Solutions Of Ammonium Salts Research Articles

Realumination of zeolite Y under acidic conditions

Dealuminated zeolites Y were treated with aqueous solutions of various acids and ammonium salts to investigate the realumination behavior under acidic conditions. From the results of 27Al MAS NMR, 29Si MAS NMR and FT-IR measurements, it was found that a part of non-framework aluminum species in the dealuminated zeolite Y is effectively reinserted into the zeolite framework in CH3COONH4 and C6H5COONH4 aqueous solutions. Pyridine adsorption experiments also revealed that most of incorporated aluminum species generate tetrahedrally coordinated framework aluminum species, namely Brönsted acid sites. Although the realumination also proceeded in H2SO4 and CH3COOH aqueous solutions, large amounts of incorporated aluminum species were not necessarily responsible for generation of Brönsted acid sites. Framework connected aluminum species, presumably as 3-fold-coordinated Lewis acidic framework aluminum species, were mainly generated. In the TEM image of the realuminated zeolite Y, needle-like crystals with ca. 25–80 nm in length were observed, which are probably due to AlOOH generated from non-framework aluminum species.

Determination of Bromate and Bromide in Seawater by Ion Chromatography, with an Ammonium Salt Solution as Mobile Phase, and Inductively Coupled Plasma Mass Spectrometry

A method has been developed for determination of bromate and bromide in water containing high concentrations of chloride (e.g. seawater). Separation of bromate and bromide on an anion-exchange column was followed by ICP–MS detection. To reduce interference of chloride with determination of bromate and bromide, and to avoid clogging, ammonium salts, for example NH4H2PO4, (NH4)2HPO4, (NH4)2CO3, and NH4NO3 were examined as mobile-phase components. It was found that mobile phase containing 20 mM NH4NO3 at pH 5.80 was compatible with the anion-exchange column and enabled reasonable resolution and separation of bromate and bromide within 7 min. Detection limits for bromate and bromide ranged from 2.0 to 3.0 μg L−1 for direct injection of 50 μL sample without matrix elimination. The proposed method was used for analysis of bromate and bromide in seawater.

Search for Extraterrestrial Life Using Chiral Molecules: Mandelate Racemase as a Test Case

We have investigated an enzymatic racemization reaction as a marker for extraterrestrial life, which resulted in a change in optical rotation of a mandelic acid over time, as measured by polarimetry. Mandelate racemase was active in aqueous buffer in a temperature range between 0 degrees C and 70 degrees C and also in concentrated ammonium salt solutions and water-in-oil microemulsions in a temperature range between -30 degrees C and 60-70 degrees C; however, the enzyme was not active in several organic cryosolvents. Thus, we have demonstrated that concentrated ammonium salt solutions and water-in-oil microemulsions, both of which are able to form on extraterrestrial planets and moons in the presence of liquid water, are suitable media for enzyme reactions at subzero temperatures. Kinetic data for the mandelate racemase reaction obtained by polarimetry, while reproducible and internally consistent, differed significantly from several sets of data obtained previously by other methods such as chromatography and hydrogen-deuterium exchange. However, we conclude that reactions yielding a polarimetric signal, such as the racemizations employed in this work, are suitable mechanisms by which to utilize a change in chirality over time as a tool to detect signs of life.

The hydrophobic hydration in aqueous solutions of allyl-substituted ammonium salts

The complex dielectric permittivity for the series of aqueous allyl-substituted ammonium salt solutions is investigated in microwave range (13–25 GHz) in a wide range of salt concentrations. The measurements were made at 298 K for diallylammonium and diallylmethylammonium trifluoroacetates and in the temperature interval 288–308 K for diallyldimethylammonium chloride. The values of dielectric constant ε s and parameters of the dielectric relaxation process were calculated. The increase of relaxation time τ in comparison with pure water is observed for all investigated solutions. It indicates the decrease of orientation mobility of water molecules in the H-bond network upon action of allyl-substituted ammonium ions connected with hydrophobic hydration of these ions.

Dielectric film for biosensor application

The surface of dielectric barium strontium titanate (BST) film was modified by a self-assembled monolayer (SAM) of mono-dodecyl phosphate (DDPO 4) from aqueous solutions of alkyl phosphate ammonium salts. The phosphate terminal groups were believed to anchor to the Ti atoms through oxygen bridges with the terminal methyl groups exposed outwardly, resulting in a highly hydrophobic surface with an advancing water contact angle (CA) of 99.8°, compared with the original CA 40.8° of the bare BST surface. X-ray photoelectron spectroscopy (XPS) showed the dense coverage of the SAM and immobilized BSA layer. The microscopic features and the biosensing properties were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS) in the presence of [Fe(CN) 6] 3−/4− as a redox couple. AFM images revealed that bovine serum albumin (BSA) was well-immobilized on the DDPO 4-modified BST surface. The EIS showed a significant increase in the electron-transfer resistance. Specific binding of anti-BSA on the immobilized BSA surface was evidenced by AFM imaging and EIS. It was demonstrated that the specific binding of anti-BSA can be quantitatively detected by measuring the electron-transfer resistance. The investigation indicated the potential application of the dielectric film for electrochemical biosensors.

Experimental evidence for the homochiral aggregation of ammonium salts in solution

NMR and X-ray evidence for the homochiral aggregation of chiral ammonium picrates from racemic solutions is presented.

Formation of Langmuir−Blodgett Films of a Clay and a Water-Soluble Alkylammonium Cation

We have studied the formation of ultrathin hybrid films composed of a water-soluble alkylammonium cation (trimethyloctadecylammonium caiton: TMODAH+) and clay nanosheets at an air-water interface. When a chloroform solution of the ammonium salt of TMODAH+Cl- was spread onto a surface of an aqueous clay suspension in a Langmuir trough, a stable monolayer of the water-soluble ammonium cation was formed by hybridization with the clay nanosheets at the air-water interface. Surface pressure--molecular area (pi-A) isotherm curve of the hybrid monolayer shifted to the smaller molecular area side with the increase in the concentration of the ammonium salt in the solution or with the decrease in that of the clay in the suspension. In some cases, the lift-off areas in the pi-A isotherm curves were less than the cross-sectional area of an alkyl chain (ca. 0.19 nm2). These results indicated that some ammonium cations spread onto the clay suspension were dissolved into the aqueous subphase before the hybridization with the clay nanosheets. The hybrid monolayers were transferred onto a glass plate in a layer-by-layer way by horizontal dipping to form a hybrid multilayerd film. Interestingly, the densities of TMODAH+ determined by the infrared spectral analysis were constant in the hybrid multilayers prepared from the clay suspensions at the same concentration, regardless of the concentrations of the ammonium salt solutions. XRD patterns of the films showed that the cations of TMODAH+ would lie down on the clay layer in the hybrid film.

Deactivation of Formate Dehydrogenase (FDH) in Solution and at Gas‐Liquid Interfaces

Enzymes, increasingly important in the synthesis of fine chemicals and pharmaceutical intermediates, are often insufficiently stable under reacting conditions. We have investigated the stability, in homogeneous aqueous solution and at gas-liquid interfaces, of formate dehydrogenase (FDH), important for cofactor regeneration, from Candida boidinii and overexpressed in E. coli. When exposed to mechanical stress, residual activity, [E](t)/[E](0), and residual protein were found to scale proportionally with gas-liquid surface area in the bubble column, verifying a surface-driven process, and with time and total throughput in a gear pump, but did not seem to be influenced much by shear in a Couette viscometer. All FDH variants are deactivated by chaotropes but not kosmotropes: the first-order deactivation constant k(d) correlates well with the Jones-Dole coefficient B but not well with the surface tension increment deltasigma of various concentrated ammonium salt solutions. This finding might provide guidance for focusing the search for quantitative theories of Hofmeister effects.

Suppression of alpha-cyano-4-hydroxycinnamic acid matrix clusters and reduction of chemical noise in MALDI-TOF mass spectrometry.

Progress in high-throughput MALDI-TOFMS analysis, especially in proteome applications, requires development of practical and efficient procedures for the preparation of proteins and peptides in a form suitable for high acquisition rates. These methods should improve successful identification of peptides, which depends on the signal intensity and the absence of interfering signals. Contamination of MALDI samples with alkali salts results in reduced MALDI peptide sensitivity and causes matrix cluster formation (widely reported for CHCA matrix) observed as signals dominating in the range below m/z 1200 in MALDI spectra. One way to remove these background signals, especially for concentrations of peptides lower than 10 fmol/microL, is to wash matrix/sample spots after peptide cocrystallization on the MALDI plate with deionized water prior to analysis. This method takes advantage of the low water solubility of the CHCA compared to its alkali salts. We report here that the application of some ammonium salt solutions, such as citrates and phosphates, instead of deionized water greatly improves the efficiency of this washing approach. Another way to reduce matrix cluster formation is to add ammonium salts as a part of the MALDI matrix. The best results were obtained with monoammonium phosphate, which successfully suppressed matrix clusters and improved sensitivity. Combining both of these approaches-the addition of ammonium salts in the CHCA matrix followed by one postcrystallization washing step with ammonium buffer-provided a substantial ( approximately 3-5-fold) improvement in the sensitivity of MALDI-MS detection compared to unwashed sample spots. This sample preparation method resulted in improved spectral quality and was essential for successful database searching for subnanomolar concentrations of protein digests.

Modeling of Activity Coefficients of Aqueous Solutions of Quaternary Ammonium Salts with the Electrolyte-NRTL Equation

Ionic liquids (ILs) have been studied recently as potential “green” solvents because of their negligible vapor pressure. Modeling the phase behavior of such liquids with water and organic solvents and their partitioning between aqueous and organic phases is vital for an evaluation of their many potential uses. Unfortunately, phase behavior data for the popular imidazolium and pyridinium salts are still somewhat limited. However, a wealth of data exists for aqueous solutions of quaternary ammonium salts, a class of compounds that includes potentially interesting ILs. Therefore, as a first step toward modeling the phase behavior of IL solutions, we show how a conventional electrolyte model, the electrolyte nonrandom two-liquid (NRTL) model proposed by Chen et al. (AIChE J. 1982, 28, 588), can be applied to model activity coefficients of quaternary ammonium salts in water. This model requires two parameters per salt that must be fit to the experimental data. Particular attention is paid to computing these bi...

Surface study of the corrosion of carbon steel in solutions of ammonium salts using Mössbauer spectrometry

The effect of the NO3− anion on the corrosion of carbon steel in a solution of 0.1M NH4Cl (pH 5.5) was studied by galvanostatic polarization and Mossbauer spectrometry. The anion has an inhibiting effect by decreasing the expansion rate of generalized corrosion of carbon steel in a solution of 0.1M NH4Cl. Mossbauer spectroscopy shows that a superficial compound is formed on the electrode surface as a result of corrosion, presenting no magnetic ordering. Its parameters show the initial stage of corrosion. We assume that at this stage the main corrosion product is a mixture of ferrihydrite Fe(III) and FeOOH (α and/or γ).

Physicochemical properties, surface morphology and particle size distribution of precipitated silicas

AbstractThe results presented are from a study on the production of highly dispersed silicas by their precipitation from solutions of sodium metasilicate and ammonium salts. The applied ammonium salts were NH4HCO3 and (NH4)2CO3. The precipitation process was conducted in the absence or presence of 1 wt.% non‐ionic surfactant (Rokanol K‐7, Rokafenol N‐6 or Rokafenol N‐9).The highly dispersed silicas obtained were subjected to a physicochemical analysis typical for fillers. The analysis included estimation of the bulk density and the capacities to absorb water, dibutyl phthalate and paraffin oil. Particle size and morphology were evaluated using scanning electron microscopy. In addition, particle size distribution for the precipitated silicas was examined by dynamic light scattering.Silicas with the best physicochemical properties were obtained by precipitation using ammonium hydrogen carbonate. In particular, the silica precipitated in the presence of 1 wt.% Rokafenol N‐9 demonstrated a magnificent capacity to absorb paraffin oil. Copyright © 2003 John Wiley & Sons, Ltd.

A Facile Direct Synthesis of Bimetallic CuIIZnII Complexes with Ethylenediamine Revealing Different Types of Chain Crystal Structures

AbstractUnactivated copper metal powder and zinc oxide readily react with ethylenediamine (en) in nonaqueous [methanol, dimethylformamide (dmf), dimethyl sulfoxide (dmso), acetonitrile] solutions of ammonium salts under ambient conditions producing, in high yields, a series of heterobimetallic complexes of general formula [Cu(en)2ZnX4]·(Solv), where X = Cl, Br, NCS, CH3COO (OAc); Solv = dmf, dmso, CH3CN, H2O. The single‐crystal X‐ray analysis of the complexes reveals chain structures, which are based on the completion of the octahedral coordination of CuII by two bridging X atoms from ZnX42−. The ZnX42− is shown to be a distorted tetrahedron (Cl, Br, NCS) or a very distorted octahedron (OAc) and to behave as a one‐ or two‐linking centre bridging ligand. The chains are found to be zigzag [Cu(en)2ZnCl4]·dmso (1), [Cu(en)2ZnCl4]·dmf (2), [Cu(en)2Zn(NCS)4]·CH3CN (3), quasi linear [Cu(en)2Zn(OAc)4] (4), or helical, [Cu(en)2Zn(NCS)4]· 0.5H2O (5), depending on the nature of the anion and solvent. Complex 4 represents the first compound containing Zn(OAc)42− to be crystallographically authenticated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Supernormal optical characteristics in doped quaternary ammonium salt KDP crystals

Abstract Potassium dihydrogen phosphate, KH2PO4 (KDP) crystals with different concentrations of quaternary ammonium salt in solution were grown. In this paper, unusual transmittance ratio properties of KDP are reported. The transmittance ratio is smaller than unity at some locations. These results indicate that the plane wave effect and optical activity are highly displaced in KDP crystals, and the effect is varies in three-dimensional positions.

Passive penetration of nitrate through the plasma membrane of Paracoccus denitrificans and its potentiation by the lipophilic tetraphenylphosphonium cation

Previously, it has been shown that treatment of Paracoccus denitrificans cells with phenylglyoxal inhibits the methyl-viologen-linked nitrate reductase activity by blocking the nitrate transporter. This inhibition disappears if tetraphenylphosphonium cation (TPP +) is added to the assay medium. In the present paper, the following evidence suggests that the effect of TPP + results from an increased transmembrane anion permeability and not from transporter reactivation or cell lysis. (1) Beside nitrate, TPP + also mediated the utilisation of chlorate, which normally lacks access to the cytoplasm. (2) The TPP + pathway had about hundred-times higher K m values for nitrate and chlorate than nitrate reductase in Triton X-100 permeabilised cells. (3) Although the uncoupler CCCP alone failed to overcome the PG block, it stimulated the operation of the TPP + pathway. (4) The method of continuous variations allowed the transport stoichiometry TPP +/NO 3 − to be determined as 3, indicating charge compensation for nitrate movement and the subsequent transmembrane two-electron redox reaction. Anion uptake was also measured independently from passive swelling of uncoupled spheroplasts in iso-osmotic solutions of ammonium salts. The permeability to nitrate lay in the permeability sequence Cl −<NO 3 −<ClO 4 −<SCN − and was further enhanced by TPP +.

A rapid synthesis route for the preparation of CdS nanoribbons by microwave irradiation

A rapid synthesis route for the preparation of CdS nanoribbons has been developed. CdS nanoribbons of about 4 nm in diameter have been prepared by the microwave irradiation of an ethylenediamine (en) solution of 1-pyrrlidine dithio carboxylic acid ammonium salt (APDTC) and cadmium chloride under ambient air. The nanoribbons are characterized by high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), energy-dispersive X-ray analysis, absorption spectroscopy, diffuse reflection spectroscopy, and PL spectroscopy.

Decamolybdodicobaltate(III) heteropolyanion: structural, spectroscopical, thermal and hydrotreating catalytic properties

The ammonium decamolybdodicobaltate(III) salt: (NH 4) 6[Co 2Mo 10O 38H 4]·7H 2O (here in Co 2Mo 10) has been prepared and characterized. Then, their structural, spectroscopic and thermal properties have been investigated by some physical–chemical techniques as XRD, FT-IR, Raman, DRS, SEM–EDAX,TG, DTA, and temperature programmed reduction (TPR). According to these properties, some Co 2Mo 10/γ-Al 2O 3 catalysts have been prepared by equilibrium impregnation of the support with aqueous solution of ammonium salts. The Co 2Mo 10 isothermal adsorption on γ-Al 2O 3 at room temperature has been also investigated in the Mo range of 15–150 μmol Mo/ml. The hydrotreating (HDS of thiophene and HYD of cyclohexene) catalytic activity has been compared to both γ-Al 2O 3 supported Anderson phase [(NH 4) 3[CoMo 6O 24H 6]·7H 2O (here in CoMo 6)] and Co–Mo conventional catalysts. The improving of activity for the Co 2Mo 10 and CoMo 6 based catalysts is related to the heteropolyoxometalates adsorption process as to preparative conditions; whereas, the different activity between heteropoly-systems are undoubtedly related to the particular structure of the Co 2Mo 10 heteropolyanion.

Efficiency of Extraction of Petroleum Acids in an Extractor with Sieve Plates. Method of Calculation

TIn developing zero—waste technology for extraction of petroleum acids from light crude cuts with ammonia water [ 1], a process was created for removing unsaponifiables from an aqueous solution of petroleum acid ammonium salts ( AS PAAS) with an extracting agent. This process produces quality distilled petroleum acids. High—temperature vacuum distillation of unsaponifiables, used in treatment of fuel cuts with caustic soda, is not applicable in this case due to the thermal instability of PAAS. Moreover, this method is not economically rational . The studies showed that the naphtha cut is the most appropriate extracting agent for this purpose.

Thin-layer chromatographic studies of the mobility of pesticides through soil-containing static flat-beds

The chromatographic behavior of some pesticides has been studied on silica, soil, and mixed layers containing soil, with aqueous ammonium or sodium salt solutions, with or without added N -cetyl- N,N,N -trimethylammonium bromide (CTAB), with pure organic solvents, and with aqueous CTAB systems. One interesting aspect of this study is the migration of pesticides such as phosphamidon and dimethoate through pure soil. Several important binary separations have been achieved, sulfur-containing pesticides have been successfully separated from those with chlorine, phosphorus, or both phosphorus and sulfur in their molecules. Phosphorus-containing pesticides were found to migrate faster than those not containing phosphorus, in a variety of mobile phases, irrespective of the nature of the stationary phase. The trend in the relative mobilities of pesticides on the different stationary phases used is also reported.

Regioselective dimerization of ferulic acid in a micellar solution.

Dehydrodimers of hydroxycinnamates play an important role in the cross-linking of plant cell walls. An aqueous solution of quaternary ammonium salts with a long aliphatic chain is known to spontaneously organize itself into micelles with the ionic part at the outer sphere. It is shown that regioisomeric ferulic acid dehydrodimers can be obtained in one step from trans-ferulic acid after attachment to these micelles and using the biomimetic peroxidase-H2O2 system. The surfactant hexadecyltrimethylammonium hydroxide yielded trans-4-(4-hydroxy-3-methoxybenzylidene)-2-(4-hydroxy-3-methoxyphenyl)-5-oxotetrahydrofuran-3-carboxylic acid (25%), (E,E)-4,4'-dihydroxy-5,5'-dimethoxy-3,3'-bicinnamic acid (21%), and trans-5-[(E)-2-carboxyvinyl]-2-(4-hydroxy-3-methoxyphenyl)-7-methoxy-2,3-dihydrobenzofuran-3-carboxylic acid (14%), whereas the surfactant tetradecyltrimethylammonium bromide gave 4-cis, 8-cis-bis(4-hydroxy-3-methoxyphenyl)-3,7-dioxabicyclo[3.3.0]octane-2,6-dione (18%) as the main product. The use of micelles appears to be not only a new way to synthesize regioisomeric ferulic acid dehydrodimers but may also help to understand the regiospecificity of dimeric hydroxycinnamate formation in vivo.