bath (USE) and by means of an ultrasonic homogeniser (HOM), extraction by means of Soxhlet apparatus (SOX), and solid phase extraction. Experimental optimization of all techniques has been carried out using a soybean flour. Subsequent analyses of the extracts were carried out by liquid chromatography with UV detection. The maximum yields of daidzein and genistein were obtained by extraction with the SOX, USE, and HOM techniques. The maximum yields of apigenin and biochanin A from herb samples were obtained by SFE.     

Optimization by factorial design of focused microwave assisted extraction of polycyclic aromatic hydrocarbons from marine sediment

The Focused Microwave (FMW) assisted extraction for organic contaminant analysis, such as polycyclic aromatic hydrocarbons (PAHs), in environmental matrices, was studied and optimized using a factorial design. The effects and interactions of five parameters on the extraction recovery were investigated in a few experiments with a good accuracy: irradiation power and time, volume and nature of solvent, and percentage of moisture of the matrix. The results show that the percentage of water added to the freeze-dried matrix can significantly increase the extraction recovery. The irradiation power has also a positive effect. The choice of solvent is significant: a mixture of heptane/ethanol (80/20, v/v) allows better results than dichloromethane. Some interactions between percentage of moisture and the two previous parameters have been demonstrated: the effect of power and nature of solvent depends on the water content. Some optimal conditions have been established: 10 mL of heptane/ethanol (80/20, v/v), extraction time of 2 min, and different possible pairs of moisture content and irradiation power (140 W and 0% of moisture or 20 W and 40% of moisture) according to the need and wish of the experimentalist; or 10 mL of dichloromethane, extraction time of 2 min, 20 W and 40% of moisture. These optimized conditions provide very good recoveries compared to conventional extraction such as Soxhlet (near 100%) for the model matrix (a marine sediment) used for the factorial design. FMW extraction is a good alternative to Soxhlet extraction with reduction of time and reduction of solvent volume. This study shows that it is possible to substitute chlorinated solvent by a less toxic solvent, like a mixture of heptane and ethanol.     

New extraction method for the analysis of linear alkylbenzene sulfonates in marine organisms. Pressurized liquid extraction versus Soxhlet extraction

A new method has been developed for the determination of linear alkylbenzene sulfonates (LAS) from various marine organisms, and compared with Soxhlet extraction. The technique applied includes the use of pressurized liquid extraction (PLE) for the extraction stage, preconcentration of the samples, purification by solid-phase extraction (SPE) and analysis by liquid chromatography with fluorescence detection. The spiked concentrations were added to the samples (wet mass of the organisms: Solea senegalensis and Ruditapes semidecussatus), which were homogenized and agitated continuously for 25 h. The samples were extracted by pressurized hot solvent extraction using two different extraction temperatures (100 and 150 degrees C) and by traditional Soxhlet extraction. The best recoveries were obtained employing pressurized hot solvent extraction at 100 degrees C and varied in the range from 66.1 to 101.3% with a standard deviation of between 2 and 13. Detection limit was between 5 and 15 microg kg(-1) wet mass using HPLC-fluorescence detection. The analytical method developed in this paper has been applied for LAS determination in samples from a Flow-through exposure system with the objective of measuring the bioconcentration of this surfactant.