Solvent-free Microwave-assisted Extraction Research Articles

Phytochemical and Pharmacological Properties of a Traditional Herb, Strobilanthes Cusia (Nees) Kuntze.

The present investigation aimed to determine the effectiveness of bioactive components extracted from Hom herbs (Strobilanthes cusia (Nees) Kuntze) using the solvent-free microwave-assisted extraction (MAE) method. The obtained bioactive components were analyzed for total phenolic content (TPC) and active ingredient content. The Hom extracts were examined for antioxidant, antibacterial, anti-inflammatory, cytotoxic, and anticancer activities. The comparative analysis of extraction methods MAE was studied by using different solvents such as ethanol (EtOH), 50% ethanol (50EtOH) and distilled water (DW). The results obtained by the MAE method with DW as solvent show the TPC of 104.41±1.36mg GAE/g crude and tryptanthrin 0.1138±0.0014mg/g crude and indigo 0.0622±0.0015mg/g crude. Comparatively, values ​​detected in the 50% EtOH extract were not significantly different at the 95% confidence level. At the same time, levels of indirubin were detected at levels equivalent to that of ethanol extracts. The DW extract from MAE had an IC50 value against the DPPH scavenging assay of 0.1927±0.0756mg/ml, comparable to the test results of extracts of ethanol and 50% ethanol. The bioactive extracted using the MAE with water as solvent had minimum inhibitory concentration (MIC) and could suppress infection at 10mg/disc. It was also observed that the extracts from the conventional extraction technique using ethanol as the solvent continued to be highly effective against Bacillus cereus even after employing the EtOH or 50% EtOH. Hom extract's MIC value representing inhibiting B. cereus was 0.625mg/disc. Still, EtOH-extracted Hom demonstrated the highest cytotoxicity against 16HBEo- by reducing cell survival rate by less than 50% while the others did not. Interestingly, Hom that had been extracted using 50EtOH and DW with MAE had an anticancer impact on A549 by reducing the survival rate in a dose-dependent manner.

Chemical composition and antifungal activity of Cinnamomum camphora chvar. Borneol essential oil obtained using solvent-free microwave-assisted method

Cinnamomum camphora chvar. Borneol is an important commercial tree species in China as its essential oil contains abundant endo-borneol. Hydrodistillation (HD) is a mainstream technique for the separation of C. camphora chvar. Borneol essential oil. The shortcomings of HD include low extraction efficiency, high energy consumption, and long extraction time, emphasizing the need for the application of a fast and efficient procedure for recovering C. camphora chvar. Borneol essential oil. To determine the optimal conditions for the effective extraction, solvent-free microwave-assisted extraction (SFME) was used in conjunction with the Box-Behnken response surface design. The optimal conditions resulted in a maximum essential oil yield of 42.03 ± 1.56 mg/g. These results showed that SFME is an efficient, green, and economical method for obtaining essential oil with a higher proportion of endo-borneol compared to HD. Furthermore, C. camphora chvar. Borneol essential oil exhibited remarkable inhibitory activity against the five Fusarium spp. species that cause potato dry rot. The results could provide useful information regarding the comprehensive utilization of C. camphora chvar. Borneol essential oil as a new botanical pesticide in agriculture and food production.

Optimization of solvent-free microwave-assisted extraction of antioxidant compounds from Lagenaria siceraria fruit by response surface methodology

Abstract Lagenaria siceraria (bottle gourd) fruit is highly celebrated for its nutritional as well as therapeutic properties. The present study was undertaken with the aim of exploring an efficient green solvent-free microwave-assisted extraction method for bioactives from this fruit. Optimization was done according to response surface methodology (RSM), where microwave power (W) and time (s) were independent factors, and percent extraction yield, total phenolic content (TPC), total flavonoid content (TFC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant potential (FRAP) and iron chelating activity (ICA) were the responses. TPC, TFC, DPPH radical scavenging activity, FRAP and ICA were highest at 480 W and 60 s. The TPC was 288.9 mg GAE · g−1 DW (milligram gallic acid equivalent per gram dry weight), TFC was 214.1 mg RE · g−1 (rutin equivalent per gram DW), anti-radical activity was 32.96%, FRAP was 289.7 mg AAE · g−1 (mg ascorbic acid equivalents per gram) and ICA was 19.52%. The results of the study thus demonstrate that the solvent-free microwave-assisted extraction method, which utilised an optimum power of 480 W and a time of 60 s, is an effective and green method for extraction of antioxidant compounds from bottle gourd fruit.

Solvent-Free Microwave-Assisted Extraction of Volatile Organic Compounds from Ananas comosus (Pineapple) Waste and Possible Skincare Products Development

Solvent-Free Microwave-Assisted Extraction (SFME) is a green analytical technique that uses no organic solvent in the extraction process. A significant amount of fruit waste such as seeds, rinds and peels are discarded daily by food processing operations, causing many environmental concerns. As an alternative approach to fruit-specific waste minimization, including pineapple waste, those fruit waste can be used to recover potentially valuable Volatile Organic Compounds (VOCs) to utilize as value-added products. This study aims to extract VOCs from different parts of matured pineapple fruit waste, including core and peel, for skincare products development. This process uses SFME to extract VOCs from pineapple waste. Extractions were performed at three different experimental conditions by varying microwave power and extraction time of 300 W for 15 min, 500 W for 10 min, and 700 W for 5 min, respectively. The highest yield of 47.20% was obtained for the extraction performed with 500 W power and 10 min extraction time. Volatile Organic Compounds extracted by SFME were identified and characterized using gas chromatography-mass spectroscopy (GC/MS). Major VOCs extracted from the pineapple waste include Heptadecane, γ-dodecalactone, Hexadecane, γ-decalactone and Decanal. However, the highest VOCs were found in the pineapple core over the peel. Extracted VOCs were used to formulate a moisturizing cream and tested for its organoleptic properties, pH and spreadability. Result suggests favourable organoleptic properties such as white to off-white, non-greasy and no phase separation. The formulated moisturizing cream was able to retain the pH of 6.32±0.01 at the temperature of 27±2 ℃, and the spreadability of 4.76±0.11. Findings of the study reveal that SFME extracted VOCs of pineapple waste show promising potential in natural skincare products development.
 Keywords: Pineapple waste, Volatile Organic Compounds, Solvent-free Microwave-Assisted Extraction, GC-MS, Moisturizing cream

Green extraction of hemp (Cannabis sativa L.) using microwave method for recovery of three valuable fractions (essential oil, phenolic compounds and cannabinoids): a central composite design optimization study.

Solvent-free microwave-assisted extraction (MAE) is a green extraction method capable of boosting the yield and quality profile of hemp essential oil when compared with other conventional extraction techniques. During this process, two by-products are produced, namely the aqueous residue containing bioactive phenolics and the residual deterpenated biomass, which can be used for further extraction and purification of phytocannabinoids. To date, the hemp industry has not utilized these products, although they can be valuable for the food, cosmetic, nutraceutical and pharmaceutical market. This study assessed and optimized the variables affecting MAE efficiency, namely microwave irradiation power, extraction time and added water, which were studied using a central composite design approach, and results were used to optimize the extraction process for recovering three valuable fractions: essential oil, polyphenols and phytocannabinoids. The products obtained using the optimized conditions were characterized in terms of yield, chemical profile and antioxidant potential. Moreover, the by-products obtained during the optimized run were further analyzed in terms of their biological activity using both enzymatic and non-enzymatic assays. The aqueous residue demonstrated a powerful α-glucosidase inhibition, a good activity in terms of superoxide radical scavenging activity, a modest efficacy in terms of inhibition of advanced glycation end products formation and no activity in terms of lipase inhibition. The residual deterpenated biomass did not possess significant biological activity. This work demonstrated valorization of industrial hemp essential oil and its by-products, obtained by a sustainable and eco-friendly extraction method, through an almost waste-free approach. Cannabinoids as well as other valuable bioactive compounds such as glycosidic flavones may be recovered from the residues of the essential oil extraction, representing interesting substances in the pharmaceutical, cosmetic and nutraceutical fields. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Cinnamomum camphora fruit peel as a source of essential oil extracted using the solvent-free microwave-assisted method compared with conventional hydrodistillation

In the present study, essential oil from Cinnamomum camphora fruit peel was first separated and characterized by GC-MS. Solvent-free microwave-assisted extraction (SFME) was performed to isolate the essential oil, and the extraction procedure was optimized using a Box–Behnken design. The optimum SFME conditions yielded 80.35 ± 1.88 mg/g of essential oil with 76% moisture content, using a microwave irradiation power of 420 W and an irradiation time of 22 min. No obvious difference was observed between physical constants of essential oil extracted by SFME and hydrodistillation (HD). Scanning electron microscopy micrographs demonstrated more disruption of C. camphora fruit peel cells treated with SFME than by conventional HD. SFME was proposed as an energy-saving, high-efficiency, and environmentally friendly method, as evidenced by its higher yield and volumetric mass transfer coefficient, larger proportions of oxygen compounds, lower consumption of electricity, and lower amounts of CO2 release and water waste compared to conventional HD. The results show that a once-discarded part of C. camphora can be utilized as a source for the production of essential oil.

Solvent-free Microwave-assisted Extraction of Essential Oil and Hydrosol from Piper longum Linn. Fruit and Evaluation of Antioxidant Activities

In this study, essential oil (EO) of Piper longum Linn. fruit was isolated by solvent-free microwave-assisted extraction (SFME) and hydrodistillation (HD) with hydrosols obtained as a by-product. Optimal conditions of SFME to get a maximum EO yield were optimized applying the Box-Behnken design. Chemical compositions and anti-oxidative activities of the obtained EOs and hydrosols were also determined. Results indicated that the maximum isolation rate of EO by SFME under the optimal conditions (microwave irradiation power 572 W, microwave irradiation time 37.37 min, and percentage humidity of the matrix 59.00 %) was 0.75 %, which was significantly higher than 0.50 % by HD method. GC-MS analysis indicated that the EOs isolated by the SFME and HD methods, presented 50 and 36 compounds constituting 95.99 % and 98.52 % of the total peak area, respectively. The principal components of both oils were sesquiterpenes and aliphatics. SFME EO contained more terpenoids than HD EO. The predominant components of SFME and HD hydrosols were eugenol (25.44 % and 22.82 %, respectively) and linalool (14.10 % and 22.37 %, respectively). Trans-isoeugenol, observed for the first time in P. longum fruit, was presented in SFME hydrosol and took up 14.33 % of all the detected compounds. Both the EO and hydrosol extracted by SFME possessed better antioxidant properties than those from the HD method, which indicated that SFME was a superior approach to simultaneously obtain the two products.

Influence of the Isolation Method to the Composition and Antimicrobial and Antioxidative Activity of Winter Savory (Satureja montana L.) Essential Oil

This research aimed to analyse the chemical composition, as well as the antimicrobial and antioxidative abilities of the Satureja montana L. essential oil. Essential oils were obtained from raw plant material by solvent-free microwave-assisted extraction (WSEO1) and dry plant material by microwave-assisted extraction (WSEO2) and hydrodistillation by Clevenger apparatus (WSEO3). The essential oil composition was determined by gas chromatography/mass spectroscopy analysis (GC/MS), while antioxidative activity was determined by DPPH assay. Antimicrobial activity was characterised by the determination of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Proteus vulgaris ATCC 8427 and Klebsiella pneumoniae ATCC 700603. The results indicated that the highest number of different compounds was detected in WSEO2. Aromatic compounds were found to be dominant in WSEO2 and WSEO3 with 47 % and 56 % of total compounds detected, while oxygen-containing monoterpenes with 28 % were dominant in WSEO1. p-Cymene, limonene, cis-sabinene hydrate, carvacrol, thymol and germacrene D were the main compounds present in all essential oil samples. MIC value against all analysed microorganisms was in the range of 1.62-15.52 mg/ml for WSEO1, and 0.20-2.91 mg/ml for both WSEO2 and WSEO3. The EC50 values for WSEO1, WSEO2 and WSEO3 were 3.25, 0.42 and 0.33 mg/ml after 120 min of incubation, respectively. The WSEO2 and WSEO3 showed better antimicrobial and antioxidative activity compared to the WSEO1 probably due to the differences detected in essential oil composition.

Microwave-assisted solvent-free extraction of essential oil from Coleus aromaticus: anti-phytopathogenic potential for fruit post-harvesting.

This work evaluates the fungicidal effect of essential oil from Coleus aromaticus (C. aromaticus) by solvent-free microwave-assisted extraction with a yield of 0.54%. Fourier-transform infrared spectroscopy was utilised to identify the functional groups, which were O-H, C-O, C-H, and C=C. Gas chromatography-mass spectrometry analysis was performed to determine the primary essential oil components, namely, thymol (92.62%), thymoquinone (2.64%), creosol (1.77%), linalool (1.68%), p-Cymene-2,5-diol (0.73%), and p-Cymene (0.56%). The inhibitory effect of essential oil extracted from C. aromaticus against the isolated fungi, Aspergillus niger from mango, was investigated. The mycelial growth inhibition of the extracted essential oil by the poisoned food test and disc diffusion assay showed the reduction at 79.63 ± 1.7 and 70.45 ± 6.54%, respectively. In vivo experiment was conducted with artificially wounded and unwounded mangoes, applying the extracted essential oil to the wounded mangoes inoculated with A. niger that could decrease the disease incidence from 100 to 58.33 ± 14.43%. Meanwhile, the treatment of the extracted essential oil did not affect the quality of the mango and it also shows improvement in weight loss reduction of the mango in comparison to the chemical fungicide and untreated mango. Hence, essential oil from C. aromaticus by solvent-free microwave-assisted extraction could be used as an effective control for the fruit spoilage and potential source of fruit preservative.

Extraction Bioactive Compound of Pegagan (Centella Asiatica L.) using Solvent-Free Microwave-Assisted Extraction

Gotu Kola (Centella asiatica L.), known as pegagan is a plant with many benefits, including used to repair burns, hypertrophic wound healing, and as an inflammatory agent. C. asiatica grows in tropical Asia and grows in various countries such as Indonesia, Philippines, China, India, Sri Lanka, and Madagascar. C. asiatica has four bioactive components, namely asiatic acid, asiaticoside, madecassic acid, and madecassoside. Microwave-Assisted Extraction (MAE) is one of the methods for extracting bioactive compounds of pegagan leaf. In this study, the extraction of pegagan bioactive compounds carried out using the Solvent-Free Microwave-Assisted Extraction (SFME) method. This research used a box-behnken design model for the optimization process. The variables used are mass of material (20, 40, 60 g), power (150, 300, 450 W), and time of extraction (30, 60, 90 min). The highest yield is 4,5474% at 450 watt microwave power, 20 g mass pegagan leaves, and 60 min extraction time. Mass of material is the factor that has significant effect on yield. Modelling from this research is appropriate which has lack-of-fit > 0,1, and R2 89,67%. The content of bioactive compounds carried out by analyzing the total phenolic content of the product. The most substantial phenol content is 2398,649 μgAGE/ml.

Solvent free-microwave green extraction of essential oil from orange peel (Citrus sinensis L.): effects on shelf life of flavored liquid whole eggs during storage under commercial retail conditions

This study compares the extraction of essential oil (EO) from orange peel (Citrus sinensis L.) by three different methods, namely solvent-free microwave assisted extraction (SFME), traditional hydrodistillation (HD) and cold-pressing (CP), in terms of efficiency and chemical composition using gas chromatography coupled to mass spectrometry (GC–MS). Microstructure analysis of the behaviour of the epithelial cells of the orange peel bark was carried out by scanning electron microscopy (SEM). Results showed that the traditional HD extraction method caused greater modifications of the cellular structure than the SFME method. The comparison between SFME and HD indicated that SFME showed advantages such as faster kinetics and higher efficiency with similar yields (0.40% dry basis in 30 min by SFME versus 3 h by HD). The antioxidant activity of EO was evaluated in vitro by the DPPH assay, resulting in high radical scavenging activity exceeding 80%. The EO was added at three levels (0.1, 0.3, and 0.5%, v/v) to liquid whole egg in order to evaluate its effect on oxidative stability and organoleptic attributes (colour and odour) during simulated cold commercial retail conditions. The thiobarbituric acid reactive substances assay showed that the EO addition significantly reduced the lipid oxidation. The results obtained confirm orange peel EO as a promising functional food ingredient.

The Scenario of Pharmaceuticals and Development of Microwave Assisted Extraction Techniques

Microwave-assisted extraction (MAE) or simply microwave extraction is a relatively new extraction technique that combines microwave and traditional solvent extraction. Application of microwaves for heating the solvents and plant tissues in extraction process, which increases the kinetic of extraction, is called microwave-assisted extraction. The use of MAE in natural products extraction started in the late 1980, though the technological developments, it has now become one of the popular and cost-effective extraction methods available today, and several advanced MAE instrumentations and methodologies have become available, e.g., pressurized microwave-assisted extraction (PMAE) and solvent-free microwave-assisted extraction (SFMAE). This chapter provides an overview of the MAE and presents a number of specific proto collateral products extraction.

Optimization of solvent-free microwave assisted extraction of essential oil from Cinnamomum camphora leaves

Essential oils extraction from Cinnamomum camphora leaves was performed using the solvent-free microwave assisted extraction (SFME) method and the optimal conditions were determined. Response surface methodology combined with a Box–Behnken design was used to determine the optimal operational conditions, which were found to be as follows: moisture content of 60%, microwave irradiation time of 23 min and microwave irradiation power of 580 W. A second order kinetic model was used for the extraction processes, and the obtained C. camphora essential oils were analyzed by GC–MS analysis. SFME performed better than conventional hydrodistillation with regard to extraction efficiency (3.51 ± 0.12% in 23 min versus 3.35 ± 0.10% in 240 min), initiate extraction rate (3.3772 versus 0.1868), extraction rate constant (0.3002 versus 0.0152), extraction capacity (3.67% versus 3.51%), oxygenated compound content (83.93% versus 74.81%), energy consumption (0.22 kW h versus 4 kW h), and environmental impact (177.87 g CO2 versus 3200 g CO2). These results demonstrated that the SFME process is an efficient, time- and energy- saving and eco-friendly method, that shows great potential as a preferable alternative protocol to traditional method of extraction of essential oil from C. camphora leaves and other plant matrices.

Extraction of essential oils from damask rose using green and conventional techniques: Microwave and ohmic assisted hydrodistillation versus hydrodistillation

Damask rose is cultivated as the main species used in the production of rose water and relevant essential oils (EOs) of rose for its fragrance and therapeutic applications. Since the flowers are highly perishable, the extraction of oil should be done rapidly in order to produce rose EO successfully and optimally. Solvent free microwave-assisted extraction (SFME) and ohmic assisted hydrodistillation (OAHD) are advanced and green distillation techniques, which utilize microwave, and ohmic heating processes respectively for the extraction of EOs. In this study, SFME and OAHD of EOs were performed on fresh flowers of damask rose, and the findings were compared with the traditional hydrodistillation (HD). The findings of EO analysis indicated considerable alterations in EOs compounds extracted by SFME and OAHD methods compared with the traditional HD. To reach the desirable temperature of extraction (nearly 100 °C) and to get the first EO droplets’ evaporation with steam, the mixture was heated for 2.50 ± 0.29 min in SFME and for 17.33 ± 0.33 min in OAHD, while for the HD the heating had to take more than 40 min (42.66 ± 0.32 min). The total extraction time of EOs extracted from damask rose by using the green extraction procedures (SFME and OAHD) were compared with HD extraction method. Extraction by SFME occurred much earlier than extraction by OAHD. Also in this study, the analysis of EOs indicated that the chemical profile of damask rose may fluctuate quantitatively with respect to the constituents and structure of the extracted molecules. This would depend on the system of extraction that influences the characteristics of the EOs.

Effects of Drying and Extraction Methods on the Quality and Antioxidant Activity of Sea Buckthorn (Hippophae rhamnoides) Berries and Leaves

Sea buckthorn is a promising source of bioactive compounds. However, there is limited information on the effect of post harvest drying and extraction of sea buckthorn on its antioxidant capacity. The effect of freeze, air, and solar dryingon the extraction yield of sea buckthorn berries and leaves was evaluated with respect to their bioactive content. Sequential extraction with solvents of different polarity and solvent-free microwave-assisted extraction were applied. Freeze-drying has better performance in the berries’ extracts, while air-drying has better performance in the leaves’ extracts. All data were analyzed by Multi Factor Analysis of Variance (ANOVA) and Duncan's post-hoc tests at a level of α = .05. Although the extraction yield in the sequential extraction of sea buckthorn berries is significantly better, the leaves’ extracts exhibit superior radical scavenging ability. Accelerated solar drying appears to preserve sea buckthorn leaves without degrading their antioxidant content. The components responsible for the high antioxidant activity of leaves’ extracts were found to be several flavonoids and polyphenols. The extract obtained by the microwave extraction of fresh berries exhibits moderate antioxidant activity compared to the polar extracts of freeze-dried berries.

Novel solvent-free microwave-assisted extraction coupled with low-density solvent-based in-tube ultrasound-assisted emulsification microextraction for the fast analysis of organophosphorus pesticides in soils

A novel and rapid solventless microwave-assisted extraction coupled with low-density solvent-based in-tube ultrasound-assisted emulsification microextraction has been developed for the efficient determination of nine organophosphorus pesticides in soils by GC analysis with microelectron capture detection. A specially designed, homemade glass tube inbuilt with a scaled capillary tube was used as an extraction device to collect and measure the separated extractant phase easily. Parameters affecting the efficiencies of the developed method were thoroughly investigated. From experimental results, the following conditions were selected for the extraction of organophosphorus pesticides from 1.0 g of soil sample to 5 mL of aqueous solution under 226 W of microwave irradiation for 2.5 min followed by ultrasound-assisted emulsification microextraction with 20 μL toluene for 30 s and then centrifugation at 3200 rpm for 3 min. Detections were linear in the range of 0.25-10 ng/g with detection limits between 0.04 and 0.13 ng/g for all target analytes. The applicability of the method to real samples was assessed on agricultural contaminated soils and the recoveries ranged between 91.4 and 101.3%. Compared to other methods, the present method was shown to be highly competitive in terms of sensitivity, cost, eco-friendly nature, and analysis speed.

Chemical Composition and Antioxidant Activity of Algerian Juniperus phoenicea L. Extracts

Essential oils of Algerian Juniperus phoenicea L. obtained from leaves and berries by hydrodistillation (HD) and from berries by Solvent Free Microwave Assisted Extraction (SFMAE) were investigated using both capillary GC and GC-MS techniques. The monoterpene hydrocarbons constituted the most prominent group of constituents (43.2-86.5 %) in the three essential oils with α-pinene (34.4-80.8 %) as the main compound. Leaves ethanol extract was analyzed in terms of the dosage in total phenolic and flavonoids contents. Gallic acid equivalent representing total phenolic constituents of the extract was 308 mg GAE/g; and quercetin equivalent representing total flavonoids was 20 mg QE/g. The antioxidant potential of the samples was evaluated using two separate methods, inhibition of free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and reducing power. All essential oils showed a relatively weak antioxidant capacity. No improvement of the antioxidant activity by SFMAE technique has been detected. J. phoenicea ethanol extract was found to be remarkably effective toward DPPH inhibition, compared to chemical antioxidant BHT (IC = 9.8±0.1 and 28±0.7 mg/l, respectively); for reducing power test it has also exhibited high activity in comparison with all studied essential oils and the chemical standard (BHT).

Solvent-free microwave-assisted extraction of fluoroquinolones from soil and liquid chromatography-fluorescence determination

Presented hereafter is a novel method entailing solvent free microwave-assisted extraction (MAE) and HPLC equipped with Fluorimetric Detector (HPLC-FD) for the simultaneous determination at μg kg −1 concentration of eight fluoroquinolone antibiotics (FQs) (Ciprofloxacin, Danofloxacin, Enrofloxacin, Flerofloxacin, Levofloxacin, Marbofloxacin, Norfloxacin and Orbifloxacin) in agricultural soils. The extraction was quantitatively performed, in a single step, by using an aqueous solution containing Mg(II) as complexing agent, thus avoiding consumption of organic solvents. The optimal MAE conditions have been established through a chemometric approach by considering temperature, irradiation time and matrix moisture or solvent, as the most important recognized variables affecting the extraction yield. Satisfying recoveries (69–110%, spikes 0.03–0.5 mg kg −1) were gained with a single MAE cycle of 20 min, at 80 °C in 20% (w/v) Mg(NO 3) 2 solution as leaching agent. MAE-SPE recoveries at 10 μg kg −1, concentration near method quantification limits (MQLs), were in the range 60–85%. Good repeatability and within-lab reproducibility were observed (both in the range 1–16%). The applicability of the method to real samples was assessed on natural contaminated soils. Compared to ultrasonic-assisted extraction (UAE), MAE was shown to be highly competitive in terms of extraction efficacy and analysis speed.

An organic solvent-free microwave-assisted extraction of some priority pollutants of phenols in lake sediments.

Alkaline water was used for the microwave-assisted extraction of some priority pollutants of phenols in sediments, i.e. phenol (Ph), 2-chlorophenol (2CP), 2,4-dichlorophenol (2,4DCP), 4-chlorophenol (4CP), 4-dinitrophenol (4NP) and pentachlorophenol (PCP). This organic solvent-free extraction procedure was optimized by studying the parameters such as pH, volume of the alkaline water, extraction pressure and time. Under the optimized conditions, the recoveries of phenols were in the range of 80% to 110%. The extracts were then cleaned-up and concentrated by microcolumn solid phase extraction (SPE) and determined by gas chromatography-flame ionization detection system. The relative standard deviation of the overall-method for most phenol determinations was about 5.0% (n = 6). The proposed method, which needs little volume (1 mL) of ethanol for SPE, has been applied to determine these phenols in sediment samples, and the analytical results are in good agreement with those achieved by Soxhlet extraction.