在线加压溶剂微提取-湍流色谱-高效液相色谱法同时测定管花肉苁蓉中3种苯乙醇苷

建立了在线加压溶剂微提取-湍流色谱-高效液相色谱(online PLME-TFC-HPLC)法,并将其应用于管花肉苁蓉中松果菊苷、毛蕊花糖苷和异毛蕊花糖苷3种苯乙醇苷类成分含量的同时测定。微量样品粉末(0.5 mg)置于空预柱芯中并用正相硅胶填充,得到提取池后装入预柱套(Security Guard^TM)。将预柱套置于70℃柱温箱中,将一根长聚醚醚酮(PEEK)管线(1000 mm×0.13 mm)连于预柱套末端,采用0.1%(v/v)甲酸水为提取溶剂,以2.5 mL/min的速度流经PEEK管线,产生高压,实现管花肉苁蓉的在线加压溶剂微提取,通过TurboFlow cyclone色谱柱在线净化和富集。引入两个电子六通阀,将整个分析过程分为提取阶段和洗脱阶段,并在洗脱阶段将TurboFlow cyclone色谱柱中的分析物反冲至Capcell PAK C₁₈ AQ分析柱上,以0.1%(v/v)甲酸水-乙腈为流动相进行梯度洗脱,以340 nm为检测波长同时定量分析松果菊苷、毛蕊花糖苷和异毛蕊花糖苷3种苯乙醇苷类成分。结果表明,3种苯乙醇苷类在1~200 mg/L范围内线性良好,相关系数r均大于0.999,定量限分别为0.50 mg/L(松果菊苷)、0.25 mg/L(毛蕊花糖苷)和0.38 mg/L(异毛蕊花糖苷),加标回收率为83.13%~114.00%,相对标准偏差为1.89%~13.34%。该方法简便、快速、可靠,不仅节约了药材和溶剂的使用量,而且极大地简化了前处理方法,省时省力,同时显著降低了化学成分在提取过程中降解的几率,适用于管花肉苁蓉中苯乙醇苷类化合物的含量测定。     

Study on the PEG‐based microwave‐assisted extraction of flavonoid compounds from persimmon leaves

A method for PEG‐based microwave‐assisted extraction (MAE) of flavonoid compounds from persimmon leaves has been successfully developed. The extraction efficiency of total flavonoid content was evaluated by the chromatographic peak areas of quercetin and kaempferol, which are two bioactive components typically found in persimmon leaves. The best combination of extraction parameters was obtained with response surface methodology. A microwave power of 525 W, liquid to solid ratio of 17:1 mL/g, and PEG aqueous solution concentration of 60% w/w were identified as the optimum parameters. Extraction dynamics analysis indicated that the quercetin, kaempferol, and total flavonoid contents were rising with increasing extraction time up to 20–25 min, from which point onwards they all decreased. Under the optimum conditions, quercetin, kaempferol, and total flavonoid contents obtained from the sample were 1.20 ± 0.05, 0.64 ± 0.11, and 16.90 ± 0.06 mg/g, respectively. Compared with ethanol‐based MAE, and ethanol‐based and PEG‐based ultrasonic‐assisted extractions, PEG‐based MAE had higher efficiency for the extraction of flavonoid compounds from persimmon leaves. Overall, PEG‐based MAE represents an efficient choice for the extraction of bioactive substances from traditional Chinese medicines.     

Separation of acteoside and linarin from Buddlejae Flos by high‐speed countercurrent chromatography and their anti‐inflammatory activities

Buddleja officinalis Maxim., a deciduous, flowering shrub, is used as a traditional Chinese medicine; the bioactivity of B. officinalis is primarily due to flavonoids and phenylethanoid glycosides. In the study, acteoside and linarin were successfully isolated from B. officinalis by high‐speed countercurrent chromatography with a two‐phase solvent system composed of ethyl acetate: n‐butanol: water (5:0.8:5, v/v/v). The purities of acteoside and linarin were determined to be 97.3 and 98.2%, respectively, using one‐step high‐speed countercurrent chromatography separation. The chemical structures of the two compounds were identified by electrospray ionization‐mass spectrometry and nuclear magnetic resonance. After separation, the anti‐inflammatory effects of the two compounds were evaluated using lipopolysaccharide‐induced human umbilical vein endothelial cells. Acteoside and linarin inhibited the expression of nitric oxide, tumor necrosis factor α and interleukin 1β, which demonstrated that acteoside and linarin possessed anti‐inflammatory activity.     

Rapid preparative separation of six bioactive compounds from Gentiana crassicaulis Duthie ex Burk. using microwave‐assisted extraction coupled with high‐speed counter‐current chromatography

A rapid method combining microwave‐assisted extraction (MAE) and high‐speed counter‐current chromatography (HSCCC) was applied for preparative separation of six bioactive compounds including loganic acid ( I ), isoorientin‐4′‐O‐glucoside ( II ), 6′‐O‐β‐d ‐glucopyranosyl gentiopicroside ( III ), swertiamarin ( IV ), gentiopicroside ( V ), sweroside ( VI ) from traditional Tibetan medicine Gentiana crassicaulis Duthie ex Burk. MAE parameters were predicted by central composite design response surface methodology. That is, 5.0 g dried roots of G. crassicaulis were extracted with 50 mL 57.5% aqueous ethanol under 630 W for 3.39 min. The extract (gentian total glycosides) was separated by HSCCC with n‐butanol/ethyl acetate/methanol/1% acetic acid water (7.5:0.5:0.5:3.5, v/v/v/v) using upper phase mobile in tail‐to‐head elution mode. 16.3, 8.8, 12., 25.1, 40.7, and 21.8 mg of compounds I–VI were obtained with high purities in one run from 500 mg of original sample. The purities and identities of separated components were confirmed using HPLC with photo diode array detection and quadrupole TOF‐MS and NMR spectroscopy. The study reveals that response surface methodology is convenient and highly predictive for optimizing extraction process, MAE coupled with HSCCC could be an expeditious method for extraction and separation of phytochemicals from ethnomedicine.     

Screening of glycoside isomers in P. scrophulariiflora using ionic liquid‐based ultrasonic‐assisted extraction and ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

A powerful ionic liquid‐based ultrasonic‐assisted extraction (ILUAE) method combined with ultra‐performance liquid chromatography coupled to electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (UPLC/ESI‐QTOFMSⁿ) was employed in the rapid simultaneous screening of iridoid glycosides, phenylethanoid glycosides, and cucurbitacin glycosides from P. scrophulariiflora. The ILUAE procedure was optimized over several ultrasonic parameters, including the ultrasonic power, concentration of the ionic liquid, and solid–liquid ratio. A comparison with conventional heat‐reflux extraction and regular UAE demonstrated that the optimized approach yielded a high extraction efficiency (Picroside I, 2.84%; Picroside II, 3.57%; 6‐O‐E‐feruloyl catalpol, 2.20%) within a short extraction time of 30 min. Negative ion mode ESI‐QTOFMS² analysis of the fragmentation reactions of the [M–H]^– ions was conducted to characterize the diagnostic ions related to the glycosyl moieties, aglycone units, and the type and substituted position of the ester groups. Interestingly, the positional isomers of the iridoid glycosides could be easily discriminated based on the characteristic ions. A total of 15 glycosides, including three groups of iridoid glycoside isomers and two groups of phenylethanoid glycoside isomers, were conveniently identified within 13.5 min. Moreover, 6'‐O‐vanilloyl catalpol was identified in P. scrophulariiflora for the first time. The method developed here was further validated by measuring the recovery, correlation coefficient (R²), and reproducibility (RSD, n = 5) of three iridoid glycosides: 89.60%–109.02%, 0.9991–0.9998, and 0.93%–1.44%, respectively. This study demonstrated the capabilities of ILUAE combined with UPLC/ESI‐QTOFMSⁿ for the rapid screening of glycosides in P. scrophulariiflora. This method offers an approach to similar studies on other natural plants. Copyright © 2012 John Wiley & Sons, Ltd.     

Ionic‐liquid‐based ultrasound/microwave‐assisted extraction of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one and 6‐methoxy‐benzoxazolin‐2‐one from maize (Zea mays L.) seedlings

We evaluated an ionic‐liquid‐based ultrasound/microwave‐assisted extraction method for the extraction of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one and 6‐methoxy‐benzoxazolin‐2‐one from etiolated maize seedlings. We performed single‐factor and central composite rotatable design experiments to optimize the most important parameters influencing this technique. The best results were obtained using 1.00 M 1‐octyl‐3‐methylimidazolium bromide as the extraction solvent, a 50°C extraction temperature, a 20:1 liquid/solid ratio (mL/g), a 21 min treatment time, 590 W microwave power, and 50 W fixed ultrasonic power. We performed a comparison between ionic‐liquid‐based ultrasound/microwave‐assisted extraction and conventional homogenized extraction. Extraction yields of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one and 6‐methoxy‐benzoxazolin‐2‐one by the ionic‐liquid‐based ultrasound/microwave‐assisted extraction method were 1.392 ± 0.051 and 0.205 ± 0.008 mg/g, respectively, which were correspondingly 1.46‐ and 1.32‐fold higher than those obtained by conventional homogenized extraction. All the results show that the ionic‐liquid‐based ultrasound/microwave‐assisted extraction method is therefore an efficient and credible method for the extraction of 2,4‐dihydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one and 6‐methoxy‐benzoxazolin‐2‐one from maize seedlings.     

Simultaneous separation of triterpenoid saponins and flavonoid glycosides from the roots of Glycyrrhiza uralensis Fisch by pH‐zone‐refining counter‐current chromatography

Glycosides including triterpenoid saponins and flavonoid glycosides are the main constituents of Glycyrrhiza uralensis Fisch (licorice) and exhibit prominent pharmacological activities. However, conventional methods for the separation of glycosides always cause irreversible adsorption and unavoidable loss of sample due to their high hydrophilicities. The present paper describes a convenient method for the simultaneous separation of triterpenoid saponins and flavonoid glycosides from licorice by pH‐zone‐refining counter‐current chromatography. Ethyl acetate/n‐butanol/water (2:3:5, v/v) with 10 mM TFA in the upper organic stationary phase and 10 mM ammonia in the lower aqueous mobile phase was used as the biphasic solvent system. Three triterpenoid saponins and two flavonoid glycosides including licorice‐saponin A3 (63.3 mg), glycyrrhizic acid (342.2 mg), 3‐O‐[β‐d ‐glucuronopyranosyl‐(1 → 2)‐β‐d ‐galactopyranosyl]glycyrrhetic acid (56.0 mg), liquiritin apioside (232.6 mg), and liquiritin (386.5 mg) were successfully obtained from licorice ethanol extract (2 g) in one step. This method subtly takes advantage of the common acidic properties of triterpenoid saponins and flavonoid glycosides, and obviously is much more efficient and convenient than the previous methods. It is also the first time that the separation of acidic triterpenoid saponins by using pH‐zone‐refining counter‐current chromatography has been reported.     

Separation of three phenolic high‐molecular‐weight compounds from the crude extract of Terminalia Chebula Retz. by ultrasound‐assisted extraction and high‐speed counter‐current chromatography

This study presents an efficient strategy for separation of three phenolic compounds with high molecular weight from the crude extract of Terminalia chebula Retz. by ultrasound‐assisted extraction and high‐speed counter‐current chromatography. The ultrasound‐assisted extraction conditions were optimized by response surface methodology and the results showed the target compounds could be well enriched under the optimized extraction conditions. Then the crude extract was directly separated by high‐speed counter‐current chromatography without any pretreatment using n‐hexane/ethyl acetate/methanol/water (1:7:0.5:3, v/v/v/v) as the solvent system. In 180 min, 13 mg of A, 18 mg of B, and 9 mg of C were obtained from 200 mg of crude sample. Their structures were identified as Chebulagic acid (A, 954 Da), Chebulinic acid (B, 956 Da), and Ellagic acid (C) by ¹H NMR spectroscopy.     

Ionic‐liquid‐based,manual‐shaking‐ and ultrasound‐assisted,surfactant‐enhanced emulsification microextraction for the determination of three fungicide residues in juice samples

A novel manual‐shaking‐ and ultrasound‐assisted surfactant‐enhanced emulsification microextraction method was developed for the determination of three fungicides in juice samples. In this method, the ionic liquid, 1‐ethyl‐3‐methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, instead of a volatile organic solvent was used as the extraction solvent. The surfactant, NP‐10, was used as an emulsifier to enhance the dispersion of the water‐immiscible ionic liquid into an aqueous phase, which accelerated the mass transfer of the analytes. Organic dispersive solvent typically required in common dispersive liquid–liquid microextraction methods was not necessary. In addition, manual shaking for 15 s before ultrasound to preliminarily mix the extraction solvent and the aqueous sample could greatly shorten the time for dispersing the ionic liquid into aqueous solution by ultrasound irradiation. Several experimental parameters affecting the extraction efficiency, including type and volume of extraction solvent, type and concentration of surfactant, extraction time, and pH, were optimized. Under the optimized conditions, good linearity with the correlation coefficients (γ) higher than 0.9986 and high sensitivity with the limit of detection ranging from 0.4 to 1.6 μg/L were obtained. The average recoveries ranged from 61.4 to 86.0% for spiked juice, with relative standard deviations from 1.8 to 9.7%. The proposed method was demonstrated to be a simple, fast, and efficient method for the analysis of the target fungicides in juice samples.     

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.     

Efficient sample preparation method based on solvent‐assisted dispersive solid‐phase extraction for the trace detection of butachlor in urine and waste water samples

In this work, an efficient sample preparation method termed solvent‐assisted dispersive solid‐phase extraction was applied. The used sample preparation method was based on the dispersion of the sorbent (benzophenone) into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre‐concentration of the butachlor, the cloudy solution was centrifuged and butachlor in the sediment phase dissolved in ethanol and determined by gas chromatography with flame ionization detection. Under the optimized conditions (solution pH = 7.0, sorbent: benzophenone, 2%, disperser solvent: ethanol, 500 μL, centrifuged at 4000 rpm for 3 min), the method detection limit for butachlor was 2, 3 and 3 μg/L for distilled water, waste water, and urine sample, respectively. Furthermore, the preconcentration factor was 198.8, 175.0, and 174.2 in distilled water, waste water, and urine sample, respectively. Solvent‐assisted dispersive solid‐phase extraction was successfully used for the trace monitoring of butachlor in urine and waste water samples.     

Rapid determination of the volatile components in tobacco by ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction with gas chromatography‐mass spectrometry

An ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction was first employed to determine the volatile components in tobacco samples. The method combined the advantages of ultrasound, microwave, and headspace solid‐phase microextraction. The extraction, separation, and enrichment were performed in a single step, which could greatly simplify the operation and reduce the whole pretreatment time. In the developed method, several experimental parameters, such as fiber type, ultrasound power, and irradiation time, were optimized to improve sampling efficiency. Under the optimal conditions, there were 37, 36, 34, and 36 components identified in tobacco from Guizhou, Hunan, Yunnan, and Zimbabwe, respectively, including esters, heterocycles, alkanes, ketones, terpenoids, acids, phenols, and alcohols. The compound types were roughly the same while the contents were varied from different origins due to the disparity of their growing conditions, such as soil, water, and climate. In addition, the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction method was compared with the microwave‐assisted extraction coupled to headspace solid‐phase microextraction and headspace solid‐phase microextraction methods. More types of volatile components were obtained by using the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction method, moreover, the contents were high. The results indicated that the ultrasound‐microwave synergistic extraction coupled to headspace solid‐phase microextraction technique was a simple, time‐saving and highly efficient approach, which was especially suitable for analysis of the volatile components in tobacco.     

Characterization of antioxidant phenolics in Syringa vulgaris L. flowers and fruits by HPLC‐DAD‐ESI‐MS

In this study the polyphenolic composition of lilac flowers and fruits was determined for the first time. For the identification of compounds, accurate molecular masses and formulas, acquired by LC and ESI‐TOF‐MS and fragmentation pattern given by LC‐ESI/MS/MS analyses, were used. Our chromatographic system in conjunction with tandem MS was found to be valuable in the rapid separation and determination of the multiple constituents in methanolic extracts of lilac flowers and fruits. Altogether 34 phenolics, comprising 18 secoiridoids, seven phenylpropanoids, four flavonoids and five low‐molecular‐weight phenols, were identified. As marker compounds two secoiridoids (oleuropein and nuzhenide), two phenylpropanoids (acteoside and echinacoside) and rutin were quantified by validated methods. As a result of quantitative analysis, it was confirmed that flowers contain significant amounts of phenylpropanoids (acteoside, 2.48%; echinacoside, 0.75%) and oleuropein (0.95%), while in fruits secoiridoid oleuropein (1.09%) and nuzhenide (0.42%) are the major secondary metabolites. The radical scavenging activities of the extracts and the constituents were investigated by DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) and ABTS [2,2′‐azino‐bis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid)] assays. Both extracts show remarkable antioxidant activities. Our results clearly show that lilac flowers and fruits are inexpensive, readily available natural sources of phenolic compounds with pharmacological and cosmetic applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Extraction and isolation of flavonoid glycosides from Flos Sophorae Immaturus using ultrasonic‐assisted extraction followed by high‐speed countercurrent chromatography

A method of ultrasonic‐assisted extraction followed by high‐speed countercurrent chromatography was established for the extraction and isolation of three flavonoid glycosides, i.e. rutin, narcissin, and nicotiflorin from Flos Sophorae Immaturus. The effects of ultrasonic‐assisted extraction factors for the main flavonoid compound (rutin) from Flos Sophorae Immaturus were optimized using Box–Behnken design combined with response surface methodology. The optimum conditions were determined as ultrasonic power 83% (600 W), solvent‐to‐material ratio 56:1, methanol concentration 82% v/v, and extraction time 60 min. Three bioactive flavonol glucosides, rutin, narcissin, and nicotiflorin were isolated from Flos Sophorae Immaturus using high‐speed countercurrent chromatography. The separation was performed with a two‐phase solvent system containing ethyl acetate/n‐butanol/methanol/water (4:0.9:0.2:5, v/v). Amounts of 87 mg of rutin, 10.8 mg of narcissin, and 1.8 mg of nicotiflorin were isolated from 302 mg of crude extract of Flos Sophorae Immaturus in a one‐step separation within 160 min with purities of 99.3, 98.0, and 95.1%, respectively, as determined by HPLC with diode array detection. Their structures were characterized by UV, MS, and NMR spectroscopy. It was demonstrated that the established method was simple, fast, and convenient, which was feasible to extract and isolate active flavonoid glycosides from Flos Sophorae Immaturus.     

应用高效液相色谱和电喷雾质谱联用技术分析鉴定车前草中的苯乙醇苷化合物

本文采用高效液相色谱与电喷雾质谱联用技术在线分析鉴定了车前草提取物中的三种苯乙醇苷化合物。实验采用反相C18色谱柱,0.2%的醋酸水溶液和乙腈梯度洗脱,车前草中的苯乙醇苷化合物得到很好的分离。在电喷雾质谱负离子条件下,获得了三种苯乙醇苷化合物的分子离子峰,分子量信息,进一步通过质谱的源内CID技术得到相应化合物的结构信息。通过得到的这些信息与文献中的已知化合物或标准品对照从而推断出化合物的结构。     

Anti‐inflammatory bioactive equivalence of combinatorial components β‐carboline alkaloids identified in Arenaria kansuensis by two‐dimensional chromatography and solid‐phase extraction coupled with liquid–liquid extraction enrichment technology

Bioactive equivalent combinatorial components play a critical role in herbal medicines. However, how to discover and enrich them efficiently is a question for herbal pharmaceuticals researchers. In our work, a novel two‐dimensional reversed‐phase/hydrophilic interaction high‐performance liquid chromatography method was established to perform real‐time components trapping and combining for preparation and isolation of coeluting components. Arenaria kansuensis was taken as an example, and solid‐phase extraction coupled with liquid–liquid extraction as a simple and efficient method for enriching trace components, reversed phase column coupled with hydrophilic interaction liquid chromatography XAmide column as two‐dimensional chromatography technology for isolation and preparation of coeluting constituents, enzyme‐linked immune‐sorbent assay as bio‐guided assay, and anti‐inflammatory bioactivity evaluation for bioactive constituents. A combination of 12 β‐carboline alkaloids was identified as anti‐inflammatory bioactive equivalent combinatorial components from A. kansuensis , which accounts for 1.9% w/w of original A. kansuensis . This work answers the key question of which are real anti‐inflammatory components from A. kansuensis and provides a fast and efficient approach for discovering and enriching trace β‐carboline alkaloids from herbal medicines for the first time. More importantly, the discovery of bioactive equivalent combinatorial components could improve the quality control of herbal products and inspire a herbal medicine based on combinatorial therapeutics.     

Ultra‐high‐pressure‐assisted extraction of wedelolactone and isodemethylwedelolactone from Ecliptae Herba and purification by high‐speed counter‐current chromatography

Ultra‐high‐pressure extraction combined with high‐speed counter‐current chromatography was employed to extract and purify wedelolactone and isodemethylwedelolactone from Ecliptae Herba. The operating conditions of ultra‐high‐pressure extraction were optimized using an orthogonal experimental design. The optimal conditions were 80% aqueous methanol solvent, 200 MPa pressure, 3 min extraction time and 1:20 (g/mL) solid–liquid ratio for extraction of wedelolactone and isodemethylwedelolactone. After extraction by ultra‐high pressure, the extraction solution was concentrated and subsequently extracted with ethyl acetate; a total of 2.1 g of crude sample was obtained from 100 g of Ecliptae Herba. A two‐phase solvent system composed of petroleum ether–ethyl acetate–methanol–water (3:7:5:5, v/v) was used for high‐speed counter‐current chromatography separation, by which 23.5 mg wedelolactone, 6.8 mg isodemethylwedelolactone and 5.5 mg luteolin with purities >95% were purified from 300 mg crude sample in a one‐step separation. This research demonstrated that ultra‐high‐pressure extraction combined with high‐speed counter‐current chromatography was an efficient technique for the extraction and purification of coumestans from plant material.     

Trace Analysis of Methyl Tert‐butyl Ether in Water Samples Using New Ultrasound‐assisted Dispersive Liquid‐liquid Microextraction and Gas Chromatography‐flame Ionization Detection

In this study, simple and efficient ultrasound‐assisted dispersive liquid‐liquid microextraction combined with gas chromatography (GC) was developed for the preconcentration and determination of methyl‐tert‐butyl ether (MTBE) in water samples. One hundred microliters of benzyl alcohol was injected slowly into 10 mL home‐designed centrifuge glass vial containing an aqueous sample with 30% (w/v) of NaCl that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and 2 μL of separated benzyl alcohol was injected into a gas chromatographic system equipped with a flame ionization detector (GC‐FID) for analysis. Several factors influencing the extraction efficiency such as the nature and volume of organic solvent, extraction temperature, ionic strength and centrifugation times were investigated and optimized. Using optimum extraction conditions a detection limit of 0.05 μg L^‐1 and a good linearity (r² = 0.998) in a calibration range of 0.1‐500 μg L^‐1 were achieved. This proposed method was successfully applied to the analysis of MTBE in tap, well and a ground water sam ple contaminated by leaking gasoline from an underground storage tank (LUST) in a gasoline service station.     

Green and enhanced extraction of coumarins from Cortex Fraxini by ultrasound‐assisted deep eutectic solvent extraction

Green and enhanced extraction of bioactive ingredients from medicinal plants has become a hot research field, and deep eutectic solvents have been considered as a novel kind of sustainable solvents in the extraction process. In this study, hydrogen bond acceptor (choline chloride, etc.) and hydrogen bond donor (l ‐malic acid, etc.) were used to prepare different kinds of deep eutectic solvents to extract coumarins from Cortex Fraxini. The extraction conditions, including the composition and moisture content of deep eutectic solvents, extraction time, and liquid‐solid ratio, were systematically optimized basing on the extraction yield of coumarins. To further investigate the extraction mechanism, Fourier transform infrared spectroscopy was performed, and the microstructures of Cortex Fraxini powders were observed before and after extraction using scanning electron microscope. Results showed that the novel ultrasound‐assisted extraction with conditions of deep eutectic solvent containing betaine/glycerin (1:3), aqueous solution (20%), solid‐liquid ratio (15 mg/mL), and extraction time (30 min) exhibited the best extraction yields for the four target coumarins and much better extraction efficiency than with conventional solvent extractions. This suggests that the new ultrasound‐assisted deep eutectic solvent extraction could be used as a green and high‐efficient approach for extraction of the main coumarins from Cortex Fraxini.     

Monitoring the oleuropein content of olive leaves and fruits using ultrasound‐ and salt‐assisted liquid–liquid extraction optimized by response surface methodology and high‐performance liquid chromatography

A novel and rapid ultrasound‐ and salt‐assisted liquid–liquid extraction coupled with high‐performance liquid chromatography has been optimized by response surface methodology for the determination of oleuropein from olive leaves. Box–Behnken design was used for optimizing the main parameters including ultrasound time (A), pH (B), salt concentration (C), and volume of miscible organic solvent (D). In this technique, a mixture of plant sample and extraction solvent was subjected to ultrasound waves. After ultrasound‐assisted extraction, phase separation was performed by the addition of salt to the liquid phase. The optimal conditions for the highest extraction yield of oleuropein were ultrasound time, 30 min; volume of organic solvent, 2.5 mL; salt concentration, 25% w/v; and sample pH, 4. Experimental data were fitted with a quadratic model. Analysis of variance results show that BC interaction, A², B², C², and D² are significant model terms. Unlike the conventional extraction methods for plant extracts, no evaporation and reconstitution operations were needed in the proposed technique.