Separation of inorganic anions on a triazole-functionalized ion exchanger in ion chromatography

The retention behavior of inorganic anions on a triazole-based stationary phase was first examined in ion chromatography. It was initially designed for hydrophilic interaction liquid chromatography and was simply prepared by introducing the triazole groups onto the surface of silica gel via click chemistry. Effective separation of common inorganic anions, including iodate, chloride, bromide, nitrate and iodide, was achieved with Na(2)SO(4) eluent. The logarithm of the retention factor of analytes was observed to be linear with the logarithm of the eluent concentration, and the slopes of the plots were almost the same as those of the ideal theoretical value. The eluent pH value in the range of 3.4-7.0 had little effect on the separation. The utility of the column was demonstrated for the determination of UV-absorbing anions in saliva and tap water.     

Histidine as the functional group for a chelating ion exchanger

In the chelating ion exchanger synthesized, the amino group of histidine is attached chemically via the azide method to the carboxyl group of Amberlite IRC-50. A flow system based on a spectrophotometric detector, with 4-(2-pyridylazo) resorcinol as reagent, is described for fast assays of eluted cations. The pH dependence of the metal extraction is reported for Ag(I), Au(III), Cu(II), Fe(III), Hg(II), Ni(II) and Zn(II) ions. The resin exhibits no affinity for the alkali or alkaline earth metals. The uptake of traces of the specified elements from synthetic samples by a short (90 mm) column of the histidine-containing resin was in the range 94–100% and the retained metals were readily eluted by means of 2 M hydrochloric or hydrobromic acid. In column operation, mercury was quantitatively recovered even in the presence of large excesses of various ligands. The recoveries of the trace metals were good at the usual pH of natural waters.     

A carbon-13 NMR study of the ion pair structure of the dibenzo[b,f]pentalene dianion

The ¹H and ¹³C NMR chemical shifts of dibenzo[b, f]pentalene and its 5,10-dimethyl derivative are presented and compared with those of the corresponding dilithium dianions. As probed by the relative ¹³C NMR chemical shifts, the charge distribution within the dianion system is clearly dependent on the actual ion pair state. This condition is demonstrated by varying the solvent and temperature. The polarization of charge towards the pentalene carbons, i.e. the preferred cation positions, is observed on going to tight ion pair conditions. Further support for this model is gained from ⁷Li NMR. The limitations of the use of ¹H and ¹³C NMR chemical shifts to measure charge distributions within anion systems are discussed.     

NMR study of the spatial structure of synthetic pyrethroids

The spatial isomers of the new synthetic analogs of ethyl permithrinic ether and permethrin were investigated by NMR (¹H, ¹³C, DEPT (distortionless enhancement by polarization transfer), COSY (correlation spectroscopy), CHCORR (heteronuclear (C, H) shift correlation spectroscopy), ROESY (rotating-frame Overhauser effect spectroscopy)). Several tendencies were revealed in the ¹H and ¹³C chemical shifts of the α atoms of the substituents in the 2nd and 3rd positions of the cyclopropane ring. For substituents cis-orientated relative to the ester group, the spectra show a paramagnetic shift of the ¹H signals and the diamagnetic shift of the ¹³C signals relative to the trans-orientated substituents. The ¹H and ¹³C chemical shifts of the α atoms of the substituents in the 2nd and 3rd positions of the cyclopropane ring permit an unambiguous determination of the stereochemistry of ethyl permethrinic ether and permethrin analogs.     

The structure of the ion: An ion kinetic energy spectrometry study

The kinetic energy release (T) values for the loss of CO from ions from five compounds have been obtained and are consistent with at least two different structures for the ion. This result is supported by the T value obtained for the decomposition of the molecular ions.     

Clotrimazole-triiodide ion association as an ion exchanger for a triiodide ion-selective electrode.

A novel triiodide ion-selective electrode based on a clotrimazole-triiodide ion pair as a membrane carrier was prepared. It has a linear response to triiodide from 8 x 10(-6) to 5 x 10(-3) M with a slope of -68.9 mV per decade and a detection limit of 5 x 10(-6) M. The electrode response is independent of the pH of the solution in the pH range 2-9. It has a very short response time and can be used for at least 3 months without any considerable divergence in the potentials. The proposed sensor revealed very good selectivities for I3- over a variety of other anions. It was used as an indicator electrode in the potentiometric titration of triiodide ions and in an indirect potentiometric determination of clotrimazole in pharmaceutical preparations.     

Zirconium arsenophosphate as an ion exchanger

Zirconium arsenophosphate (ZAP) a new inorganic ion exchanger has been synthesized under varying conditions of precipitation. The material possesses good chemical and thermal stabilities and regeneration power. It shows no breakdown on irradiation with a gamma dose of ～10⁹ rad. ZAP shows high affinity for univalent ions like Rb⁺, Ag⁺ and Tl⁺. The Kd-values have been determined for a number of metal ions from acid media. The stoichiometry of metal ion uptake was checked using almost carrier-free radiotracers. Sixteen binary/ternary separations of metal ions are reported on a ZAP column.     

A 1H NMR study of the tropylium ion,partially oriented in a lyotropic solvent

The ¹H NMR spectrum of tropylium fluoroborate dissolved and oriented in a lyotropic decyl sulphate phase has been recorded and analysed. Direct as well as indirect H? H coupling constants have been obtained. The vibrationally uncorrected proton skeleton structure deviates slightly from a regular heptagon. The deviations are between two and three times larger than those of benzene from a hexagon, previously observed in the same solvent.     

Theoretical study of the interaction between sodium ion and a cyclopeptidic tubular structure

DFT calculations have been carried out to describe the pathway of a sodium ion along the stacking direction of a tubular structure set up by five cyclopeptidic units, which can be considered a suitable model of a hollow tubular structure of indefinite length. A lattice of points inside the tubular structure is defined and the DFT interaction energy values with a sodium ion are obtained. The data allow predicting a zigzag path of the ion inside the hosting structure.     

NMR study of the structure of the nitration intermediate of furfural

The structure of the intermediate obtained in the come of the nitrationof 2-furancarboxaldehyde was investigated by means of ¹H and ¹³C NMR. It was shown unambiguously that this intermediate is 2-acetoxy-2-diacetogymethyl-5-nitro-2,5-dihydrofuran.     

The study of macromolecular structure by pulsed NMR

NMR has been widely used to determine chemical structure. The analysis of many important physical and physico-chemical properties such as molecular weight and mobility, the effect of crosslinking and entanglements and of solvents temperature, the role of crystalline regions and chain flexebility may be achieved very readily and simply these techniques. Once methods of analysis are understood and evaluated, they may serve only for the analysis of radiation effects but also for other forms of chemical treatment, the role of additives, orientation, and understanding and evaluation of important physical aspects, for which many of these polymers are intended. The use of pulsed NMR can also be used to evaluate radiation chemistry under different conditions, and it is expected that this knowledge could be extended to biological and medical systems, where a knowledge of the physical arrangements, mobility, entangled and other molecular properties and especially arrangement can be very important, yet difficult to measure.     

The temperature dependence of ion exchanger sorption capacity in the glycine-nickel nitrate-ANKB-35 ion exchanger system from 298 to 338 K

The complex formation and ion exchange processes in the glycine-nickel(II) ion-ANKB-35 polyampholyte system were studied. The composition of complex ions sorbed by the ion exchanger was determined, and the equilibrium characteristics of their sorption at different temperatures were calculated. Original Russian Text ? A.V. Astapov, Yu.S. Peregudov, M.V. Enyutina, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 6, pp. 1165–1168.     

Metal ion binding to parvalbumin. A proton NMR study

The 1H NMR spectra of carp parvalbumin saturated with Ca2+, Cd2+, La3+ and Lu3+ were compared, using 2D 1H NMR techniques as well as conventional 1H NMR spectra. The Ca2+ and Cd2+ saturated parvalbumin (with both high affinity Ca2+-binding sites occupied) gave rise to very similar spectra. This shows that these two species have almost identical protein conformations. The 1H NMR spectrum from the Ln3+ saturated parvalbumins deviated from the other two and it was therefore concluded that Cd2+ is a better probe for Ca2+ than Ln3+ in parvalbumin and probably also for related calcium binding proteins. The addition of excess of divalent metal ions, such as Mg2+ or Ca2+, causes small changes in the chemical shift of some methyl resonances. This is presumably caused by binding of these metal ions to a third site close to the CD site which is made up of the carboxylic groups from Glu 60 and Asp 61.     

Calculation on ion exchange capacity for an ion exchanger using the potentiometric titration

We calculated the characteristics of a phosphoric cation exchanger and studied an accurately computable method for ion exchange capacity for a type of potentiometric titration curve. The ion exchanger was prepared by phosphorylation of a styrene‐divinylbenzene copolymer. The ion exchange capacity was 5.7 meq/g. The experimental pK values versus χ in a phosphoric cation exchanger can explain a linear equation. The ΔpK values were obtained from the slope of a linear equation. The ΔpK values were the differences of pK values between the apparent equilibrium constant at complete and zeroth neutralization of the ion exchanger. The experimental pK values at χ = 0.5 (χ:degree of neutralization of ion exchanger) showed good agreement with the theoretical data. When it was titrated with NaOH and Ba(OH)₂ solutions, a good agreement between experimental and theoretical pK values for various χ was found in all potentiometric titration curves. The potentiometric titration curve near the inflection point in the case of divalent ions was changed more sharply than that for monovalent ions. The plot of ∂pH/∂g versus g (number of moles of alkali to 1 g of ion exchanger) was fitted to the Lorenzian distribution, from which ion exchange capacity was accurately evaluated. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3181–3188, 2000     

Zirconium vanadophosphate as an inorganic ion exchanger

Zirconium vanadophosphate was characterized as a stable inorganic ion exchager. The ion-exchange capacity was measured as 1.75 meq. H⁺ g^?1 at room temperature and it is stable up to 300°C. The exchanger is selective for devalent cations and the order of sorption of cations was found to be M²⁺ > M⁺ > M³⁺ M⁴⁺. Separations of Co²⁺?Ni²⁺, Cu²⁺?Hg²⁺ and Cr(VI)?Cr³⁺ were achieved on a column containing the ion exchanger. Copper could be separated from other base metals in geochemical samples. Differential thermal analysis showed an endothermic peak in the range of 65–420°C due to the dehydration of the ion exchanger with a low activation energy of 7.79 kcal mol^?1, which follows first-order kinetics. The ion exchanger did not show any further decomposition up to 1000°C. Infrared studies confirmed the presence of

groups which act as exchange sites for the cations. X-ray diffraction studies revealed that the compound is crystalline, with a crystal structure resembling that of the mineral muscovite.     

An NMR study of thallium nitrate ion association in liquid ammonia

²⁰⁵Tl and¹H magnetic resonance frequencies have been determined for liquid ammonia solutions of TlClO₄ and TlNO₃ as a function of electrolyte concentration (5×10^–4 to 9.8 M) and temperature. The dependence of the resonance frequency on concentration suggests the presence of free, fully solvated thallium ions, ion pairs, and higher-order ion aggregates. Analysis of lowconcentration²⁰⁵Tl data between 0 and 30°C allowed the determination of TlNO₃ ion-pair association constants and thermodynamic parameters (H_A=+6.5 kcal-mole^–1, S_A=+36 e.u.). A preciptous decrease in²⁰⁵Tl resonance frequency was observed for NH₃ to TlNO₃ mole ratios below 3:1, suggesting the formula (NH₃)₃Tl⁺ NO ₃ ^– for the fully solvated, contact ion pair.     

NMR spectroscopic study of hydrolyzed aluminum ion adsorption on silica gel

Aluminum ion adsorption on the surface of nanodisperse silica particles is investigated by NMR spectroscopy as depending on Al(NO)₃ content in solutions. It is established that Al(H₂O ₆ ³⁺ aquacomplexes are poorly sorbed by silica gel. The highest sorbability is inherent in AlO₄Al₁₂(OH)₂₄(H₂O ₁₂ ⁷⁺ hydroxocomplex. The transfer of this complex to an adsorption layer is accompanied by its partial decomposition and the distortion of the tetrahedral geometry of the environment of the central aluminum atom.     

NMR spectral study of the structure of 2-amino-4-thiazolinones

As a consequence of partial double bond nature of the exocyclic C-N bond, 2-methylamino-4-thiazolinone exists in DMSO-D₆ as a mixture of E and Z conformers of the amino form with predominance of the sterically favored E conformer. 2-Phenylimino-4-thiazolidinone in the same solvent exists as a mixture of the E and Z isomers of the imino form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 544–548, April, 1986.