Facilitated transfer of alkali-metal cations by dibenzo-18-crown-6 across the electrochemically polarized interface between an aqueous solution and a hydrophobic room-temperature ionic liquid

The facilitated transfer of alkali metal cations (Li+, Na+, K+, Rb+, Cs+) by dibenzo-18-crown-6 (DB18C6) across the electrochemically polarizable interface between an aqueous solution (W) and a hydrophobic ionic liquid, N-octadecylisoquinolinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ([C18Iq][TFPB]), has been studied using cyclic voltammetry at the interface formed at the tip of a micropipet. In cyclic voltammograms (CVs), the current due to the facilitated transfer of the cations by DB18C6 from W to [C18Iq][TFPB] can be measured within the polarized potential window of the [C(18)Iq][TFPB]|W interface. The stoichiometry of the complexes in [C18Iq][TFPB] for Li+, Na+, K+, and Rb+ are found to be 1:1 while for the Cs+ transfer both 1:1 and 1:2 complexes are likely to be formed. The formation constants of the 1:1 complexes for Li+, Na+, K+, and Rb+ in [C18Iq][TFPB], , evaluated from CVs are log = 5.0, 7.0, 8.2, and 7.3, respectively. The value for K+ is 1 order of magnitude greater than that for Na+. This higher selectivity of DB18C6 to K+ over Na+ in [C18Iq][TFPB] compared with that in molecular solvents suggests that the RTIL provides a unique solvation environment for the complexations of DB18C6 with the ions.     

Infrared multiphoton dissociation of alkali metal-coordinated oligosaccharides

Infrared multiphoton dissociation (IRMPD) of alkali metal-coordinated oligosaccharides was obtained in a Fourier transform mass spectrometer. Fragmentation of the oligosaccharides was observed for Li+- and Na+-coordinated species. For larger alkali metal ions (K+, Rb+, and Cs+), the major products were the alkali metal ions. IRMPD experiments were performed on milk oligosaccharides, and the dissociation thresholds were determined. The threshold values were found to differ for the isomers. It is suggested that the threshold may be useful for differentiating isomeric compounds. Additionally, oligosaccharide alditols from biological samples were analyzed. Comparison of the collision-induced dissociation (CID) and IRMPD spectra of oligosaccharide alditols revealed that IRMPD could be used as a complementary method to obtain structural information.     

Screening metal binding selectivities of macrocycle mixtures by HPLC--ESI-MS and postcolumn reactions

A rapid method for the screening of metal binding selectivities of host compounds in mixtures is presented. This method involves the separation of mixtures of hosts by HPLC, followed by postcolumn complexation with one or more metals, then analysis by mass spectrometry. The intensities of the host-guest complexes in the mass spectra correlate with the binding selectivities of the hosts. The method was applied to a series of lariat ethers that were synthesized as ion-selective reagents for ion-selective electrodes. The compounds most selective for Na+ vs Li+ and K+ were identified. Additionally, a mixture of substituted calixarenes was screened for alkali-metal-binding selectivity. These compounds were determined to be selective for Cs+ over Rb+, K+, and Na+.     

Viscosity and thermal conductivity of binary eutectics of alkali metals in the vapor phase

Values calculated for the dynamic viscosity and thermal conductivity are presented for vapors of binary eutectics of the alkali metals at temperatures from 800 to 1500 K and at pressures from 100 to 8×10⁵ Pa. Data are presented for the vapors of the systems Li + Na, Na + Rb, Na + Cs, K + Rb, K + Cs, Na + K, and Rb + Cs. The values of the concentrations of the five components in the vapor phase of each binary eutectic are also presented. The accuracy of the calculated viscosities is estimated to be within 4–5% and the accuracy of the calculated thermal conductivities is estimated to be within 8–10%.     

Ionizable (Thia)calix[4]crowns as highly selective 226Ra2+ ionophores

The 226Ra2+ selectivity of the ionizable (thia)calix[4]crowns 1-4 was determined in the presence of a large excess of the most common alkali and alkaline earth cations. Selective 226Ra2+ (2.9 x 10(-)(8) M) extraction occurs even at extremely high M(n+)/226Ra2+ ratios of 3.5 x 10(7) [M(n+) = Na+, K+, Rb+, Cs+, Mg2+, Ca2+, and Sr2+ (1M)] and an ionophore concentration of 10(-4) M. The selectivity coefficients log(K(Ra)(ex)/K(M)(ex)) are approximately 3.5 for Mg2+, Ca2+, and Sr2+. In the presence of Ba2+, which has very similar chemical properties, only the thiacalix[4]crown-6 derivative 4 showed a selectivity for 226Ra2+. In addition to the remarkable 226Ra2+ selectivities, the effective pH range (pH 8-13) of the thiacalix[4]crown dicarboxylic acids (3 and 4) allows for full regeneration of the ionophores at lower pH values (pH <6).     

Influence of structural variation in room-temperature ionic liquids on the selectivity and efficiency of competitive alkali metal salt extraction by a crown ether

An improved method for the preparation of 1-alkyl-3-methylimidazolium hexafluorophosphates provides a series of room-temperature ionic liquids (RTILs) in which the 1-alkyl group is varied systematically from butyl to nonyl. For competitive solvent extraction of aqueous solutions of alkali metal chlorides with solutions of dicyclohexano-18-crown-6 (DC18C6) in these RTILs, the extraction efficiency generally diminished as the length of the 1-alkyl group was increased. Under the same conditions, extraction of alkali metal chlorides into solutions of DC18C6 in chloroform, nitrobenzene, and 1-octanol was undetectable. The extraction selectivity order for DC18C6 in the RTILs was K+ > Rb+ > Cs+ > Na+ > Li+. As the alkyl group in the RTIL was elongated, the K+/ Rb+ and K+/Cs+ selectivities exhibited general increases with the larger enhancement for the latter. For DC18C6 in 1-octyl-3-methylimidazolium hexafluorophosphate, the alkali metal cation extraction selectivity and efficiency were unaffected by variation of the aqueous-phase anion from chloride to nitrate to sulfate.     

The effects of alkali impurities on the superconductivity and powder characteristics of YBa2Cu3O7

The effects of alkali impurities, Li, Na, K, Rb, and Cs, on the superconducting properties and powder characteristics of YBa₂Cu₃O₇ were investigated. The superconducting temperature of YBa₂Cu₃O₇ drops to the 70 K range in the presence of Li (0.2 mole Li/mole 1-2-3 oxide), while samples containing Rb, K, or Cs show little superconductivity deterioration. An intermediate effect between these two extremes was found for Na. The powder characteristics, inlcuding aggregate hardness, particle size, and particle morphology, of YBa₂Cu₃O₇ are also affected by the alkali impurities. In particular, during calcination both Li and Na enhance the intergrain bonding, resulting in increased difficulty in power comminution, while K and particularly Rb have the opposite effect.     

Cs(+) Speciation on Soil Particles by TOF-SIMS Imaging

Soil particles exposed to CsI solutions were analyzed by imaging time-of-flight secondary ion mass spectrometry and also by scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). The results showed that Cs(+) could be detected and imaged on the surface of the soil particles readily at concentrations down to 160 ppm, which corresponds to 0.04 monolayer. Imaging revealed that most of the soil surface consisted of aluminosilicate material. However, some of the surface was more quartzic in composition, primarily SiO(2) with little Al. It was observed that adsorbed Cs(+) was associated with the presence of Al on the surface of the soil particles. In contrast, in high SiO(2) areas of the soil particle where little Al was observed, little adsorbed Cs(+) was observed on the surface of the soil particle. Using EDS, Cs(+) was observed only in the most concentrated Cs(+)-soil system, and Cs(+) was clearly correlated with the presence of Al and I. These results are interpreted in terms of multiple layers of CsI forming over areas of the soil surface that contain substantial Al. These observations are consistent with the hypothesis that the insertion of Al into the SiO(2) lattice results in the formation of anionic sites, which are then capable of binding cations.     

Immobilization of crown ether carboxylic acids on silica gel and their use in column concentration of alkali metal cations from dilute aqueous solutions

Eight crown ethers with pendent carboxylic acid groups are immobilized on silica gel and utilized for column concentration of alkali metal cations from dilute aqueous solutions. The column concentration selectivity and efficiency are found to be strongly influenced by (1) the cavity size of the crown ether unit, (2) conformational positioning of the proton-ionizable side arm with respect to the crown ether cavity, and (3) capping of residual silanol surface groups with trimethylsilyl functions. By use of a chromatographic stripping technique, selective column concentration of Na(+), K(+), (Rb(+) and Cs(+)), and Cs(+) by different functionalized silica gels has been achieved.     

Recognition of potassium ion in water by 15-crown-5 functionalized gold nanoparticles.

Reported here is an efficient recognition of K+ by 15-crown-5 functionalized gold nanoparticles in aqueous matrix containing physiologically important cations, such as Li+, Cs+, NH4+, Mg2+, Ca2+, and excess amount of Na+. Upon exposure to K+, the colloidal solution changes from red to blue, in response to surface plasmon absorption of dispersed and aggregated nanoparticles. The concentration ranges of K+ detected in this study are 0.099-0.48 mM and 7.6 microM-0.14 mM, when concentrations of colloidal gold are 54.9 and 7.1 nM, respectively. Recognition of K+ and formation of the aggregates are proposed via a sandwich complex of 2:1 between 15-crown-5 moiety and K+. Also discussed is the possibility of a preorganized structure of 15-crown-5 at the water-organic interface for the efficient complexation with K+.     

Laser desorption/in situ chemical ionization aerosol mass spectrometry for monitoring tributyl phosphate on the surface of environmental particles

The possibility of using real-time aerosol mass spectrometry (RTAMS) for the detection of surface-adsorbed tributyl phosphate (TBP) as an alkali metal adduct has been investigated. Environmental particles contain variable amounts of easily ionizable alkali metals. During laser desorption of surface-adsorbed TBP molecules, Na+ and K+ ions are generated by the interaction of the laser radiation with the particle's material. The alkali metal ions serve as in situ chemical ionization reagents of the neutral analyte molecules. The effect of laser fluence on the signal intensities of the potassium ion and cationized TBP was also studied. The best performance of the instrument was observed with laser fluences that produce high abundances of K+ but low abundances of ions from the particle's bulk material. The relatively low laser fluence, necessary to produce potassium ions, prevents the excessive fragmentation of the analyte. The instrument is capable of real-time monitoring of submonolayer coverage of TBP on the surface of micron-sized particles.     

Design and synthesis of a more highly selective ammonium ionophore than nonactin and its application as an ion-sensing component for an ion-selective electrode

A novel ammonium ionophore, which exhibits superior NH4+ selectivity compared with that of the natural antibiotic nonactin, was successfully designed and synthesized based on a 19-membered crown compound (TD19C6) having three decalino subunits in the macrocyclic system. This bulky decalino subunit is effective for (1) increasing the structural rigidity of the cyclic compound, (2) introducing the "block-wall effect", which prevents forming a complex with a large ion, and (3) increasing the lipophilicity of the ionophore molecule. In the ammonium ionophore design, the first factor contributes to increasing the NH4+ selectivity relative to smaller ions such as Li+, Na+, or even the closest size, K+, and the second factor increases the NH4+ selectivity over larger ions such as Rb+ and Cs+. The X-ray structural analysis proved that TD19C6 forms a size-fit complexwith NH4+ in its crown ring cavity. As an application of this ionophore, an ion sensor (ion-selective electrode) was prepared, which exhibited NH4+ to K+ and Na+ selectivity of 10 and 3,000 times, respectively. This electrode showed a better performance compared to the electrode based on nonactin, which is the only ammonium ionophore presently used in practical applications.     

Relative sensitivity factors of inorganic cations in frozen-hydrated standards in secondary ion MS analysis

We describe the measurement, at 100 K, of the SIMS relative sensitivity factors (RSFs) of the main physiological cations Na+, K+, Mg2+, and Ca2+ in frozen-hydrated (F-H) ionic solutions. Freezing was performed by either plunge freezing or high-pressure freezing. We also report the measurement of the RSFs in flax fibers, which are a model for ions in the plant cell wall, and in F-H ionic samples, which are a model for ions in the vacuole. RSFs were determined under bombardment with neutral oxygen (FAB) for both the fibers and the F-H samples. We show that referencing to ice-characteristic secondary ions is of little value in determining RSFs and that referencing to K is preferable. The RSFs of Na relative to K and of Ca relative to Mg in F-H samples are similar to their respective values in fiber samples, whereas the RSFs of both Ca and Mg relative to K are lower in fibers than in F-H samples. Our data show that the physical factors important for the determination of the RSFs are not the same in F-H samples and in homogeneous matrixes. Our data show that it is possible to perform a SIMS relative quantification of the cations in frozen-hydrated samples with an accuracy on the order of 15%. Referencing to K permits the quantification of the ionic ratios, even when the absolute concentration of the referencing ion is unknown. This is essential for physiological studies of F-H biological samples.     

层状金属有机框架材料用于水溶液中137Cs的高效去除

¹³⁷Cs主要来源于核武器试验和核电站产生的放射性废物, 具有高溶解度和高迁移率的特点, 因此从放射性废液中有效去除 ¹³⁷Cs是一项长期的挑战。本研究通过溶剂热法合成了一种二维层状阴离子骨架材料SZ-6, 并对其吸附性能进行了系统的研究。利用单晶衍射仪、X射线衍射仪和扫描电子显微镜等对SZ-6的结构、形貌和稳定性进行了表征与测试。采用批实验研究了水溶液中Cs ⁺的吸附行为。结果表明: 在浓度为10 mg/L的Cs ⁺溶液中, SZ-6的吸附动力学可在5 min内达到平衡, 是目前去除Cs ⁺最快的吸附剂材料之一; SZ-6在pH4~12范围内表现出良好的去除能力; 在过量Na ⁺、K ⁺、Ca ²⁺竞争阳离子存在的情况下仍具有较好的选择性。     

Chemical characterization of individual, airborne sub-10-nm particles and molecules

A nanoaerosol mass spectrometer (NAMS) is described for real-time characterization of individual airborne nanoparticles. The NAMS includes an aerodynamic inlet, quadrupole ion guide, quadrupole ion trap, and time-of-flight mass analyzer. Charged particles in the aerosol are drawn through the aerodynamic inlet, focused through the ion guide, and captured in the ion trap. Trapped particles are irradiated with a high-energy laser pulse to reach the "complete ionization limit" where each particle is thought to be completely disintegrated into atomic ions. In this limit, the relative signal intensities of the atomic ions give the atomic composition. The method is first demonstrated with sucrose particles produced with an electrospray generator. Under the conditions used, the particle detection efficiency (fraction of charged particles entering the inlet that are subsequently analyzed) reaches a maximum of 10(-4) at 9.5 nm in diameter and the size distribution of trapped particles has a geometric standard deviation of 1.1 based on a log-normal distribution. A method to deconvolute overlapping multiply charged ions (e.g. C3+ and O4+) is presented. When applied to sucrose spectra, the measured C/O atomic ratio is 1.1, which matches the expected ratio from the molecular formula. The spectra of singly charged bovine serum albumin (BSA) molecules are also presented, and the measured and expected C/N/O atomic ratios are within 15% of the each other. Also observed in the BSA spectra are signals from 13C and 32S which arise from 40 and approximately 34 atoms per molecule (particle), respectively. Potential applications of NAMS to atmospheric chemistry and biotechnology are briefly discussed.     

Thiazole-containing benzo-crown ethers: a new class of ammonium-selective ionophores

A new class of crown ethers containing heterocyclic units has been designed to develop synthetic NH4+-selective ionophores whose resulting potentiometric properties in solvent polymeric membranes are superior or at least comparable to those of nonactin. It was found that the derivatives of thiazole containing dibenzo-18-crown-6 (1; TDB18C6) incorporated in PVC-based membranes provide enhanced NH4+ selectivities over alkali metal cations, especially over Na+, compared to those of the nonactin-doped membranes: for example, the selectivity coefficients, log K(POT)NH4+J (J = Li+, Na+, K+), for the 2-nitrophenyloctyl ether (NPOE) plasticized PVC membranes doped with the hexyl chain-substituted TDB18C6 (2) were -4.9, -3.9, and -1.3, while those for the same type of membranes with nonactin -4.4, -3.0, and -1.0, respectively. Unlike other synthetic NH4+-selective neutral carriers reported to date, TDB18C6-type compounds result in potentiometric performance highly comparable to that of the nonactin-based ones except their slightly higher detection limits (approximately 3 x 10(-6) vs 7 x 10(-7)). The complex formation between TDB18C6 and NH4+ was identified from 1H NMR spectra. The 1:1 complex formation constant of TDB18C6 with NH4+ in solvent polymeric membranes estimated using the method suggested by Bakker et al. and the NH4+ selectivity coefficient over K+ (K(POT)NH4+,K+) are approximately 200 times smaller than that of nonactin (1.8 x 10(7) vs 3.6 x 10(9)).     

Physicochemical Reasons for the Use of TiOHPO4 for Treatment of Liquid Radioactive Waste

Heterogeneous exchange of the proton of hydrated titanyl hydrogen phosphate with Li, Na, K, Rb, and Cs cations in aqueous solutions was studied potentiometrically. The sorption equations were proposed. The concentration and thermodynamic equilibrium constants were calculated. The optimal pH range of the solution providing effective sorption of radioactive cesium on hydrated titanyl hydrogen phosphate was determined. The decrease in the efficiency of radiocesium sorption from liquid waste with a high content of competing nonradioactive alkali metal cations is due to a decrease in the pH of this solution in the course of the sorption. To provide efficient sorption removal of radiocesium, the pH should be maintained in the range 4-7, or the sodium form of the sorbent should be used. The selectivity of radiocesium sorption on TiOHPO₄ in the presence of excess sodium cation was estimated.     

Formation of high-mass cluster ions from compound semiconductors using time-of-flight secondary ion mass spectrometry with cluster primary ions

The detection of high-mass, nonstoichiometric, GaxAsy and InxPy secondary ion clusters using time-of-flight secondary ion mass spectrometry is reported for the first time. The GaxAsy and InxPy clusters are detected in both positive and negative ion spectra and extend to masses of at least 6000 dalton (Da). Consecutive clusters differ by the addition of one gallium (indium) atom. This leads to nonstoichiometric clusters at high mass (i.e., Ga15As3 at 1270 Da) which are metastable above a critical mass. The relative secondary ion yields of high-mass GaxAsy clusters detected using several primary ion sources (Cs+, Bi+, Bi3+, Bi32+, Bi52+, C60+, and C602+) are compared. The relative secondary ion yield of high-mass GaxAsy clusters is significantly enhanced by the use of cluster primary ions and the best relative secondary ion yield is obtained using Bi3+ primary ions. An application of the high-mass GaxAsy clusters is presented, in which these clusters are utilized to distinguish between contaminant levels of Ga and bulk GaAs structure in a depth profile of a MnAs/GaAs heterojunction. These results illustrate improved analysis of inorganic materials using cluster primary ions and break the paradigm of stoichiometric secondary cluster ion formation for SIMS of inorganic compounds.     

Melt-assisted phase transformations of A/W/Mn/SiO<Subscript>2</Subscript> (A = Li,Na, K,Rb, Cs) composite catalysts

This paper analyzes results obtained in studies of A/W/Mn/SiO₂ (A = Li, Na, K, Rb, Cs) composite catalysts for the oxidative coupling of methane (OCM). Particular attention is paid to phase transformations. It is pointed out that the SiO₂ matrix is an active catalytic component of the composites, rather than an inert carrier of additives, and that the heterogeneous OCM process involves melts based on alkali metal tungstates, along with polycrystalline manganese oxides. The effects of the cation ratio and synthesis method on the phase composition of the A/W/Mn/SiO₂ (A = Li, Na, K, Rb, Cs) materials is examined.     

Comparative studies on the solvent extraction of transition metal cations by calixarene, phenol and ester derivatives

The ionophore solvent extraction of various alkali metal and transition metal cations from the aqueous phase to the organic phase was carried out by using diazo-coupling calix[n]arenes [p-(4-phenylazophenylazo)calix[4]arene (L1) and p-phenylazocalix[6]arene (L2)], phenol derivatives [2,6-dimethyl-3-phenylazophenol (L3), 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol (L4), 2-chloro-4-nitro(phenylazo)-5-sec-butyl-2-phenol (L5) and 2-chloro-4-nitro(phenylazo)-5-tert-butyl-2-phenol (L6)], and ester derivatives [quinoline-8-benzoate (L7), phenyl-1,4-dibenzoate (L8), p-tolyltiobenzoate (L9)]. It was found that, all the compounds (L1-L9) examined showed selectivity for transition metal cations such as Ag+, Hg+ Hg2+, and poor efficiency for alkali metal cations (Na+ and K+). The best extraction efficiency was obtained with L1 and L4.