Porous Polypropylene Hollow Fiber Membrane Research Articles

Supramolecular Solvent-Based Vortex-Assisted Hollow Fibre Liquid-Phase Microextraction Technique Combined With High Performance Liquid Chromatography for the Determination of Estrogens in Milk Samples

A fast, simple, environmental friendly and strong sample clean-up ability method for the determination of three estrogens (17β-estradiol (17β-E2), estrone (E1), and diethylstilbestrol (DES)) in milk samples has been developed by using supramolecular solvent-based vortex-assisted hollow fibre liquid-phase microextraction (SS-VA-HF-LPME) and high performance liquid chromatography. Method is based on estrogens was extracted from aqueous samples into a supramolecular solvent which were made up of n-octanol and ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM] BF4) impregnated in the wall pores and also filled inside the porous polypropylene hollow fiber membrane followed by vortex-mixing. The supramolecular solvent has better compatibility with the polarity of target analytes and the driving forces for the extraction include hydrogen bonding, hydrophobic and π-cation interactions between the analytes and the vesicular aggregates, thereby leading to high recoveries. Vortex can provide mild and effective mixing of sample solution and increase the contact between analytes and boundary layers of the hollow fibre. Therefore the mass transfer rate was enhanced. The parameters that affect the recoveries were studied and optimized. HF of 4 cm length was used and the pH 4.0 was employed. The percentages of n-octanol and [BMIM]BF4 were 10% and 3%, respectively. The extraction equilibrium time was 4 min. The method provided good linearity (andgt;0.998), repeatability (RSD% = 1.24–4.36), low detection limit (0.10–0.22 ng mL−1), and high enrichment factor (330).

Electrochemical determination of anticancer drug, flutamide in human plasma sample using a microfabricated sensor based on hyperbranchedpolyglycerol modified graphene oxide reinforced hollow fiber-pencil graphite electrode

Flutamide (FLT) is a non-steroidal anti-androgen drug that has a specific anti-androgenic activity so that it is used in the treatment of prostate cancer. FLT may also be used to treat excess androgen levels in women. A sensitive electrochemical sensor based on hyperbranchedpolyglycerol functionalized- graphene oxide developed, using ionic liquid mediated hollow fiber-pencil graphite electrode (HF/HBP-GO/PGE) as a working electrode for determination of an anticancer drug, flutamide (FLT. In this design, a two centimeter piece of porous polypropylene hollow fiber membrane was impregnated with ionic liquid (1-Pentyl-3-methylimidazoliumbromide), and a graphite rod modified with hyperbranchedpolyglycerol/graphene oxide (HBP-GO), was located inside the fiber lumen. The modified electrode exhibits sorption activity, high sensitivity, stability and applicability over a wide range of concentration of FLT. The morphology and the electrochemical properties of the modified electrode were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The effect of the amount of graphene oxide (GO), scan rate, pH, concentration of ionic liquid, extraction time and agitation rate on electrochemical behavior of flutamide molecules was investigated. The square wave voltammetric method showed a linear behavior over the drug concentration range 0.1–110 μM. The limit of detection (LOD) and the limit of quantification (LOQ) were found to be 0.029 μM and 0.099 μM, respectively. The proposed sensor was applied for determination of FLT in human plasma sample with satisfactory results.

Practical designs of membrane contactors and their performances in CO2/CH4 separation

Porous polypropylene (PP) hollow fiber membrane contactors operated by either single absorption processes or combined absorption/desorption processes using water have been investigated for use in the production of biomethane from simulated biogas. To observe the effect of operating parameters on the membrane contactors, the connection of modules, flow rates, and operating pressures were tuned. For CO2/CH4 separation, operations using single absorption processes produced a good yield (85%) of high purity CH4 (97%). Connections in series containing two absorption modules facilitated CO2 absorption due to an increase in contact area at the liquid–gas interface. In the combined absorption/desorption processes, CH4 was recovered in 75% yield and 98% purity using two 1″ absorption modules and four 2″ desorption modules connected in series. Although the results were somewhat poorer than those of the single absorption processes due to limits in desorption performance, the combined process provided the potential for producing renewable methane as a fuel for vehicles. Furthermore, for the single absorption processes, the PP hollow fiber membrane contactor was operated continuously, while the membrane used in the combined absorption/desorption processes required periodic maintenance to maintain an acceptable performance.

In situ pre-concentration and voltammetric determination of trace lead and cadmium by a novel ionic liquid mediated hollow fiber-graphite electrode and design of experiments via Taguchi method

In this research a single-use voltammetry sensor, incorporating a three electrodes configuration was developed, using ionic liquid mediated hollow fiber-graphite supported nanomagnetite working electrode. These electrodes coupled with differential pulse voltammetry (DPV) provided a screening tool for in-situ pre-concentration and determination of trace levels of Pb(II) and Cd(II). In this design, a two-centimeter piece of porous polypropylene hollow fiber membrane was impregnated with homogeneous mixture of nanomagnetic particles/ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), and a graphite rod was located inside the fiber lumen. In this sensor, synthesized nanoparticles such as zero-valent Iron (ZVI), nanomagnetite (NM) and magnetic hollow spheres (MHS), dispersed in the ionic liquid, were used for one-step simultaneous purification, pre-concentration and trapping of pb(II) and Cd(II) ions from water samples. The Taguchi method was applied as an experimental design to determine optimum conditions for lead and cadmium ions removal. The experiments were designed, in two steps, according to Taguchi's method, OA16 L18 (21×35) and OA16 L16 (21×43) orthogonal were arrayed to the optimize experimental runs. Various affective parameters were investigated. The effect of all the input parameters on the output responses was analyzed using analysis of variance (ANOVA). The results revealed that the metal removal was influenced primarily by the amount of nanoparticle (52.18%) and agitation rate (19.71%). The extraction time (8.97%) and mercury acetate concentration in the electrolyte (7.6%) had little significant influence on metal removal efficiency. The performance characteristics of the developed method were evaluated by assessing response linearity and precision. The method was suitable for the quantitation of pb(II) and Cd(II) ions in the concentration range of 2–13000ng.mL−1 and 0.6–6500ng.mL−1 for Cd(II) and Pb(II) ions respectively. The detection limits recorded for Cd(II) and Pb(II) were 0.61 and 0.19ng.mL−1 with relative standard deviation (RSD) of 4.6%, and 2.3%, respectively. Moreover, successful applications of the sensing device to real water samples were demonstrated.

Supramolecular solvent-based hollow fiber liquid phase microextraction of benzodiazepines

A new, efficient, and environmental friendly hollow fiber liquid phase microextraction (HF-LPME) method based on supramolecular solvents was developed for extraction of five benzodiazepine drugs. The supramolecular solvent was produced from coacervation of decanoic acid aqueous vesicles in the presence of tetrabutylammonium (Bu4N+). In this work, benzodiazepines were extracted from aqueous samples into a supramolecular solvent impregnated in the wall pores and also filled inside the porous polypropylene hollow fiber membrane. The driving forces for the extraction were hydrophobic, hydrogen bonding, and π-cation interactions between the analytes and the vesicular aggregates. High-performance liquid chromatography with photodiode array detection (HPLC-DAD) was applied for separation and determination of the drugs. Several parameters affecting the extraction efficiency including pH, hollow fiber length, ionic strength, stirring rate, and extraction time were investigated and optimized. Under the optimal conditions, the preconcentration factors were obtained in the range of 112–198. Linearity of the method was determined to be in the range of 1.0–200.0μgL−1 for diazepam and 2.0–200.0μgL−1 for other analytes with coefficient of determination (R2) ranging from 0.9954 to 0.9993. The limits of detection for the target benzodiazepines were in the range of 0.5–0.7μgL−1. The method was successfully applied for extraction and determination of the drugs in water, fruit juice, plasma and urine samples and relative recoveries of the compounds studied were in the range of 90.0–98.8%.

Determination of non-steroidal anti-inflammatory drugs in urine by hollow-fiber liquid membrane-protected solid-phase microextraction based on sol–gel fiber coating

A new rapid, simple and effective cleanup procedure is demonstrated for the determination of ibuprofen, naproxen and diclofenac in urine samples by using hollow-fiber liquid membrane-protected solid-phase microextraction (HFLM-SPME) based on sol–gel technique and gas chromatography–flame ionization detector (GC–FID). In this technique, a sol–gel coated fiber was protected with a length of porous polypropylene hollow fiber membrane which was filled with water-immiscible organic phase. Subsequently the whole device was immersed into urine sample for extraction. Poly(ethylene glycol) (PEG) grafted onto multi-walled carbon nanotubes (PEG-g-MWCNTs) was used as extraction phase to prepare the sol–gel SPME fiber. Important parameters influencing the extraction efficiency such as desorption temperature and time, organic solvent, extraction temperature and time, pH, stirring speed and salt effect were investigated and optimized. Under the optimal conditions, the method detection limits (S/N=3) were in the range of 0.03–0.07ngmL−1 and the limits of quantification (S/N=10) between 0.08 and 0.15ngmL−1. Relative standard deviations for intra-day and inter-day precisions were 4.8–9.0% and 4.9–8.1%, respectively. Subsequently, the method was successfully applied to human urine fractions after administration of ibuprofen, naproxen and diclofenac.

Development of a new and environment friendly hollow fiber-supported liquid phase microextraction using vesicular aggregate-based supramolecular solvent

Hollow fiber-based liquid phase microextraction (HF-LPME) using conventional solvents is limited by their relative instability and high volatility. The use of supramolecular solvents as a liquid membrane phase could overcome these inconveniences due to their negligible vapour pressure and high viscosity. In the present study, a novel and highly flexible method was developed based on supramolecular solvents constructed of vesicles of decanoic acid, which were used for the first time as a solvent in HF-LPME. This solvent is produced from the coacervation of decanoic acid aqueous vesicles by the action of tetrabutylammonium (Bu(4)N(+)). In this work, halogenated anilines as model compounds were extracted from water samples into a supramolecular solvent impregnated in the pores and also filled inside the porous polypropylene hollow fiber membrane. The extracted anilines were separated and determined by high-performance liquid chromatography. The technique requires minimal sample preparation time and toxic organic solvent consumption, and provides a significant advantage over conventional analytical methods. The important parameters influencing the extraction efficiency were studied and optimized utilizing two different optimization methods: one variable at a time and the Box-Behnken design. Under the optimum conditions, the preconcentration factors were in the range of 74 to 203. Linearity of the method was obtained in the range of 1.0-100 μg L(-1) with the correlation coefficients of determination (R(2)) ranging from 0.9901 to 0.9986. The limits of detection for the target anilines were 0.5-1.0 μg L(-1). The relative standard deviations varied from 3.9% to 6.0%. The relative recoveries of the three halogenated anilines from water samples at a spiking level of 20.0 μg L(-1) were in the range of 90.4-107.4%.

Liquid–liquid–solid microextraction based on membrane-protected molecularly imprinted polymer fiber for trace analysis of triazines in complex aqueous samples

A novel liquid–liquid–solid microextraction (LLSME) technique based on porous membrane-protected molecularly imprinted polymer (MIP)-coated silica fiber has been developed. In this technique, a MIP-coated silica fiber was protected with a length of porous polypropylene hollow fiber membrane which was filled with water-immiscible organic phase. Subsequently the whole device was immersed into aqueous sample for extraction. The LLSME technique was a three-phase microextraction approach. The target analytes were firstly extracted from the aqueous sample through a few microliters of organic phase residing in the pores and lumen of the membrane, and were then finally extracted onto the MIP fiber. A terbutylazine MIP-coated silica fiber was adopted as an example to demonstrate the feasibility of the novel LLSME method. The extraction parameters such as the organic solvent, extraction and desorption time were investigated. Comparison of the LLSME technique was made with molecularly imprinted polymer based solid-phase microextraction (MIP-SPME) and hollow fiber membrane-based liquid-phase microextraction (HF-LPME), respectively. The LLSME, integrating the advantages of high selectivity of MIP-SPME and enrichment and sample cleanup capability of the HF-LPME into a single device, is a promising sample preparation method for complex samples. Moreover, the new technique overcomes the problem of disturbance from water when the MIP-SPME fiber was exposed directly to aqueous samples. Applications to analysis of triazine herbicides in sludge water, watermelon, milk and urine samples were evaluated to access the real sample application of the LLSME method by coupling with high-performance liquid chromatography (HPLC). Low limits of detection (0.006–0.02 μg L −1), satisfactory recoveries and good repeatability for real sample (RSD 1.2–9.6%, n = 5) were obtained. The method was demonstrated to be a fast, selective and sensitive pretreatment method for trace analysis of triazines in complex aqueous samples.

Characterization of an anion-exchange porous polypropylene hollow fiber membrane for immobilization of ABL lipase

Hollow fiber membrane offers the advantage to integrate catalytic conversion, product separation and catalyst recovery into a single separation process compared to conventional systems. Polypropylene (PP) hollow fiber membrane is a chemically inert and stable membrane with high potential for enzyme immobilization. The surface properties of polypropylene have been modified by radiation induced graft polymerization. Samples were prepared by grafting of glycidylmethacrylate (GMA) using gamma radiation, at different monomer concentrations and irradiation dose. The resulting epoxy was converted into a diethylamino group as an anion-exchange medium to bind the lipase molecules. Surface properties of the grafted and amine treated samples were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM) and contact angle measurements. AFM revealed higher surface roughness for grafted samples than that of virgin polymer. SEM micrographs illustrated that the porous network was retained at high degree of grafting. Contact angle measurements showed excellent wetting properties with water for the grafted and amine treated membranes. Thermal properties were studied using differential scanning calorimeter (DSC) and thermogravimetic analysis (TGA). It was observed that grafting occurred mainly in the amorphous region of the membranes. Activity and operational stability of ABL lipase, isolated from Arthobacter sp. were assayed after immobilizing it to the modified PP hollow fiber. Immobilized lipase retained 20U/g activity after ten hydrolysis cycles and 68% residual activity after 12 weeks of storage.

On-site polymer-coated hollow fiber membrane microextraction and gas chromatography–mass spectrometry of polychlorinated biphenyls and polybrominated diphenyl ethers

Porous polypropylene hollow fiber membrane coated with a conjugated polymer was used as an on-site sampling device for the extraction of polychlorinated biphenyls and polybrominated biphenyl ethers from coastal sea water samples. The coated hollow fiber membrane was placed in a vial containing the sample, and the target compounds extracted via manual shaking of the vials at the site of sample collection. For each extraction, two fibers were used. After extraction, the fibers with the adsorbed analytes were brought back to the laboratory for further processing. Care was taken to preserve the integrity of the analytes and to avoid contamination during transport; after extraction, the fibers were carefully removed and placed in air-tight crimper vials which were stored in an ice-box. The analytes were desorbed by solvent in the laboratory and analyses were carried out using gas chromatography/mass spectrometry. This method was highly reproducible with relative standard deviations in the range of 1–9%. Recoveries from spiked water samples ranged from 83% to 98%. Low limits of detections between 0.04 and 0.21 ng l −1 were achieved. The extraction efficiency was compared with solid-phase microextraction.

Hollow fiber membrane-protected solid-phase microextraction of triazine herbicides in bovine milk and sewage sludge samples

A porous polypropylene hollow fiber membrane (HFM)-protected solid-phase microextraction (HFM-SPME) procedure in conjunction with gas chromatography/mass spectrometric analysis for use in the determination of triazine herbicides in bovine milk samples is described. A 65-μm polydimethylsiloxane-divinylbenzne (PDMS–DVB) SPME fiber was protected by an HFM. HFM-SPME experimental parameters such as fiber type, extraction time, extraction temperature and salt concentration were investigated and optimized. The relative standard deviations for the reproducibility of the optimized HFM-SPME method varied from 4.30 to 12.37%. The correlation coefficients of the calibration curves were between 0.9799 and 0.9965 across a concentration range of 0–200 μg l−1. The method detection limits for triazines in bovine milk were in the range of 0.003–0.013 μg l−1 and limits of quantification were in the range of 0.006–0.021 μg l−1. The suitability of HFM-SPME was extended to the analysis of the herbicides in sewage sludge samples. The results demonstrate that HFM-SPME was an efficient pretreatment and enrichment procedure for complex matrices.

Hollow fiber membrane-protected solid-phase microextraction of triazine herbicides in bovine milk and sewage sludge samples

A porous polypropylene hollow fiber membrane (HFM)-protected solid-phase microextraction (HFM-SPME) procedure in conjunction with gas chromatography/mass spectrometric analysis for use in the determination of triazine herbicides in bovine milk samples is described. A 65-μm polydimethylsiloxane-divinylbenzne (PDMS–DVB) SPME fiber was protected by an HFM. HFM-SPME experimental parameters such as fiber type, extraction time, extraction temperature and salt concentration were investigated and optimized. The relative standard deviations for the reproducibility of the optimized HFM-SPME method varied from 4.30 to 12.37%. The correlation coefficients of the calibration curves were between 0.9799 and 0.9965 across a concentration range of 0–200 μg l −1. The method detection limits for triazines in bovine milk were in the range of 0.003–0.013 μg l −1 and limits of quantification were in the range of 0.006–0.021 μg l −1. The suitability of HFM-SPME was extended to the analysis of the herbicides in sewage sludge samples. The results demonstrate that HFM-SPME was an efficient pretreatment and enrichment procedure for complex matrices.

Development and application of polymer-coated hollow fiber membrane microextraction to the determination of organochlorine pesticides in water

A novel extraction procedure coupled with gas chromatography–mass spectrometric detection for quantification of organochlorine pesticides (OCPs) in water is described. Amphiphilic polyhydroxylated polyparaphenylene (PH-PPP) was synthesized and coated on the surfaces of a porous polypropylene hollow fiber membrane (HFM). Due to the high porosity of the HFM, maximum active surface area to achieve high extraction efficiency is expected. The polymer-coated HFM was used for the extraction of 15 OCPs from water. The extraction efficiency was compared with emerging and established methods such as liquid-phase microextraction (LPME), solid-phase microextraction (SPME) and stir bar sorptive extraction (SBSE) techniques. We term the current procedure as polymer-coated hollow fiber microextraction (PC-HFME). PC-HFME showed good selectivity and sensitivity. Detection limits for OCPs were in the range of 0.001–0.008 μg l −1. The sensitivity and selectivity of the coated HFM could be adjusted by changing the characteristics of the coated PH-PPP film.