Extraction and preconcentration of polychlorinated dibenzo-p-dioxins using the cloud-point methodology: Application to their determination in water samples by high-performance liquid chromatography

A new analytical method based on the cloud-point extraction (CPE) methodology combined with high-performance liquid chromatography is used in this study for the extraction and quantification of polychlorinated dibenzo-p-dioxins. These compounds are extracted by using the non-ionic surfactant polyoxyethylene 10 lauryl ether (POLE) from different aqueous systems: fresh, brackish and sea waters. After the cloud-point extraction, which also allowed a preconcentration of the PCDDs being studied, the samples were analysed using a HPLC–UV system under the optimum chromatographic conditions. The proposed method showed very satisfactory recovery percentages for the PCDDs under study and standard deviation values lower than 2%.

The results obtained were finally compared with those found using the traditional liquid–liquid extraction method.     

Application of non-ionic surfactant in the microwave-assisted extraction of alkaloids from Rhizoma Coptidis

The feasibility of employing non-ionic surfactant oligoethylene glycol monoalkyl ether (Genapol X-080) as an alternative and effective solvent for the microwave-assisted extraction of alkaloids from Rhizoma Coptidis was demonstrated. When compared with commonly used solvents, 5% Genapol X-080 enhanced the extraction efficiency. Under optimal conditions, i.e. 5% acidified Genapol X-080 (v/v), microwave-assisted extraction for 10 min at 100 °C, the extraction recovery of alkaloids reached 92.8% in a one-step extraction. The efficiency of cloud-point preconcentration of three alkaloids was in the range 93.6-94.7% with relative standard deviation lower than 3.3% by the proposed procedure. Furthermore, the combination of microwave-assisted extraction and cloud-point extraction was shown to be a green, rapid and effective approach for alkaloids preconcentration of Rhizoma Coptidis samples.     

Cloud point extraction and separation of copper and lanthanoids using Triton X-100 with water-soluble p-sulfonatocalix[4]arene as a chelating agent

A method is presented for the cloud-point extraction and separation of copper and lanthanoid ions. A water-soluble calixarene, p-sulfonatocalix[4]arene (C4AS), is used as the chelating agent and Triton X-100 is chosen as the surfactant. The factors affecting the extraction efficiency, such as pH, the concentrations of Triton X-100 and C4AS, equilibration time and centrifugation time, were evaluated. The results demonstrate that there are different extraction behaviors for Cu(II) and Ln(III). Cu(II) can be separated from Ln(III) using C4AS as the chelating agent under weakly acidic conditions. The method may be used to remove trace copper from the lanthanoids.     

Cloud-point extraction,preconcentration, and spectrophotometric determination of palladium in water samples

The possibility of using Thio-Michler's Ketone (TMK), 4,4′-bis(dimethylamino) thiobenzophenone, for palladium(II) concentrated by micellar extraction at the cloud-point temperature, and later spectrophotometric determination, was investigated. Under the optimum conditions, preconcentration of 50?mL of water samples in the presence of 0.1% (w/v) octylphenoxy polyethoxy ethanol (Triton X-114), 2?×?10^?6?mol?L^?1?TMK and 1?×?10^–3?mol?L^?1 buffer solution (pH?=?3.0) gave the limit of detection of 0.47?ng?mL^?1, and the calibration graph was linear in the range of 2–50?ng?mL^–1. The recovery under optimum working conditions was higher than 97%. The proposed method has been applied to the spectrophotometric determination of palladium(II) in natural water samples after cloud-point extraction with satisfactory results.     

Determination of disulfoton in surface water samples by cloud-point extraction and gas chromatography

This article proposes an alternative method, using cloud-point extraction and gas chromatography, for extraction and determination of disulfoton in water samples. For cloud-point extraction, the nonionic surfactant Triton X-114 was used. Before gas chromatography, a cleanup stage for surfactant removal from the extracts was optimized. Cleanup used two columns, in series, containing silica gel and Florisil, with methanol:hexane (1?:?1) as eluent, resulting in the removal of more than 95% of the Triton X-114. Factors such as ionic strength (>0.5?mol?L^?1) and surfactant concentration (1.0% w/v) increased the extraction efficiency of the cloud-point methodology, yielding disulfoton recoveries of almost 100%. Compared with liquid–liquid extraction, the cloud-point methodology was more efficient, with a better detectability, and resulted in a significant reduction in solvent volume.     

Determination of pyrrolizidine alkaloids in comfrey by liquid chromatography-electrospray ionization mass spectrometry

Symphytum officinale L. (comfrey) is a medicinal plant commonly used in decoctions and aliments. Besides therapeutic bioactive compounds present in the herb, it is found to contain hepatotoxic pyrrolizidine alkaloids (PAs), such as lycopsamine and others. In the present study, PAs such as lycopsamine, echimidine and lasiocarpine were determined using electrospray liquid chromatography-mass spectrometry (LC-MS) with the method precision (relative standard deviation, RSD) <10%. Detection of lycopsamine, symviridine and their N-oxides could be confirmed with a newly developed method based on HPLC ion-trap and orbitrap MS with electrospray ionization interface. With LC-MS, quantitative analysis of lycopsamine in the botanical extract was carried out. The effect of extraction solvent was optimized by sonication and methanol: H₂O (50:50) was selected. Then a rapid method based on pressurized hot water extraction (PHWE) was employed for the extraction of lycopsamine from comfrey followed by the comparison with heating under reflux with the RSD ranging from 2.49% to 19.32%. Our results showed a higher extraction efficiency for heating under reflux compared with PHWE. It was proposed that the lower extraction efficiency for PHWE was attributable to dissolved nitrogen from air which caused the reduction in the solubility of lycopsamine in the compressed hot solvent. In this study, quantitative analysis of PAs in comfrey was demonstrated. In addition, it was found that the use of subcritical water for extractions depended on the physical properties of the dissolved solutes and their tendency to degrade under the chosen extraction conditions.     

Solvent extraction and self-assembly of nanosized aggregates of p-tert-butyl thiacalix[4]arenes tetrasubstituted at the lower rim by tertiary amide groups and monocharged metal cations in the organic phase

New p-tert-butyl thiacalix[4]arenes functionalized with morpholide and pyrrolidide groups at the lower rim in cone, partial cone, and 1,3-alternate conformations were synthesized, and their receptor properties for monocharged cations (alkali metal and silver ions) were studied using the picrate extraction method and dynamic light scattering (DLS). To evaluate the ability of the p-tert-butyl thiacalix[4]arene derivatives to recognize metal ions, liquid-liquid extraction of their picrate salts has been carried out in a mutually saturated water-dichloromethane system. The degrees of extraction and the extraction constants for monocharged metal cations (Li⁺, Na⁺, K⁺, Cs⁺) have been determined. The ability of the systems, consisting of host and guest molecules, to self-assembly was proved by DLS using a Zetasizer Nano ZS particle size analyzer. It was shown that all the investigated thiacalix[4]arenes are able to form nanoscale particles with silver cations under the experimental conditions. The pyrrolidide derivative in the cone conformation showed both self-association and aggregation processes with lithium cations. The degree of extraction for all the investigated systems that formed nanoscale aggregates in the organic phase was more than 67% and the extraction constants, log K_ex determined by the picrate extraction method, more than 6.     

Comparison of direct thermal desorption with water distillation and superheated water extraction for the analysis of volatile components of Rosa damascena Mill. using GCxGC-TOF/MS

The composition of the volatile components from Rosa damascena Mill. was investigated using comprehensive two-dimensional gas chromatography with time of flight mass spectrometry (TOF/MS). The samples were collected from Turkey and were extracted by water distillation (WD), superheated water extraction (SWE) and direct thermal desorption (DTD). It was found that superheated water extraction gave a slightly higher oil yield than water distillation. The major compounds found in volatiles of R. damascena Mill. were linalool, phenylethylalcohol, citronellol, nerol and geraniol. Phenylethylalcohol content was significantly higher using the DTD (36.52%) and SWE (38.14%) techniques compared to the WD (1.92%) technique. A lower content of monoterpene alcohols was found in volatiles extracted using the DTD method (73.69%) compared to the SWE (86.51%) and WD (86.56%) techniques reflecting the main finding that DTD extracts showed a greater total number of different components than either of the other two methods. The number of volatile components identified with a percentage higher than 0.05% were 54, 37, and 34 for the DTD, SWE and WD techniques, respectively. This highlighted DTD as a promising method for qualitative analysis of rose oil which can yield comprehensive results without the traditional obligation for costly and time consuming extraction techniques.     

Micelle-mediated extraction of tanshinones from Salvia miltiorrhiza bunge with analysis by high-performance liquid chromatography

The feasibility of employing non-ionic surfactant oligoethylene glycol monoalkyl ether (Genapol X-080) as an alternative and effective solvent for the extraction of tanshinones from Salvia miltiorrhiza bunge was studied for the first time. Various experimental conditions were investigated to optimize the extraction. Under optimum conditions, i.e. 10% Genapol X-080 (w/v), liquid/solid ratio of 20:1 (ml g⁻¹), ultrasonic-assisted extraction for 45 min, the extraction recovery of the tanshinones reached the highest value. When compared with commonly used solvents, 10% Genapol X-080 yielded almost the same extraction efficiency as methanol and dichloromethane-methanol (1:4). For the pre-concentration of tanshinones by cloud-point extraction (CPE), sodium chloride was added to the solution to facilitate the phase separation and increase the pre-concentration factor by reducing the volume of the surfactant-rich phase.     

Determination of senkirkine and senecionine in Tussilago farfara using microwave-assisted extraction and pressurized hot water extraction with liquid chromatography tandem mass spectrometry

Tussilago farfara (Kuan Donghua) is an important Chinese herbal medicine which has been shown to contain many bioactive compounds and widely used to relieve cough and resolve phlegm. However, besides therapeutic bioactive compounds, this herb has been found to contain toxic pyrrolizidine alkaloids (PAs), mainly senkirkine and traces of senecionine. In this report, conditions for microwave-assisted extraction (MAE) and pressurized hot water extraction (PHWE) were optimized for the extraction of the PAs. The results were compared against heating under reflux. It was found that the binary mixture of MeOH:H₂O (1:1) acidified using HCl to pH 2-3 was the optimal solvent for the extraction of the PAs in the plant materials. Liquid chromatography (LC) with ultra-violet (UV) detection and electrospray ionization mass spectrometry (ESI-MS) in the positive mode was used for the determination and quantitation of senkirkine and senecionine in the botanical extract. The proposed extraction methods with LC/MS allow for the rapid detection of the major and the minor alkaloids in T. farfara in the presence of co-eluting peaks. With LC/MS, the quantitative analysis of PAs in the extract was done using internal standard calibration and the precision was found to vary from 0.6% to 5.4% on different days. The limits of detection (LODs) and limits of quantitation (LOQs) for MAE and PHWE were found to vary from 0.26 μg/g to 1.04 μg/g and 1.32 μg/g to 5.29 μg/g, respectively. The method precision of MAE and PHWE were found to vary from 3.7% to 10.4% on different days. The results showed that major and minor alkaloids extracted using MAE and PHWE were comparable to that by heating under reflux. Our data also showed that significant ion suppression was not observed in the analysis of senkirkine and senecionine in the botanical extracts with co-eluting peaks.     

Pressurized fluid extraction of carotenoids from Haematococcus pluvialis and Dunaliella salina and kavalactones from Piper methysticum

Pressurized fluid extraction (PFE) was examined as an alternative technology for the extraction of carotenoids in the green algae Haematococcus pluvialis and Dunaliella salina and kavalactones in Piper methysticum. The extraction process was optimized by varying the key extraction factors of solvent, sample-solvent ratio, temperature, and time. The selectivity and efficiency of extraction parameters were determined with high performance liquid chromatography (LC) and LC-mass spectrometry (LC-MS). Results showed that PFE utilization of conventional solvents under controlled temperature and pressure in an oxygen and light-free environment could result in the use of less solvent in a shorter period of time. PFE showed higher or equal extraction efficiencies as compared with traditional solvent extractions while maintaining the integrity of chemical components. PFE showed high potential for extraction of natural products and nutraceuticals, particularly labile and light sensitive chemicals.     

Extraction and determination of phenolic derivatives in water samples by using polyoxyethylene surfactants and liquid chromatography with photodiode array detection

Methodology based on the cloud-point phenomenon was applied to the comparative study of 3 different polyoxyethylene nonionic surfactants in order to extract and preconcentrate a group of phenolic derivatives in water samples; these phenolic compounds, which were determined by liquid chromatography with UV detection, included 11 pollutants given priority by the U.S. Environmental Protection Agency. The optimum conditions for the extraction and preconcentration of phenolic compounds were established for each surfactant. The surfactant that gave the best extraction and preconcentration of the analytes under study was polyoxyethylene 6 lauryl ether (C12E6) with detection limits of <3.5 microg/L for all the phenolic compounds tested. The method was applied to seawater and depurated wastewater samples.     

Cloud-point extraction combined with HPLC for determination of larotaxel in rat plasma: a pharmacokinetic study of liposome formulation

A simple and efficient method based on cloud-point extraction combined with high-performance liquid chromatography was developed and validated for the determination of larotaxel in rat plasma. Nonionic surfactant Triton X-114 was chosen as the extraction solvent. Variable parameters affecting the cloud-point extraction efficiency, for example the nature and concentration of surfactant, NaOH concentration, incubation temperature, and time were evaluated and optimized. Chromatographic separation was accomplished on a Diamonsil C(18) column (150 mm × 4.6 mm, 5 μm) using a mobile phase consisting of acetonitrile and 0.1% phosphoric acid with pH 4.0 (60:40, v/v). The calibration curve showed good linearity over the range of 0.05-10 μg/mL. Under the optimum conditions, the method was shown to be reproducible and reliable with intraday precision below 5.7%, interday precision below 7.2%, accuracy within ±3.5%, and mean extraction recovery of 91.8-94.2%. The validated method was successfully applied to the pharmacokinetic study of larotaxel in rat plasma after a single intravenous administration of larotaxel injection and larotaxel-loaded liposome, respectively. The results indicated that the larotaxel-loaded liposome led to significant differences in pharmacokinetic profile.     

Homogeneous ionic liquid microextraction of the active constituents from fruits of Schisandra chinensis and Schisandra sphenanthera

Homogeneous ionic liquid microextraction (HILME) was developed for the extraction of schizandrin, schisantherin A and deoxyschizandrin from Schisandra chinensis and Schisandra sphenanthera. 1-Butyl-3-methylimidazolium tetrafluoroborate ([C₄MIM][BF₄]) aqueous solution was used as extraction solvent, and ammonium hexafluorophosphate ([NH₄][PF₆]) was used as ion-pairing agent. 1-Butyl-3-methylimidazolium hexafluorophosphate ([C₄MIM][PF₆]), which is barely soluble in water, was formed in situ, and was used as sample solution. High-performance liquid chromatography (HPLC) was employed for separation and determination of the analytes. The calibration curve showed good linear relationship (r > 0.9998). The recoveries were between 69.71% and 88.33% with RSDs lower than 4.86%. External standard method was adopted in the proposed method, and internal standard method was applied for the evaluation of the proposed method. The two methods were compared and the results indicated that the proposed method was acceptable and simple. The HILME is free of volatile organic solvents, and represents lower expenditures of sample, extraction time and solvent, compared with ultrasonic and Soxhlet extraction. There was no obvious difference in the extraction yields of active constitutions obtained by the three extraction methods.     

Development of new cleanup method of polychlorinated dibenzo-p-dioxins/dibenzofurans in fish by freezing-lipid filtration

Freezing-lipid filtration as a new method has been developed for the rapid determination of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) in biological samples. This method can effectively reduce the time of sample pretreatment, labor and amount of solvents compared with conventional methods. By freezing-lipid filtration procedure, about 90% of lipids in extract could be removed without any significant loss of PCDD/Fs. For further cleanup of extracts after freezing-lipid filtration, automatic parallel LC columns including silica gel, alumina and carbon columns were applied. During automatic parallel LC columns cleanup, most of co-extracted interferences such as residue lipids and fatty acids could be eliminated and dioxins could be separated from many other dioxin-like congeners such as polychlorinated biphenyls by this procedure. The extracts after cleanup were analyzed by high-resolution gas chromatography (HRGC)/high-resolution mass spectrometry (HRMS) using an isotope dilution method. The average recoveries and relative standard deviation (R.S.D.) of 17 native congeners in the spiked fish samples at 8-80 pg/g (n = 3) were ranged between 85.3 and 117.2% and 5.7-20.3%, respectively.     

Cloud-Point Extraction Combined with LC–MS for Analysis of Memantine in Rat Plasma

The feasibility of using cloud-point extraction as a simple and effective means of recovery of memantine from rat plasma before LC–MS analysis has been demonstrated. A non-ionic surfactant Triton X-114 was used for extraction of the memantine. On increasing the temperature to the cloud point, phase separation occurred, resulting in an aqueous phase, and a surfactant-rich phase containing most of the analytes. The extraction conditions, for example amount of surfactant, temperature, NaOH concentration, and time of incubation, were optimized. Chromatographic separation was accomplished on a C₁₈ analytical column with 56:44 (v/v) methanol–0.2% aqueous formic acid as isocratic mobile phase at a flow rate of 0.8 mL min^?1. Under the optimum experimental conditions recovery was satisfactory (91–101%) without interference from the surfactant. The method was shown to be reproducible and reliable with intraday precision below 6.6%, interday precision below 14.3%, and linear range from 1 to 400 ng mL^?1. The method was successfully applied to a pharmacokinetic study of memantine in rats after oral and intravenous administration.     

同位素稀释的气相色谱/高分辨质谱联用测定食品中二噁英和共平面多氯联苯

采用HRGC/HRMS和同位素稀释定量技术对样品中17种4~8个氯原子取代的二噁英和呋喃(PCDDs/Fs)与12种共平面多氯联苯(PCBs)定量分析。样品经索式抽提、FMSPowerPrep系统净化、浓缩,利用高分辨气相色谱/高分辨质谱联用仪的多离子检测方式,同位素稀释技术对样品中的目标化合物进行定性和定量。该方法的检出限为pg/g水平。13C同位素内标回收率范围为47%~100%。对3个CRM鱼样中17个PCDDs/Fs和4个PCBs的检测值均在标准定值允许误差范围内。对5个不同的实际样品鱼进行测定表明,样品的回收率在48%~100%之间,回收率的相对标准偏差小于20%;对同一样品进行定量检测的精密度测试结果表明,17种PCDDs/Fs浓度的RSD低于16%,12种PCBs浓度的RSD低于11%。本方法定量分析重现性良好。     

Pressurized liquid extraction versus other extraction techniques in micropreparative isolation of pharmacologically active isoflavones from Trifolium L. species

As a new sample preparation technique, pressurized liquid extraction (PLE), in combination with reversed-phase liquid chromatography (RP-LC) and photodiode-array (PDA) detection were used for the isolation and determination of phytoestrogenic isoflavones in hydrolyzed extracts obtained from aerial parts of five Trifolium L. (clover) species. To optimize the effectiveness of PLE procedure, variable extraction parameters: methanol and acetone (or their 75% aqueous solutions), as extraction solvents, temperatures (75, 100 and 125 °C) and the changeable number of static extraction cycles were tested. Additionally, two other micropreparative techniques: ultrasound-assisted extraction (UAE), and conventional solvent extraction (CSE), under optimized conditions, were also used and compared. Optimum extraction efficiency, expressed in the highest yield of biochanin A, formononetin, daidzein and genistein from plant material, with PLE, using methanol-water (75:25, v/v) as an extraction solvent, an oven temperature of 125 °C and three 5-min static extraction cycles, was obtained.     

Determination of metabolites in Uncaria sinensis by HPLC and GC-MS after green solvent microwave-assisted extraction

Uncaria sinensis (Oliv.) Havil (Rubiaceae) has been used as an important Traditional Chinese Medicine (TCM) herb for the treatment of fevers and various nervous disorders. The major bioactive secondary metabolites from different classes of chemical compounds, i.e. organic acid, flavonoid and alkaloid, present in this TCM herb, namely catechin, caffeic acid, epicatechin and rhynchophylline, were extracted by microwave-assisted extraction (MAE) method with ultra-pure water as the extraction solvent. The optimal extraction conditions for this green solvent MAE method were found to be 100 °C for 20 min. The recoveries of the compounds were found to be comparable to that of heating under reflux using ultra-pure water for 60 min. The method precision (RSD, n = 6) was found to vary from 0.19% to 5.60% for the proposed method on different days for the secondary metabolites. Simultaneously, the key primary metabolites such as sucrose and phenylalanine for the biosynthesis of bioactive secondary metabolites were successfully characterized by GC-MS. Furthermore, an approach using the combination of primary and secondary metabolite profiling based on their chemical fingerprints with Principal Component Analysis (PCA) was successfully developed to evaluate the quality of U. sinensis obtained from different sources. This approach was shown to be feasible in discriminating U. sinensis from different origins and thus a potential application for the quality control of other medicinal herbs.     

N-Methylimidazolium modified magnetic particles as adsorbents for solid phase extraction of genomic deoxyribonucleic acid from genetically modified soybeans

N-Methylimidazolium modified magnetic particles (MIm-MPs) were prepared and applied in the solid phase extraction of genomic deoxyribonucleic acid (DNA) from genetically modified soybeans. The adsorption of MIm-MPs for DNA mainly resulted from the strong electrostatic interaction between the positively charged MPs and the negatively charged DNA. The elution of DNA from MPs–DNA conjugates using phosphate buffer resulted from the stronger electrostatic interaction of phosphate ions with MPs than DNA. In the extraction procedure, no harmful reagents (e.g. phenol, chloroform and isopropanol, etc.) used, high yield (10.4 μg DNA per 30 mg sample) and high quality (A₂₆₀/A₂₈₀ = 1.82) of DNA can be realized. The as-prepared DNA was used as template for duplex-polymerase chain reaction (PCR) and the PCR products were analyzed by a sieving capillary electrophoresis method. Quick and high quality extraction of DNA template, and fast and high resolution detection of duplex PCR products can be realized using the developed method. No toxic reagents are used throughout the method.