Effective on‐line high‐speed shear dispersing emulsifier technique coupled with high‐performance countercurrent chromatography method for simultaneous extraction and isolation of carotenoids from Lycium barbarum L. fruits

An efficient combination strategy based on high‐speed shear dispersing emulsifier technique and high‐performance countercurrent chromatography was developed for on‐line extraction and isolation of carotenoids from the fruits of Lycium barbarum. In this work, the high‐speed shear dispersing emulsifier technique has been employed to extract crude extracts using the upper phase of high‐performance countercurrent chromatography solvent system composed of n‐hexane?dichloromethane?acetonitrile (10:4:6.5, v/v) as the extraction solvent. At the separation stage, the high‐performance counter‐current chromatography process adopts elution–extrusion mode and the upper phase of the solvent system as stationary phase (reverse‐phase mode). As a result, three compounds including zeaxanthin, zeaxanthin monopalmitate, and zeaxanthin dipalmitate with purities of 89, 90, and 93% were successfully obtained in one extraction‐separation operation within 120 min. The targeted compounds were analyzed and identified by high‐performance liquid chromatography, mass spectrometry, and NMR spectroscopy. The results indicated that the present on‐line combination method could serve as a simple, rapid, and effective way to achieve weak polar and unstable compounds from natural products.     

Electronic structure and conformational analysis of P218: An antimalarial drug candidate

P218 is one of the very important and recent lead compounds for antimalarial research. The 3D structural and electronic details of P218 are not available. In this article, quantum chemical studies to understand the possible 3D structures of P218 are reported and compared with 3D structures from the active site cavities of hDHFR and PfDHFR. The neutral P218, can adopt open chain as well as cyclic arrangements. Under implicit solvent condition a zwitterionic‐cyclic conformer is found to be quite possible. Microsolvation studies using explicit water molecules indicate that one water molecule may bridge the two ends of zwitterionic‐cyclic P218. It was observed that the protonation occurs preferentially at N¹ position of the 2,4‐diaminopyrimidine ring, with a proton affinity of 274.49 kcal/mol (implicit solvent phase) and 236.35 kcal/mol (gas phase). A dimer of P218 may be zwitterionic dimer, the dimer formation can release upto ～28.60 kcal/mol (implicit solvent phase).     

Atmospheric pressure thermospray ionization using a heated microchip nebulizer

When a standard atmospheric pressure chemical ionization (APCI) or atmospheric pressure photoionization (APPI) ion source is used without applying the corona discharge or photoirradiation, atmospheric pressure thermospray ionization (APTSI) of various compounds can be achieved. Although largely ignored, this phenomenon has recently gained interest as an alternative ionization technique. In this study, this technique is performed for the first time on a miniaturized scale using a microchip nebulizer. Sample ionization with the presented microchip‐APTSI (µAPTSI) is achieved by applying only heat and gas flow to a nebulizer chip, without any other methods to promote gas‐phase ionization. To evaluate the performance of the described µAPTSI setup, ionization efficiency for a set of test compounds was monitored as the microchip positioning, temperature, nebulizer gas flow rate, sample solution composition, and solvent flow rate were varied. The µAPTSI mass spectra of the test compounds were also compared to those obtained with ESI and APCI. The µAPTSI produces ESI‐like spectra with low background noise, favoring the formation of protonated or deprotonated molecules of compounds that are ionizable in solution. Multiple charging of peptides without in‐source fragmentation was also observed. Unlike ESI, however, the µAPTSI source can tolerate the presence of mobile phase additives like trifluoroacetic acid (TFA) without significant ion suppression. The µAPTSI source can be used with standard mass spectrometer ion source hardware, being a unique alternative to the present interfacing techniques. Copyright © 2009 John Wiley & Sons, Ltd.     

Charcoal open tubular traps for the analysis of air and headspace samples

5 cm × 0.3 mm i.d. glass capillary tubes coated with fine charcoal particles are used for the analysis of organic compounds, particularly tri- and tetrachloroethylene, benzene, and toluene, in air and headspace samples. Due to their small size, these traps are easy to use with capillary GC. As, e.g. 20 ml of gas can be sucked through this trap in 20 s, it is a simple technique providing high sensitivity; compared to headspace with split injection, sensitivity is increased by a factor exceeding 100. The column effluent is split into FID and ECD in such a way that small as well as large amounts of the chlorinated compounds can be detected.     

A trapping column for the coupling of reversed-phase liquid chromatography and capillary gas chromatography

A new technique for coupling reversed-phase liquid chromatography (RPLC) with gas chromatography is described. A fraction eluting from an RPLC column is trapped on a short column packed with polymeric adsorbent. After the mobile phase has been displaced with water, the analytes are desorbed with ethyl acetate. Following a delay time to enable the water to be flushed to waste, the ethyl acetate containing the analytes is introduced into the gas chromatograph under conditions suitable for partially concurrent solvent evaporation, i.e. below the solvent boiling point and at a rate just exceeding the evaporation rate. Post-column addition of water to the RPLC eluent helps to prevent breakthrough of compounds which are only modestly retained on the trapping column. The relationship between the capacity factors of the analytes on the trapping column and the required dilution factor is discussed. Polycyclic aromatic hydrocarbons are used as test compounds to study the system.     

Rapid analysis of the essential oil components of dried Zanthoxylum bungeanum Maxim by Fe2O3‐magnetic‐microsphere‐assisted microwave distillation and simultaneous headspace single‐drop microextraction followed by GC–MS

In this work, microwave distillation assisted by Fe₂O₃ magnetic microspheres (FMMS) and headspace single‐drop microextraction were combined, and developed for determination of essential oil compounds in dried Zanthoxylum bungeanum Maxim (ZBM). The FMMS were used as microwave absorption solid medium for dry distillation of dried ZBM. Using the proposed method, isolation, extraction, and concentration of essential oil compounds can be carried out in a single step. The experimental parameters including extraction solvent, solvent volume, microwave power, irradiation time, and the amount of added FMMS, were studied. The optimal analytical conditions were: 2.0 μL decane as the extraction solvent, microwave power of 300 W, irradiation time of 2 min, and the addition of 0.1 g FMMS to ZBM. The method precision was from 4 to 10%. A total of 52 compounds were identified by the proposed method. The conventional steam distillation method was also used for the analysis of essential oil in dried ZBM and only 31 compounds were identified by steam distillation method. It was found that the proposed method is a simple, rapid, reliable, and solvent‐free technique for the determination of volatile compounds in Chinese herbs.     

Selektive Verbreiterung von 1H-NMR Restsignalen deuterierter Lösungsmittel

¹H {²H} off-resonance noise decoupling experiments with incompletely deuterated compounds result in a selective broadening of those residual proton signals which are split by H/D couplings. By this technique hidden resonance lines which are overlapped by solvent signals can be easily detected, as is demonstrated by the analysis of acetone/acetone-d₆ mixtures. Typical experimental details are given.     

A liquid–liquid extraction technique for phthalate esters with water-soluble organic solvents by adding inorganic salts

In the presence of inorganic salts, the mixture solution of some water-soluble organic solvents and water can form two clearly separated phases. One is the organic solvent rich phase, the other is the water rich phase. In the phase separation process, hydrophobic solutes dissolved in the mixture solution such as phthalate esters can be extracted into the organic solvent rich phase quantitatively. Based on this phase separation phenomenon, a liquid–liquid extraction technique of phthalate esters using water-soluble organic solvents as organic phases was developed. Several important parameters affecting the extraction efficiency including the kind and the amount of water-soluble organic solvents, the kind and the amount of inorganic salts and the pH of the sample solutions were carefully studied. This new extraction technique has been applied to the HPLC analysis for water lixivium of plastic wrapping film. Under the optimized conditions, detection limits of 1.5, 2.3, 1.0, 2.6, 1.3 and 3.0 ng mL⁻¹ were obtained for diethylphthalate, di-n-propylphthalate, di-iso-butylphthalate, dicyclohexylphthalate, di-n-octylphthalate and di-n-nonylphthalate ester respectively. The strongpoints of this new liquid–liquid extraction technique are the easy phase separation, rapid partition equilibrium, less toxicity and very good compatibility with subsequent HPLC determinations.     

Combination of supercritical fluid extraction with counter‐current chromatography to isolate anthocyanidins from the petals of Chaenomeles sinensis based on mathematical calculations

Supercritical fluid extraction (SFE) coupled with high‐speed counter‐current chromatography (HSCCC) was successfully used for the extraction and on‐line isolation of the anthocyanidins from the petals of Chaenomeles sinensis in two stages. The SFE parameters were optimized by an orthogonal test, and the solvent systems of SFE and HSCCC were calculated and optimized with the help of a multiexponential function model. In the first stage, the lower phase of the solvent system of n‐butanol/tert‐butyl methyl ether/acetonitrile/0.1% aqueous TFA (0.715:1.0:0.134:1.592, v/v/v/v) was used as both the SFE modifier and the HSCCC stationary phase, after extraction, the extractants were pumped into HSCCC column, and then eluted with the corresponding upper phase to isolate the moderately hydrophobic compounds. In the second stage, the upper phase of the solvent system of n‐butanol/ethyl acetate/acetonitrile/0.1% aqueous TFA (1.348:1.0:0.605:2.156, v/v/v/v) was used as both the SFE modifier and the HSCCC stationary phase, followed by elution with the corresponding lower phase to separate the hydrophobic compounds. With the help of two‐stage SFE/HSCCC, six compounds including delphinidin‐3‐O‐glucoside (Dp3G), cyanidin‐3‐O‐glucoside (Cy3G), peonidin‐3‐O‐glucoside (Pn3G), delphinidin (Dp), peonidin (Pn), and malvidin (Mv) were successfully separated within 300 min. The targeted compounds were identified by UV spectrophotometry, MS, and NMR spectroscopy. This research has opened up great prospects for the industrial application of SFE–HSCCC for the automatic extraction and separation of unstable compounds.     

Comparison of different extraction methods for the determination of essential oils and related compounds from aromatic plants and optimization of solid-phase microextraction/gas chromatography

Different extraction methods for the subsequent gas chromatographic determination of the composition of essential oils and related compounds from marjoram (Origanum majorana L.), caraway (Carum carvi L.), sage (Salvia officinalis L.), and thyme (Thymus vulgaris L.) have been compared. The comparison was also discussed with regard to transformation processes of genuine compounds, particularly in terms of expenditure of time. Hydrodistillation is the method of choice for the determination of the essential oil content of plants. For investigating the composition of genuine essential oils and related, aroma-active compounds, hydrodistillation is not very useful, because of discrimination and transformation processes due to high temperatures and acidic conditions. With cold solvent extraction, accelerated solvent extraction, and supercritical fluid extraction, discrimination of high and non-volatile aroma-active components as well as transformation processes can be diminished, but non-aroma-active fats, waxes, or pigments are often extracted, too. As solid-phase microextraction is a solvent-free fully automizable sample preparation technique, this was the most sparing to sensitive components and the most time-saving method for the rapid determination of the aroma compounds composition in marjoram, caraway, sage, and thyme. Finally, solid-phase microextraction could be successfully optimized for the extraction of the aroma components from the plants for their subsequent gas chromatographic determination.     

Polycaprolactone-based block copolymers. II. Morphology and crystallization of copolymers of styrene or butadiene and ε-caprolactone

Three series of amorphous semicrystalline poly(styrene-b-ε-caprolactone)s have been synthesized with polystyrene blocks of 6000 (series A), 40000 (series B), and 70000 (series C) molecular weight, respectively. In these materials, the polymer miscibility evolves from a situation where a diffuse interphase involves the major part of the volume of the copolymer (series A) to a sharp phase separation as observed for copolymers with the longest PS block (series C). The crystallization of PCL blocks is mainly governed by the phase morphology. In copolymers of series A, the crystallization rate of PCL blocks is slowed down the more as the miscibility with PS increases, and ultimately the degree of crystallinity X_c decreases significantly. When phase separation is sharp, X_c changes dramatically at the phase inversion and decreases when PS forms the continuous phase. At the inversion X_c depends on the mean size of the PCL microdomains as compared with the thickness of the crystalline lamellae. The periodicity of the phase morphology as observed by TEM is influenced by the solvent used in casting films, whereas monolamellar monocrystals can be obtained by a self-seeding technique.     

Three‐phase solvent systems for the comprehensive separation of a wide variety of compounds from Dicranostigma leptopodum by high‐speed counter‐current chromatography

A three‐phase solvent system was efficiently applied for high‐speed counter‐current chromatography to separate secondary metabolites with a wide range of hydrophobicity in Dicranostigma leptopodum. The three‐phase solvent system of n‐hexane/methyl tert‐butyl ether/acetonitrile/0.5% triethylamine (2:2:3:2, v/v/v/v) was selected for high‐speed counter‐current chromatography separation. The separation was initiated by filling the column with a mixture of intermediate phase and lower phase as a stationary phase followed by elution with upper phase to separate the hydrophobic compounds. Then the mobile phase was switched to the intermediate phase to elute the moderately hydrophobic compounds, and finally the polar compounds still retained in the column were fractionated by eluting the column with the lower phase. In this research, 12 peaks were eluted out in one‐step operation within 110 min, among them, eight compounds with acceptable purity were obtained and identified. The purities of β‐sitosterol, protopine, allocryptopine, isocorydione, isocorydine, coptisine, berberrubine, and berberine were 94.7, 96.5, 97.9, 86.6, 98.9, 97.6, 95.7, and 92.8%, respectively.     

Determination of n-octanol–water partition coefficients by hollow-fiber membrane solvent microextraction coupled with HPLC

A novel direct method has been developed for determination of n-octanol–water partition coefficients by hollow-fiber membrane solvent microextraction (HFMSME) combined with high-performance liquid chromatography (HPLC). The compound of interest is dissolved in water with sonication and a hollow fiber containing octanol inside is placed in the sample solution to perform microextraction. After microextraction the concentrations in both the aqueous and n-octanol phases are analyzed by HPLC with UV detection. The method was evaluated with ten reference compounds and shown to be suitable for determination of the partition coefficients of organic compounds accurately, cheaply, simply, and quickly. Previously unknown n-octanol–water partition coefficients have been obtained for other compounds by use of the hollow-fiber membrane solvent-microextraction technique. Figure Schematic diagram of equipment used for hollow-fiber solvent microextraction. (1) hollow cone-shaped support; (2) aqueous sample; (3) porous hollow-fiber membrane tube (PHFMT); (4) n-octanol phase; (5) sealed end of PHFMT; (6) container (15 mL); (7) stir bar; (8) magnetic stirrer     

Large‐scale separation of acetylcholinesterase inhibitors from Zanthoxylum nitidum by pH‐zone‐refining counter‐current chromatography target‐guided by ultrafiltration high‐performance liquid chromatography with ultraviolet and mass spectrometry screening

A new strategy by converging ultrafiltration high‐performance liquid chromatography with ultraviolet and mass spectrometry and pH‐zone‐refining counter‐current chromatography was developed for the rapid screening and separation of potential acetylcholinesterase inhibitors from the crude alkaloidals extract of Zanthoxylum nitidum. An optimized two‐phase solvent system composed of chloroform/methanol/water (4:3:3, v/v) was used in this study. And, in the optimal solvent system, 45 mM hydrochloric acid was added to the aqueous stationary phase as the retainer, while 5 mM triethylamine was added to the organic mobile phase as the eluter. As a result, with the purity of over 95%, five alkaloids including jatrorrhizine ( 1 , 340 mg), columbamine ( 2 , 112 mg), skimmianine ( 3 , 154 mg), palmatine ( 4 , 226 mg), and epiberberine ( 5 , 132 mg) were successfully purified in one step from 3.0 g crude alkaloidals extract. And their structures were identified by ultraviolet, mass spectrometry, ¹H and ¹³C NMR spectroscopy. Notably, compounds 2 , 4 and 5 were firstly reported in Z. nitidum. In addition, acetylcholinesterase inhibitory activities of compounds 1–5 were evaluated, and compounds 3, 4 and 5 exhibited stronger acetylcholinesterase inhibitory activity (IC₅₀ values at 8.52 ± 0.64, 14.82 ± 1.21 and 3.12 ± 0.32 μg/mL, respectively) than berberine (IC₅₀ value at 32.86 ± 2.14 μg/mL, positive control). The results indicated that the proposed method is an efficient technique to rapidly screen acetylcholinesterase inhibitors from complex samples, and could be served as a large‐scale preparative technique for separating ionizable active compounds.     

An Electric Criterion to Evaluate Glass Transition Temperature: Dielectric Relaxation Measurements

In this contribution, a dielectric measurement technique for the evaluation of phase transition temperature and the study of physical aging on polymeric thin films is considered. This kind of measurement provides the possibility of displaying phase transitions with a high degree of precision. Furthermore, it can be considered alternatively to techniques not applicable in the case of thin films, such as Differential Scanning Calorimetry (DSC). In this work, owing to the high sensitivity of the utilized experimental set-up, a glass transition T_G of 156 K, with a precision equal to 0.3%, and a melting T_M = 220 K have been assessed for 4 µm thick Polydimethylsiloxane (PDMS) films. Performing measurement as a function of time, it was possible to monitor physical aging phenomena, mainly consisting in a change of dielectric properties. As expected, the time evolution of the aging phenomena can be described by a simple logarithmic law.     

Preparative isolation of flavonoid compounds from Oroxylum indicum by high‐speed counter‐current chromatography by using ionic liquids as the modifier of two‐phase solvent system

A preparative high‐speed counter‐current chromatography method for isolation and purification of flavonoid compounds from Oroxylum indicum was successfully established by using ionic liquids as the modifier of the two‐phase solvent system. Two flavonoid compounds including baicalein‐7‐O‐diglucoside and baicalein‐7‐O‐glucoside were purified from the crude extract of O. indicum by using ethyl acetate–water–[C₄mim][PF₆] (5:5:0.2, v/v) as two‐phase solvent system. 36.4 mg of baicalein‐7‐O‐diglucoside and 60.5 mg of baicalein‐7‐O‐glucoside were obtained from 120 mg of the crude extract. Their purities were 98.7 and 99.1%, respectively, as determined by HPLC area normalization method. The chemical structures of the isolated compounds were identified by ¹H‐NMR and ¹³C‐NMR.     

Polyol-induced partitioning of essential oils in water/acetonitrile solvent mixtures

Polyol-induced extraction (PIE) is applied to the extraction of essential oils, using glycerol as a mass separating agent. In 1:1 acetonitrile (ACN)/water solvent mixtures, two immiscible phases can be generated. PIE as an alternative extraction technique was assessed by the extraction of the main flavor and fragrance compounds that comprise six essential oils. In the extraction of eugenol (4-allyl-2-methoxyphenol) from clove buds, the partition coefficients were determined and the % recovery and thermodynamic data in the temperature range of ?20 to 20°C were calculated. The main components present in each essential oil extract were identified through gas chromatography/mass spectrometry (GC/MS) and the compositional profile was compared to traditional extraction techniques. The optimized extraction conditions (?10°C, 1:1 ACN/water (v/v), 20% glycerol) for eugenol at ?10°C give a partition coefficient (K_PC) of 87 and an extraction efficiency of 97% in the acetonitrile-rich phase. The eugenol migration to the organic phase is a spontaneous process (ΔG°?=??9.3?kJ/mol) and an endothermic process (ΔH°?=?9.2?kJ/mol) with entropy being the driving force behind the reaction (ΔS°?=?70?J/K, TΔS°?=?18.4?kJ). The technique was applied to five other essential oils (cinnamon bark, caraway seed, spearmint leaf, peppermint leaf, and anise seed oils) with similar results.     

Application of supercritical fluid extraction coupled with counter–current chromatography for extraction and online isolation of unstable chemical components from Rosa damascena

Supercritical fluid extraction (SFE) coupled with high‐speed counter‐current chromatography (HSCCC) was successfully used for the extraction and online isolation of the unstable compounds from Rosa damascene in a single extraction and separation operation in two stages. The solvent systems of SFE/HSCCC were optimized with the help of multiexponential function model. At the first stage, the upper phase of the solvent system of n‐butanol–tert‐butyl methyl ether–acetonitrile–0.1% aqueous TFA (1.7:1.0:0.8:4.0, v/v/v/v) was used as both the SFE entrainer and the HSCCC stationary phase, and the target compounds were eluted with the corresponding lower phase to separate the hydrophobic compounds. At the second stage, the upper phase of the solvent system of n‐hexane–ethyl acetate–methanol–water (3.2:1.0:2.8:2.6, v/v/v/v) was used as both the SFE entrainer and the HSCCC stationary phase, followed by elution with the corresponding lower phase to separate the moderate hydrophobic compounds. Six compounds including formononetin, delphinidin, cyaniding, 5,6,4′‐trihydroxy‐7,8‐dimethoxy flavone, 5,3′‐dihydroxy‐7,8‐dimethoxy flavone, and 5‐hydroxy‐6,7,8,3′,4′‐pentamethoxy flavone were successfully separated in one extraction–separation operation within 300 min. The targeted compounds were identified by MS and NMR spectroscopy. This research has opened up great prospects for industrial application of SFE/HSCCC to the extraction and separation of unstable compounds.     

Three‐phase hollow‐fiber liquid‐phase microextraction based on deep eutectic solvent as acceptor phase for extraction and preconcentration of main active compounds in a traditional Chinese medicinal formula

A three‐phase hollow‐fiber liquid‐phase microextraction based on deep eutectic solvent as acceptor phase was developed and coupled with high‐performance capillary electrophoresis for the simultaneous extraction, enrichment, and determination of main active compounds (hesperidin, honokiol, shikonin, magnolol, emodin, and β,β′‐dimethylacrylshikonin) in a traditional Chinese medicinal formula. In this procedure, two hollow fibers, impregnated with n‐heptanol/n‐nonanol (7:3, v/v) mixture in wall pores as the extraction phase and a combination (9:1, v/v) of methyltrioctylammonium chloride/glycerol (1:3, n/n) and methanol in lumen as the acceptor phase, were immersed in the aqueous sample phase. The target analytes in the sample solution were first extracted through the organic phase, and further back‐extracted to the acceptor phase during the stirring process. Important extraction parameters such as types and composition of extraction solvent and deep eutectic solvent, sample phase pH, stirring rate, and extraction time were investigated and optimized. Under the optimal conditions, detection limits were 0.3–0.8 ng/mL with enrichment factors of 6–114 for the analytes and linearities of 0.001–13 μg/mL (r² ≥ 0.9901). The developed method was successfully applied to the simultaneous extraction and concentration of the main active compounds in a formula of Zi‐Cao‐Cheng‐Qi decoction with the major advantages of convenience, effectiveness, and environmentally friendliness.     

Preparative separation of bioactive constitutes from Zanthoxylum planispinum using linear gradient counter‐current chromatography

Counter‐current chromatography is a chromatographic technique with a support‐free liquid stationary phase. In the present study, a successful application of linear gradient counter‐current chromatographic method for preparative isolation of bioactive components from the crude ethanol extract of Zanthoxylum planispinum was presented. The application of n‐hexane/ethyl acetate/methanol/water quaternary solvents, in terms of “HEMWat” or “Arizona” solvent families, in gradient elution mode was evaluated. Results indicated that slightly proportional changes of biphasic liquid systems provided the possibility of gradient elution in counter‐current chromatography, maintaining stationary phase retention in the column. With the selected quaternary solvent systems composed of n‐hexane/ethyl acetate/methanol/water (2:1:2:1 and 3:2:3:2, v/v), and optimized gradient programs, in total seven fractions were separated in 4.5 h. Most of the purified compounds could be obtained at the milligram level with over 80% purity. The present study indicated that the linear gradient counter‐current chromatographic approach possessed unique advantages in terms of separation efficiency, exhibiting great potential for the comprehensive separation of complex natural extracts.