Kinds Of Membranes Research Articles

In vitro percutaneous absorption of piroxicam through synthetic membranes and abdominal rat skin

The in vitro release of piroxicam from carbomer gels and its penetration through isopropyl myristate impregnated membranes and abdominal rat skin were investigated. Attempts were made to relate the differences in the release rate with physicochemical properties of the drug and the vehicle. The results showed that piroxicam is released from the topical gel formulations and diffuses through skin. It is suggested that although piroxicam flux across abdominal rat skin was lower than through isopropyl myristate membranes, this kind of membranes can be used in preliminary screening among the different piroxicam formulations.

L-Menthol, oleic acid and lauricidin in absorption enhancement of free and sodium salt of diclofenac using ethanol treated silicone membrane as model for skin.

The mechanism of l-menthol, oleic acid and lauricidin as enhancers on percutaneous absorption was examined using diclofenac (DH) as a hydrophobic drug and sodium diclofenac (DNa) as a hydrophilic drug in in vitro diffusion experiments with two kinds of membranes: ethanol-treated and untreated silicone membranes; these were models for the lipid and pore pathways of skin. A 20% w/w ethanol-aqueous solution decreased the flux of DH but increased the flux of DNa significantly across the treated membrane compared with those fluxes across the untreated membrane, suggesting that DH penetrated by the lipid pathway and DNa by the pore pathway. The permeability of DNa through the pore pathway decreased significantly across the treated membrane with the addition of oleic acid and lauricidin. l-Menthol increased the permeability coefficients of DH and DNa more in a treated membrane than in an untreated one, showing the same tendency as in rat skin. Thus, while oleic acid and lauricidin did not increase the permeation of DNa by the pore pathway, l-menthol appeared to enhance the permeation of the drug by both the lipid and pore pathways.

Control of Pore Sizes in Macroporous Chitosan and Chitin Membranes

A novel method for the preparation of macroporous chitosan and chitin membranes is suggested, which employs silica particles as porogen. The macroporous chitosan membranes were prepared by (1) casting an acidic chitosan solution that contains silica particles, (2) removing the solvent by evaporation, and (3) dissolving the silica particles by immersing the membranes into an alkaline solution. This simple method provides chitosan membranes with high porosity and satisfactory mechanical strength, the pore sizes of which can be easily controlled by varying the size of silica particles. The effects of various evaporation conditions and amount of silica on the flow rate of water through the membranes were investigated. In order to prevent their dissolution in acidic solutions, the chitosan membranes were cross-linked under alkaline conditions, using epichlorohydrin as the cross-linking agent. Macroporous chitin membranes were prepared by acetylating the chitosan membranes with acetic anhydride in methanol. In contrast to the uncross-linked chitosan membranes, which are soluble in dilute acidic solutions and insoluble in alkaline solutions, the chitin membranes are insoluble both in acidic and basic solutions. Both kinds of membranes can be employed in affinity or ion-exchange bioseparations.

Vitamin A supplementation inhibits chemiluminescence and lipid peroxidation in isolated rat liver microsomes and mitochondria.

In the present study we investigated if administration of vitamin A could protect rat liver microsomes and mitochondria from in vitro peroxidation. Appreciable decrease of chemiluminescence and lipid peroxidation was measured in microsomal membranes from rats receiving vitamin A, with respect to control animals. In membranes derived from control animals, the fatty acid composition was profoundly modified when subjected to in vitro peroxidation mediated by ascorbate-Fe++, with a considerable decrease of 20:4 n6 and 22:6 n3 in mitochondria and 18:2 n6 and 20:4 n6 in microsomes. As a consequence the peroxidizability index, a parameter based on the maximal rate of oxidation of specific fatty acids was higher in supplemented animals than in control group when both kind of membranes were analyzed. These changes were less pronounced in membranes derived from rats receiving vitamin A. These results are in agreement with previous results that indicated that vitamin A may act as an antioxidant protecting membranes from deleterious effects.

Role of plasticizers on the characteristics of poly(vinyl chloride)-membrane lithium-selective electrodes based on phenanthroline derivatives

Ion selectivities of PVC-membrane lithium-selective electrodes based on 2,9-dibutyl-1,10-phenanthroline were tested for various plasticizers which were used as solvent mediators to incorporate the carrier into the membrane. Selectivity coefficients were measured by several methods, including separate and mixed solutions methods. It was confirmed that differences in the method gave only small differences in the measured selectivity coefficients. Among the plasticizers used, o-nitrophenyl phenyl ether gave the best lithium selectivity towards other alkali and alkaline earth metal cations. The selectivity attained was log kLi,Na=–3.3 (2000 times preference for Li+ over Na+), which proves to be the best lithium-selective electrode so far reported in the literature. The impedance measurement was carried out for two kinds of membranes with different plasticizers, to find out the mechanism of the improved lithium selectivity. It was found that the membrane resistance has only slight correlation with the improved lithium selectivity. The high rate of cation–neutral carrier complexation (1:2 ratio) was inferred to be the significant factor in determining high lithium selectivities. The role of plasticizers as a medium of complexation was demonstrated.

Skimmed milk demineralization by electrodialysis: Conventional versus selective membranes

Electrodialysis (ED) is a membrane technique that is useful in the demineralization of dairy products. In this work, experimental results obtained in batch electrodialysis of skimmed milk are presented. Two kinds of membranes were used: the first kind were conventional membranes in PVC and the second were monovalent ion selective membranes which are now available on the market. This latter type of membrane permits the transport of monovalent ions but limits the passage of large ions which have a high valency. The limiting current was measured as a function of feed flow into the stack. The results obtained when using both types of membranes were compared for elimination rate of K +, Na +, Cl −1, Ca 2+, Mg 2+ and PO 4 3− ions as well as for current efficiency and electric power consumption in the separation process.

Optimization of multicomponent pervaporation for removal of volatile organic compounds from water

Optimal operation of a hollow fiber membrane module for pervaporative removal of multicomponent volatile organic compounds (VOCs) from wastewater was studied. A shell-and-tube heat-exchange ttype of hollow fiber module was considered for treatment of a wastewater containing toluene, trichloroethane (TCE) and methylene chloride. Three kinds of membranes, i.e., poly (dimethylsiloxane) (PDMS), polyether- block-polyamides (PEBA) and polyurethane (PUR) membranes, were studied. A mathematical model of the module was developed. The flux equations of the model were derived using mass transfer coefficient as described in our previous study. A cost model of the system was used to study the effect of different process and design variables on annual treatment cost. The effects of multicomponent feed mixtures, liquid boundary layer mass transfer resistance, and downstream pressure on the module performance and process economics were studied. A multidimensional optimization technique was used to determine the operation conditions for minimum cost. The sensitivity of the operation cost with respect to different process variables was also studied. The annual treatment cost was found to be relatively insensitive to the downstream pressure in the low pressure iange (for example, 0–2000 Pa for toluene removal, 0–3000 Pa for TCE removal and 0–1500 Pa for methylene chloride removal). The optimal downstream pressure increased with the increase of Henry's law constant of the compounds. The capital cost was found to be dominant in the total treatment cost at laminar flow regime, while the operating cost is diminant cost at turbulent flow regime.

Short-chain phosphatidylcholines as superior detergents in solubilizing membrane proteins and preserving biological activity.

The solubilization of plasma and organelle membranes by diheptanoylphosphatidylcholine (DHPC) has been studied. This short-chain phosphatidylcholine is shown to act as a mild detergent, solubilizing effectively both kinds of membranes at DHPC concentrations of 10-20 mM (0.5-1%). The size of the resulting mixed protein-lipid-DHPC micelles ranges between 5 and 8 nm. The protein conformation and hence the enzymatic activity are well preserved over a rather large DHPC concentration range (up to 4-5 times the DHPC concentration required for solubilizing the membranes). Evidence is presented that short-chain phosphatidylcholines are superior to most detergents commonly used by biochemists. This is true not only regarding its excellent dispersing power on both phospholipid bilayers (Gabriel & Roberts, 1986) and biological membranes but also as to its capacity to preserve the native protein structure and hence enzymatic activity in the solubilized state. Due to its special properties DHPC lends itself very well not only to membrane solubilization but also to the purification of the solubilized membrane proteins and reconstitution of the proteins into simple lipid bilayers. Concerning the mechanism of membrane solubilization, evidence indicates that DHPC interacts primarily with the lipid bilayer of the membrane and not with the membrane proteins. DHPC solubilizes membranes by being distributed into the lipid bilayer and breaking it up. In the resulting small mixed micelles, the protein remains associated with its preferred intrinsic membrane lipids and is thus stabilized. The protein-intrinsic lipid complex is successfully shielded from unfavorable contacts with H2O by DHPC-intrinsic lipid interactions.

Topography of the heme prosthetic group of cytochrome b-559 in the photosystem II reaction center.

The topography of the heme prosthetic group of cytochrome b-559 of the photosystem II reaction center was determined from measurement of the orientation of its alpha- and beta-polypeptides in thylakoid membranes of spinach chloroplasts and in osmotically disrupted cells of the cyanobacterium Synechocystis sp. PCC 6803. The accessibility to trypsin proteolysis of an epitope located near the solvent-exposed N-terminus of the beta-subunit was compared to that of the alpha-subunit, whose N- and C-termini had previously been localized from the trypsinolysis pattern to the stromal and lumenal sides of spinach thylakoid membranes, respectively [Tae et al. (1988) Biochemistry 27, 9075-9080; Vallon et al. (1989) Biochim. Biophys. Acta 975, 132-141]. The N-terminal epitope of the cyanobacterial beta-subunit was modified by introducing a tridecapeptide epitope, previously found to be immunoreactive, from the C-terminal region of the spinach chloroplast alpha-subunit. This epitope had no homology with the cyanobacterial alpha-subunit. The cells with the hybrid beta-subunit retained full photosynthetic activity. The intactness of membranes from osmotically shocked cyanobacteria was tested by trypsin inaccessibility to (a) the alpha-subunit C-terminus and (b) the manganese-stabilizing protein (MSP) of the oxygen-evolving complex that is on the lumenal side of the membrane. The loss after trypsinolysis of most of the beta-subunit immunoreactivity, under conditions where (i) the alpha-subunit was cleaved near the N-terminus in both spinach thylakoids and osmotically shocked cyanobacterial membranes and (ii) the MSP protein in cyanobacteria was not disrupted, implied that the orientation of the beta-subunit was parallel to that of the alpha-subunit in both kinds of membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Permeation denuder for sampling and continuous analysis of gases Part 1. System configuration, basic studies and application to atmospheric ammonia and sulfur dioxide

The application of tubular and planar permeation denuders for introduction of gaseous compounds into flow-injection systems is presented. Construction details of the permeation denuders are given and different configurations of implementation in flow systems are described. The principles and experimental requirements of concentrating gaseous compounds are outlined. Collection efficiency of the permeation denuders is determined in dependence of gas flow rate, kind of membrane and composition of absorber solution using ammonia and sulfur dioxide as test gases. A brief discussion of calibration procedures is presented. The suitability of the proposed method is exemplified in the determination of ambient ammonia and sulfur dioxide using various detection schemes.

Membrane Technology Developments Aim at Variety of Applications

The first commercial membrane for use in large-scale separation of gas mixtures was announced by Monsanto on Nov. 14, 1979. Since that time, the kinds of membranes and their applications have proli...

Clay membrane electrodes specific to cationic surfactants—applications

Amphiphilic-cation-specific electrodes most often use a specific membrane composed of a homogeneous mixture of a polymer (PVC), a plasticizer and a carrier of the amphiphilic ion. Generally, the carrier is dissolved in this kind of membrane. However, electrodes could also be constructed using heterogeneous membranes, in which the carrier is insoluble. We used laponite, a synthetic clay, as the carrier of cationic surfactant to prepare electrodes. These clay membrane electrodes performed as well as electrodes using a homogeneous memebrane; they could be used for potentiometric studies and determinations of the solubility product of salt of the surfactant.

Binding of Umami Substance to Plasma Membrane Isolated from Bovine Circumvallate Papillae

Fractionation of several kinds of membranes from the taste organ, circumvallate papillae, of bovine has been done to investigate localization of the umami substance binding site. Monosodium glutamate (MSG) and nucleotides are known as umami substances. The membrane fractions obtained from a series of centrifugation were examined for radioactive MSG binding activities by the ligand-binding methods, indicating a synergistic effect between MSG and nucleotides. They were also measured for activities of the marker enzymes. The membrane fraction that seemed to be rich in plasma membrane, on the basis of the marker enzyme activities, had specific MSG binding activity. These results suggest that umami substances bound to the plasma membrane of circumvallate papillae.

Desorption of counter-ions followed with labelled ions and water dissociation in perfluorinated quaternary ammonium membranes and Nafion 125 membranes

Desorption and exchange phenomena have been studied in perfluorinated quaternary ammonium membranes (QAM) by means of radiotracers. In these anion exchange membranes, counter-ion desorption followed with 36Cl gave higher results than co-ion desorption followed with 22Na. The cation exchange Nafion 125 membrane gave similar results. When these two kinds of membranes, equilibrated in 0.1 M NaCl at pH 7, are desorbed in water at this pH, pH decreases with QAM and increases with Nafion 125. These shifts in pH values are observed over a wide range of pH around 7. These results can be explained by a larger water dissociation due to the catalyzing action of the exchange sites.

The sol—gel approach to prepare candidate microporous inorganic memebranes for membrane reactors

In catalytic membrane reactors, the membrane can play a multiple role such as promotion of an integrated catalytic reaction but also partitioning of the reactants and separation of the products. For these applications permselective membranes may be used that can work at high temperature (gas or liquid phase), in organic solvents or in contact with biomass. One type of possible membranes are the ceramic membranes which exhibit a connected microporosity. This kind of membrane can at present be made using the latest developments in sol-gel processing. We used this process to prepare various microporous ceramic membranes in aqueous media: Zr02, A1203, LaOCI; and in organic media: Si02, Zr02. Attention has been paid to the microstructure of these membranes in order to identify the main parameters governing the evolution of these membrane materials during their preparation. The main feature of these membranes is the presence of non-aggregated nanosized particles after calcination. A peptization reaction and/or a chemical modification of the precursors has been shown to be of prime interest in the control of the precursor reactivity and in limiting the condensation rate so as to avoid inhomogeneous and rough products. Non-aggregated ceramic particles down to 4 nm in size can thus be obtained and result in microporous membrane formation.

The sol-gel approach to prepare candidate microporous inorganic membranes for membrane reactors

In catalytic membrane reactors, the membrane can play a multiple role such as promotion of an integrated catalytic reaction but also partitioning of the reactants and separation of the products. For these applications permselective membranes may be used that can work at high temperature (gas or liquid phase), in organic solvents or in contact with biomass. One type of possible membranes are the ceramic membranes which exhibit a connected microporosity. This kind of membrane can at present be made using the latest developments in sol-gel processing. We used this process to prepare various microporous ceramic membranes in aqueous media: ZrO 2, Al 2O 3, LaOCl; and in organic media: SiO 2, ZrO 2. Attention has been paid to the microstructure of these membranes in order to identify the main parameters governing the evolution of these membrane materials during their preparation. The main feature of these membranes is the presence of non-aggregated nanosized particles after calcination. A peptization reaction and/or a chemical modification of the precursors has been shown to be of prime interest in the control of the precursor reactivity and in limiting the condensation rate so as to avoid inhomogeneous and rough products. Non-aggregated ceramic particles down to 4 nm in size can thus be obtained and result in microporous membrane formation.

In VitroPassive and Iontophoretically Assisted Transport of Salbutamol Sulphate Across Synthetic Membranes

The passive and electrically assisted transport of salbutamol sulphate through four synthetic membranes was investigated. Two of these were hydrophilic (Visking 18/32 and Celgard-3401®) and two hydrophobic (Celgard-2400® and Celgard-4500®). Significant differences in passive membrane transport were observed. The hydrophilic Celgard membrane gave similar passive transport rates to Visking 18/32. However, slower rates were observed with the hydrophobic membranes, the rate for Celgard-4500 being 4-5 fold smaller than Visking 18/32 and that for Celgard-2400 being negligible over a period of 6 hours. The passive release of salbutamol sulphate from the hydrogel across the hydrophilic membranes was matrix-controlled, whereas the membrane was the rate-limiting element for passive release through the hydrophobic membranes. Application of an electrical potential giving rise to iontophoretic currents in the range 0.100 to 0.500 mA led to an increase in drug transport rate and this effect became larger as the current was increased. The quantity of drug transported in a given time period increased linearly with time for both kind of membranes. However the relative increase in transport induced by current was greatest with the hydrophobic membranes.

Materials And Fabrication Processes For Highly Accurate X-Ray Masks

AbstractThis paper discusses the properties of materials for x-ray masks used in synchrotron radiation lithography system. Through computer simulations and experimental analysis, we evaluate three kinds of membranes (Si, SiN, SiC) in terms of mechanical distortions, surface smoothness and optical transmittance. SiC exhibits the smallest distortion, but SiN has the best characteristics in the surface smoothness and the optical transmittance. By virtue of their high x-ray absorption coefficient and dry etching capabilities, Ta, W and Re are selected as potential absorber materials. We study their stress control characteristics, etching characteristics and the relation between their Young's modulus and distortions. We find that Ta is an excellent absorber because of its good stress controllability and good etching characteristics, such as a high etch rate and etch selectivity. By adopting a Ta/SiN structure, highly accurate masks can be fabricated by a process in which patterning the absorber is carried out before removing the bulk Si.

圧力場および電場を駆動力とする膜分離の特性と今後の課題

Recently, separation technique of fine particles from suspension with membrane using overlapped driving forces of pressure field and electric field has been widely used in pharmaceutical industry, food industry, biological industry and so on.Electrophoresis and electroosmosis are very important phenomena for electrodialysis, electro -ultrafiltration, electroosmotic dewatering of sludge, isoelectric focusing, etc. Therefore, the former-equations concerning electrophoresis and electrodialysis are discussed from a practically available point of view.This paper deals with the following subjects.(1) The effect of particle concentration of suspension on electrophoretic velocity is discussed. This problem is very important in the case where concentrative suspension is treated practically.(2) Equation of electroosmotic flow rate passing through particle packed bed, respective membranes combined in series and in parallel with different kinds of membranes.(3) Electrokinetic phenomena in the nonaqueous dispersion system and the applications of these phenomena to separation are introduced.(4) The characteristics of electro-ultrafiltration and problems in electro-ultrafiltration to be solved are discussed.(5) Recent studies on continuous separation of biochemical substances such as protein, enzyme, hormone, etc. are reviewed and in the cases of scale up and continuous operation for separation apparatus, problems to be solved hereafter are considered.

Preparation and properties of polyimide ultrafiltration membranes

Four kinds of polyimide ultrafiltration membrane were prepared. Experiments are described that measured and analyzed their separation properties and chemical stabilities as a function of the formation conditions. The results showed that the concentration, additive contents and temperature of the coagulation bath had the greatest effects on the processes of membrane formation. Through the measurements of organic solvent fluxes and retention, it was found that there was a linear correlation between the solvent flux and viscosity under the same operating conditions for each membrane. After the membranes had been immersed in thirty organic solvents for about 200 hr, it was demonstrated that the four kinds of membrane had different stabilities which were related to the solubility parameters.