Retention in analytical ion exchange chromatography-1. Strong electrolytes on strong ion exchangers

A retention equation of general validity is adapted to ion exchange chromatography providing a self-consistent interpretation of retention of solutes and system peaks. Discussion is limited to eluent mixtures containing ions of invariant charge and to stationary phases with pH-independent surface charge. An interpretation is proposed for the retention volume of system peaks in binary eluents (mixtures of two eluent counter-ions). Retention volumes of labelled counter-ions of the eluent appear to provide useful information about the chromatographic system with clear interpretation in any multicomponent eluent.     

Mass transfer in shell-core inorganic TIP1 ion exchanger

The ion exchange processes of (OAc^–) and (OAc^–) proceeding in shell-core inorganic ion exchanger Ti (HPO₄)₂·1/2H₂O has been studied and the diffusion equation whose boundary conditions are satisfied by a shell-core model was solved. Based on the equation solved and experimental data, the diffusion coefficients corresponding to the exchange process (OAc^–) and Li⁺–H⁺ (OAc^–) at 17°C are found to be 7.7×10^–9 and 6.2×10^–8 cm² s^–1 and the activation energies 3.4×10⁴ and 5.0×10³ J mol^–1, respectively. Compared to the gel type of styrene-divinylbenzene strong acid exchanger with 20% cross linking, it can be concluded that the rate of or exchange is 3.5 times faster than that in the organic exchanger.TIP was obtained from the Salt Lake Institute of the Academy of Science of China.     

Doubly charged ion mass spectra: 1-Aliphatic nitriles

The doubly charged ion mass spectra for 12 aliphatic nitriles (1–9 carbon atoms) have been obtained using an Hitachi RMU-7L double focusing mass spectrometer. These spectra show some characteristic features such as extensive loss of hydrogen and the grouping of ions in the spectra into n-1 groups where n is the number of carbon atoms in the molecule (n<6). There are no indications of HCN or CN loss in the doubly charged ion spectra of the monosubstituted nitriles. SCF calculations of the energy and structure of doubly charged ions in the propionitrile spectra have been carried out.     

Gas-phase positive ion chemistry of 1-bromo-1-chloro-2,2,2-trifluoroethane (halothane) upon electron ionization within an ion trap mass spectrometer

The positive ion chemistry occurring within an ion trap mass spectrometer upon electron ionization of 1-bromo-1-chloro-2,2,2-trifluoroethane, the important anaesthetic halothane, has been mapped by means of collision-induced decomposition and ion/molecule self-reaction experiments. Ionized halothane (M+*) reacts with neutral halothane to form the ionized olefin [ClBrC=CF2]+*. via HF elimination. Among the ionic fragments, [M-Br]+ and [M-F]+ react with halothane via chloride abstraction while [M-Cl]+ is unreactive under the same experimental conditions. Substituted methyl cations CHFX+ and CF2X+ (X = F, Cl, Br) undergo halide transfer processes, their reactivity being highest for X = F. Ionized carbenes CXY+ (X,Y = F,F; H,Br; H,Cl; H,F) react with halothane to form CClXY+ and CBrXY+, whereas CF+ inserts into the C-Cl bond to form CF3+ and CClF2+. Finally, Br+ and Cl+ react with halothane by charge transfer. Collision-induced dissociation experiments disclosed interesting rearrangements involved in the dissociations of +CHX-CF3 ions (X = Br, Cl), which undergo fluorine migration and elimination of CF2, as already observed for +CCl2-CF3 in a previous investigation.     

TOF-SIMS and XPS-investigations of ion implanted single crystal 1b-diamonds

Near surface zones of (48)Ti- and (52)Cr-implanted single crystal diamonds (1b-MCD) were characterized by XPS, TOF-SIMS and white light interference microscopy (WLI). By the combination of WLI and TOF-SIMS it was possible to calibrate the depth scale of TOF-SIMS and XPS depth profiles quantitatively. The adjustment of TOF-SIMS and XPS elemental depth profiles in the implantation maximum increases the quantitative detection limit of the implanted elements by more than two orders of magnitude and enables the interpretation of results from wear simulation experiments. Peak fits of XPS C(1s)-photolines indicate the fraction and chemical nature of carbide-like structures in the implantation zone. Qualitative hints on carbide compounds are possibly included in the reconstructed TOF-SIMS spectra but this information can presently only be extracted with the aid of XPS analyses.     

Fluoride ion catalyzed isomerization of 2-aryl-F-butenes [1]

A kinetic study of the fluoride ion catalyzed isomerization of a series of 2-aryl$\text{F}$1-butenes shows the reactions to be pseudo first order in olefin at constant fluoride ion concentration. The resultant Hammett plot is non-linear witb a concave downward break near $\text{σ}$=0. A two step mechanism involving formation of a carbanionic intermediate is proposed. A change in the rate limiting step causes the break in the Hammett plot. Carbanion trapping experiments are also reported.     

Quantitative characterization of ion pairing and cluster formation in strong 1:1 electrolytes

Aqueous solutions of 1:1 strong electrolytes are considered to be the prototype for complete ionic dissociation. Nonetheless, clustering of strong 1:1 electrolytes has been widely reported in all atom molecular dynamics simulations, and their presence is indirectly implicated in a diverse range of experimental results. Is there a physical basis for nonidealities such as ion pairing and cluster formation in aqueous solutions of strong 1:1 electrolytes? We attempt to answer this question by direct comparison of results from detailed molecular dynamics simulations to experimentally observed properties of 1:1 electrolytes. We report the analysis of a series of lengthy molecular dynamics simulations of alkali-halide solutions carried out over a wide range of physiologically relevant concentrations using explicit representations of water molecules. We find evidence for pronounced nonideal behavior of ions at all concentrations in the form of ion pairs and clusters which are in rapid equilibrium with dissociated ions. The phenomenology for ion pairing seen in these simulations is congruent with the multistep scheme proposed by Eigen and Tamm based on data from ultrasonic absorption experiments. For a given electrolyte, we show that the dependence of cluster populations on concentration can be described through a single set of equilibrium constants. We assess the accuracy of calculated ion pairing constants by favorable comparison to estimates obtained by Fuoss and co-workers and based on conductometric experiments. Ion pairs and clusters form on length scales where the size of individual water molecules is as important as the hard core radius of ions. Ion pairing results as a balance between the favorable Coulomb interactions and the unfavorable partial desolvation of ions needed to form a pair.     

Complexation of metal ion with poly(1-vinylimidazole) resin prepared by radiation-induced polymerization with template metal ion

Poly(1-vinylimidazole) (PVI) resin was prepared with Ni²⁺, Co²⁺, or Zn²⁺ as a template to study the adsorption of metal ions. The metal-1-vinylimidazole complex was copolymerized and crosslinked with 1-vinyl-2-pyrrolidone by γ-ray irradiation and the template metal ion was removed by treating the polymer complex with an acid. These PVI resins adsorbed metal ions more effectively than the PVI resin prepared without the template. The number of adsorption sites (As) and the stability constant (K) of Ni²⁺ complex were larger for the PVI resin prepared with the Ni ion template, caused by the smaller dissociation rate constant of Ni ion from the resin. The composition of the Ni²⁺ complex in the resin remained constant. This suggests that the complexation proceeded via a one-step mechanism.     

Gravimetric determination of uranyl ion with 2-hydroxy-1-naphthaldehyde /2H-1N/

The precipitation of uranyl ion with 2-hydroxy-1-naphthaldehyde /2H–1N=HL/ was studied. The solid complex /orange crystals/ was characterized by IR, UV-Vis spectra. Uranium was determined as U₃O₈ after calcination of the complex at 850°C /37.78% U experimental, 36.64% U calculated for C₂₂H₁₄O₆U, UO₂L₂/. Using a statistical experimental design, the best conditions for quantitative precipitation were obtained. A gravimetric method for the determination of UO ₂ ²⁺ is proposed by weighing the complex after drying at 110°C.On leave from Instituto de Química, U.N.A.M.     

1, 1-Dithiolato-bridged heterobimetallic complexes containing a transition metal ion and oxouranium(VI)

Summary Anionic complexes [UO₂(1, 1-dithiolate)₂]^2– interact strongly with transition metal ions to yield a new class of dithiolato-bridged heterobimetallic complexes MUO₂(1, 1-dithiolate)₂ (M=Co^II, Ni^II, Cu^II, Zn^II or Pb^II, 1, 1-dithiolate = isomaleonitrile dithiolate (i-MNT^2–) and trithiocarbonate (CS ₃ ^2– )). (Et₄N)₂[UO₂(i-MNT)₂] and (Et₄N)₂[UO₂(CS₃)₂] have also been prepared. The complexes have been characterized by elemental analysis, i.r., u.v.-vis. and e.s.r. spectral studies. The heterobimetallic complexes are non-electrolytic, whereas (Et₄N)₂-[UO₂ (i-MNT)₂] and (Et₄N)₂[UO₂(CS₃)₂] are 21 electrolytes. The i.r. data indicate symmetrical bidentate bridging behaviour for the dithiolate ligands. Magnetic moments, electronic spectra and e.s.r. studies are commensurate with a square planar environment around Co^II, Ni^II and Cu^II.     

An ion trap-ion mobility-time of flight mass spectrometer with three ion sources for ion/ion reactions

This instrument combines the capabilities of ion/ion reactions with ion mobility (IM) and time-of-flight (TOF) measurements for conformation studies and top-down analysis of large biomolecules. Ubiquitin ions from either of two electrospray ionization (ESI) sources are stored in a three dimensional (3D) ion trap (IT) and reacted with negative ions from atmospheric sampling glow discharge ionization (ASGDI). The proton transfer reaction products are then separated by IM and analyzed via a TOF mass analyzer. In this way, ubiquitin +7 ions are converted to lower charge states down to +1; the ions in lower charge states tend to be in compact conformations with cross sections down to ～880 Ų. The duration and magnitude of the ion ejection pulse on the IT exit and the entrance voltage on the IM drift tube can affect the measured distribution of conformers for ubiquitin +7 and +6. Alternatively, protein ions are fragmented by collision-induced dissociation (CID) in the IT, followed by ion/ion reactions to reduce the charge states of the CID product ions, thus simplifying assignment of charge states and fragments using the mobility-resolved tandem mass spectrum. Instrument characteristics and the use of a new ion trap controller and software modifications to control the entire instrument are described.     

Positive/negative liquid secondary ion mass spectrometry ofLn-EDTA (1:1) complexes. Formation of molecular ion adducts with neutral species of the matrix orLn-EDTA

Summary The mass spectra of 1:1 complexes ofEDTA with lanthanide cations (Ln=Sm, Eu, Gd, Tb or Dy) upon positive/negative LSIMS are presented. In glycerol used as a matrix, adduct-ions such as [M+H]⁺, [M+H+nGly]⁺, [2M+H]⁺, [2M+H+Gly]⁺ (positive LSIMS) or [M-H]^–, [M-H+nGly]^–, [2M-H]^–, [2M-H+Gly]^– (negative LSIMS), wheren=1–3, are formed. Reactions leading to the formation of adduct-ions are suggested.

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Positive/negative Liquid-Sekundärionen-Massenspektrometrie vonLn-EDTA-(1:1)-Komplexen. Bildung von molekularen Ionenaddukten mit neutralen Spezies aus der Matrix oderLn-EDTA

Zusammenfassung Die Massenspektren von 1:1-Komplexen vonEDTA mit Lanthanidenkationen (Ln=Sm, Eu, Gd, Tb oder Dy) mittels positiver/negativer LSIMS werden präsentiert. In Glycerin als Matrix bilden sich Adduktionen wie [M+H]⁺, [M+H+nGly]⁺, [2M+H]⁺, [2M+H+Gly]⁺ (positive LSIMS) oder [M-H]^–, [M-H+nGly]^–, [2M-H]^–, [2M-H+Gly]^– (negative LSIMS), wobein=1–3. Es werden Reaktionen vorgeschlagen, die zur Bildung von Adduktionen führen.

     

Simulated ion trajectory and induced signal in ion cyclotron resonance ion traps

We present a numerical method for computation of electrostatic (trapping) and time-varying (excitation) electric fields and the resulting ion trajectory and detected time-domain-induced voltage signal in a rectangular (or cubic) ion cyclotron resonance (ICR) ion trap. The electric potential is calculated by use of the superposition principle and relaxation method with a large number of grid points (e.g., 100 × 100 × 100 for a cubic trap). Complex ICR experiments and spectra may now be simulated with high accuracy. Ion trajectories may be obtained for any combination of trapping and excitation modes, including quadrupolar or cubic trapping in static or dynamic mode; and dipolar, quadrupolar, or parametric excitation with single-frequency, frequency-sweep (chirp), or stored waveform inverse Fourier transform waveforms. The resulting ion trajectory may be represented either as its three dimensional spatial path or as two-dimensional plots of x-, y-, or z-position, velocity, or kinetic energy versus time in the absence or presence of excitation. Induced current is calculated by use of the reciprocity principle, and simulated ICR mass spectra are generated by Fourier transform of the corresponding time-domain voltage signal.     

Determination of aflatoxins B1 and B2 using ion mobility spectrometry

This paper describes total determination of aflatoxins B1 and B2 in pistachio samples using corona discharge ion mobility spectrometry (IMS). A new injection port was designed to introduce liquid samples into the IMS. Using this port, the liquid solvent (methanol) containing standard aflatoxins or an extracted sample was directly introduced into the injection port. Calibration curves resulting from experimental analyses were linear within two orders of magnitude and relative standard deviations (R.S.D.) were less than 10%. The limit of detection (LOD) was found to be 0.25 ng for both aflatoxins. Addition of ammonia as the dopant to the carrier gas improved the LOD by a factor of 2.5. Pistachio samples were analyzed to demonstrate the capability of the proposed method in detecting aflatoxins in real samples.     

HSAB principle and nickel(II) ion reactivity towards 1-methyhydantoin

1-Methylhydantoin and its novel nickel(II) complex [Ni(H₂O)₄(1-mhyd)₂] were prepared and identified, by elemental analysis, single crystal X-ray determination and MS methods. In addition, the complex was characterized by spectroscopic (IR, UV-Vis), magnetic and thermal techniques. The ligand reveals an interesting supramolecular architecture with both classical and non-conventional extended HB bonding networks. All rings and chains formed due to this HB bonding are embedded into the undulated pattern. A single crystal X-ray diffraction analysis of the complex shows that the nickel ion is coordinated by deprotonated hydantoin and water ligands in a N₂O₄ tetragonal arrangement. In the [Ni(H₂O)₄(1-mhyd)₂] structure both inter and intramolecular hydrogen bonds are created with the participation of water molecules.The ESI-MS method confirmed mono-nuclearity of the complex while electronic spectroscopy proved the tetragonal and pseudooctahedral geometries around the metal ion in the solid state and solution, respectively. By application of the “average environment rule”, 10Dq parameters were obtained for the hypothetical, hexa-coordinate [Ni(1-mhyd)₆] approximation or rather more realistic [Ni(1-mhyd)₃] chelate. Based on this the mhyd ligand was ranked in the spectrochemical series close to ammonia. The general consideration of the structure of the hydantoin complexes as a function of the metal ion hardness within the framework of the HSAB theory has been provided. Both the ligand and the complex were found to be non-toxic agents against breast (MCF-7), lung carcinoma epithelial (A549) and mouse fibroblasts (Balb/3T3) cancer cell lines.