Membrane permeation method

The membrane permeation method is used to study protein diffusion through a thin membrane, from a reservoir at high concentrahon (donor... 

An enrichment is defined as a separation process that results in the increase in concentration of one or mote species in one product stream and the depletion of the same species in the other product stream. Neither high purity not high recovery of any components is achieved. Gas enrichment can be accompHshed with a wide variety of separation methods including, for example, physical absorption, molecular sieve adsorption, equiHbrium adsorption, cryogenic distillation, condensation, and membrane permeation. 

Passive diffusion through the lipid bilayer of the epithelium can be described using the partition coefficient between octanol/water (log P) and A log P (the difference between the partition into octanol/water and heptane/ethylene glycol or heptane/ octanol) [157, 158], The lipophilicity of the drug (log P) (or rather log D at a certain pH) can easily be either measured or calculated, and is therefore generally used as a predictor of drug permeability. Recently, a method using artificial membrane permeation (PAMPA) has also been found to describe the passive diffusion in a similar manner to the Caco-2 cell monolayers [159]. 

There are several approaches to estimating absorption using in vitro methods, notably Caco-2 and MDCK cell-based methods or using methods that assess passive permeability, for example the parallel artificial membrane permeation assay (PAMPA) method. These are reviewed elsewhere in this book. The assays are very useful, and usually have an important role in the screening cascades for drug discovery projects. However, as discussed below, the cell-based assays are not without their drawbacks, and it is often appropriate to use ex vivo and/or in vivo absorption assays. 

Fukushi and Hiiro et al. [24] described a method for determining total carbon dioxide in seawater by capillary isotachoelectrophoresis following isolation of the carbon dioxide by membrane permeation. 

Batzl-Hartmann C, Hurst L, Maas R (2002) Method for the improvement of parallel artificial membrane permeation assay (PAMPA) by using an additional hydrophilic membrane. German Patent Application 4. 

The suitability and general applicability of an artificial membrane and PAMPA in vitro permeation methods were evaluated for their ability to predict drug absorption potential in comparison to Caco-2 cell literature data [57], A linear correlation (R2 = 0.957) was obtained between artificial membrane Papp and human absorption data, indicating the good predictive ability of the proposed method for HP compounds with greater differentiation of drugs with /a below 50% [57],... 

Artificial Membrane Methods Used to Estimate Drug Absorption 9.7.1 Parallel Artificial Membrane Permeation Assay... 

Another in vitro method for permeability screening was parallel artificial membrane permeation assay (PAMPA) initially reported by Kansy. In a PAMPA permeability screen, the Caco-2 cell mono-layer membrane is replaced by an artificially generated membrane. Versions of different artificial membranes that lack active transporter systems and pores have been developed to mimic the in vivo transcellular intestinal epithelial cell barrier. Therefore, the PAMPA screen only measures the intrinsic... 

Permeation was allowed to proceed for 90 min to equilibrate the membranes. This method permitted at least 10 mL of solution to permeate through even the low-flux membrane. Instead of taking the original concentration for the calculation of percent rejection of the solutes, the concentration after equilibration was used. 

Backflushing is another way of cleaning heavily fouled membranes. The method is widely used to clean capillary and ceramic membrane modules that can withstand a flow of solution from permeate to feed without damaging the... 

Other important considerations in process bioseparations are fluid management and membrane rejuvenation methods. Crossflow, or flow tangential to the membrane surface, induces shear at the membrane surface and helps reduce concentration polarization. This flow pattern also creates lift forces that counteract the deposition of particulate matter on the membrane resulting from permeation flow normal to the membrane surface. (See Section I.A.)... 

A separation is diluted when the distillate or the bottom product is less than 5 wt% with respect to the feed. The distillation (simple, extractive or azeotropic) might not be the most economical, but other methods, such as liquid-liquid extraction, stripping, crystallization, adsorption, or membrane permeation, should be tried. The decision depends on the mixture composition and the nature of the components. 

The classification of separation methods suitable for the four mentioned selectors is summarized in Table 3.10. Note that azeotropic distillation, membrane permeation and melt crystallization are the most expensive, but unavoidable in handling more complex mixtures. 

The measurement of sorption, diffusion and permeability coefficients takes place as a rule using one of three methods sorption of the gases in the polymer, permeation through a membrane (film or sheet) into a sealed container or permeation through a membrane into a gas stream. As far as possible sorption methods should be used together with permeation methods that are specific for the measured gas/polymer system in order to uncover any possible anomalies or errors in the measurements by comparison of results. 

In the characterization of porous membranes by liquid or gaseous permeation methods, the interpretation of data by the hyperbolic model can be of interest even if the parabolic model is accepted to yield excellent results for the estimation of the diffusion coefficients in most experiments. This type of model is currently applied for the time-lag method, which is mostly used to estimate the diffusion coefficients of dense polymer membranes in this case, the porosity definition can be compared to an equivalent free volume of the polymer [4.88, 4.89]. 

Macroscopic Methods Sorption Rate (12) IR spectroscopy (16, 17) Frequency response (20) Chromatography (12) ZLC (13) Differential adsorption bed (21) TAP reactor (22) Imaging (23) Membrane permeation (14,15) Effectiveness factor (18, 19) Tracer methods (12)... 

All parameters used in equations (1) and (2) were calculated from single gas adsorption and membrane permeation experiment. The numerical method for solving above equations were MOL(Method Of Line). These calculations were executed using LSODE solver(FORTRAN code). 

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