Hydroxide and hydronium ion adsorption — A survey

The propensity of hydroxide and hydronium ions to accumulate at interfaces is the subject of ongoing scientific debate. Electrokinetic and surface force measurements suggest elevated interfacial concentrations of hydroxide ions across a wide range of pHs. Contrary to this, however, surface-sensitive spectroscopic techniques and molecular dynamic (MD) simulations indicate that hydronium ions have strong surface affinity under similar conditions. Here we review results obtained for gas/water, oil/water and solid/water interfaces. Emphasis is placed on ion adsorption phenomena occurring on polymer films of different hydrophobicity and structure. The results clearly show that asymmetric water ion adsorption is independent of the hydrophobicity of the solid surface. Recently obtained data reveal significant effects of the hydroxide and hydronium ions even on the charging of hydrophobic polymers in the presence of multivalent electrolytes and on the charging of zwitterionic lipid membranes.     

Positive ion — negative ion coincidence spectroscopy of O2 and H2 using synchrotron radiation

Kinetic studies of the reactions of neutral lead clusters with NO₂, NO and O₂ were performed at 300 K. Reaction with NO₂ is rapid, with the observed second-order rate constants for most clusters being between 0.2 and 5 × 10^?11 cm³/s. There is a general trend of increasing rate with cluster size, although a few clusters display unusually high or low rates compared to ones of neighboring size. The reactions with NO are considerably slower by factors ranging from about 5 to 10. Reaction products are observed by laser ionization at 193 and 222 nm in conjunction with time-of-flight mass spectrometry. At lower fluence, the association products Pb _x (NO₂)⁺ and Pb _x (NO₂) ₂ ⁺ are observed in the case of reactions with NO₂. At higher laser fluence, Pb _x ⁺ and Pb _x O _x ^?1+ dominate the mass spectra of Pb _x reactions with NO₂, showing that the products fragment to more stable oxides. No reaction with oxygen was observed for any cluster, setting upper limits on the rates of 5 × 10^?14 cm³/s.     

Molecular dynamics and ion mobility spectrometry study of model β-hairpin peptide, trpzip1

Here, we explore the conformations of gas phase, protonated tryptophan zipper 1 (trpzip1) ions and its six derivatives by an enhanced sampling molecular dynamics, specially the integrated tempering sampling molecular dynamics simulation (ITS-MDS). The structural distributions obtained from ITS-MDS are compared with results obtained from matrix-assisted laser desorption ionization (MALDI)-ion mobility-mass spectrometry (IM-MS). The IM-MS measured collision cross-section (CCS) profiles compare well with the calculated CCS profiles obtained from ITS-MDS. Although β-turn structures are preferred for solution phase species, the ITS-MDS and IM-MS structural analysis suggests that the γ-turn structures are preferred for gas-phase, unsolvated trpzip1 [M + H](+) ions. In addition, the data suggests that the energy landscape of the gas phase peptide ions is sensitive to the site of protonation as well as intramolecular interactions involving the lysine side chain.     

Salts of o,o′-diphenylenephenyloxonium ion

Summary o,o-Diphenylenephenyloxonium sulfate was prepared by us for the first time by heating an aqueous solution of o-phenoxy-o-biphenyldiazonium sulfate; a series of salts of this cation was prepared from this substance by double exchange reactions and the properties of these salts were studied.     

The distonic ion ·CH2CH2CH+OH,keto ion CH3CH2CH=O +·, enol ion CH3CH=CHOH+·, and related C3H6O+· radical cations. Stabilities and isomerization proclivities studied by dissociation and neutralization-reionization

Metastable ion decompositions, collision-activated dissociation (CAD), and neutralization-reionization mass spectrometry are utilized to study the unimolecular chemistry of distonic ion ^·CH₂CH₂CH^?OH (2^+·) and its enol-keto tautomers CH₃CH=CHOH^?· (1 ^+·) and CH₃CH₂CH=O ^+· (3^+·). The major fragmentation of metastable 1^+·–3^+· is H^· loss to yield the propanoyl cation, CH₃CH₂C≡O⁺. This reaction remains dominant upon collisional activation, although now some isomeric CH₂=CH-CH⁺ OH is coproduced from all three precursors. The CAD and neutralization-reionization (⁺NR⁺) spectra of keto ion 3 ^+· are substantially different from those of tautomers 2^+· and 1^+·. Hence, 3^+· without sufficient energy for decomposition (i. e. , “stable” 3^+·) does not isomerize to the ther-modynamically more stable ions 2^+· or 1^+·, and the 1,4-H rearrangement H-CH₂CH₂CH=O^+·(3 ^+·) → CH₂CH₂CH⁺ O-H (2 ^+·) must require an appreciable critical energy. Although the fragment ion abundances in the ⁺ NR ⁺ (and CAD) spectra of 1 ^+· and 2 ^+· are similar, the relative and absolute intensities of the survivor ions (recovered C₃H₆O^+· ions in the ⁺NR⁺ spectra) are markedly distinct and independent of the internal energy of 1 ^+· and 2 ^+·. Furthermore, 1 ^+· and 2 ^+· show different MI spectra. Based on these data, distonic ion 2 ^+· does not spontaneously rearrange to enol ion 1 ^+· (which is the most stable C₃H₆O^+· of CCCO connectivity) and, therefore, is separated from it by an appreciable barrier. In contrast, the molecular ions of cyclopropanol (4 ^+·) and allyl alcohol (5 ^+·) isomerize readily to 2 ^+·, via ring opening and 1,2-H^? shift, respectively. The sample found to generate the purest 2 ^+· is α-hydroxy-γ-butyrolactone. Several other precursors that would yield 2 ^+· by a least-motion reaction cogenerate detectable quantities of enol ion 1 ^+·, or the enol ion of acetone (CH₂=C(CH₃)OH^+·, 6 ^+·), or methyl vinyl ether ion (CH₃OCH=CH ₂ ^+· , 7 ^+·). Ion 6 ^+· is coproduced from samples that contain the —CH₂—CH(OH)—CH₂— substructure, whereas 7 ^+· is coproduced from compounds with methoxy substituents. Compared to CAD, metastable ion characteristics combined with neutralization-reionization allow for a superior differentiation of the ions studied.     

A highly sensitive colorimetric and ratiometric sensor for fluoride ion

A new benzoimidazole-naphthalimide derivative 4 was synthesized and its photophysical properties were studied. This compound showed highly selectively and sensitive colorimetric and ratiometric sensing ability for fluoride anion.     

Effect of the porosity of PS–DVB-copolymers on ion chromatographic behavior in inverse size-exclusion and ion chromatography

Small and highly pressure-stable PS-DVB copolymers of different porosity had been prepared by a two-step swelling procedure which enabled variation of diluent composition, an important characteristic affecting the porosity. The polymers were characterized by inverse size-exclusion chromatography and scanning electron microscopy. Subsequent chloromethylation and amination resulted in anion exchangers suitable for ion chromatography.The pore volume and the pore-size distribution is substantially affected by the fraction of the solvens component in the diluent. It was apparent from scanning electron microscopy that surface structure and the size of the polymer particles was not affected by diluent composition. The functionalization process led to a decrease in pore volume. The pore-size distribution remained unchanged during functionalization, which can be explained in terms of partial closing of all pore sizes. The chromatographic efficiency of the functionalized polymers in ion chromatography was highly dependent on diluent composition and the extent of functionalization was determined by the total pore volume.The composition of the diluent is an excellent tool for optimization of polymers used for the synthesis of surface-functionalized anion exchangers.     

Determination of cis-permethrin,trans-permethrin and associated metabolites in rat blood and organs by gas chromatography–ion trap mass spectrometry

An analytical method was developed to measure cis-permethrin and trans-permethrin in different biological rat matrices and fluids (whole blood, red blood cells, plasma, brain, liver, muscle, testes, kidneys, fat and faeces). The method was also suitable for the simultaneous quantification of their associated metabolites [cis-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (cis-DCCA), trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (trans-DCCA) and 3-phenoxybenzoic acid (3-PBA)] in blood (whole blood, red blood cells, plasma) and liver. The target analytes were derivatised in samples using a methanolic/hydrochloric acid solution and then extracted with toluene. The analysis was performed by gas chromatography, and detection using ion trap tandem mass spectrometry. The selectivity obtained for complex matrices such as rat organs allowed the use of a purification step to be avoided for most of the matrices investigated. In the case of fat, where permethrin is suspected to accumulate, a dedicated purification step was developed. In fluids, the limits of quantification were at the 50 ng/mL level for the parent compounds and 3-PBA and at 25 ng/mL for cis-DCCA and trans-DCCA. For solid matrices excluding fat, the limits of quantification ranged from 50 ng/g for muscle to 100 ng/g for brain and testes for both cis-permethrin and trans-permethrin. The extraction recoveries ranged primarily between 80 and 120 % for the matrix tested. The stability of blood samples was tested through the addition of 1 % v/v formic acid. The methods developed were applied in a toxicokinetic study in adult rats. cis-Permethrin and the metabolites were detected in all corresponding matrices, whereas trans-permethrin was detected only in blood, plasma and faeces.     

Studies on the Copolymerization of Propylene and Butadiene with Supported Titanium Catalysts (I)——Copolymerizat ion and Characterizat ion of the Products

Copolymerizations of propylene and butadiene in various ratios with two kinds of supported catalysts, i.e. TiCl4/MgCl2/AlEt3 and TiCl4/MgCl2/AlEt3/ethyl Bonzoate(EB). have been investigated. The results show that these two catalysts are quite effective for propylene-butadiene copolymerization but behave in different features. Characterizations of the copolymerization products by solvent extraction, IR, 13C NMR, X-ray diffraction and DTA show that blocked propylene-propylene and butadiene-butadiene sequences exist in polymer chain and the butadiene units are exclusively in trans-1,4 configuration.     

NMR, DTA, and impedance spectroscopy studies of ion mobility, phase transitions, and ionic conductivity in K1 − x (NH4) x SbF4 crystals

The ion mobility, phase transitions, and ionic conductivity in the crystal phases in the KF-NH₄F-SbF₃ system were studied by NMR, DTA, and impedance spectroscopy. An analysis of the ¹⁹F and ¹H NMR spectra showed how the character of ionic motions in the fluoride and proton sublattices changed with temperature. The types and temperature ranges of ionic motions were determined. Diffusion of the fluoride and partially ammonium ions was found to be the dominant form of ionic motion in the high-temperature modifications formed as a result of phase transitions. According to the electrophysical data, the high-temperature K_{1 ? x} (NH₄) _x SbF₄ phases (0.05 ≤ x ≤ 0.75) are superionic, their conductivity reaching ～10^?2–10^?3 S/cm at 450–500 K.     

Triggers for β-sheet formation at the hydrophobic-hydrophilic interface: high concentration, in-plane orientational order, and metal ion complexation

Amyloid formation plays a causative role in neurodegenerative diseases such as Alzheimer's disease or Parkinson's disease. Soluble peptides form β-sheets that subsequently rearrange into fibrils and deposit as amyloid plaques. Many parameters trigger and influence the onset of the β-sheet formation. Early stages are recently discussed to be cell-toxic. Aiming at understanding various triggers such as interactions with hydrophobic-hydrophilic interfaces and metal ion complexation and their interplay, we investigated a set of model peptides at the air-water interface. We are using a general approach to a variety of diseases such as Alzheimer's disease, Parkinson's disease, and type II diabetes that are connected to amyloid formation. Surface sensitive techniques combined with film balance measurements have been used to assess the conformation of the peptides and their orientation at the air-water interface (IR reflection-absorption spectroscopy). Additionally, the structures of the peptide layers were characterized by grazing incidence X-ray diffraction and X-ray reflectivity. The peptides adsorb to the air-water interface and immediately adopt an α-helical conformation. This helical intermediate transforms into β-sheets upon further triggering. The factors that result in β-sheet formation are dependent on the peptide sequence. In general, the interface has the strongest effect on peptide conformation compared to high concentrations or metal ions. Metal ions are able to prevent aggregation in bulk but not at the interface. At the interface, metal ion complexation has only minor effects on the peptide secondary structure, influencing the in-plane structure that is formed in two dimensions. At the air-water interface, increased concentrations or a parallel arrangement of the α-helical intermediates are the most effective triggers. This study reveals the role of various triggers for β-sheet formation and their complex interplay. Our main finding is that the hydrophobic-hydrophilic interface largely governs the conformation of peptides. Therefore, the present study implies that special care is needed when interpreting data that may be affected by different amounts or types of interfaces during experimentation.     

L-Arginine and zinc ion effect on recognition and hydrolysis rate of adenosine 5′-triphosphate

Zn²⁺ can interact with adenosine 5′-triphosphate (ATP) by electrostatic and coordination interactions, and the interaction sites between Zn²⁺ and ATP vary at different pH in the ATP–Zn²⁺ binary system. Non-covalent interactions exist between the carboxyl of arginine (Arg) and Zn²⁺, which led to competition between ATP and Arg to interact with Zn²⁺ in the ATP–Zn²⁺–Arg ternary system. Kinetics studies show that the hydrolysis rate constant of ATP in the ATP–Zn²⁺ binary system was 2.44?×?10^?2?min^?1, about 11-fold faster than that (2.27?×?10^?3?min^?1) in the ATP–Zn²⁺–Arg ternary system. This may be attributed to coordination interactions between the carboxyl of Arg and Zn²⁺ and the decreased activity of zinc ion toward the phosphate groups via nucleophilic attack. A mechanism that the hydrolysis occurred through an addition–elimination mechanism is proposed.     

Determination of chloride ion by electrochemiluminescence and investigation of the mechanism

The electrochemiluminescence (ECL) of luminol in aqueous alkaline solution was studied.Trace amounts of chloride showed significant effect on the efficiency of light emission of luminol as a posi-tive trigonometrical wave pulse was exerted on the solution. The detection limit for the chloride is5.0 ×10~(-6) mol/L and the linear calibration range extends up to 1.0 ×10~(-2) mol/L; the relative standarddeviation for 1.0 ×10~(-5) mol / L chloride is 5%. The influencing factors for chloride determination arealso discussed. The possible mechanism for the electrochemiluminescence reaction may be due to theoxidation of chloride ion in the solution to ClO~-, and the latter acts on luminol and then gives outluminescence. The method has been applied to determine the total chloride in tap water with satisfactoryresults.     

Vibrational spectra and structure of the heptahydrodiborate ion, [B2H7]− in glycol ethers

The i.r. and Raman spectra of the heptahydroborate ion, [B₂H₇]⁻, and its deuterated derivative, [B₂D₇]⁻, have been obtained in solution and assignments have been made of the observed bands. The data are interpreted as indicating a bent C₂ structure in solution. Normal coordinate calculations based on this model are presented.     

Reactions of O−. with methyl benzoate: A negative ion chemical ionization and Fourier transform ion cyclotron resonance study

The reactions of O*- with methyl benzoate have been examined by the measurement of negative ion chemical ionization (NICI) mass spectra using a CI source, with confirmatory studies carried out on a Fourier transform ion cyclotron resonance mass spectrometer. Reaction mechanisms have been elucidated using isotopically labeled esters. Nucleophilic attack at the carbonyl carbon and the aromatic ring were important reaction pathways. Nucleophilic attack at the carbonyl carbon was followed by the production of products (C6HsCO2- and CH3OCO2-) characteristic of radical, beta-fragmentation. Using 18O-labeled methyl benzoate, the SN2 reaction was found to account for a smaller percentage, 21(+/-1)%, of the benzoate product. Aromatic ring attack resulted in formation of [M + O - H]- and [M - 2H]*- ions. Although aryl hydrogens accounted for most H2*+ abstracted by O*-, evidence for abstraction of HarylH*+alkyl and HalkylH*+alkyl was also found. Although present at much lower abundance, dehydrobenzoate, dehydrophenoxy, and C7H6*- ([M - 2H - CO2]*-) radical anions were also observed. An Haryl/Halkyl exchange associated with formation of the benzoate anion was attributed to an Halkyl abstraction that occurred within the methanol/dehydrobenzoate ion-dipole complex. The [M - 2H]*-, dehydrobenzoate, dehydrophenoxy, and [M - 2H - CO2]*- ion signals were quenched by reaction with O2. Conditions required for production of O*- spectra under NICI conditions were also examined.     

The asilomar conference on ion spectroscopy,October 16–20, 2009

The ASMS conference on ion spectroscopy brought together at Asilomar on October 16–20, 2009 a large group of mass spectrometrists working in the area of ion spectroscopy. In this introduction to the field, we provide a brief history, its current state, and where it is going. Ion spectroscopy of intermediate size molecules began with photoelectron spectroscopy in the 1960s, while electronic spectroscopy of ions using the photodissociation “action spectroscopic” mode became active in the next decade. These approaches remained for many years the main source of information about ionization energies, electronic states, and electronic transitions of ions. In recent years, high-resolution laser techniques coupled with pulsed field ionization and sample cooling in molecular beams have provided high precision ionization energies and vibrational frequencies of small to intermediate sized molecules, including a number of radicals. More recently, optical parametric oscillator (OPO) IR lasers and free electron lasers have been developed and employed to record the IR spectra of molecular ions in either molecular beams or ion traps. These results, in combination with theoretical ab initio molecular orbital (MO) methods, are providing unprecedented structural and energetic information about gas-phase ions.     

β-cyclodextrin as the vehicle for forming ratiometric mercury ion sensor usable in aqueous media, biological fluids, and live cells

The selective and sensitive detection methods for toxic transition-metal ions, which are rapid, facile, and applicable to the environmental and biological milieus, are of great importance. In this study, we designed a β-CD-based ratiometric sensor for detecting mercury ions in aqueous media, some biological fluids, and live cells. In this sensing platform, the thiocarbamido-containing probe dye was covalently linked onto the hydrophilic β-CD rim, which is conducive to complexing with metal ion, while the donor dye was anchored inside hydrophobic β-CD cavity via the adamantyl moiety, which is good for avoiding self-aggregation and enhancing the quantum yield of the donor dye. Upon associating with mercury ion, the probe dye undergoes ring-opening process and serves as the energy acceptor and constitutes the FRET system with the donor dye; by this way ratiometric detection of mercury ion in water can be realized with the detection limit of 10 nM. The cyclodextrin plays a crucial role for the sensing system; it not only accommodates both the donor dye and the probe dye which can form FRET system upon addition of Hg(2+) but also makes the sensor water-soluble and cell membrane permeable. This nontoxic sensing platform can be used for mercury ion detection in aqueous medium, biological fluids, and live cells (L929 and Hela). We also found that, upon being taken up by L929 cells, the sensor exhibited no cytotoxicity, and the cell proliferation was not affected.     

Bioadsorption and ion exchange of Cr3+ and Pb2+ solutions with algae

Heavy metals can be removed from effluents and recovered using physico-chemical mechanisms as biosorption processes. In this work “Arribada” seaweed biomass was employed to assess its biosorptive capacity for the chromium (Cr³⁺) and lead (Pb²⁺) cations that usually are present in waste waters of plating industries. Equilibrium and kinetic experiments were conducted in a mixed reactor on a batch basis. Biosorption equilibrium and fluid-solid mass transfer constants data were analyzed through the concept of ion exchange sorption isotherm. The respective equilibrium exchange constants (K _eqCr=173.42, K _eqPb=58.86) and volumetric mass transfer coefficients ((k _mCr a)′=1.13×10⁻³ s⁻¹, (k _mPb a)′=0.89×10⁻³ s⁻¹) were employed for the dynamic analysis of Cr and Pb sorption in a fixed-bed flow-through sorption column. The breakthrough curves obtained for both metals were compared with the predicted values by the heterogeneous model (K _eqCr=171.29, K _eqPb=60.14; k _mCr a=7.81×10⁻² s⁻¹, k _mPb a=2.43×10⁻² s⁻¹), taking into account the mass transfer process. The results suggest that these algae may be employed in a metal removal/recovery process at low cost. An erratum to this article can be found at     

Synthesis and characterization of M(II) (M = Cd,Hg and Pb) complexes with naphthodiaza-crown macrocyclic ligand and study of metal ion recognition by fluorescence, 1H NMR spectroscopy,and DFT calculation

To find metal ion recognition by L (L = O₂N₂-donor naphthodiaza-crown macrocyclic ligand), the complexes [ML]²⁺ (M = Cd, Hg and Pb) were synthesized and characterized by IR, ¹H, ¹³C NMR, and mass spectrometry, as well as elemental microanalysis. Hg(II) showed perceptible enhancement of the fluorescence of L in which ultra-low limit of detection for Hg(II) by L was determined as 1 nM in ethanol and DMSO. L reserved selectivity of Hg(II) in its binary mixtures with metal cations in solution. A 1 : 1 stoichiometry was found for the interaction of Hg(II) with L while Benesi–Hildebrand method was applied to calculate its complexation binding constant (K_BH) employing fluorescence spectrophotometry. The monitoring of the chemical shifts in ¹H NMR spectra of these complexes demonstrated that the central macrocycle of L was tailored for the size of Hg(II). Density functional theory calculations using B₃LYP/6–31G* basis set demonstrated that the macrocycle cavity of L was properly fitted for complex formation with Hg(II) cation, while both Cd(II) and Pb(II) cations did not form strong bonds with L from inadequate cation size. The present study shows detection method of Hg(II) and also possible application of naphthodiaza as an appropriate fluorophore macrocyclic ligand for detecting other metal ions.