中空纤维分散液膜富集稀土元素

采用2-乙基己基膦酸单-2-乙基己基酯(HEHEHP)-正庚烷为萃取剂,盐酸为反萃取剂,中空纤维膜作支撑膜,研究中空纤维分散液膜技术富集稀土镱(Yb~(3+))离子。考察了体系物性:反萃分散相中反萃剂浓度、萃取剂浓度、萃取剂与反萃剂体积比、料液相p H值、稀土离子浓度;流体流动状态:反萃分散相与料液相流速变化等因素对富集稀土离子的影响。中空纤维分散液膜富集Yb~(3+)的最佳条件为:萃取剂浓度为0.25 mol/L,反萃取剂HCl浓度为4.00 mol/L,萃取剂与反萃剂体积比为10∶40,料液相p H=2.80,稀土离子浓度为0.025 mol/L。反萃分散相体积流量和料液相体积流量较小时,萃取率随流量的增加呈现逐渐增大的趋势。若两相体积流量过大,反萃过程进行不完全,萃取率反而下降。研究结果表明,中空纤维分散液膜技术可实现稀土离子的有效富集。     

Electro membrane extraction combined with capillary electrophoresis for the determination of amlodipine enantiomers in biological samples

Electro membrane extraction as a new microextraction method was applied for the extraction of amlodipine (AM) enantiomers from biological samples. During the extraction time of 15 min, AM enantiomers migrated from a 3 mL sample solution, through a supported liquid membrane into a 20 μL acceptor solution presented inside the lumen of the hollow fiber. The driving force of the extraction was 200 V potential, with the negative electrode in the acceptor solution and the positive electrode in the sample solution. 2-Nitro phenyl octylether was used as the supported liquid membrane. Using 10 mM HCl as background electrolyte in the sample and acceptor solution, enrichment up to 124 times was achieved. Then, the extract was analyzed using CD modified CE method for separation of AM enantiomers. Best results were achieved using a phosphate running buffer (100 mM, pH 2.0) containing 5 mM hydroxypropyl-α-CD. The range of quantitation for both enantiomers was 10-500 ng/mL. Intra- and interday RSD (n=6) were less than 14%. The limits of quantitation and detection for both enantiomers were 10 and 3 ng/mL respectively. Finally, this procedure was applied to determine the concentration of AM enantiomers in plasma and urine samples.     

Liquid-phase microextraction with porous hollow fibers, a miniaturized and highly flexible format for liquid-liquid extraction

Since 1999, substantial research has been devoted to the development of liquid-phase microextraction (LPME) based on porous hollow fibers. With this technology, target analytes are extracted from aqueous samples, through a thin supported liquid membrane (SLM) sustained in the pores in the wall of a porous hollow fiber, and further into a microL volume of acceptor solution placed inside the lumen of the hollow fiber. After extraction, the acceptor solution is directly subjected to a final chemical analysis by liquid chromatography (HPLC), gas chromatography (GC), capillary electrophoresis (CE), or mass spectrometry (MS). In this review, LPME will be discussed with focus on extraction principles, historical development, fundamental theory, and performance. Also, major applications have been compiled, and recent forefront developments will be discussed.     

A novel approach to automation of dynamic hollow fiber liquid-phase microextraction

An automated dynamic two-phase hollow fiber microextraction apparatus combined with high-performance liquid chromatography was developed for extraction and determination of chlorophenoxy acid (CPA) herbicides from environmental samples. The extraction device, called TT-extractor, consists of a polypropylene hollow fiber mounted inside a stainless steel tube by means of two tee-connectors in flow system. An organic solvent, which fills the lumen and the pores of the hydrophobic fiber, is pumped through the fiber repeatedly and the sample is pumped along the outer side of the fiber. The factors affecting the dynamic hollow fiber liquid-phase microextraction (DHF-LPME) of target analytes were investigated and the optimal extraction conditions were established. To test the applicability of the designed instrument, CPAs were extracted from environmental aqueous samples. The limits of detection (LODs) as low as 0.5 μg/L, linear dynamic range in the range of 1-100 μg/L and the relative standard deviations of <7% were obtained. The developed method can provide perconcentration factors as large as 230. A hollow fiber membrane can be used at least 20 times with neither loss in the efficiency nor carryover of the analytes between runs. The system is cheap and convenient and requires minimal manual handling.     

Fundamental studies on the electrokinetic transfer of net cationic peptides across supported liquid membranes

By the application of an electrical potential difference (25 V), 37 different peptides were extracted from 500 μL aqueous sample (10 mM formic acid, positive electrode), through a supported liquid membrane (SLM) impregnated in the walls of a porous hollow fiber, and into 25 μL aqueous acceptor solution (100 mM formic acid, negative electrode) present inside the lumen of the fiber. Most of the peptides were obtained by tryptic digestion of cytochrome c and bovine serum albumin, which yielded complex samples for extraction. Three different SLMs were utilized to correlate the peptides extractability with the highly variable physical-chemical properties of the peptides. The first SLM (pure eugenol) provided an electromembrane extraction system for hydrophobic and intermediate peptides (hydrophilicity values below 0.2), where the extraction of peptides into the SLM was mainly based on solvent interactions. The second SLM (1-octanol/di-isobutylketone/di-(2-ethylhexyl) phosphate) extracted both hydrophobic and hydrophilic peptides (hydrophilicity values in the range from -2 to+1) successfully, and the transfer of peptides was principally based on ionic interactions with di-(2-ethylhexyl) phosphate. The third SLM (1-octanol/15-crown-5 ether) was selective for hydrophobic peptides (negative hydrophilicity values), and complexation of the peptides with the crown ether was important for the migration of peptides into the acceptor solution.     

Electrokinetic migration of acidic drugs across a supported liquid membrane

Electrokinetic cross membrane extraction of acidic drugs was demonstrated for the first time. The acidic drugs were extracted from an alkaline aqueous donor solution (300 microl), through a thin supported liquid membrane of 1-heptanol sustained in the pores of the wall of a porous hollow fiber, and into an aqueous alkaline acceptor solution (30 microl) present inside the lumen of the hollow fiber by the application of a d.c. electrical potential. The negative electrode was placed in the donor solution, and the positive electrode was placed in the acceptor solution. Optimal extractions were accomplished with 1-heptanol as the supported liquid membrane, with 50 V as the driving force, and with pH 12.0 in both the donor and acceptor solutions, respectively (NaOH). Equilibrium extraction conditions were obtained after 5 min of operation with the whole assembly agitated at 1200 rpm. Eleven different acidic drugs were extracted with recovery values between 8 and 100%, and initial data supported that electrokinetic cross membrane extraction provided repeatable data and linear response between original donor concentration and final acceptor concentration of the acidic model compounds.     

中空纤维膜液相微萃取-高效液相色谱法测定醋酸氯己定痔疮栓中的醋酸氯己定

建立了中空纤维膜液相微萃取-高效液相色谱（HPLC）测定醋酸氯己定痔疮栓中醋酸氯己定含量的方法。将样品用醋酸水溶液萃取5次,配成样品溶液,然后用装有正辛醇的中空纤维膜进行液相微萃取,萃取液用高效液相色谱测定。醋酸氯己定的质量浓度为0.5 ～ 16 mg/L时与其峰面积呈良好的线性关系,加样回收率大于98.0%,相对标准偏差低于4.0%。该方法样品处理简单、快速,灵敏度与不经过液相微萃取的HPLC方法相比提高了约24倍,醋酸氯己定痔疮栓中的其他物质对测定无干扰。     

Functionalization of cellulose dialysis membranes for chiral separation using beta-cyclodextrin immobilization

A membrane-based chiral separation system for the separation of racemic tryptophan solutions is developed by the covalently binding beta-cyclodextrin onto the surface of commercial cellulose membranes. The immobilization process is monitored by XPS. AFM demonstrates the evolutionary transition of membrane surface morphology before and after the CD immobilization. Due to their different complexation with immobilized CD, dialysis transport experiments show d-tryptophan preferential permeability through the immobilized CD membranes, and the enantioselectivity is 1.10. A model based on the existence of a thin chiral solution layer of amino acid at the interface between the feed solution and the membrane has been proposed. This chiral separation model has been verified using the chiral separation results of racemic amino acids and binding constants of amino acids with CD. The effect of membrane's pore size on enantioselectivity has also been investigated. The immobilized CD membrane, having MWCO 1000, exhibits the highest enantioselectivity to the racemic tryptophan solution.     

Development of a static and exhaustive extraction procedure for field passive preconcentration of chlorophenols in environmental waters with hollow fiber-supported liquid membrane

A static and exhaustive extraction mode of hollow fiber-supported liquid membrane was developed for field sample passive pretreatment of environmental water samples. The extraction device was prepared by immobilizing dihexyl ether in the wall of a polypropylene hollow fiber membrane (60 cm length, 50 μm wall thickness, and 280 μm id) as liquid membrane and filling the fiber lumen with 0.1 M NaOH as acceptor, and closing the two ends of the fiber with an aluminum foil. Passive extraction was conducted by immersing the device into 15 mL water samples modified with 0.01 M HCl and 20% m/v NaCl. Model analytes including 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol were transferred into acceptor with extraction efficiencies over 79% in 10 h at room temperature, and determined by high-performance liquid chromatography. The proposed method has the enrichment factor of 394-498 and LOD of 0.3-0.4 μg/L for the three chlorophenols. Humic acid and salinity in the environmentally relevant range had no significant influence on the extraction, and chlorophenols in various environmental waters were determined with spike recoveries between 71.6 and 120%. The static passive extraction nature benefited field sample pretreatment without power, whereas the exhaustive extraction mode effectively eliminated the sample matrix effects.     

加电中空纤维膜萃取-离子色谱法测定乙酸丁酯中的无机阴离子

以去离子水为萃取剂,通过加电膜萃取装置萃取了乙酸丁酯中的无机阴离子.在600 V直流电压作用下,乙酸丁酯中的4种无机阴离子经中空纤维膜膜孔进入膜内的去离子水中,采用离子色谱对萃取液进行分析.最佳萃取条件为:施加电压600 V;搅拌速度600 r/min;萃取时间5 min.应用本方法测定乙酸丁酯样品,4种无机阴离子的线...     

Extraction of surfactin from fermentation broth with n-hexane in microporous PVDF hollow fibers: Significance of membrane adsorption

In order to avoid foaming behavior and the formation of stable emulsions in traditional extraction, non-dispersive extraction of surfactin from the fermentation broth of Bacillus subtilis ATCC 21332 culture with n-hexane was studied in microporous polyvinylidene fluoride (PVDF, pore size 0.2 μm) hollow fiber module. In this work, the broth was pretreated by acid precipitation and the precipitate was then dissolved in NaOH solution, and the treated broth was passed through the lumen side of the module and n-hexane was flowed across the shell side. Experiments were performed at a fixed pH of 8.0 and a flow rate of both phases of 2.5 mL min⁻¹ but at different surfactin concentrations (300–3000 mg L⁻¹). Under the conditions studied, it was shown that surfactin was adsorbed onto the surface of the fibers, instead of being extracted by n-hexane and transported through the pores of the fibers into bulk n-hexane phase. The adsorption capacity was determined and the adsorption dynamics was analyzed. The purity of surfactin desorbed from the fibers with ethanol was found to be higher than that obtained after solvent extraction with n-hexane.     

Electrospun superhydrophobic polystyrene hollow fiber as a probe for liquid–liquid microextraction with gas chromatography‐mass spectrometry

A superhydrophobic polystyrene hollow fiber was electrospun around a copper spring collector. This approach led to the construction of a hollow fiber membrane, and the copper spring acted as a scaffold. The characteristic properties of the hollow fiber were studied by scanning electron microscopy. The membrane was used as a probe to transfer the extracting solvent from aquatic media to a gas chromatograph. After performing the liquid–liquid microextraction procedure on 10 mL of water sample by octanol, the whole solution was passed through the prepared polystyrene hollow fiber. Propanol, containing 2 mg/L lindane as the internal standard, was used for desorption and an aliquot of 2 μL of the desorbing solvent was subsequently injected into gas chromatography with mass spectrometry. Effects of different parameters influencing the extraction efficiency were optimized. The limits of detection and quantification were 2 and 6 ng/L, respectively. The relative standard deviations at a concentration level of 100 ng/L were between 2 and 6% (n = 3) while the method linearity ranged from 6 to 200 ng/L. Some real water samples were analyzed by the developed method and relative recoveries were in the range of 76–107%.     

Ion‐pair‐based hollow‐fiber liquid‐phase microextraction combined with high‐performance liquid chromatography for the simultaneous determination of urinary benzene,toluene, and styrene metabolites

In the current study, a novel technique for extraction and determination of trans,trans‐muconic acid, hippuric acid, and mandelic acid was developed by means of ion‐pair‐based hollow fiber liquid‐phase microextraction in the three‐phase mode. Important factors affecting the extraction efficiency of the method were investigated and optimized. These metabolites were extracted from 10 mL of the source phase into a supported liquid membrane containing 1‐octanol and 10% w/v of Aliquat 336 as the ionic carrier followed by high‐performance liquid chromatography analysis. The organic phase immobilized in the pores of a hollow fiber was back‐extracted into 24 μL of a solution containing 3.0 mol/L sodium chloride placed inside the lumen of the fiber. A very high preconcentration of 212‐ to 440‐fold, limit of detection of 0.1–7 μg/L, and relative recovery of 87–95% were obtained under the optimized conditions of this method. The relative standard deviation values for within‐day and between‐day precisions were calculated at 2.9–8.5 and 4.3–11.2%, respectively. The method was successfully applied to urine samples from volunteers at different work environments. The results demonstrated that the method can be used as a sensitive and effective technique for the determination of the metabolites in urine.     

Micro-scale membrane extraction of glyphosate and aminomethylphosphonic acid in water followed by high-performance liquid chromatography and post-column derivatization with fluorescence detector

A carrier-mediated supported liquid membrane micro-extraction using single hollow fiber membrane suitable for the determination of the herbicide glyphosate and its main metabolite aminomethylphosphonic acid in water is reported. A solution of 0.20 M Aliquat-336, a cationic carrier, in di-n-hexyl ether was selected as the supported liquid. A 20 microL of 1.0 M potassium chloride as the acceptor phase was filled in the membrane lumen. The membrane was immersed in a 20 mL of pH 9.0 sample solution. After 60-min extraction, the acceptor phase was analyzed by high-performance liquid chromatography with post-column derivatization. The enrichment factors were found to be 853 and 136 for glyphosate and aminomethylphosphonic acid, respectively. The method detection limits are 0.22 microg/L for glyphosate and 3.40 microg/L for aminomethylphosphonic acid. The procedure was validated and showed good accuracy and precision over a large linear dynamic range. The validated method was tested for the analysis of both analytes in spiked groundwater with good success.     

Biodegradation of toluene in a membrane biofilter

A membrane biofilter is used to biodegrade toluene in the gas phase. Active microorganisms are immobilized on the outside of a hollow fiber membrane cartridge and air containing toluene as the contaminant is passed through the membrane fibers. A porous polysulfone membrane containing water in the pore is used through which both toluene and oxygen are diffused to the biofilm attached to the outside surface. High conversion of toluene (84%) is achieved with a 16 second gas-phase residence time, based on total internal volume of the hollow fibers. A mathematical model is then developed to estimate toluene removal efficiencies at higher air flow rates.     

Non-invasive monitoring of fouling in hollow fiber membrane via UTDR

Fouling is the most critical problem associated with membrane separations in liquid media. But it is difficult to control the inevitable membrane fouling because of its invisibility, especially on the inside surface of hollow fiber membranes. This study describes the extension of ultrasonic time-domain reflectometry (UTDR) for the real-time measurement of particle deposition in a single hollow fiber membrane. A transducer with a frequency of 10 MHz and polyethersulfone hollow fiber membranes with 0.8 mm inside diameter (ID) and 1.2 mm outside diameter (OD) were used in this study. The fouling experiments were carried out with 1.8 g/L kaolin suspension at flow rates 16.7 and 10.0 cm/s. The results show that UTDR technique is able to distinguish and recognize the acoustic response signals generated from the interfaces water/upper outside surface of the hollow fiber, lumen upside surface/water, water/lumen underside surface and lower outside surface/water in the single hollow fiber membrane module in pure water phase. The systemic changes of acoustic responses from the inside surfaces of the hollow fiber in the time- and amplitude-domain with operation time during the fouling experiments were detected by UTDR. It is associated with the deposition and formation of the kaolin layer on the inside surfaces. Further, the acoustic measurement indicates that the deposited fouling layer is denser on the lumen underside surface of the hollow fiber than that on the lumen upside surface as a result of weight. Moreover, it is found that the fouling layer grows faster on the inside surface of the hollow fiber at a flow rate of 10.0 cm/s than that at 16.7 cm/s due to the lower shear stress. The fouling layer formed is thicker at a flow rate of 10.0 cm/s than that at 16.7 cm/s. The flux decline data and SEM analysis corroborate the ultrasonic measurement. Overall, this study confirms that UTDR measurement will provide not only a new protocol for the observation of hollow fiber membrane fouling and cleaning, but also a quantitative approach to the optimization of the membrane bioreactor system.     

Extraction and preconcentration of tylosin from milk samples through functionalized TiO2 nanoparticles reinforced with a hollow fiber membrane as a novel solid/liquid‐phase microextraction technique

The aim of this study was to introduce a novel, simple, and highly sensitive preparation method for determination of tylosin in different milk samples. In the so‐called functionalized TiO₂ hollow fiber solid/liquid‐phase microextraction method, the acceptor phase is functionalized TiO₂ nanoparticles that are dispersed in the organic solvent and held in the pores and lumen of a porous polypropylene hollow fiber membrane. An effective functionalization of TiO₂ nanoparticles has been done in the presence of aqueous H₂O₂ and a mild acidic ambient under UV irradiation. This novel extraction method showed excellent extraction efficiency and a high enrichment factor (540.2) in comparison with conventional hollow fiber liquid‐phase microextraction. All the experiments were monitored at λ_max = 284 nm using a simple double beam UV‐visible spectrophotometer. A Taguchi orthogonal array experimental design with an OA₁₆ (4⁵) matrix was employed to optimize the factors affecting the efficiency of hollow fiber solid/liquid‐phase microextraction such as pH, stirring rate, salt addition, extraction time, and the volume of donor phase. This developed method was successfully applied for the separation and determination of tylosin in milk samples with a linear concentration range of 0.51–7000 μg/L (r² = 0.991) and 0.21 μg/L as the limit of detection.     

Separation of Trivalent Samarium through Facilitated Stripping Dispersion Hollow Fiber Liquid Membrane Using p204 as Mobile Carrier

The separation of Sm(III) through stripping dispersion hollow fiber liquid membrane system (SDHFLM) containing feed phase adding acetate buffer solution and dispersion solution with HCl solution as the stripping solution and membrane solution of di(2‐ethylhexyl) phosphoric acid (p204) dissolved in kerosene, has been studied. A set of factors were studied, including pH value, initial concentration of Sm(III) and different ionic strength of feed phase, volume ratio of membrane solution and stripping solution (O/W), HCl concentration, carrier concentration, different stripping agents of dispersion phase on Sm(III) separation. Experimental results indicate that the optimum separation conditions of Sm(III) were obtained as that HCl concentration was 4.00 mol/L, p204 concentration was 0.150 mol/L, and volume ratio of membrane solution and stripping solution (O/W) was 1.00 in the dispersion phase, and pH value was 4.60 in the feed phase. Ionic strength had no obvious effect on separation of Sm(III). When initial Sm(III) concentration was 1.00×10^?4 mol/L, the separation rate of Sm(III) was up to 93.5% in 85 min. The kinetic equation was developed in terms of the law of mass diffusion and the theory of interface chemistry. The modeled results were in good agreement with the experiment data.     

Stripping dispersion hollow fiber liquid membrane containing carrier PC-88A and HNO3 for the extraction of Sm3+

Stripping dispersion hollow fiber liquid membrane system（SDHFLM） containing feed phase adding acetate buffer solution and dispersion solution with HNO₃ solution as the stripping solution and membrane solution of 2-ethyl hexyl phosphoric acid-mono-2-ethylhexyl ester（PC-88A） dissolved in kerosene,has been studied for the extraction of Sm³⁺.Many factors including pH value, volume ratio of membrane solution to stripping solution（OAV） and carrier concentration on Sm³⁺ extraction were investigated. Experimental results indicate that the optimum extraction conditions of Sm³⁺ were obtained as that PC-88A concentration was 0.120 mol/L,and OAV was 1.00 in the dispersion phase,and pH value was 4.80 in the feed phase.When initial Sm³⁺ concentration was 1.20×10^-4 mol/L,the extraction percentage of Sm³⁺ was up to 92.8%in 160 min.     

水和生物体液中曲马多镇痛药的中空纤维膜液相微萃取

使用中空纤维膜液相微萃取技术(LPME-HFM)建立了从水和生物样品(尿和血浆)中提取曲马多的方法。在室温(20 ℃)下用聚偏氟乙烯中空纤维膜过滤提取样品。萃取过程中用4 μL甲苯作为萃取溶剂。用度冷丁作为内标,气相色谱法-氢火焰离子化检测器分析测定,最低检测限达0.01 mg/L(自来水、尿)或0.05 mg/L(血浆)。和传统的液液萃取方法相比,该方法集萃取和浓缩一步完成,更简便、快速、绿色环保。