Salt Matrix Research Articles

High-Melting Oxide Fibres: Fabrication, Properties, and Use

The mechanism of structure formation in fibrous oxides with complex architectonics, including metal oxide nanoparticles, nanopores, and microcapillaries, was established. Synthesis of oxide fibres includes two stages. In the first stage, thermal transformation of the polymer matrix and dissociation of salts with formation of metal oxides take place in heat treatment up to 600° C. Structural transformations of the oxides in the fibres and alteration of their physicochemical properties take place in the second stage. The oxide fibres have high porosity, a developed surface, and high reactivity due to the nanosize factor. Based on calculation of the size of the metal oxide crystallites, it was found that crystallographic transformations of the oxides cause dispersion of matter. The structural transformations of fibrous oxides are accompanied by a change in the character of the porosity and pore size. The mechanisms obtained can be used to predict the properties and regulate manufacturing technology for nanostructural fibrous oxide materials.

Multi-element analysis of sea water from Sepetiba Bay, Brazil, by total reflection x-ray fluorescence spectrometry using synchrotron radiation

Trace elements in the surface waters of Sepetiba Bay were studied by total reflection x-ray fluorescence spectrometry using synchrotron radiation (SRTXRF). The bay is located in the south of Rio de Janeiro State, Brazil. The water samples were collected at 21 sampling stations, prepared in order to preconcentrate the metallic elements with ammonium pyrrolidinedithiocarbamate and to remove the salt matrix. Samples were spiked with an internal standard (Se) and the precipitated dithiocarbamates of trace elements were separated by filtration through a Millipore filter, then transferred to a Perspex reflector and digested with HNO3 for SRTXRF measurement. Elemental concentrations of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo and Pb were determined and a comparison was made between the results obtained and the values given in the literature for sea water. Copyright © 2005 John Wiley & Sons, Ltd.

Analysis of guanidine in high salt and protein matrices by cation-exchange chromatography and UV detection

A simple and sensitive HPLC method for quantitative determination of guanidine in high salt and protein matrices was developed. The HPLC system consisted of an Agilent 1100 pump with an online degasser, a UV detector, an autosampler, and Dionex CS 14 cation-exchange guard (4 mm × 50 mm) and analytical (4 mm × 250 mm) columns. The mobile phase was 3.75 mM methanesulfonic acid (MSA) with a flow rate of 1 mL/min. The other analysis parameters were: 50 μL injection volume, 195 nm UV detection, and 21 min runtime. The limit of quantitation (LOQ) for guanidine HCl was determined to be 0.25 mg/L and the standard curve ranged from 0.25 mg/L to 10 mg/L. Sample preparation was required for the samples containing high protein concentrations. Proteins were removed by centrifuging a sample in a 30 K NanoSep centrifugal filter at 15,300 × g for 20 min. The method could determine guanidine accurately in sample matrices containing up to 200 mM sodium ion or up to 50 mM potassium ion. The method can be used for clearance testing of guanidine in biopharmaceutical products.

Effect of salt species on electrochemical properties of gel-type polymer electrolyte based on chemically crosslinking rubber

In our study, for ion–polymer interaction in gel-type polymer electrolyte (GPE), two kinds of ions were used. GPE systems were composed of Mg or Li salt, organic solvent (γ-BL), and polymer matrix prepared by chemical crosslinking of NBR with poly(ethylene glycol)methylethermethacrylate (PEGMEM) having polar group ( CH 2 CH 2 O ) in the side chain of monomer. GPE consisting of Li + ion had higher ionic conductivity than that of Mg 2+ ion at below 100 wt.% of electrolyte content (1 M salt/γ-BL). On the other hand, GPE consisting of Mg 2+ ion had higher ionic conductivity than that consisting of Li + ion at over 120 wt.% of electrolyte content (1 M salt/γ-BL). The maximum liquid electrolyte content was 200 wt.% for all GPE systems. And the highest ionic conductivity of 3.3 × 10 −2 S cm −1 was achieved for the case of Mg 2+-GPE with 200 wt.% of liquid electrolyte contents at 20 °C. The interaction between ionic species and polymer matrix in GPE was investigated by using Fourier transform infrared spectroscopy (FT-IR). Also, cyclic voltammogram of Mg 2+-GPE confirmed the electrochemical property of divalent cation with two electron-transfer reactions.

Mechanochemical synthesis of nanoparticles

The results of recent investigation of the mechanochemical synthesis of inorganic nanoparticles are reviewed. It was demonstrated that, by selecting suitable chemical reaction paths, stoichiometry of starting materials and milling conditions, mechanochemical processing can be used to synthesise a wide range of nanocrystalline particles dispersed within a soluble salt matrix. Selective removal of the matrix phase by washing the resulting powder with appropriate solvents can yield nanoparticles of the desired phase. This technique has been shown to have advantages over other methods of producing nanoparticles in terms of low cost, small particle sizes, low agglomeration, narrow size distributions and uniformity of crystal structure and morphology.

Enhancing the Efficiency of Anodic Stripping Voltammetry in Systems Permitting a Change of the Solution without Opening the Circuit

A new design for a transducer for voltammetric stripping analysis was proposed. It allows electroaccumulation and electrostripping stages to be carried out in the solutions of different compositions without opening a circuit. The potentialities of the transducer were demonstrated in the analysis of samples containing complex salt and organic matrices without their preliminary mineralization.

Drug release from carbomer:carbomer sodium salt matrices with potential use as mucoadhesive drug delivery system

In vitro mucoadhesion, water uptake, and drug release of nystatin (N) from matrices of carbomer (C) and lyophilized carbomer sodium salt (CNa L) mixtures were evaluated. Matrices with different ratios C:CNa L were prepared by direct compression. Commercial C as well as lyophilized powder (C L) were used. In vitro mucoadhesion increased as the proportion of C in the matrix was raised. The same effect was observed when C was replaced by C L. Matrices in which C was replaced by C L showed an increase of both water uptake and release rates. Besides, the release of N from matrices C L:CNa L exhibited a kinetics with Super Case II ( n>1) mechanism. However, for C:CNa L matrices, drug release was slower and exhibited a biphasic profile with a first stage characterized by either an anomalous ( n<1, for C≥50%) or a Case II ( n ∼ 1.0, C<50%) mechanisms. After that period, the mechanism changed to Super Case II transport ( n>1).

Determination of trace lead in the high salt matrix of comestible CaCO 3 by an isotope dilution method with detection by inductively coupled plasma-mass spectrometry

The determination of trace lead in a CaCO 3 matrix by isotope dilution coupled anion-exchange and quadrupole-based inductively coupled plasma-mass spectrometry was established. The matrix of CaCO 3 seriously affected the determination by clogging the cones of the instrument was removed by the anion-exchange resin column. Effects such as dead time, mass bias, dwell time and the amount of isotopic agent spiked were discussed and corrected. The detection limit estimated by 3× standard deviation of the procedure blank was 2.94 ng g −1. The results indicated that the lead concentration in all samples tested was far less than 3%, the legislated limit. The recovery mostly ranged from 90 to 110%. The relative standard deviation was found to be <1%.

Trace lead measurement and on-line removal of matrix interference in seawater by isotope dilution coupled with flow injection and ICP-MS

Isotope dilution analysis method coupled with flow injection and inductively coupled plasma mass spectrometry (ID-FI-ICP-MS), enabled trace lead concentration in seawater to be determined and the high salt concentration in the matrix, such as Na +, Ca 2+ and Mg 2+, to be removed on-line. The operational parameters of the FI system including pH for the chelating reaction, concentration of 8-hydroxyquinoline-5-sulfonic acid (8-HQS), sample loading time and injection speed, washing time and speed, eluting acid concentration and eluting speed, and instrumental parameters for ICP-MS were optimized and selected. Accurate results could be achieved because the isotope ratios required can be precisely measured in the range of the eluting peak by means of ID-FI-ICP-MS. The 3 σ detection limit was 0.204 ng ml −1. The trace lead concentration of seawater in south Xiamen, China was 0.988 ± 0.039 ng ml −1. The recoveries of spiked Pb standard in seawater and standard reference water (GBW 08607) were 97.9 and 101.0%, respectively, with a relative standard deviation of 0.98%. This method can be used to determine trace lead concentration in high salt matrix samples, and is especially useful when the eluting peaks do not have a Gaussian-distribution.

Ultrahigh Surface Area Nanoporous Silica Particles via an Aero-Sol−Gel Process

We describe a new salt-assisted aero-sol-gel approach to produce spherical nanosized mesoporous silica particles. As an alternative to expensive templating mediums in prior works, salt (NaCl) was employed as a templating medium because it is thermally stable, recyclable, and easily leached. Furthermore, we demonstrate the ability to carry out traditional sol-gel chemistry within an aerosol droplet. The role of salt in sol-gel chemistry and aerosol processing was investigated as a function of hydrolysis time. It was verified that salt accelerates the kinetics of silica gelation, and simultaneously becomes an excellent templating medium to support nano-sized pores inside silica structures in the aerosol processing route. The presence of salt results in a roughly ten-fold increasing in the pore specific surface area and pore volume, subsequent to leaching of the salt matrix. The surface area and pore volume of the as-produced nanoporous silica particles was found to increase with increasing sol-gel hydrolysis time.

Sensing Element of a Benzopurpurin 4B-Based Optical Sensor for Determining the Acidity of Etch Solutions

Deposition conditions are studied, and a Langmuir–Blodgett film (LBF) based on the benzopurpurin 4B indicator immobilized in the polyamide acid salt matrix is obtained. The protolytic properties of the indicator are studied in water, micelles of cationic and nonionic surfactants, and LBFs. It is shown that, in going from water to the cited micelles and LBFs, pKind is shifted to the acidic region by 3.25, 1.18, and 2.30 pH units, respectively. The possibility of using the produced LBF as the sensing element of an optical sensor for the determination of the acidity of solutions in the pH range 1–0 is demonstrated. The LBF is applied to the determination of the acidity of solutions in etch baths. The response time in the operating range is 10–20 s; the standard deviation is no more than 4%.

In vitro evaluation of microdialysis–electrothermal vaporization inductively coupled plasma mass spectrometry hyphenation system for continuous monitoring of trace metal ions in simulated biological systems

An on-line microdialysis sampling coupled with flow injection (FI) electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) hyphenation system has been developed for continuous monitoring of trace Zn, Cu, Mn and Pb ions in microdialysates, with good temporal resolution and high sensitivity. In order to achieve efficient removal of the salt matrix in the dialysate, the characteristics of three matrix modifiers, NH4NO3, NH4H2PO4 and Pd, were evaluated. The influence of the temperature program on the separation efficiency and the analytical signals was also studied in this work. With microdialysis sampling, the temporal resolution for monitoring was limited by very low perfusion rate to 12 min. The detection limits were 2.20 μg L−1 (Zn), 0.15 μg L−1 (Cu), 1.13 μg L−1 (Mn) and 3.13 μg L−1 (Pb) and the stability precision (RSD at 10 μg L−1 analyte ions) was <15% RSD. The performance of the proposed method was evaluated in vitro by monitoring step changes in the concentrations of analyte ions in the external microdialysis medium.

Sorbent Extraction of Some Metal Ions on a Gas Chromatographic Stationary Phase Prior to Their Flame Atomic Absorption Determinations

An enrichment/separation system for atomic absorption spectrometric determinations of Cu(Ⅱ), Fe(Ⅲ), Ni(Ⅱ) and Co(Ⅱ) has been established. The procedure is based on the adsorption of the analytes as calmagite chelates on Chromosorb-102. The effects of some parameters including pH, amount of ligand, salt matrix, flow rates of sample and eluent solutions were investigated. Under optimized conditions, the relative standard deviation of the combined method of sample treatment, preconcentration and determination with FAAS (N=5) is generally lower than 5%. The limit of detection (3σ) was between 6.0-112.9 ㎍/L. The results were used for preconcentration of analytes from some sodium and ammonium salt.

Identification of O-Isobutyl S-(2-Diethylaminoethyl) Methylthiophosphonate Chemical Neutralization Products in Bitumen–Salt Matrices

Products of the chemical neutralization of O-isobutyl S-(2-diethylaminoethyl) methylthiophosphonate, a VX Group warfare agent, in bitumen–salt matrices were studied by gas chromatography–mass spectrometry. Forty-four compounds were characterized by their electron impact ionization mass spectra and gas chromatographic retention indices on standard nonpolar polydimethylsiloxane phases; seven of these compounds were determined as derivatives. The structures of 26 compounds were identified, including structures of 24 O-isobutyl S-(2-diethylaminoethyl) methylthiophosphonate neutralization products. To solve this problem, chromatographic retention indices of unknown compounds were evaluated using reference data for their structural analogues. Partition coefficients in the binary heterophase hexane–octanol system were determined for the major components.

(Pb1xCdx)S Nanoparticles Embedded in a Conjugated Organic Matrix, as Studied by Photoluminescence and Light-Induced X-ray Photoelectron Spectroscopy

Elliptically shaped (Pb1–xCdx)S nanoparticles (NPs) of average size 2.3 × 2.9 nm (minor axis × major axis) have been prepared via reaction of a solid [oligo(p-phenylene-ethynylene) dicarboxylate]Pb0.9Cd0.1 salt matrix, with gaseous H2S. A significantly long emission lifetime, with multi-exponential behavior, is detected in time-resolved photoluminescence measurements, substantially different from the decay patterns of pure PbS and CdS NPs within the same organic matrix. Evidence for the co-existence of Cd and Pb within the same particle is provided by light-induced X-ray photoelectron spectroscopy.

Progress in lithium polymer battery R&D

In this paper the characteristics and performance of composite polymer electrolytes formed by dispersing selected ceramic (e.g. γ-LiAlO 2, Al 2O 3, SiO 2) powders in poly(ethylene oxide)–lithium salt (e.g. PEO–LiCF 3SO 3) matrices, are reported and discussed. Particular emphasis is devoted to the role of these composite electrolytes in providing the conditions for stabilizing the interface with the lithium metal electrode, as well as for enhancing the electrolyte’s overall transport properties. Finally, results based on tests of practical prototypes demonstrate that these unique properties allow the development of new types of high performance, rechargeable lithium polymer batteries.

Kinetics of fluoride release from zinc oxide-based cements

Considerable attention has been given to the release of the cariostatic fluoride ion from glass-based dental cements (dental silicate and glass ionomer). In these, the total available fluoride content is not precisely known since fluorine is distributed between the cross-linked aqueous salt matrix, partially dissolved glass, and undissolved glass. In analogous cements based on zinc oxide the fluoride is added as highly soluble SnF 2. The object of this study is to compare the F − ion release profiles of commercial zinc polycarboxylate and zinc phosphate containing 4.4 and 3.6% SnF 2, respectively. Mixed cements were clamped in split ring moulds to produce discs of 10 mm×1 mm after storage at 37°C for 1 h. Each was weighed and immersed in 10 ml of deionised water. When this changed, at 13 time intervals up to 98 days, the fluoride content was measured using an ion selective electrode. The mean ( N=3) values obtained were expressed cumulatively [F] in μmol F ion/g cement. The total [F] released was 111 for the zinc polycarboxylate and 286 for zinc phosphate compared with total F in the cements of 561 and 464, respectively. When the cumulative [F] was plotted versus t 1/2 close associations were found for both cements. For the polycarboxylate the regression line [F]=10.6 t 1/2+9.9 fitted well over the whole 98 days ( R=0.997). For the phosphate a better fit regression line was obtained using results upto 32 days only; [F]=36.8t 1/2−8.4 (R=0.999). For t>32 days results increasingly deviated from this line. These results fitted a regression line of the form [F]=81.7 log e t−87.3 ( R=0.9997). Comparisons are made with data from previous authors both for zinc phosphate cement and glass-based cements and with diffusion theory of F ion release. It is concluded that zinc-based cements provide some indications of how glass-based cements may behave over long periods of release and that zinc phosphate is the material of clinical choice for orthodontic cementation if maximal fluoride release is the prime criterion.

INVESTIGATION OF SALICYLATE INTERFERENCE ON ANION SELECTIVE ELECTRODES1*

Several types of ion-selective membranes were tested to decrease the salicylate interference in clinical measurements of chloride. The study included electrodes with methyldodecylammonium salt and membrane matrices of poly(vinyl chloride) (PVC), silicone rubber (SR) and cellulose triacetate (CTA). The first two membranes were modified by the ultra- filtration (UF) and nanofiltration (NF) membranes, respectively, the cellulose triacetate membrane was modified by alkaline hydrolysis. The most significant and useful decrease by one and half order of magnitude of log KCl, Sal pot was observed for the silicone rubber membrane with additional nanofilter membrane. Dedicated to Prof. George Baiulescu on his 70th anniversary

Reaction chemistry of plutonium with vanadium pentoxide in molten salts

Vanadium pentoxide, V 2O 5, has been proposed as an oxidant for the stabilization of reduced forms of plutonium within pyrochemical salt residues from plutonium pyrochemical processes at the Rocky Flats Environmental Technology Site because of its large reduction potential and its ability to react via normal solid-state reactions. However, when V 2O 5 was used to oxidize actual process residues results were highly variable. This paper discusses the reaction chemistry of PuCl 3, Pu° and PuOCl with V 2O 5 under a variety of conditions, including in the presence and absence of a NaCl/KCl salt matrix. This work is the first systematic study of the solid-state oxidation of plutonium species by vanadium pentoxide. For PuCl 3 a greater than or equal to 1:1 V 2O 5:PuCl 3 ratio is needed for complete oxidation. Increasing the amount of V 2O 5 from 1 to 2 equivalents increases the contribution of side reactions, including reactions of V 2O 5 with the process equipment and/or salt matrix, and produces undesirable non-volatile ternary and quaternary vanadium compounds. The oxidation of PuOCl is similar to that of PuCl 3. Greater than a 1:1 V 2O 5:PuOCl ratio is required to achieve adequate conversion of PuOCl to PuO 2. Oxidation of Pu° by V 2O 5 is more complex than the PuCl 3 or PuOCl oxidations. Complete oxidation of Pu° to Pu(IV) in the presence of the salt matrix does not occur with up to 6 equivalents of V 2O 5. However, conversion of Pu° to Pu(IV) occurs rapidly in the absence of the salt matrix.

Physical Consequences of a Mechanically Interlocked Architecture: Benzylic Amide Catenane NH Stretching Vibrations as Sensitive Probes for Weakly Hydrogen-Bonding Environments

Computer simulations show that the sensitivity of the NH stretch frequency of a benzylic amide [2]catenane to variations of the salt matrix originates from its mechanically interlocked molecular architecture, in which hydrogen bonds of various strength coexist. The picture shows the interlocked [2]catenane and the hydrogen bonds inside it.