Gradient thin-layer chromatography of plant extracts

Summary A modified Niederwieser chamber for stepwise gradient elution, consisting of a PTFE capillary to store the series of eluents and a horizontal glass sandwich chamber with a glass distributor was used for the chromatographic separation of complex plant extracts (Seboren, Hemorigen and Pectosol) used in therapy. Densitograms demonstrate markedly improved separations of the extracts in comparison to isocratic elution.Produced by Polish Reagents, Melgiewska 18, 20-234 Lublin, Poland     

Isolation of essential oils from tobacco by gas co-distillation/solvent extraction

Summary The essential oils have been isolated from tobacco leaves using a simple gas co-distillation apparatus. The method involves co-distillation with water under the continuous stream of an inert gas with subsequent single solvent extraction of the distillate. The extract is analysed on GC and GC/MS in splitless injection mode without further concentration. The method was evaluated for reproducibility using n-octadecane as an internal standard. The distillation-extraction procedure was reporducible with an average deviation of ±3% for the major constituents. The present method was applied to the analyses of the essential oils of other agricultural products.Dedicated to Dr. L. S. Ettre on the occasion of his 60th birthday.     

Arsenic extraction and speciation in carrots using accelerated solvent extraction, liquid chromatography and plasma mass spectrometry

Arsenic present in freeze-dried carrots was extracted using accelerated solvent extraction (ASE). Several parameters, including selection of the dispersing agent, extraction time, number of extraction cycles, particle size and extraction temperature, were evaluated to optimize the ASE method. Filtering and treatment with C-18 SPE cartridges were also evaluated as part of the sample preparation procedure before speciation analysis. The method was validated by spiking single arsenical and mixed arsenical standards on the dispersing agent and on portions of freeze-dried carrot prior to extraction. LC-ICP-MS was used to determine individual arsenic species in the carrot extracts. A weak anion-exchange column was used for the separation of As(III), As(v), monomethylarsonic acid (MMA), dimethylarsinic acid and arsenobetaine. Optimized sample preparation conditions were applied to the extraction of arsenic in nine freeze-dried carrot samples. Total arsenic concentration in the carrot samples ranged from less than 20 ng g(-1) to 18.7 microg g(-1), dry mass. Extraction efficiency, defined as the ratio of the sum of individual arsenic species concentrations to total arsenic, ranged from 80 to 102% for freeze-dried carrots with arsenic concentrations greater than the limit of quantitation. Inorganic As(III) and As(v) were the only species found in samples that contained less than 400 ng g(-1) total arsenic. MMA and an unidentified arsenic compound were present in some of the samples with higher total arsenic content.     

Comparison of extraction techniques and modeling of accelerated solvent extraction for the authentication of natural vanilla flavors

Accelerated solvent extraction (ASE) of vanilla beans has been optimized using ethanol as a solvent. A theoretical model is proposed to account for this multistep extraction. This allows the determination, for the first time, of the total amount of analytes initially present in the beans and thus the calculation of recoveries using ASE or any other extraction technique. As a result, ASE and Soxhlet extractions have been determined to be efficient methods, whereas recoveries are modest for maceration techniques and depend on the solvent used. Because industrial extracts are obtained by many different procedures, including maceration in various solvents, authenticating vanilla extracts using quantitative ratios between the amounts of vanilla flavor constituents appears to be unreliable. When authentication techniques based on isotopic ratios are used, ASE is a valid sample preparation technique because it does not induce isotopic fractionation.     

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.     

Separation and preparative isolation of phenolic dialdehydes by on-line overpressured layer chromatography

The Reimer-Tiemann reaction carried out in a heterogeneous solid-liquid medium was found to give the isomeric dialdehydes 2-hydroxy-1,3-benzenedicarboxaldehyde and 4-hydroxy-1,3-benzenedicarboxaldehyde. The PRISMA model was employed to optimize the eluent mixture, and with careful choice of silica gel high-performance thin-layer chromatographic plates, the two isomers could be isolated and purified by on-line overpressured layer chromatography.     

加速溶剂萃取-快速液相色谱法测定纺织品中烷基苯酚和烷基苯酚聚氧乙烯醚

建立了纺织品中烷基苯酚和烷基苯酚聚氧乙烯醚的加速溶剂萃取-快速液相色谱测定方法。加速溶剂萃取法基本实现了样品前处理的自动化,简化了操作流程;快速液相色谱分析方法(利用核壳型快速分析色谱柱)大大缩短了样品分析时间(色谱分析时间小于5 min)。该方法在提高工作效率的同时节省了有机溶剂,且易于在普通实验室普及的常规液相色谱仪上实现,具有较强的实用性。     

Determination of pharmaceuticals in biosolids using accelerated solvent extraction and liquid chromatography/tandem mass spectrometry

An analytical method was developed to quantitatively determine pharmaceuticals in biosolid (treated sewage sludge) from wastewater treatment plants (WWTPs). The collected biosolid samples were initially freeze dried, and grounded to obtain relatively homogenized powders. Pharmaceuticals were extracted using accelerated solvent extraction (ASE) under the optimized conditions. The optimal operation parameters, including extraction solvent, temperature, pressure, extraction time and cycles, were identified to be acetonitrile/water mixture (v/v 7:3) as extraction solvent with 3 extraction cycles (15 min for each cycle) at 100 °C and 100 bars. The extracts were cleaned up using solid-phase extraction followed by determination by liquid chromatography coupled with tandem mass spectrometry. For the 15 target pharmaceuticals commonly found in the environment, the overall method recoveries ranged from 49% to 68% for tetracyclines, 64% to 95% for sulfonamides, and 77% to 88% for other pharmaceuticals (i.e. acetaminophen, caffeine, carbamazepine, erythromycin, lincomycin and tylosin). The developed method was successfully validated and applied to the biosolid samples collected from WWTPs located in six cities in Michigan. Among the 15 target pharmaceuticals, 14 pharmaceuticals were detected in the collected biosolid samples. The average concentrations ranged from 2.6 μg/kg for lincomycin to 743.6 μg/kg for oxytetracycline. These results indicated that pharmaceuticals could survive wastewater treatment processes, and accumulate in sewage sludge and biosolids. Subsequent land application of the contaminated biosolids could lead to the dissemination of pharmaceuticals in soil and water environment, which poses potential threats to at-risk populations in the receiving ecosystems.     

Determination of phthalate esters in soil by microemulsion electrokinetic chromatography coupled with accelerated solvent extraction

A novel method using microemulsion electrokinetic chromatography combining accelerated solvent extraction was developed for quantitative analysis of six phthalate esters (PAEs) including dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate, as well as dioctyl phthalate. The effect of each individual component within the microemulsions, i.e. oil phase, surfactant and co-surfactant on resolution of the analytes was systematically studied. Baseline separation of six PAEs was achieved within 26?min by using the microemulsion buffer containing a 60?mmol/L borate buffer at pH 9.0, 0.5% v/v n-octane as oil droplets, 100?mmol/L sodium cholate as surfactant and 5.0% v/v 1-butanol as co-surfactant. The purposed accelerated solvent extraction-microemulsion electrokinetic chromatography method was successfully applied to the determination of trace amount of PAEs in soil samples collected from three different fields in areas of Fujian Province and the contents of dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate and dioctyl phthalate were 0.63-0.68, 0.32-0.63, 2.53-3.96, 0-1.75, 7.32-11.7 and 0-3.46mg/kg, respectively. It was validated that the results were consistent with those obtained by GC-MS method.     

Adsorption thin-layer chromatography and viscometry of polystyrenes in solvent mixtures

The effect of the thermodynamic quality of solvent mixtures on the adsorption behavior of macromolecules under dynamic conditions was investigated. The chromatographic behavior of polystyrenes (PSs) in various mixed eluents was studied under conditions of adsorption and size-exclusion thin-layer chromatography as well as at the exclusion-adsorption transition point with silica gel KSKG adsorbent. The thermodynamic quality of the solvent mixtures used in the chromatographic experiments was determined viscometrically. The dependences of the intrinsic viscosity of PSs on solvent composition for solvent-non-solvent, two solvents, and theta-solvent-solvent mixtures were obtained. A correlation was found between Snyder's polarity indices for the solvent mixtures used in polymer chromatography under "critical conditions" and the intrinsic viscosity values of PSs in the same mixtures.     

Correlation between chemical composition and radical scavenging activity of 10 commercial essential oils: Impact of microencapsulation on functional properties of essential oils

A comparative study was carried out on the essential oils of 10 aromatic plants that are extensively used in Egypt for their distinctive aroma and functional properties. Each essential oil (EO) was characterized by means of gas chromatography-mass spectrometry (GC–MS) analysis and evaluated for its radical scavenging activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis (2-ethyl-benzolhiaxoline-6-sulfonic acid)(ABTS) assays. The phenolic content of the 10 EOs was in the descending order: clove > thyme > majoram > basil > anise > chamomile > cinnamon > dill > ginger > rosemary. The radical scavenging activity of the EOs was correlated to the presence of phenolic compounds, such as eugenol, thymol, carvacrol and trans-anethol, or the synergism between the antioxidant activity of nonphenolic compounds such as terpinene-4-ol, α-terpinene, curcumene and chamazulene. Clove essential oil exhibited the highest oil content and radical scavenging activity so it was encapsulated, separately, in three coating materials. Sodium alginate showed the highest retention, encapsulation efficiency and loading capacity of clove EO. Microencapsulation in sodium alginate and chitosan improved the antioxidant activity and phenolic content of the encapsulated clove EO compared with carboxymethyl cellulose. The results support the possibility of using the encapsulated EOs as natural and easy handle antioxidants.     

Optimised accelerated solvent extraction of PCBs and PAHs from compost

This study is the first thorough method optimisation for accelerated solvent extraction (ASE) of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from chemically dried compost. For PCBs, optimised solvent composition, temperature, pressure, number of static cycles, duration, and flush volume were as follows: toluene/acetone 1?:?3 (v/v), 120°C, 2000?psi, 3?×?5?min, and 50%, respectively. Limits of quantification and method precision were between 0.16 and 2.46?µg?kg^?1 dw and 6–17% respectively for individual PCBs. Absolute recoveries of isotope-labelled extraction standards used for each of the analytes ranged from 65 to 105% and relative recoveries were between 85 and 99%. The method proofed to be robust and was successfully applied to different compost samples.

The optimisation of PAHs extraction was performed and resulted in the following conditions: solvent: hexane/acetone 1/3 (v:v), temperature: 140°C, pressure: 1500?psi, extraction time: 3?×?5?min, and 50% flush volume. Limits of detection and method precision for individual PAHs were between 1.1 and 37.2?µg?kg^?1?dw and 12–34% respectively. Absolute and relative recoveries ranged from 24 to 68% and from 85 to 99%, respectively. Optimal extraction conditions for PAHs were more difficult to determine due to the inhomogeneous distribution of PAHs in samples. However, the method appeared to be feasible and suggestions for further improvements are presented.     

Comparison of Eucalyptus cinerea essential oils produced by hydrodistillation and supercritical carbon dioxide extraction

The essential oil of Eucalyptus cinerea is reported to possess a higher 1,8-cineole content than other Eucalyptus species. Variations in the quantitative and qualitative characteristics of E. cinerea oil produced by hydrodistillation (HD) and supercritical carbon dioxide extraction (SCE) techniques and a comparison between glycoside-bound and free volatile constituents produced by HD have been studied. It was found that HD produced higher oil (free volatiles) content (3.1%) as compared with SCE (1.1%), whereas bound volatiles constituted only about 0.4%. Gas chromatographic (GC) analysis of the oil samples revealed significant difference in their chemical composition. The essential oil (free volatiles) produced by HD contained 1,8-cineole (85.1%) as the major constituent, followed by a-terpineol (7.2%) and limonene (4.4%). In the bound volatile fraction produced by HD, 1,8 cineole (20.6%), alpha-terpineol (7.6%), p-cymene (6.3%), and limonene (4.5%) were found as major constituents. The extract produced by SCE was dominated by 1,8-cineole (70.4%), a-terpineol (8.6%), globulol (3.1%), aromadendrene (2%), citronellal (1.7%), viridiflorol (1.3%), phytol (1.1%) and terpinen-4-ol (1%). Although HD produced higher oil yields, SCE produced better extract in terms of the number of components detected.     

加速溶剂萃取-凝胶色谱净化高效液相色谱法测定动物源性食品中的胆固醇

采用加速溶剂萃取-凝胶色谱净化建立了动物源性食品中胆固醇检测的高效液相色谱方法。结果表明,胆固醇浓度在1.0~40.0mg/L范围内线性关系良好,加标回收率为89.1%~99.8%,相对标准偏差为3.1%~7.8%。该方法准确、灵敏度高,适用于富含脂类的动物源性食品中胆固醇的检测。     

Analysis of essential oils by direct sampling from plant secretory structures and capillary gas chromatography

It is of fundamental importance to know the true composition of the essential oil produced by the secretory structures of a plant, both from a biogenetic and a chemotaxonomic point of view. This paper considers a method which combines direct sampling with on-column CGC and studies the oils directly from the secretory structures: some examples are given (Humulus lupulus L., Tagetes erecta L., and Tagetes patula L.). For each plant, the composition of the distilled oil is compared to that obtained by direct sampling, and a photograph of the secretory structures taken by electroscanning microscopy is given.     

Application of accelerated solvent extraction coupled with high-performance counter-current chromatography to extraction and online isolation of chemical constituents from Hypericum perforatum L

Accelerated solvent extraction (ASE) coupled with high-performance counter-current chromatography (HPCCC) was successfully used for the extraction and online isolation of five chemical constituents from the plant Hypericum perforatum L. The upper phase of the solvent system of ethyl acetate-methanol-water (5:2:5, v:v:v) was used as both the ASE solvent and the HPCCC stationary phase. Two hydrophobic compounds including 28.4 mg of hyperforin with a HPLC purity of 97.28% and 32.7 mg of adhyperforin with a HPLC purity of 97.81% were isolated. The lower phase of ethyl acetate-methanol-n-butanol-water (5:2:2.5:12, v:v:v:v) was used as both the ASE solvent and CCC stationary phase. Three hydrophilic compounds of 12.7 mg of 3,4,5-O-tricaffeoylquinic acid with a HPLC purity of 98.82%, 15.2 mg of 1,3,5-O-tricaffeoylquinic acid with a HPLC purity of 99.46% and 42.5mg of 3-O-caffeoylquinic acid with a HPLC purity of 96.90%, were obtained in a one-step extraction-separation process with less than 3h from 10.02 g of raw material of H. perforatum. The targeted compounds isolated, collected and purified by HPCCC were analyzed by high performance liquid chromatography (HPLC), the chemical structures of all five compounds above mentioned were identified by UV, MS and NMR.     

Comparison of the oxidative stability of soybean and sunflower oils enriched with herbal plant extracts

The present study was conducted to determine and compare the oxidative stability of soybean and sunflower oils using differential scanning calorimetry (DSC). These edible oils were enriched with marjoram (Origanum majorana L.), thyme (Thymus vulgaris L.), and oregano (Origanum vulgare L.) extracts at three different concentrations and synthetic antioxidant (BHA). The fatty acid composition of studied oils was determined by gas chromatography mass spectrometry to evaluate the content of unsaturated fatty acids that are sensitive to oxidation process. Oil samples were heated in the DSC at different heating rates (4.0, 7.5, 10.0, 12.5, and 15.0 °C min^?1) and oxidation kinetic parameters (activation energy, pre-exponential factor, and oxidation rate constant) were calculated. The results showed that the oxidative stability of sunflower oil samples enriched with oregano extracts and soybean oil supplemented with thyme extracts was improved compared to samples without the addition of herbal plant extracts and the synthetic antioxidant.     

Microwave-assisted extraction and accelerated solvent extraction with ethyl acetate-cyclohexane before determination of organochlorines in fish tissue by gas chromatography with electron-capture detection

Focused open-vessel microwave-assisted extraction (FOV-MAE), closed-vessel microwave-assisted extraction (CV-MAE), and accelerated solvent extraction (ASE) were used for extraction before determination of organochlorine compounds (polychlorinated biphenyls, DDT, toxaphene, chlordane, hexachlorobenzene, hexachlorocyclohexanes, and dieldrin) in cod liver and fish fillets. Wet samples were extracted without the time-consuming step of lyophilization or other sample-drying procedures. Extractions were performed with the solvent mixture ethyl acetate-cyclohexane (1 + 1, v/v), which allowed direct use of gel-permeation chromatography without solvent exchange. For FOV-MAE, the solvent mixture removed water from the sample matrix via azeotropic distillation. The status of water removal was controlled during extraction by measuring the temperature of the distillate. After water removal, the temperature of the distillate increased and the solvent mixture became less polar. Only the pure extraction solvent allowed quantitative extraction of the organochlorine compounds. For CV-MAE, water could not be separated during the extraction. For this reason, the extraction procedure for wet fish tissue required 2 extraction steps: the first for manual removal of coextracted water, and the second for quantitative extraction of the organochlorine compounds with the pure solvent. Therefore, CV-MAE is less convenient for samples with high water content. For ASE, water in the sample was bound with Na2SO4. The reproducibility for each technique was very good (relative standard deviation was typically <10%); the slightly varying levels were attributed to deviations during sample cleanup and the generally low levels.