Concentration Of Alkali Metal Ions Research Articles

Synthesis, Cation-Binding and Optical Spectral Studies of Photoemmitive Benzothiazole Crown Ethers

Crown ethers 1–4, encompassing a photoemittive benzothiazole chromophore have been synthesised using standard protocols. Alkali metal picrate extraction profiles reveal that compared to the known crown ethers, benzothiazole benzo-15-crown-5 1 and benzothiazole dibenzo-18-crown-6 3 exhibit relatively higher % extraction for K+ than Na+ ions. The UV-visible and fluorescence spectra of 1–4, in comparison to their neutral forms were found to be red shifted on protonation due to enhanced intramolecular charge transfer transition. The ortho-substituted benzothiazole crowns 2–4 showed higher Stokes shifts compared to the para analog 1 in the presence of CF3CO2H, presumably due to H-bond assisted conformational restriction. No changes were noticeable in the absorption spectra in the presence of alkali metal ions. Even, fluorescence properties of 1–4 were not found to be drastically perturbed by these ions. While 1 exhibited slight quenching at alkali metal ion concentration over 10-folds with respect to that of 1, interestingly, 2–4 showed a slight enhancement of fluorescent intensity at least up to 10-fold concentration of metal ions over those of 2–4. Further increase of metal ion concentrations produces quenching effects. This behavior has been tentatively explained by invoking electrostatic interaction between these cations and the benzothiazole nitrogen ligand.

The modification of ABS resin by introducing metal salts of unsaturated acids

Graft polymerization of methacrylic acid onto ABS resin was carried out using BPO as an initiator in THF solution. Degree of grafting increased with reaction time and reached 35% in 10 hrs. Carboxyl groups were converted to carboxylates (metal salts) by refluxing MAA-g-ABS and the metal acetate in THF. In the solid graft polymers in solid, the infrared absorption of the asymmetrical C= O vibration of the carboxylic acid shifted to lower wavenumbers with increasing metal ion concentration. The absorption peak for the carboxylate anion is shifted to higher wavenumbers with the increase of alkali metal ion concentration, however, for the Mg2+ salt, it is shifted to lower wavenumbers. The surface and volume resistivities of the K+ and Na+ salts of MAA-g-ABS were 9.0 × 109 Ω□ and 9.5 × 109 Ω at 80% neutralization, respectively, and decreased with alkali metal ion concentration. The electric resistance of Li+, Mg2+ and Zn2+ salts decreased only slightly. The modulus of the K+ salt of MAA-g-ABS decreased with neutralization, whereas in Li+, Mg2+ and Zn2+ salts, the modulus increased with increasing metal ion concentration.

Complex formation analysis of water-soluble calixarenes by capillary zone electrophoresis

The equilibria of complex formation reactions between various kinds of cations and anionic calixarenes in an aqueous solution were analyzed by capillary zone electrophoresis on the basis of the change in electrophoretic mobility of the calixarenes. The apparent electrophoretic mobility of the calixarenes decreased with increasing concentrations of alkali metal ions and quaternary ammonium ions. Equilibrium constants were determined by a non-liner least-squares analysis using the changes in apparent electrophoretic mobility. The complex formation constants obtained with alkali metal ions were in the order of 10 2.3–10 3.0, and those with quaternary ammonium ions were 10 2.9–10 4.2, providing less selectivity among them. The selectivity of the calixarene toward alkali metal and quaternary ammonium ions in aqueous solution involves flexible structure, and compensative interactions of electrostatic and hydrophobic interactions. From the results obtained in this work, the electrophoretic method has proved to be useful for analyzing the reactivity of anionic calixarene in aqueous solution.

Modification of the adhesion properties of PTFE by a magnesium treatment

Despite the many advantages of fluoropolymers, their inability to bond readily can pose problems. Following work published elsewhere on the development of surface pre-treatments for polytetrafluoroethylene (PTFE) using solutions of solvated electrons, we consider here the peel adhesion of a rubbery epoxy to PTFE thus treated. In all cases, the solvated electron treatment increases adhesive properties. When low concentrations of alkali metal ions are added to the solution, the improvement of adhesion is more marked. Various possible mechanisms leading to improved adhesion are discussed.

A simple fluorescent chemosensor for alkaline-earth metal ions

In acetonitrile solutions, the deprotonated form of 1-pyrenebutyric acid (1) forms 1:2 (metal:ligand) complexes with Zn2+, Cu2+, Fe2+, Fe3+, and earth alkali metal ions. The complexation process leads two pyrene moieties in close contact, so that dimers are formed, causing strong changes in the absorption and fluorescence spectra. Taking advantage of these changes, very low concentrations of earth alkali metal ions can be detected, suggesting 1 as a good prototype of a new family of fluorescent sensors.

Selective transport of Li–Na and Li–K binary systems across a cation exchange membrane under an electric field

Abstract The selective transport for Li–Na and Li–K systems through cation exchange membranes under an electric field was measured as a function of voltage, feed concentration, and the number of membranes used in the chamber. The transfer rate of metal ions and permeation selectivity were evaluated by conducting experiments both in a single and multistage continuous one-pass flow mode of operation. The results are analyzed on the basis of the concentration of alkali metal ions from the feed and recovery side overflows. A comparison of the results obtained from both the single stage and multistage experiments showed that higher selectivity was obtained for the Li–K system compared to the Li–Na system. For the multistage operation, the permeation and selectivity of Li + and K + through five and 11 membranes were examined. A high separation factor was obtained when 11 membranes were used. The efficiency of the recovery of metal ions using membranes may be expressed by the calculation of the separation factor and the metal ion concentration obtained from the recovery solution and further enhanced by increasing the number of membranes used.

Propargylic Sulfone-Armed Lariat Crown Ethers: Alkali Metal Ion-Regulated DNA Cleavage Agents

Alkali metal ion concentrations within cells are regulated during the cell cycle and may be significantly altered in cancer cells versus normal cells. Thus, the selective destruction of cancer cells might be achieved by agents that marry alkali metal ion recognition elements, such as crown ethers, with DNA-cleaving moieties. We have prepared a series of propargylic sulfone-armed lariat crown ethers, which bind sodium and potassium ions and exhibit little affinity for lithium ions, as determined by a picrate extraction assay. We have investigated the supercoiled DNA cleavage efficiency of these lariat crown ethers in the presence of various alkali metal ions. Monomeric propargylic sulfone-armed crown ethers 9b and 10b cleave DNA at physiologically relevant pH and exhibit modest increases in DNA cleavage efficiency in the presence of potassium and sodium as compared to lithium. In Tris-containing buffer, the monomeric lariat crown ether 10b cleaves DNA in a sodium ion-dependent fashion, producing 66% more DNA cleavage in the presence of 5.7 mM sodium than in the absence of added sodium. The dimeric propargylic sulfone-armed lariat crown ether 11 cleaves DNA over 10-fold better in the presence of potassium than in the presence of lithium. While the level of metal ion discrimination exhibited by these compounds is rather modest, they do represent the first successful attempt to marry molecular recognition of specific alkali metal ion with covalent modification of DNA.

Salt-Bridge Supported Bilayer Lipid Membrane Modified with Calix[n]arenes as Alkali Cation Sensors

ABSTRACT Potentiometric behaviors of a salt-bridge supported bilayer lipid membrane (Sb-BLM) modified with Calix[n]arene (n=4, 6, 8) derivatives are described for some alkali metal ions. The modified Sb-BLM was used as an alkali cation sensor. The membrane potentials were observed to generate Nernstian responses to the concentration of alkali metal ions in electrolyte. The Sb-BLM modified with the calix[n]arenes show high selectivity for individual alkali metal ions: Calix[8]arenes for K+, calix[6]arenes for Cs+ Calix[4]arenes show no selectivity for any alkali ions. The interacting mechanism is also discussed.

Smolder of Cellulosic Fabrics IV. Participation of Dye and Bleach Residues

The oxidative decomposition of a green-and-white checkered cel lulosic fabric, designated as FOR-1, comprised of four different yarns, was stud ied using TPR/GC and DSC techniques. Containing different alkali metal ion (AM +) and dye concentrations, these four yarns experienced directionally selec tive smolder behavior during cigarette ignition tests. Measurements were per formed on the integrated fabric and on each of the four yarns. A model explaining the anisotropic smolder and high-temperature behavior of this fabric was developed. The decomposition of a heavily bleached, cellulosic sailcloth was also studied. The results showed an increase in the fabric degradation/cleavage rate com pared to unbleached #6 cotton duck. The DSC spectra of the sailcloth, however, did not significantly differ from that of the washed cotton duck. Similar thermochemical behavior was observed in the blue-dyed denim fabric contain ing 1500 ppm potassium; the low-temperature DSC behavior of this denim was also found to be similar to that of undyed, nicotine-treated cotton duck studied in Reference [4]. These results support a model comprising the mechanisms of smolder and combustion of colored cellulosic fabrics.

Electrophoretic mobility study on ion–ion interactions in an aqueous solution

Ion–ion interactions between anions and their pairing ions in aqueous solutions were studied through the measurements of electrophoretic mobilities of analyte ions in capillary zone electrophoresis, where the electrophoretic method for the analysis of ion association reaction is shown to be more useful than the conductometric method widely used in the analysis of the reactions. The electrophoretic mobility of monovalent inorganic anions was almost identical even when the concentrations of alkali metal ions and quaternary ammonium ions in the migrating solution were varied up to 15 mM. On the other hand, the electrophoretic mobility of organic anions, such as monovalent and divalent anions, decreased with increasing concentrations of quaternary ammonium ions. Changes in the electrophoretic mobilities were analyzed by a non-linear least-squares method giving ion association constants. The results indicate that the proposed method is applicable to the analysis of such reactions to give the mobility change. The ion association constants obtained in an aqueous solution were related to the extraction constants of the ion associates, and the contributions of the association process and the distribution process were clarified.

Alkali Metal Ions Protect Mitochondrial Rhodanese against Thermal Inactivation

Incubation of bovine liver mitochondrial rhodanese in dilute, reducing solutions at temperatures ranging between 30 and 45°C conduced to a rapid loss of enzymatic activity. This inactivation was substantially reduced in the presence of millimolar concentrations of alkali metal ions, divalent cations (including Mg2+, Ca2+, and Ba2+) were ineffective. The extent of protection afforded by monovalent cations was highly dependent on their ionic radii, with K+and Na+ions being the most effective protective agents. The protection afforded by a number of anions, including thiosulfate, could be totally ascribed to the presence of the accompanying monovalent cation. The overall results indicate that K+and Na+, at concentrations and temperatures within the physiological range, substantially contribute to the stabilization of the functional structure of rhodanese.

Electrochemistry of quaternary ammonium binaphthyl salts

The redox behaviour of the binaphthyl unit in quaternary ammonium salts with an appended crown ether (3) is dramatically affected by the presence of metal cations and this effect can be used as an analytical tool to detect micromolar concentrations of alkali metal ions.

Selective Cationic Binding at the Air−Water Interface by Thin Films of Rigid Amphiphiles Bearing Laterally Attached Crown Ether Moieties

Three 4,4-didecyloxy-p-terphenyl derivatives with laterally attached crown ether units of different ring size [(1,4,7,10-tetraoxacyclododecyl)-,(1,4,7,10,13-pentaoxacyclopentadecyl)-, and (1,4,7,10,13,16-hexaoxacyclooctadecyl)-2-methyl 2,5-bis(4-decyloxyphenyl)benzoate] have been synthesized, and their Langmuir films were investigated by means of a film balance. They form well-ordered thin films when spread at the air-water interface which are characterized by two sharp breaks in their surface pressure-area isotherms separated by a large plateau. The lateral pressure in the plateau region-in which the molecules undergo a first-order phase transition with formation of a defined triple layer-significantly increases on enhancing the number of oxyethylene units in the crown ether units. Additionally, it depends on the type and concentration of alkali metal ions (Li + , Na + , K + , Rb + , Cs + ) in the subphase. Cations which fit the cavity of the appended crown ethers most significantly stabilize the films. It seems that the surface pressure in the plateau region is reminiscent of the binding constants of alkali metal ions to the crown ether units. This shows that facial amphiphiles could represent an interesting new platform for the investigation of guest-host interactions and molecular recognition processes at the air-water interface.

On the Aqueous Vibrational Spectra of Alkali Metal Oxalates

Fourier transform infrared attenuated total reflectance and Fourier transform Raman spectra of the series of aqueous alkali metal oxalates—lithium oxalate (Li2C2O4), sodium oxalate (Na2C2O4), potassium oxalate (K2C2O4), rubidium oxalate (Rb2C2O4), and cesium oxalate (Cs2C2O4)—are presented for the first time. Fourier transform Raman spectra of the solid oxalates are also presented for the first time. The solid and aqueous oxalate ions are assumed to possess D2 h and D2 d symmetry, respectively, and the assignment of fundamental vibrational modes is made accordingly. The effect of increasing alkali metal ion concentration on the aqueous spectra of these oxalates is also reported. Spectral changes are explained in terms of the ability of the respective alkali metal cations to interact with the oxalate anion in solution. It is proposed that these differences arise because the alkali metal cations associate with the aqueous oxalate anions to varying degrees, depending upon the nature of the cation. The extent of the binding is found to decrease down the alkali metal series (Li > Na > K > Rb > Cs). Similar results obtained for the tetramethylammonium cation [(CH3)4N+] suggest that it is a softer cation than cesium.

Two mechanisms of H+/OH- transport across phospholipid vesicular membrane facilitated by gramicidin A

Two rate-limiting mechanisms have been proposed to explain the gramicidin channel facilitated decay of the pH difference across vesicular membrane (delta pH) in the pH region 6-8 and salt (MCI, M+ = K+, Na+) concentration range 50-300 mM. 1) At low pH conditions (approximately 6), H+ transport through the gramicidin channel predominantly limits the delta pH decay rate. 2) At higher pH conditions (approximately 7.5), transport of a deprotonated species (but not through the channel) predominantly limits the rate. The second mechanism has been suggested to be the hydroxyl ion propogation through water chains across the bilayer by hydrogen bond exchange. In both mechanisms alkali metal ion transport providing the compensating flux takes place through the gramicidin channels. Such an identification has been made from a detailed study of the delta pH decay rate as a function of 1) gramicidin concentration, 2) alkali metal ion concentration, 3) pH, 4) temperature, and 5) changes in the membrane order (by adding small amounts of chloroform to vesicle solutions). The apparent activation energy associated with the second mechanism (approximately 3.2 kcal/mol) is smaller than that associated with the first mechanism (approximately 12 kcal/mol). In these experiments, delta pH was created by temperature jump, and vesicles were prepared using soybean phospholipid or a mixture of 94% egg phosphatidylcholine and 6% phosphatidic acid.

Kinetic properties of the sodium‐calcium exchanger in rat brain synaptosomes.

1. The kinetic properties of the internal Na+ (Na+i)- dependent 45Ca2+ influx and external Na+ (Na+o)-dependent 45Ca2+ efflux were determined in isolated rat brain nerve terminals (synaptosomes) under conditions which the concentrations of internal Na+ ([Na+]i), external Na+ ([Na+]o), external Ca2+ (Ca2+]o), and external K+ ([K+]o) were varied. Both fluxes are manifestations of Na(+)-Ca2+ exchange. 2. Ca2+ uptake was augmented by raising [Na+]i and / or lowering [Na+]o. The increase in Ca2+ uptake induced by removing external Na+ was, in most instances, quantitatively equal to the Na+i-dependent Ca2+ uptake. 3. The Na+i-dependent Ca2+ uptake (measured at 1 s) was activated with an apparent half-maximal [Ca2+]o (KCa(o)) of about 0.23 mM. External Na+ inhibited the uptake in a non- competitive manner: increasing [Na+]o from 4.7 to 96 mM reduced the maximal Na+(i)-dependent Ca2+ uptake but did not affect KCa(o). 4. The inhibition of Ca2+ uptake by Na+o was proportional to ([Na+]o)2, and had a Hill coefficient (nH) of approximately 2.0. The mean apparent half-maximal [Na+]o for inhibition (KI(Na)) was about 60mM, and was independent of [Ca2+]o between 0.1 and 1.2mM; this, too, is indicative of non-competitive inhibition. 5. Low concentrations of alkali metal ions (M+) in the medium, including Na+, stimulated the Na+i-dependent uptake. The external Na+ and K+ concentrations required for apparent half-maximal activation (KM(Na) and KM(K), respectively) were 0.12 and 0.10mM. Thus, the relationship between Ca2+ uptake and [Na+]o was biphasic: uptake was stimulated by [Na+]o < or = 10 mM, and inhibited by higher [Na+]o. 6. The calculated maximal Na+i-dependent Ca2+ uptake (Jmax) was about 1530 pmol (mg protein) -1s-1 at 30 degrees C saturating [Ca2+]o and external M+ concentration ([M+]o), and with negligible inhibition by external Na+. 7. Internal Na+ activated the Ca2+ uptake with an apparent half-maximal concentration (KNa(i)) of about 20 mM and a Hill coefficient, nH, of approximately 3.0. 8. The Jmax for the Na+o-dependent efflux of Ca2+ from 45Ca(2+)-loaded synaptosomes treated with carbonyl cyanide p-trifluormethoxy-phenylhydrazone (FCCP) and caffeine (to release stored Ca2+ and raise the internal Ca2+ concentration ([Ca2+]i) was about 1800-2000 pmol (mg protein -1s-1 at 37 degrees C. 9. When the membrane potential (Vm) was reduced (depolarized) by increasing [K+]o, the Na+i-dependent Ca2+ influx increased, and the Na+o-dependent Ca2+ efflux declined. Both fluxes changed about 2-fold per 60 mV change in Vm. This voltage sensitivity corresponds to the movement of one elementary charge through about 60% of the membrane electric field. The symmetry suggests that the voltage-sensitive step is reversible. 10. The Jmax values for both Ca2P influx and efflux correspond to a Na+-Ca2+ exchange-mediated flux of about 425-575 jumol Ca2P (1 cell water)-' s-' or a turnover of about one quarter of the total synaptosome Ca2P in 1 s. We conclude that the Na+-Ca2P exchanger may contribute to Ca2P entry during nerve terminal depolarization; it is likely to be a major mechanism mediating Ca2P extrusion during subsequent repolarization and recovery.

Catalytic Activity of Titanium Silicates Synthesized in the Presence of Alkali-Metal and Alkaline-Earth Ions

Titanium containing aluminum-free ZSM-5 (TS-1) synthesized in the presence and absence of alkali metal and alkaline earth ions are investigated as catalysts for the selective oxidation of alkanes and alkenes using aqueous H2O2 as oxidant at temperatures below 100°C. Sodium-exchanged TS-1 is not active for alkane oxidations. Similarly, no catalytic activity is observed for TS-1 synthesized in the presence of high concentrations of alkali metal ions (Si/Na <20). For both cases, the catalytic activity can be restored by washing the solid with acid solution prior to catalytic evaluation. Similar results are obtained for TS-1 synthesized in the presence of other alkali metal ions, e.g., Li, K. However, the presence of alkaline earth ions, e.g., Mg, in the synthesis gel does not have a significant effect on the catalytic activity of TS-1. Based on the catalytic data and the physicochemical properties of the samples, a plausible explanation for the above results is described. The acid treatment may be useful in overcoming the problems of synthesizing TS-1 from reagents that contain alkali metal ions, e.g., TPAOH solutions. More importantly, this treatment opens the possibility of synthesizing other titanium-containing silicate structures that require the presence of alkali metal ions in the synthesis gel for their formation.

Electron transfer between photoexcited oxaycanine dye and dithiocarbamate in LB films: counterion and pH dependence

We have investigated the electron transfer between photoexcited dioctadecyl-oxacyanine perchlorate S9 and dioctadecyldithiocarbamate incorporated in mixed monolayers both at the air/water interface and in transferred Langmuir-Blodgett films with the functional head groups in contact with an aqueous phase. The fluorescence of S9 in the mixed films at the air/water interface and in the transferred films was measured as a function of the concentration of different alkali metal ions or pH. Electron transfer from the thiocarbamate group to the excited S9 results in fluorescence quenching of the oxacyanine dye. The degree of fluorescence quenching has been found to depend on pH and on the concentration and nature of the cation in the subphase.

Effects of alkali-metal ions on the thermal decomposition of ammonium metavanadate supported on alumina

The thermal decomposition of ammonium metavandate (AMV) supported on γ-alumina (1∶1 mol) and treated with alkali-metal ions was investigated using differential thermal analysis (DTA), thermogravimetric analysis (TGA), infrared (i.r.) absorption spectroscopy and X-ray diffraction (XRD). The results revealed that the presence of alkali-metal ions did little to affect the thermal decomposition processes of AMV supported on alumina. However, these ions enhanced creation of V4+ ions by heating the samples in air at 400 °C. The oxides produced underwent a solid-solid interaction at 500–700 °C, forming alkali-metal vanadates. The formation of these spinels was found to be strongly dependent on the degree of diffusion and the concentration of the alkali-metal ions. Moreover, the addition of a higher concentration of alkali-metal ions inhibits the formation of aluminium vanadate while enhancing the crystallinity of γ- to δ-alumina.

Transfer of alkali metal ions across the water-nitrobenzene interface facilitated by poly(oxyethylene)dodecyl ethers

The transfer behaviour of alkali metal ions across the water-nitrobenzene interface facilitated by nonionic surfactants poly(oxyethylene)dodecyl ethers (C 12E x ) were investigated by means of cyclic voltammetry. The results show a linear dependence of the reversible half-wave potential Δ w nφ 1/2 on the logarithm of the concentration of alkali metal ions in the aqueous phase. Therefrom, the apparent free energy change of ion transfer facilitated by C 12E x , ‡ w n G 0 tr, was determined. The results indicate that the ion transfer facilitated by C 12E x is attributable to the formation of a hydrophobic complex of alkali metal ion with C 12E x and its ion pairs with the counter anion, and the rate of transfer is controlled by the diffusion of C 12E x from the bulk nitrobenzene phase to the interface.