Optimization of the extraction of paclitaxel from Taxus baccata L. by the use of microwave energy

A simple and rapid microwave-assisted extraction (MAE) procedure was developed and optimized for the extraction of paclitaxel (Taxol) from the needles of yew trees Taxus baccata L. grown in Iranian habitats. The samples, immersed in a methanol-water mixture, were irradiated with microwaves in a closed-vessel system. The method was evaluated using a factorial design approach based on parameters such as extraction time, temperature, methanol concentration in water (v/v), and the ratio of grams of sample to 10 mL of solvent. Statistical treatment of the results revealed that the selected parameters were all significant except the extraction time. Optimum conditions would be 1.5 g samples in 10 mL solvent (90% methanol), an extraction temperature of 95 degrees C, and an extraction time of 7 min. The extracts has been analyzed by reverse-phase high-performance liquid chromatography with UV detection (LC/UV) at 227 nm for quantification. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for confirmation. The main advantage of the proposed MAE method versus conventional solvent extraction (CSE) are the considerable reductions in time (7 min versus 16 h) and in solvent consumption (20 mL versus 150 mL). The MAE procedure yielded extracts that could be analyzed directly without any preliminary clean-up or solvent exchange steps. Both extraction methods show RSDs lower than 10% and lead to comparable recoveries of paclitaxel (87-92%).     

Optimization of microwave-assisted solvent extraction for volatile organic acids in tobacco and its comparison with conventional extraction methods

In the present study, a new method using microwave-assisted solvent extraction (MASE) technique followed directly GC analysis was developed for the extraction of volatile organic acids (VOAs) in tobacco. The MASE conditions (heating time, volume of extracting solvent and extraction temperature) were optimized by means of an orthogonal array design (OAD) procedure. The results suggested that extractant, temperature and heating time were statistically the most significant factors. The extracts were directly analyzed with capillary GC operating in splitless-injection mode on an Agilent HP-FFAP capillary column. Under optimum operating conditions, MASE showed significantly better recoveries than those obtained by the conventional extraction method (ultrasonic and reflux extraction), ranging from 90.6% to 103.2%. In addition, a drastic reduction of the extraction time (20 min versus 4 h) and solvent consumption (20 mL versus 100 mL) was achieved with an outstanding reproducibility (CV ≤5%).     

Application of water as a solvent in microwave-assisted extraction for analysis of PCBs and CBzs in fly ash

Polychlorinated biphenyls (PCBs) and chlorobenzenes (CBzs) are two classes of dioxin precursors formed in municipal solid waste incinerators (MSWIs); they produce negative health effects similar to those of dioxins. Reducing the analytical time required for determining the concentrations of these compounds in MSWIs is important for quickly evaluating their importance and assessing associated health risks. In the present study, water is used as a safe and environmentally friendly solvent in microwave-assisted extraction (MAE) for PCB and CBz analyses. MAE is compared with traditional Soxhlet extraction (SE) to determine the extraction efficiencies. The evaluation of extraction efficiencies shows that MAE has a high extraction efficiency compared with that of SE when water content is lower than 60%. Furthermore, the extraction time and organic solvent consumption are reduced with MAE compared with SE.     

Optimization of microwave‐assisted extraction of analgesic and anti‐inflammatory drugs from human plasma and urine using response surface experimental designs†

The performance of microwave‐assisted extraction and HPLC with photodiode array detection method for determination of six analgesic and anti‐inflammatory drugs from plasma and urine, is described, optimized, and validated. Several parameters affecting the extraction technique were optimized using experimental designs. A four‐factor (temperature, phosphate buffer pH 4.0 volume, extraction solvent volume, and time) hybrid experimental design was used for extraction optimization in plasma, and three‐factor (temperature, extraction solvent volume, and time) Doehlert design was chosen to extraction optimization in urine. The use of desirability functions revealed the optimal extraction conditions as follows: 67°C, 4 mL phosphate buffer pH 4.0, 12 mL of ethyl acetate and 9 min, for plasma and the same volume of buffer and ethyl acetate, 115°C and 4 min for urine. Limits of detection ranged from 4 to 45 ng/mL in plasma and from 8 to 85 ng/mL in urine. The reproducibility evaluated at two concentration levels was less than 6.5% for both specimens. The recoveries were from 89 to 99% for plasma and from 83 to 99% for urine. The proposed method was successfully applied in plasma and urine samples obtained from analgesic users.     

Isolation of fucoxanthin from edible brown algae by microwave-assisted extraction coupled with high-speed countercurrent chromatography

A rapid and efficient method for the separation and purification of fucoxanthin from edible brown algae by microwave-assisted extraction coupled with high-speed countercurrent chromatography was developed. The algae were first extracted using microwave-assisted extraction, then the dried extract was dissolved and directly introduced into the high-speed countercurrent chromatography system with a two-phase solvent system consisting of hexane-ethyl acetate-ethanol-water (5:5:6:4, v/v/v/v). The isolation was done in less than 75 min, and a total of 0.83 mg, 1.09 mg, and 0.20 mg fucoxanthin were obtained from 25.0 g fresh Laminaria japonica Aresch, 1.5 g dry Undaria pinnatifida (Harv) Sur, and 15.0 g dry Sargassum fusiforme (Harv) Setch, respectively. The purity of fucoxanthin determined by HPLC was over 90% and its structure was further identified by LC-ESI-MS and (1) H-NMR.     

Determination of dieldrin in wool products by gas chromatography with microwave-assisted extraction

Dieldrin is a moth-proofing agent that was banned by the Stockholm Convention in 2001. The amount of dieldrin in wool products was measured by a microwave-assisted extraction (MAE) method. The optimal conditions were as follows: extraction solvent, acetone/n-hexane (1:1 v/v); extraction temperature, 110 degrees C; extraction time, 10 min; solvent volume, 25 mL. When six samples were used, dieldrin contents determined by GC with the proposed MAE agreed closely with those by the Japanese official method using GC with solvent extraction and cleanup by column chromatography. The proposed MAE has two merits. First, the pretreatment of the MAE needs only 4 h for 11 samples, while that using the Japanese official method needs 2 days for six samples. Second, the volume of organic solvents used for the proposed method was only about one-tenth of that used in the Japanese official method. Our proposed method seems to be easy and useful for daily (routine) tests. Dieldrin contents of 28 used wool products, which were obtained from local clothing shops and ordinary homes, were determined by GC with the proposed MAE, and six products contained dieldrin (0.310-175 ppm). The dry cleaning of the woolen yarn containing 175 ppm dieldrin did not remove a significant amount of dieldrin. Therefore, it seems likely that dieldrin is still distributed slightly but widely throughout the world.     

Comparison of extraction methods for sampling of low molecular compounds in polymers degraded during recycling

The demand for mechanical recycling of plastic waste results in an increasing amount of recycled polymeric materials available for development of new products. In order for recycled materials to find their way into the material market, high quality is demanded. Thereby, a complete and closed loop of polymeric materials can be achieved successfully. The concept of high quality for recycled plastics imply that besides a pure fraction of e.g. polyethylene (PE) or polypropylene (PP), containing only minor trace amount of foreign plastics, knowledge is required about the type and amount of low molecular weight (LMW) compounds. During long-term use (service-life), products made of polymeric materials will undergo an often very slow degradation where a series of degradation products are formed, in parallel, additives incorporated in the matrix may also degrade. These compounds migrate at various rates to the surrounding environment. The release rate of LMW products from plastics depends on the initiation time of degradation and the degradation mechanisms. For polymers the formation of degradation products may be initiated already during processing, and subsequent use will add products coming from the surrounding environment, e.g. fragrance and aroma compounds from packaging. During recycling of plastics, emissions which contain a series of different LMW compounds may reach the environment leading to unwanted exposure to additives and their degradation residues as well as degradation products of polymers.Several extraction techniques are available for sampling of LMW compounds in polymers before chromatographic analysis. This paper reviews and compares polymer dissolution, accelerated solvent extraction (ASE), microwave assisted extraction (MAE), ultrasound assisted extraction (UAE), super critical fluid extraction (SFE), soxhlet extraction, head-space extraction (HS), head-space solid phase micro extraction (HS-SPME), and head-space stir bar sorptive extraction (HSSE) as appropriate sampling methods for LMW compounds in recycled polymers. Appropriate internal standards useful for these kinds of matrices were selected, which improved the possibility for later quantification. Based on the review of extraction methods, the most promising techniques were tested with industrially recycled samples of HDPE and PP and virgin HDPE and PP for method comparison.     

Alkaline extraction in combination with microwave-assisted extraction followed by solid-phase extraction treatment for polycyclic aromatic hydrocarbons in a sediment sample

Microwave-assisted extraction using 1 M KOH/methanol (alkaline-MAE) in combination with solid-phase extraction treatment was developed and applied to polycyclic aromatic hydrocarbons (PAHs) in a sediment sample. Although various conditions were examined (100 or 150 °C for 10 or 30 min), comparable concentrations of PAHs to those obtained by conventional extraction with 1 M KOH/methanol at 70 °C for 4 h were obtained, even at 100 °C for 10 min. The concentrations obtained by using MeOH at 150 °C for 30 min without KOH were lower (by 1.3-37%) than those obtained by alkaline-MAE at 150 °C for 30 min. Since the developed technique can introduce higher concentration of benzo[ghi]perylene relative to those using pressurized liquid extraction (toluene, 150 °C, 15 MPa, 10 min, two cycles), the developed alkaline-MAE is a effective technique.     

Fast microwave‐assisted extraction of rotenone for its quantification in seeds of yam bean (Pachyrhizus sp.)

The aim of this study was to find if fast microwave‐assisted extraction could be an alternative to the conventional Soxhlet extraction for the quantification of rotenone in yam bean seeds by SPE and HPLC‐UV. For this purpose, an experimental design was used to determine the optimal conditions of the microwave extraction. Then the values of the quantification on three accessions from two different species of yam bean seeds were compared using the two different kinds of extraction. A microwave extraction of 11 min at 55°C using methanol/dichloromethane (50:50) allowed rotenone extraction either equivalently or more efficiently than the 8‐h‐Soxhlet extraction method and was less sensitive to moisture content. The selectivity, precision, trueness, accuracy, and limit of quantification of the method with microwave extraction were also demonstrated.     

Isolation and purification of lignans from Magnolia biondii Pamp by isocratic reversed-phase two-dimensional liquid chromatography following microwave-assisted extraction

The dried flower buds of Magnolia biondii Pamp are one of the most widely used medicinal plants officially listed in the Chinese Pharmacopoeia. A 2-D column-switching system without sample loop trapping, where two columns were switched directly via a six-port two-position switching valve, was successfully applied for the first time to the isolation and purification of five lignans including pinoresinol dimethyl ether, magnolin, epi-magnolin A, fargesin, and demethoxyaschantin from M. biondii Pamp after microwave-assisted extraction. The introduction of the six-port switching valve instead of sample loop assured 100% recovery from the first dimension to the second, and the injection volumes of the second dimension could reach 12 mL. In this mode of operation, the solvent consumption of the 2-D approach was less than 30% that of conventional gradient methods with even larger sample size. The simultaneous operations of the two dimensions allowed the cycle time to be less than 16 min, compared to 90 min in the gradient elution single-dimension mode of operation. All of the five lignans were isolated at high purities of over 99% with approximately 95% recoveries.     

Separation and purification of furanocoumarins from Toddalia asiatica (L.) Lam. using microwave-assisted extraction coupled with high-speed counter-current chromatography

A method of microwave-assisted extraction coupled with high-speed counter-current chromatography was established for separation and purification of isopimpinellin, pimpinellin and phellopterin from Toddalia asiatica (L.) Lam. The conditions of MAE including the extraction solvent, size of sample, solid/liquid ratio, extraction temperature and extraction time were optimized by a mono-factor test. That is, 2.0 g dried powder of T. asiatica (L.) Lam of 0.30-0.15 mm size was extracted with 20 mL (solid/liquid ratio of 1:10, g/mL) methanol under 50 °C for 1 min. The crude extract was separated and purified by high-speed counter-current chromatography with hexane-ethyl acetate-methanol-water (5:5:5.5:4.5, v/v/v/v) solvent system. 0.85 mg/g of isopimpinellin, 2.55 mg/g of pimpinellin and 0.95 mg/g of phellopterin were obtained from original sample in one-step within 240 min, the purity determined by high performance liquid chromatography was 95.0%, 99.1% and 96.4%, respectively. Their chemical structures were further identified by mass spectroscopy and nuclear magnetic resonance spectroscopy. The results demonstrated that microwave-assisted extraction coupled with high-speed counter-current chromatography was a feasible, economical and efficient technique for rapid extraction, separation and purification of effective compounds from natural products.     

微波辅助萃取气相色谱-质谱联用测定蔬菜中的扑草净

研究了微波辅助萃取气相色谱．质谱联用测定植物样品中扑草净的方法，比较了几种不同溶剂的微波萃取效率，从而选取二氯甲烷为萃取溶剂，并采用三因素三水平的正交设计试验对溶剂体积、微波辐射时间、微波功率进行了优化。在优化的实验条件下分析了合成菠菜样品，对0．2μg/g和0．02μg/g的合成菠菜样品，回收率分别为99．5％和92．5％，相对标准偏差分别为5．0％和ll％，方法的线性范围为1．0—400ng／g，检出限为0．22ng／g。方法适合于分析植物样品中的扑草净。     

密闭微波辅助萃取天麻中天麻素的研究

应用密闭微波萃取装置,对中药天麻中有效成分天麻素的萃取进行了研究。分别讨论了药材颗粒粒径、提取溶剂浓度、微波提取时间和提取剂的用量对微波萃取天麻素的影响。结果表明:当药材粒径<50μm,乙醇体积分数为50%,微波辐射时间为2min,提取剂质量为药材质量的30倍时,天麻素提取率最高。此外,将微波萃取与索氏萃取和超声波萃取进行了比较。     

Analysis of polycyclic aromatic hydrocarbons in atmospheric particulate samples by microwave‐assisted extraction and liquid chromatography

A methodology based on microwave‐assisted extraction (MAE) and LC with fluorescence detection (FLD) was investigated for the efficient determination of 15 polycyclic aromatic hydrocarbons (PAHs) regarded as priority pollutants by the US Environmental Protection Agency and dibenzo(a,l)pyrene in atmospheric particulate samples. PAHs were successfully extracted from real outdoor particulate matter (PM) samples with recoveries ranging from 81.4 ± 8.8 to 112.0 ± 1.1%, for all the compounds except for naphthalene (62.3 ± 18.0%) and anthracene (67.3 ± 5.7%), under the optimum MAE conditions (30.0 mL of ACN for 20 min at 110°C). No clean‐up steps were necessary prior to LC analysis. LOQs ranging from 0.0054 ng/m³ for benzo(a)anthracene to 0.089 ng/m³ for naphthalene were reached. The validated MAE methodology was applied to the determination of PAHs from a set of real world PM samples collected in Oporto (north of Portugal). The sum of particulate‐bound PAHs in outdoor PM ranged from 2.5 and 28 ng/m³.     

Optimization and validation of a low temperature microwave-assisted extraction method for analysis of polycyclic aromatic hydrocarbons in airborne particulate matter

A low temperature microwave-assisted extraction method (MAE) is reported for the analysis of polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matter (PM). The main parameters affecting the extraction efficiency (choice of extractants, microwave power, and extraction time) were investigated and optimized. The optimized procedure requires a 20 ml mixture of acetone:n-hexane (1:1) for extraction of PAHs in PM at 150 W of microwave energy (20 min extraction time). Clean-up of MAE extracts was not found to be necessary. The optimized method was validated using two different SRM (1648-urban particulate matter and 1649a, urban dust). The results obtained are in good agreement with certified values. PAHs recoveries for both reference materials were between 79 and 122% with relative standard deviation ranging from 3 to 21%. Detection limits were determined based on blank determination using two kinds of quartz filter substrates (n = 10), which ranged from 0.001 (0.03) ng m⁻³ (pg/μg) for B(k)Ft to 1.119 (37.3) for Naph in ng m⁻³ (pg/μg), respectively. The repeatability and day-to-day reproducibility obtained in this study were in the range of 4-16 and 3-25% for spiked standards and SRM 1649, respectively. The optimized and validated MAE technique was applied to the extraction of PAHs from a set of real world PM samples collected in Singapore. The sum of particulate-bound PAHs in outdoor PM ranged from 1.05 to 3.45 ng m⁻³ while that in indoor PM (cooking emissions) ranged from 27.6 to 75.7 ng m⁻³, respectively.     

Determination of alachlor, metolachlor, and their acidic metabolites in soils by microwave-assisted extraction (MAE) combined with solid phase extraction (SPE) coupled with GC-MS and HPLC-UV analysis

A well-validated analytical method based on microwave-assisted extraction (MAE) and SPE is presented for the combined analysis of alachlor, alachlor-oxanilic acid (OXA), alachlor-ethanesulfonic acid (ESA), metolachlor, metolachlor-OXA, metolachlor-ESA residues in soils. Extraction of solutes by soil sample was carried out by MAE for 20 min at 100 degrees C in the presence of 50 mL solution (methanol/water 50:50), the extract was subsequently passed through C18 cartidges and fractionated into two fractions, the first with parent compounds (PCs) analyzed with GC-MS and the second one containing the metabolites analyzed with HPLC. For the SPE step, various types of sorbents (Environmental C18, tC18, Supelclean ENVI-carb, and LiChrolut EN) have been used, and their respective advantages and disadvantages are discussed. After the method optimization, average recovery values of all solutes were > 71% in the 50-500 microg/kg fortification range with RSD <10%. The LOQ and LOD were 10-50 and 5-10 microg/kg, respectively. The method was validated with two types of soils (1 and 2.4% organic matter) and in fresh (12 h aging), intermediate (1 wk aging), and aged (1 month aging) spiked samples. Moreover, residue levels determined after field application of alachlor or metolachlor were higher when soils were processed using this method than with a comparison method based on an overnight flask shaking (FS) of soil suspension.     

Automatic sample preparation of sulfonamide antibiotic residues in chicken breast muscle by using dynamic microwave-assisted extraction coupled with solid-phase extraction

In the work, a rapid, simple and high-throughput sample preparation method was developed for the determination of sulfonamide (SA) antibiotic residues in chicken breast muscle. The extraction and clean-up were online combined and up to 20 samples can be treated simultaneously in 6 min. The SAs were first extracted with acetonitrile under the action of microwave energy, and then the extract was directly introduced into the SPE column for on-line clean-up and concentration. Subsequently, the SAs eluted from the SPE column were determined by liquid chromatography-tandem mass spectrometry. The precisions of extraction results of 20 samples were in the range of 4.9-7.4%. The limits of detection and quantification obtained were in the range of 2.4-3.6 ng/g and 8.6-11.3 ng/g for SAs, respectively. The recoveries of SAs obtained by analyzing chicken muscles at three fortified levels (10, 50 and 500 ng/g) were in the range of 82.6-93.2%. The results of the validation process prove that the proposed method is suitable for treating numbers of complex samples simultaneously in a short time.     

Accurate quantification of polycyclic aromatic hydrocarbons in dust samples using microwave-assisted solvent extraction combined with isotope-dilution mass spectrometry

For accurate quantification of polycyclic aromatic hydrocarbons (PAHs) in dust samples, we investigated the use of microwave-assisted solvent extraction (MAE) combined with isotope-dilution mass spectrometry (IDMS) using deuterium-labelled PAHs (D-PAHs). Although MAE with a methanol/toluene mixture (1:3 by volume) at 160 °C for 40 min was best for extracting PAHs from tunnel dust among examined, the recovery yields of D-PAHs decreased with increasing molecular weight (<40% for MW ≥ 264; that of deuterium-labelled indeno[123-cd]pyrene (D-IcdP) was only 7.1%). Although the residues were extracted a second time, the observed concentrations did not change dramatically (<5%), and the recovery yields of heavier D-PAHs (i.e., MW ≥ 264) were approximately half of those of the first extract, including D-IcdP (3.4%). These results suggest that both partitioning and isotopic equilibria of PAHs and D-PAHs between sample and solvent were achieved for extractable heavier PAHs under the condition. Thus, the observed concentrations of PAHs obtained by MAE–IDMS were reasonable, even though recovery yields of D-PAHs were <50%. From the results of carbon analyses and extractable contents, lower recovery yields of D-PAHs from the tunnel dust were due to a large content of char with low extractable contents.     

微波辅助-顶空液相微萃取在线联用-高效液相色谱法测定环境水样中的敌敌畏

基于微波辅助-顶空液相微萃取联用(MAE-HS-LPME)这一样品前处理方法,采用高效液相色谱法(HPLC)对水样中的敌敌畏残留量进行了测定。对影响萃取的因素如萃取剂、微波辐射功率、萃取时间、离子强度和样品基质的pH值等进行了考察。萃取条件为: 选用二甲苯作萃取剂,萃取时间为15 min,微波辐射功率300 W,NaCl含量为5%,pH为2.5。在最佳条件下,敌敌畏的检出限(信噪比为3时)为0.96 μg/L,定量限(信噪比为10时)为3.20 μg/L,萃取富集倍数为54,实际水样的加标回收率为87.4%～103%。与传统的前处理方法相比,本方法具有简便、快速、高效、节省溶剂、选择性好、应用范围广的特点。     

Simultaneous extraction and determination of free and conjugated phytosterols in tobacco

Acid hydrolysis and alkaline saponification were incorporated into a microwave‐assisted extraction process for the simultaneous extraction of free and conjugated phytosterols from tobacco. The crude extract of the microwave‐assisted extraction was purified by C₁₈ solid‐phase extraction and then determined by high‐performance liquid chromatography. Phytosterols of cholesterol, ergosterol, stigmasterol, campesterol, and β‐sitosterol were determined by chromatographic quantification. The multiple parameters of microwave‐assisted extraction were optimized by a uniform design method. The optimal ratio of extraction ethanol solvent to tobacco mass was 30 mL/g. The microwave‐assisted extraction acid hydrolysis was carried out in sulfuric acid medium by heating for 10 min at 55°C. The microwave‐assisted extraction alkaline saponification was performed after adding excessive sodium hydroxide by heating another 10 min. The repeatability of the proposed method was acceptable with recoveries from 69.68 to 88.17% for the phytosterols. Five target phytosterols were all found in the tobacco samples, and the contents were significantly different in samples from different producing areas.