Permeation absorptive

Human colon adenocarcinoma cell line used as a permeation/ absorption model... 

Primary chemical features of a drug and its dosage form that can dictate oral bioavaUability (3) DMSO relationship between pH, ionizable groups and membrane permeation absorption Rule-of-5, active transport (in and out), Pgp, OAT prodrugs and soft drugs. 

As with permeation, absorption of the corrodent by the liner material can result in swelling of the liner, cracking, and eventual penetration to the substrate. This can lead to high stresses and debonding. Refer to Chapter 1 for a discussion of absorption. 

In addition to selecting a lining material that is resistant to the corrodent being handled, there are three other factors to be considered in the design permeation, absorption, and environmental stress cracking. Permeation, and absorption can cause... 

Loss of contents through the substrate and liner as a result of the eventual failure of the substrate. In unbonded linings it is important that the space between the liner and substrate be vented to the atmosphere, not only to allow minute quantities of permeant vapor to escape, but to prevent expansion of entrapped air from collapsing the liner. For a discussion of permeation, absorption, and environmental stress cracking, refer to Chapter 1. 

Several methods can be used for gas separation, like stagewise condensation to liquid, pressure swing adsorption, membrane permeation, absorption or combinations of these techniques (Hiller et al. 2000). 

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. 

The outer packaging must protect the tea from light and moisture absorption. Polypropylene or coated ceUophane outer wraps for paper board tea packages provide a barrier to loss of tea aroma and retard permeation of oxygen and foreign flavors. Low temperature improves storage stabiHty. Properly packaged and stored teas retain acceptable flavor for about a year. 

Permeation enhancers are used to improve absorption through the gastric mucosa. Eor example, oral dehvery of insulin (mol wt = 6000) has been reported from a water-in-oH- emulsion containing lecithin, nonesterified fatty acids, cholesterol [57-88-5], and the protease inhibitor aprotinin [9087-70-1] (23). 

The activity of absorbed hydrogen is a measure of the damage for a given material. H absorption can be easily investigated in H-permeation experiments [9]. Figure 2-20 shows experimental results for steel/aerated seawater. Significant H absorption occurs only in the range of cathodic overprotection (1/ < -0.8 V). 

Experiments on absorption and permeation of flavorants have been carried out in high nitrile barrier containers with a number of organic compounds which represent a variety of chemical functionalities. Table... 

Our studies of the absorption, permeation, and extraction properties of containers produced from high nitrile barrier resins have demonstrated that they meet or surpass the basic criteria established for retention of taste and odor characteristics of carbonated soft drinks. Sensory tests, which can isolate and identify end results as well as integrate collective effects, have confirmed this judgement and have established the general compatibility of these containers with a variety of beverage products from a taste and odor standpoint. Furthermore, these materials have the excellent physical properties required for containers which will find wide use in food and beverage packaging. 

Water Permeation and Solute Separation through the Membrane. The measurements of water permeability of the 67 membranes prepared under different conditions were carried out by using an Amicon Diaflo Cell (effective membrane area, 13.9 cm2) under a pressure of 3 kg/cm2 at 25 °C. Some results are listed in Table 1067. It is apparent that much higher water absorption and permeability than the cellulosic membrane are characteristic of the 67 membranes prepared by both the casting polymerization and conventional casting. 

Gel permeation chromatography studies using both refractive index and UV(260 nm) absorption detections have confirmed that both Acacia Senegal and Acacia seyal gums consist of three main components (Islam et al., 1997, Idris et al., 1998, Williams Phillips, 2000, Al Assaf 2006) ... 

Aspects of point 1 have aheady been included in Sections 23.2.2.1 and 23.2.2.2. Regarding point 2, a new diagnostic test for discontinuities is outlined in Section 23.5.2, absorption in Section 23.4.2, and ED failures in Sections 23.5.1.1 and 23.5.1.2. As to point 3, the ubiquitous phenomenon of permeation, which occurs wherever fluid containment by elastomers exists, is examined below. 

It might be thought as a consequence of measurements such as these that leakage factors are the main issues in fuel containment. However, although obviously important, in some cases a leak might occur only at intermittent intervals, and the associated problem might well be easily resolvable by component replacement. In contrast, the relevance of permeation to fluid containment is its continuous nature—its rate may be low, but it occurs all the time that fluid is contacting elastomer. Hence, this phenomenon is now considered in association with related processes absorption, adsorption, and diffusion. 

The molecular process termed permeation is the most fundamental physical means by which fluid can pass right through an elastomer or other polymer. Absorption and permeation, besides being interrelated, both depend on two other phenomena associated with fluid-polymer interactions, as follows ... 

Permeation When a fluid contacts one side of an elastomer membrane, it can permeate right through the membrane, escaping on the far side. The process again combines adsorption and diffusion as above, but with the additional process eventually of evaporation—treated mathematically as negative adsorption. (Permeation could also be viewed as combining one-way absorption and evaporation.) Wherever these conditions for permeation exist the phenomenon occurs, whatever the shape of the elastomer barrier— but the associated mathematics becomes complex for irregular barrier shapes. 

Estimations of Liquid-Permeation Rates from Absorption Testing... 

The interrelationships of the various coefficients associated with fluid uptake (Section 23.4.2) mean that it should be possible to estimate a rate for one of the uptake phenomena from test data for another of them. Campion proposed using this approach to estimate permeation coefficient Q from solubility coefficient s. The form of a liquid absorption plot (Figure 23.6, Section 23.4.4.1) is such that s should be obtainable from it, and inspection showed that this link was via Henry s law with concentration corrected by the polymer density p. The following expression was derived for s ... 

Then Q = Ds (Section 23.4.2), with diffusion coefficient D also measurable by absorption testing, so that Q can be estimated. Permeation rate is then obtainable for a particular sample shape at specified conditions by using the appropriate permeation equation. 

Control permeation cup test at 40°C Absorption test conducted at 40°C Prediction-absorption at elevated temperatures... 

We have been studying the novel process for CO2 separation named membrane/absorption hybrid method. The advantages of this process are that high gas permeance and selectivity were obtained. The concept of this process is shown in Fig. 1. Both feed gas and absorbent solution are supplied to the inside of hollow fibers. While Ae liquid flows upward inside the hollow fibers, absorbent solution absorbs CO2 selectively and it becomes a rich solution. Most of rich solution permeates the membrane to the permeate side maintained at reduced pressure, where it liberated CO2 to become a lean solution. Compared to a conventional gas absorption... 

---