Membranes cyclam

Run/Nin heteronuclear complexes such as (653), in which a photosensitizer [Ru(bpy)3]2+ or [Ru(phen)3]2+ is covalently attached to the Ni1 cyclam complex, have been synthesized in order to improve the efficiency of electron transfer from the photoexcited photosensitizer to the catalytic site.1 44-1646 However, these complexes did not perform particularly well, either due to unfavorable configuration of the Nin-cyclam subunit and the resulting steric hindrance or due to short lifetime of the excited states of the Ru photosensitizer moieties. A stable catalytic system has been prepared by immobilizing macrocyclic Ni11 complexes and [Ru(bipy)3]2+ in a nafion membrane.164... 

Tsukube 14) reported in 1984 a multi-armed cyclam (18) which has the ability to transport NH4+ cation through a chloroform layer (a so-called liquid membrane ). Metal ions such as K+ are not transported under similar conditions, a selectivity generally unobserved with the common crown ethers and cryptates. Since the transport rate decreases substantially when the furan rings terminating the pendant arms are... 

ISEs have been used for determination of food additives such as saccharin and cyclamate. The sensor used is based on a poly(vinyl chloride) membrane containing the analyte salt in a suitable ionic form as a positively charged site e.g., with an ammonium or basic dye cation. Such sensors are not commercially available but can be made easily in the laboratory. 

Table 3. Membrane Transport Mediated by "Multi-Armed Cyclams"...

Multi-armed cyclam" bearine furan oxygen atoms on its four arms mediated specific transport of NH cation across a liquid membrane, while H, K, and other metal cations were hardly transported under the employed conditions. Since simple cyclam derivatives fi and exhibited low transport rates of NH cation, the furan oxygen atoms attached to the cyclam ring may play an important role in complexation and transportation of NH cation. ... 

S-donor macrocycles are typically sulfur-substituted crown ethers. The mixed donor macrocycles include those with N/S, S/0, N/O, and N/S/O combinations. Calixarenes and resorcinarenes are most often 0-donors, but may contain various functional groups and thus be classified here as mixed donor macrocycles. The macrocycles most widely used in IC and liquid membrane separations have been the crown ethers, nitrogen-substituted crown ethers, cyclen, cyclam, cryptands, calixarenes, resorcinarenes, and CDs. 

The FI determination of acesulfame-K, cyclamate, and saccharin in wines, yogurts, diet soft drinks, and sweetener tablets was reported by Nikolelis and Pantoulias (2001). The detection was performed with filter-supported bilayer membranes from lyophilized egg phosphatidylcholine, using two Ag/AgCl reference electrodes biased by an external power supply at 25 mV. Transient electrochemical signals were recorded with a different time of appearance for each artificial sweetener after the injection of the sample into the flow stream, thus allowing their selective detection in mixtures. 

Nikolelis, D. P. and S. Pantoulias, 2001. Selective continuous monitoring and analysis of mixtures of acesulfame-K, cyclamate, and saccharin in artificial sweetener tablets, diet soft drinks, yogurts, and wines using filter-supported bilayer lipid membranes. Anal. Chem. 73 5945-5952. 

No methods could be found in the literature for the individual flow analysis determination of acesulfame-K. The first flow analysis method for acesulfame-K was proposed by Nikolelis et al. 2001 [72]. This method allowed the electrochemical flow injection monitoring and analysis of mixtures of acesulfame-K, cyclamate, and saccharin using stabilized systems of filter-supported bilayer lipid membranes (BLMs). Detection consisted of t time-dependent appearance of a transient ion current peak in which the time-dependence could be used to distinguish the presence of different artificial sweeteners, and the peak magnitude was related to the concentration of the artificial sweetener. The BLM-based system is able to monitor each artificial sweetener in mixtures. The apparatus for the formation of stabilized BLMs is shown in Figure 24.4. The method also offers response times of less than 1 min, which are the fastest times reported for any similar... 

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