Quaternary ammonium-containing membranes

OH -conducting, alkaline polymer free of metal ions and consisting of counter ions bound to the quaternary-ammonium containing polymer backbone has been reported with reasonable preliminary results (133-153 pm thick, 0.0092 S/cm 30°C, 100% RH) [110]. H2I Air alkaline membrane fuel cells that showed encouraging preliminary results with Pt and transition metal catalyst cathodes in CO2 free air have also been reported recently by Acta S.p.A. [111]. 

Carnitine is a vitamin-like quaternary ammonium salt, playing an important role in the human energy metabolism by facilitating the transport of long-chained fatty acids across the mitochondrial membranes. An easy, fast, and convenient procedure for the separation of the enantiomers of carnitine and 0-acylcarnitines has been reported on a lab-made teicoplanin-containing CSP [61]. The enantioresolution of carnitine and acetyl carnitine was enhanced when tested on a TAG CSP, prepared in an identical way [45]. Higher a values were reached also in the case of A-40,926 CSP [41]. 

Plastic film membranes can also contain fixed ion-exchange groups. Jyo and coworkers [79] chloromethylated Amberlite XAD-2 (cross-linked styrene-divinylbenzene copolymer of the macroreticular type) and formed quaternary ammonium groups in the product by treatment with dimethyltetradecylamine. They converted the substance into the chloride, nitrate or perchlorate form and saturated it with nitrobenzene. The presence of hydrophobic ion-exchange sites... 

Acetylcholine is an ester of choline and acetic acid, the prototype for a small family of choline ester compounds. The choline moiety of ACh contains a quaternary ammonium group that gives ACh a permanent positive charge, making it very hydrophilic and membrane impermeant. 

Liquid membranes of the water-in-oil emulsion type have been extensively investigated for their applications in separation and purification procedures [6.38]. They could also allow extraction of toxic species from biological fluids and regeneration of dialysates or ultrafiltrates, as required for artificial kidneys. The substrates would diffuse through the liquid membrane and be trapped in the dispersed aqueous phase of the emulsion. Thus, the selective elimination of phosphate ions in the presence of chloride was achieved using a bis-quaternary ammonium carrier dissolved in the membrane phase of an emulsion whose internal aqueous phase contained calcium chloride leading to phosphate-chloride exchange and internal precipitation of calcium phosphate [6.1]. 

The quaternary ammonium cation, tricaprylylmethylammonium, is a well known ion-pairing extracting agent and was used to obtain the ion-pair association complex with 5,5-diphenylhydantoinate anion. The ion-pair complex was embedded in a PVC matrix, containing NPOE as plasticizer. The membrane composition was 7.7% (w/w) electroactive material, 61.5% (w/w) NPOE and 30.8% (w/w) PVC. 

The first synthetic amphiphiles found to self-organize into bilayers, were quaternary ammonium salts bearing two long alkyl chains 1.13.47.48.49 it is interesting to note that these molecules did not contain a connector moiety between the polar and the apolar part, as in the case of the biolipids. While the physicochemical properties of these bilayers were found to be comparable to those of the biological membranes, the synthetic lipids were found to... 

As earlier reported for electrochemical sensing, often the active chromo-phore will be dispersed in a polymeric matrix. For example, Mohr and Wolfbeis reported a nitrate sensor [121] where the active chromophore is a rhodamine B dye which had been modified with an octadecyl side chain to render it hydrophobic and prevent leaching. The dye was dispersed in a plasticised PVC membrane containing a hydrophobic anion carrier (tridodecylmethylammo-nium chloride). On exposure to nitrate, the fluorescence of the dye increased. This membrane, however, only displayed Hofmeister-type selectivity and was also affected by pH. Replacing the quaternary ammonium anion carrier with a palladium phospine chloride carrier led to selectivity for nitrite [ 122], probably due to a preferential interaction between Pd and nitrite ion. 

A similar counterion-exchange sequence is obtained for anions in an anion-exchange membrane containing quaternary ammonium groups as fixed charges ... 

When an electrical potential gradient is imposed on the stack, alternate compartments become enriched and depleted in sodium chloride. A typical module of an electrodialytic salt plant has 1500 pairs of membranes, each with an effective membrane area of 1 m2. The current density is 3.65 A/dm2 at 620 V with a membrane spacing of about 0.75 mm. A brine concentrate containing about 118 g/1 of chloride can be attained. The overall current efficiency is 73% for Na+ and 85% for Cl". Typically, the membranes are divinylbenzene cross-linked polystyrene with sul-phonic acid, or quaternary ammonium exchange groups the exchange capacity is 1.8 to 2.8 meq/g at 25 °C34). 

As described in Sections 3.3.3 and 3.4.3, hollow fiber suppressors no longer represent the state-of-the-art. Thus, a micromembrane suppressor was introduced under the trade name AMMS-MPIC for ion-pair chromatography of anions. Its structure corresponds to the systems developed for ion-exchange and ion-exclusion chromatography. Like the AFS-2, the AMMS-MPIC micromembrane suppressor contains a solvent-resistant membrane that is permeable to quaternary ammonium bases. Regarding the exchange... 

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