Phase separation membrane formation

Matsuyama H, Yano H, Maki T, Teramoto M, Mishima K, and Matsuyama K. Formation of porous flat membrane by phase separation with supercritical CO2. J. Membr. Sci. 2001 194(2) 157-163. 

Enalapril Pharmaceutical formulations Dichloromethane UV—Vis 1.5—60 pg mL 1 C-FIA membrane for phase separation ion pair formation with BTB [462]... 

Rhenium Ores Benzene UV-Vis 4 mg kg 1 (dry basis) C-FLA membrane for phase separation prior crown ether formation for Mo(VI) separation [480]... 

Membrane structures can also be formed by a microphase separation process in which the outermost region of the cast membrane undergoes phase separation induced by solvent evaporation, while the bulk of the structure is formed by sol vent/non-sol vent exchange during a quench step. This type of structure formation is defined as a dry/wet phase inversion process [Pinneau et al., 1990]. 

Bottino A., Roda G.C., CapanneUi G., Munari S.M. (1991),The formation of micro-porous polyvinylidene difluoride membrane by phase separation, / Membrane Sci., 57,1-20. 

H. Matsuyama, H. Yano, T. Maki, M. Teramoto, K. Mishima, K. Matsuyama, Formation of porous flat membrane by phase separation with supercritical CO,. / Membr Sci, 194 (2), 157-163,2001. 

BOT Bottino, A., Camera-Roda, G., Capanelli, G., and Munari, S., The formation of microporous polyvinylidene fluoride membranes by phase separation, J. Membrane ScL, 57, 1, 1991. 

Bottino, A., G. Camera-Roda, G. Capannelli, and S. Munari. 1991. The Formation of Microporous Polyvinylidene Difluoride Membranes by Phase Separation. Journal of Membrane Science 57(1) 1-20. doi 10.1016/S0376-7388(00)81159-X. 

Membranes offer a format for interaction of an analyte with a stationary phase alternative to the familiar column. For certain kinds of separations, particularly preparative separations involving strong adsorption, the membrane format is extremely useful. A 5 x 4 mm hollow-fiber membrane layered with the protein bovine serum albumin was used for the chiral separation of the amino acid tryptophan, with a separation factor of up to 6.6.62 Diethey-laminoethyl-derivatized membrane disks were used for high-speed ion exchange separations of oligonucleotides.63 Sulfonated membranes were used for peptide separations, and reversed-phase separations of peptides, steroids, and aromatic hydrocarbons were accomplished on C18-derivatized membranes. 

The mixed liposomal solutions were prepared by the ethanol-injection method(13) in order to obtain completely transparent solutions. It is interesting to note that miscibility of the photochromic amphiphiles with DPPC depend on the position of bulky azobenzene. If azobenzene is incorporated close to the end of long alkyl chain, a stable mixed bilayer state cannot be formed. On the other hand, when the azobenzene moiety is located near the head group or at the center of the hydrocarbon tail, the azobenzene amphiphiles are successfully incorporated into the bilayer membrane. No individual micelle formation nor phase separation in the bilayer was observed at 25 °C by absorption spectroscopy. However, the microstructure of the mixed liposomes depends on the type of azobenzene amphiphiles. 

Based on the 96-well format, OCT-PAMPA was proposed and has proved its ability to determine (indirectly) log Poet [87]. PAM PA is a method, first developed for permeability measurements, where a filter supports an artificial membrane (an organic solvent or phospholipids) [88, 89]. With this method, the apparent permeability coefficient (log P ) of the neutral form of tested compounds is derived from the measurement of the diffusion between two aqueous phases separated by 1-octanol layer (immobilized on a filter). A bilinear correlation was found between log Pa and log Poct> therefore log Poet of unknown compounds can be determined from log Pa using a calibration curve. Depending on the detection method used a range oflog P within —2 to +5 (with UV detection) and within —2 to +8 (with LC-MS detection) was successfully explored. This method requires low compound amounts (300 pi of 0.04 mM test compound) and, as for the previous method, samples can be prepared in DM SO stock solutions. For these experiments, an incubation time of 4h was determined as the best compromise in term of discrimination. The limitation of the technique lies in the lower accuracy values... 

The first step in downstream processing is the separation of the product-rich phase from the second phase and the biocatalyst. This may be simplified if the enzyme is immobilized or if a membrane module is included in the experimental set-up. In the case of emulsion reactors, centrifugation for liquid phase separation is a likely separation process [58], although the small size of droplets, the possibility of stable emulsion formation during the reaction, particularly if surface-active... 

In an alternative approach, MIP membranes can be obtained by generating molec-ularly imprinted sites in a non-specific matrix of a synthetic or natural polymer material during polymer solidification. The recognition cavities are formed by the fixation of a polymer conformation adopted upon interaction with the template molecule. Phase inversion methods have used either the evaporation of polymer solvent (dry phase separation) or the precipitation of the pre-synthesised polymer (wet phase inversion process). The major difficulties of this method lay both in the appropriate process conditions allowing the formation of porous materials and recognition sites and in the stability of these sites after template removal due to the lack of chemical cross-linking. 

Since the discovery of the Loeb-Sourirajan technique in the 1960s, development of the technology has proceeded on two fronts. Industrial users of the technology have generally taken an empirical approach, making improvements in the technique based on trial and error experience. Concurrently, theories of membrane formation based on fundamental studies of the precipitation process have been developed. These theories originated with the early industrial developers of membranes at Amicon [19,22,24] and were then taken up at a number of academic centers. Unfortunately, much of the recent academic work is so complex that many industrial producers of phase separation membranes no longer follow this literature. 

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