Determination of adipate plasticizers in poly(vinyl chloride) by microwave-assisted extraction

A new method based on the application of microwave radiation to the extraction of adipate plasticizers from poly(vinyl chloride) PVC plastics is described. The experimental conditions for microwave-assisted extraction (i.e. extracting solvent, temperature, time and microwave power) were evaluated in terms of recovery. The optimisation was carried out with pastes of PVC plastified with di-2-ethylhexyl adipate, and extracts were measured by gas chromatography with flame ionization detection. Six different adipate plasticizers were studied, and microwave-assisted extraction was compared with supercritical fluid extraction for the extraction of adipates and phthalates from PVC matrices. It has been observed that the microwave-assisted extraction parameters evaluated are tightly interconnected. It has been shown that the efficiency of microwave-assisted extraction depends on the kind of solvent, the temperature achieved and the heating time. Moreover, the final temperature reached depends on the microwave power, the number of vessels and the irradiation time. On the other hand, microwave-assisted extraction provides higher recovery values than supercritical fluid extraction for both phthalate and adipate plasticizers.     

Optimization and comparison of MAE, ASE and Soxhlet extraction for the determination of HCH isomers in soil samples

The microwave-assisted extraction (MAE), accelerated solvent extraction (ASE) and Soxhlet extraction of two isomers of hexachlorocyclohexane, alpha-HCH and gamma-HCH, from a polluted landfill soil have been optimized following different experimental designs. In the case of microwave-assisted extraction, the following variables were considered: pressure, extraction time, microwave power, percentage of acetone in n-hexane mixture and solvent volume. When ASE extraction was studied the variables were pressure, temperature and extraction time. Finally, the percentage of acetone in n-hexane mixture and the extraction time were the only variables studied for Soxhlet extraction. The concentrations obtained by the three extraction techniques were, within their experimental uncertainties, in good agreement. This fact assures the possibility of using both ASE and MAE techniques in the routine determination of lindane in polluted soils and sediments.     

Optimization and comparison of MAE, ASE and Soxhlet extraction for the determination of HCH isomers in soil samples

The microwave-assisted extraction (MAE), accelerated solvent extraction (ASE) and Soxhlet extraction of two isomers of hexachlorocyclohexane, α-HCH and γ-HCH, from a polluted landfill soil have been optimized following different experimental designs. In the case of microwave-assisted extraction, the following variables were considered: pressure, extraction time, microwave power, percentage of acetone in n-hexane mixture and solvent volume. When ASE extraction was studied the variables were pressure, temperature and extraction time. Finally, the percentage of acetone in n-hexane mixture and the extraction time were the only variables studied for Soxhlet extraction. The concentrations obtained by the three extraction techniques were, within their experimental uncertainties, in good agreement. This fact assures the possibility of using both ASE and MAE techniques in the routine determination of lindane in polluted soils and sediments. Received: 28 January 2000 / Revised: 28 March 2000 / Accepted: 31 March 2000     

微波辅助-旋转回流提取仪的组装及其在叶下珠有机酸提取中的应用

组装了一种新型的微波辅助旋转回流装置,该装置的基本原理与微波辅助溶剂萃取的原理相同,但采用了旋转的技术以加速提取.应用该装置以正交实验筛选优化叶下珠中有机酸的提取工艺,并利用毛细管电泳技术分离测定了提取液中有机酸的含量以评价提取效果.最佳提取工艺:乙醚为溶剂,微波功率800 W,提取时间4 min,溶剂用量300 mL.在该提取条件下,平行5次提取叶下珠中丁二酸、原儿茶酸、没食子酸、咖啡酸、阿魏酸的平均含量分别为42.2、103.5、436.2、123.8、67.4 μg/g,相对标准偏差为0.87% ～3.7%,加标回收率为94% ～104%.将该法与常规的微波辅助提取法及回流提取法进行比较,结果表明,微波辅助旋转回流提取法提取效率明显优于其它2种方法.     

Comparison of accelerated solvent extraction with microwave-assisted extraction and Soxhlet for the extraction of chlorinated biphenyls in soil samples

The extraction and determination of chlorinated biphenyls (CBs) in soils and solid wastes is an ongoing subject of study. This is an overview article that compares the microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) techniques. The extraction of CBs by ASE has been optimised taking into account the variation of pressure, temperature and extraction time by means of experimental design and the Simplex approach. The recoveries obtained under the optimum conditions are compared and discussed with those obtained from MAE and Soxhlet extractions.     

Microwave-assisted Extraction of Rutin and Quercetin from Flos Sophorae

Three microwave-assisted extraction(MAE) procedures were studied. The first procedure was household microwave oven dynamic extraction(HMODE). The second procedure was special microwave oven bath extraction (SMOBE). The third procedure was microwave resonant cavity dynamic extraction (MRCDE). The results obtained by the three microwave-assisted extraction procedures were compared with those obtained by using traditional Soxhlet extraction. The results indicate that the MAE not only took a shorter time, but also simplified the procedure, and made the extraction a higher yield. At the same time the results obtained by the three MAE procedures were also compared with each other.     

Multiple response optimisation based on desirability functions of a microwave-assisted extraction method for the simultaneous determination of chloroanisoles and chlorophenols in oak barrel sawdust

A microwave-assisted extraction (MAE) method was optimised for extracting 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), pentachloroanisole (PCA), 2,4,6-trichlorophenol (TCP), 2,3,4,6-tetrachlorophenol (TeCP) and pentachlorophenol (PCP) from oak barrels. The method was optimised by using a central composite experimental design with extraction time, temperature and solvent volume as influential parameters. A desirability function was then employed in addition to the simultaneous optimisation of the compounds. The optimal conditions identified were temperature 130 degrees C, solvent volume 35 mL and extraction time 50 min. The compounds were determined by gas chromatography with electron-capture detection. MAE was compared with conventional Soxhlet extraction; the results obtained with MAE were in good agreement with those obtained by Soxhlet extraction.     

Comparison of microwave-assisted extraction of aloe-emodin in aloe with Soxhlet extraction and ultrasound-assisted extraction

This paper reports the extraction of aloe-emodin from aloe by microwave-assisted extraction.The effects of various factors,including the solvent,the ratio (mL/g) of the solvent to the sample,microwave irradiation time and microwave power,were discussed in the experiments.The yield of aloe-emodin was determined by HPLC.The optimized conditions for microwave-assisted extraction of aloe-emodin were concluded as follows: the solvent is 80% ethanol (V/V) solution,microwave irradiation time is 3 min and microwave...     

微波法提取水蓼中总黄酮的工艺研究

研究了水蓼中总黄酮的微波提取最佳工艺。采用单因素试验和正交试验考察微波功率、乙醇浓度、微波辐射时间、料液比对水蓼中总黄酮提取率的影响,优选提取工艺。最佳工艺条件为:微波功率为520W,乙醇浓度为60%,微波辐射60s,间歇辐射3次,料液比为1g∶20mL。结果表明,微波提取具有提取率高、提取速度快等特点,用于中草药的提取应用前景广阔。     

MAE–GC Determination of Methamphetamine, 3,4-Methylenedioxyamphetamine and 3,4-Methylenedioxymethamphetamine in Human Urine

Methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxymethamphetamine (MDMA) were extracted from human urine by using microwave-assisted extraction (MAE) followed by gas chromatography analysis with flame ionization detection. In order to improve the extraction efficiency, experimental parameters on the extraction, including extraction solvent and its volume, pH value of sample, extraction time and temperature were investigated. Under the optimal conditions, the average recoveries of MA, MDA and MDMA were 92.25, 85.94 and 91.50%, respectively. And the intra-day and inter-day relative standard deviations were not greater than 6.9%. The results indicate that the developed method is rapid, accurate and sensitive, and can be used for the simultaneous determination of MA, MDA and MDMA in urine for forensic application.     

Optimization of Microwave-Assisted Extraction for the Determination of Organic Flame Retardants in Acrylonitrile Butadiene Styrene

The efficiency of microwave-assisted extraction was evaluated for the determination of flame retardants in acrylonitrile butadiene styrene by optimization of the temperature, time, and solvent. A quality control sample containing 500 milligrams per kilogram Dechlorane Plus, 1000 milligrams per kilogram tetrabromobisphenol A, and 1000 milligrams per kilogram triphenyl phosphate was employed. The flame retardant concentrations obtained by microwave-assisted extraction at 120 degrees Celsius for ten minutes in tetrahydrofuran were in agreement with those for the quality control sample. The efficiency of microwave-assisted extraction was comparable to ultrasonic and Soxhlet extraction used as reference techniques. In addition, the repeatabilities of the analyses, represented as relative standard deviations, were comparable: 0.8–3.4 percent for microwave-assisted extraction, 0.3–3.3 percent for ultrasonic extraction, and 0.2–8.5 percent for Soxhlet extraction. These results suggest that microwave-assisted extraction is suitable for the determination of Dechlorane Plus, tetrabromobisphenol A, and triphenyl phosphate in acrylonitrile butadiene styrene.     

Comparison of alternative and conventional extraction techniques for the determination of zearalenone in corn

Naturally contaminated corn samples of different origin were extracted using two conventional techniques (blending and shaking) and three alternative approaches (ultrasonic extraction, accelerated solvent extraction, and microwave-assisted extraction). Use of the same extraction mixture for all trials enabled the efficiency of the various extraction techniques to be compared. Extracts were filtered and directly analyzed by LC–ESI–MS, without further clean-up. The yield from the alternative extraction techniques showed efficiency to be higher than for conventional techniques. In particular, microwave-assisted extraction was slightly superior to other techniques.     

A comparative study of solvent extraction of total petroleum hydrocarbons in soil

Three non-specific methods for the extraction of total petroleum hydrocarbons (TPH) from soil into organic solvent were compared. The techniques used for sample preparation were Soxhlet extraction, closed-vessel microwave-assisted extraction, and CEN shake extraction. The total concentrations of extracted compounds in the boiling point range of C10–C40 were determined by gas chromatography with flame ionization detection. The best recovery (99%) and repeatability (±3%) from standard oil mixtures were obtained with microwave-assisted extraction. However, the different extraction methods exhibited different behaviour when spiked soil samples were extracted. The best repeatability was obtained with CEN shake extraction (±6%) but the repeatability values for Soxhlet and microwave-assisted methods were quite high (>20%). However, the larger uncertainties of the latter extraction methods does not necessarily limit the applicability of these methods to the determination of petroleum hydrocarbons in soil, as in the assessment of soil contamination the expanded uncertainty of the result is usually not limited by analytical uncertainty, but rather by the uncertainty of the primary sampling stage. However, distinctive variation found in the chromatographic profiles illustrates that discretion should be obeyed when chromatograms obtained after application of different extraction methods on petroleum contaminated samples are to be used in the fingerprinting or age dating studies. Otherwise, misleading conclusions concerning the age of spillage could be drawn.     

Microwave-assisted extraction and large-volume injection gas chromatography tandem mass spectrometry determination of multiresidue pesticides in edible seaweed

A microwave-assisted extraction method followed by clean-up with solid-phase extraction (SPE) combined with large-volume injection gas chromatography–tandem mass spectrometry (LVI-GC-MS/MS) for the analysis of 17 pesticides in wild and aquaculture edible seaweeds has been developed. An experimental central composite design was employed to evaluate the effects of the main variables potentially affecting the extraction (temperature, time, and solvent volume) and to optimize the process. The most effective microwave extraction conditions were achieved at 125 °C and 12 min with 24 mL of hexane/ethyl acetate (80:20). SPE clean-up of the extracts with graphitized carbon and Florisil, optimized by means of the experimental design, proved to be efficient in the removal of matrix interferences. The analytical recoveries were close to 100% for all the analytes, with relative standard deviations lower than 13%. The limits of detection ranged from 0.3 to 23.1 pg g⁻¹ and the limits of quantification were between 2.3 and 76.9 pg g⁻¹, far below the maximum residue levels established by the European Union for pesticides in seaweed. The results obtained prove the suitability of the microwave-assisted extraction for the routine analysis of pesticides in aquaculture and wild seaweed samples.     

Microwave-assisted extractions of active ingredients from plants

Microwave-assisted extraction (MAE) is widely employed in the analysis and the extraction of active compounds from plants. This review summarizes the research done during the last decade on the MAE of active ingredients from plants. Advances and modifications to improve the performance of MAE are presented and discussed in detail. Modified MAE such as vacuum microwave-assisted extraction (VMAE), nitrogen-protected microwave-assisted extraction (NPMAE), ultrasonic microwave-assisted extraction (UMAE), dynamic microwave-assisted extraction (DMAE) and other advancements in MAE are also detailed in this article. In addition, the microwave extraction procedures and the important parameters influencing its performance are also included, together with the advantages and the drawbacks of each MAE techniques.     

微波辅助-旋转回流提取叶下珠中的没食子酸

A new kind of microwave-assisted circumrotation reflux extraction device was constructed and used to study the extraction technology of gallic acid from phyllanthus urmaria L.The extraction principle of the device was same as that of microwave-assisted solvent extraction but using circumrotation techniques as auxiliary stirrer to accelerate the process.Capillary electrophoresis was used to determinate gallic acid in phyllanthus urmaria L extracts in order to evaluate the extraction efficiency of the method.It was found that the most important factors influencing extraction gallic acid were solvent kind and microwave power.The optimum extraction conditions were as follows:water using as irradiate time 4 minute.Under the optimum extraction conditions,five experiments were carried out and the average extraction rate of gallic acid in phyllanthus urmaria L was 4.32 mg/g,relative standard deviations (R.S.D.) was 2.2%.Compared with other extraction methods e.g.reflux extraction and microwave-assisted extraction,better extraction efficiency was observed for the microwave-assisted circumrotation reflux extraction.     

Microwave-assisted extraction performed in low temperature and in vacuo for the extraction of labile compounds in food samples

In this study, low temperature vacuum microwave-assisted extraction, which simultaneous performed microwave-assisted extraction (MAE) in low temperature and in vacuo environment, was proposed. The influencing parameters including solid/liquid ratio, extraction temperature, extraction time, degree of vacuum and microwave power were discussed. The predominance of low temperature vacuum microwave-assisted extraction was investigated by comparing the extraction yields of vitamin C, β-carotene, aloin A and astaxanthin in different foods with that in MAE and solvent extraction, and 5.2–243% increments were obtained. On the other hand, the chemical kinetics of vitamin C and aloin A, which composed two different steps including the extraction step of analyte transferred from matrix into solvent and the decomposition step of analyte degraded in the extraction solvent, were proposed. All of the decomposition rates (K₂) for the selected analyte in low temperature, in vacuo and in nitrogen atmosphere decreased significantly comparing with that in conventional MAE, which are in agreement with that obtained from experiments. Consequently, the present method was successfully applied to extract labile compound from different food samples. These results showed that low temperature and/or in vacuo environment in microwave-assisted extraction system was especially important to prevent the degradation of labile components and have good potential on the extraction of labile compound in foods, pharmaceutical and natural products.     

Extraction and quantification of antioxidants from low-density polyethylene by microwave energy and liquid chromatography

In this paper a experimental design is applied to optimize the quantification of hindered phenol Irganox 1076, phosphite antioxidant Irgafos 168 and their oxidized product tri[2,4-di-tert-butylphenyl]phosphate from low-density polyethylene (LDPE). The developed analytical method consists of two steps: microwave-assisted extraction and reversed-phase liquid chromatography (LC) coupled with ultraviolet diode-array detector. A Plackett-Burman design was carried out in order to find the significant experimental parameters affecting the antioxidants extraction by microwave energy. These parameters were subsequently optimized by a central composite design. The performed method allows extracting the studied antioxidants at low temperature in a short time without degradation of phosphite antioxidant Irgafos 168.     

Microwave-assisted extraction of tricyclic antidepressants from human serum followed by high performance liquid chromatography determination

A microwave-assisted extraction (MAE) method has been developed and optimized for the extraction of six tricyclic antidepressants (TCAD; nordoxepin, nortriptyline, imipramine, amitriptyline, doxepin, dezypramine) from human serum. Optimal parameters of MAE (solvent and extraction temperature) for water solution of these drugs were defined. The microwave-assisted procedure developed was validated by extraction of serum samples at two concentration levels and then successfully applied to the analysis of reference material. Limit of quantification, precision and recovery were found for the studied compounds in the ranges 0.04-0.15 microg/mL, 1.57-4.34% (RSD) and 94-105%, respectively.     

微波辅助萃取鬼箭羽叶中芦丁和槲皮素

建立了鬼箭羽中主要有效成分芦丁和槲皮素的MAE-HPLC定量分析方法, 该方法具有测定准确、操作简便和分析速度快等优点. 此外, 利用扫描电镜观察了鬼箭羽叶经微波辅助萃取后植物结构的变化, 初步证明了微波辅助萃取鬼箭羽叶的萃取机理符合细胞破壁学说.