Multisyringe flow injection analysis system for automation of standard addition calibration method

In the present work, the multi-channel features of multisyringe flow injection analysis (MSFIA) were exploited for the first time to implement calibration based on standard addition method (SAM). For this, standard solutions containing different concentrations of target analyte were placed in each syringe of the multisyringe and connected to a flow network where in-line mixing of sample and standard through a merging zone approach was established prior to detection of analyte. Using this strategy, artifacts reported before in SAM using flow injection analysis were avoided as the concentration of the analyte in the resulting mixture was related to the dilution of sample and added standard within the system, and the concentration of all matrix components was kept constant during all measurements. The feasibility of the proposed MSFIA system was assessed through application to potentiometric determination of chloride ion in electroplating bath and milk samples. Results obtained for samples (n = 15) were not statistically different from those provided by titrimetric procedures, with an excellent throughput (20–31 samples h^{− 1}), comprising four-level addition of chloride ion.     

Novel Flow Injection/Potentiometric Measurement of Slightly Soluble Salts in Small Volumes: Determination of Solubility Product Constants of Some Silver Salts

Abstract

The flow injection technique is shown to provide fast, reliable and sensitive determination of solubility product constants of silver acetate, silver sulfate, silver oxide, silver bromate and silver chloride in microliter volume samples. Potentiometric detection using electrodes of the first kind and second kind was used for measuring silver ions and chloride ions, respectively. The solubilities were determined from measurement of the silver ion concentration in the saturated solutions. In the case of silver chloride, the solubility product constant was calculated from the concentrations corresponding to the intersection of the silver ion calibration curve and the chloride ion calibration curve, i.e., where the potentials of the two electrodes are equal. Tenth-molar sodium nitrate was used for all solutions to maintain constant ionic strength. At a concentration range of 1.00 × 10^?2 ? 1.00 × 10^?5 M silver, and 1.00 × 10^?2 ? 1.00 × 10^?4 M chloride, a Nernstian response of 60 m V per decade was obtained. At a sampling rate of 50–70 samples per hour, with 50 μl sample injections, high reproducibility of measurements was achieved, with a -pL 2% relative standard deviation in measured concentrations. The scope and applications of this system are discussed.     

Radiation chemistry of aqueous iodine systems under nuclear reactor accident conditions

Radiation-chemical behavior of cesium iodide solutions was investigated using a once-through flow system in relation to the behavior of radioactive iodine under the condition of nuclear reactor accidents. It was found that several factors such as initial concentration of CsI, pH and O₂ concentration have a large influence on the oxidation-reduction reactions in the radiolysis of the iodide solutions. A pulse radiolysis technique was applied to this system to obtain clearer understanding of the radiolysis mechanism, and the rate constants were measured with the several important reactions involved.     

Determination of the migration times of flow measurement markers in CEC

The electroosmotic migration times of fructose, water, and phenol have been measured in several solutions. The electroosmotic flow rate was fundamentally dependent on buffer concentration and on the concentration of additives such as sodium chloride; additives such as methanol and sodium dodecylsulfate did not influence the flow rate, yet tetrabutylammonium bromide had a significant effect.     

Differential electrolytic potentiometry, a detector in flow injection analysis for precipitaton reactions

The application of differential electrolytic potentiometry as a detection system in flow injection analysis for precipitation reactions is described. Different combinations of electrodes were investigated. The optimum conditions for the current density and the flow rate were elucidated. In the case of chloride, an Ag/AgCl-Pt pair was found to be successful. For iodide a combination of Ag-Pt electrodes was found to give good results. The relation between the concentration of analyte and the measured signal was found to be linear.     

The effect of chloride concentration and pH on pitting corrosion of AA7075 aluminum alloy coated with phenyltrimethoxysilane

The effect of chloride ion concentration and pH of solution on the corrosion behavior of aluminum alloy AA7075 coated with phenyltrimethoxysilane (PTMS) immersed in aqueous solutions of NaCl is reported. Potentiodynamic polarization, linear polarization, open circuit potential, and weight loss measurements were performed. The surface of samples was examined using SEM and optical microscopy. Elemental characterization of the coating by secondary ion mass spectrometry indicates an intermediate layer between coating and aluminum alloy surface. The corrosion behavior of the aluminum alloy AA7075 depends on chloride concentration and pH of solution. In acidic or neutral solutions, general and pitting corrosion occur simultaneously. On the contrary, exposure to alkaline solutions results in general corrosion only. Results further reveal that aluminum alloy AA7075 is susceptible to pitting corrosion in all chloride solutions with concentrations between 0.05 M and 2 M NaCl; an increase in the chloride concentration slightly shifted both the pitting and corrosion potentials to more active values. Linear polarization resistance measurements show a substantially improved corrosion resistance value in case of samples coated with PTMS as compared to uncoated samples in both neutral (pH = 7), acidic (pH = 0.85 and 3), and alkaline chloride solutions (pH = 10 and 12.85). The higher corrosion resistance of the aluminum alloy coated with PTMS can be attributed to the hydrophobic coating which acts as a barrier and prevents chloride ion penetration and subsequent reaction with the aluminum alloy.     

Conductivity of tetraphenylarsonium, tetraphenylphosphonium, triphenyltin and trioctyltin chloride and pertechnetate in nonaqueous solutions

Conductivity of tetraphenylarsonium chloride (Ph₄AsCl), tetraphenylphosphonium chloride (Ph₄PCI), tetraphenylarsonium pertechnetate (Ph₄AsTcO₄), tetraphenylphosphonium pertechnetate (Ph₄PTcO₄), triphenyltin chloride (Ph₃SnCl) and trioctyltin chloride (Oct₃SnCl) solutions in nitrobenzene and chloroform was studied. On the basis of determined molar conductivity A values at different concentrations of the electrolyte in solution, values of dissociation degree of the electrolyte α, molar conductivity at infinite dilution A₀ and dissociation costant K_i for compounds of type Ph₄(As or P) (Cl or TcO₄) were calculated. It was shown that for some of the investigated systems the Kohlrausch's empirical relation applies. In chloroform solutions a parabolic dependence of molar conductivity on electrolyte concentration was observed which testifies that a formation of ion triplets at higher electrolyte concentration can occur.     

Study of the aggregation of nonylammonium chloride in aqueous solutions of sodium chloride by vapor pressure osmometry

We determined osmotic coefficients from vapor pressure osmometry (VPO) measurements on aqueous solutions of nonylammonium chloride in the presence of NaCl at 30°C. VPO data were subsequently used to determine the critical micelle concentration (CMC) of the solutions of this surfactant. The values of this parameter obtained from VPO are well correlated with those obtained from light scattering. No premicellar aggregation was observed at surfactant concentrations below the CMC. The osmotic coefficients below the CMC may be evaluated from the extended form of the Debye–Hückel equation. Above the CMC, the dependence of the osmotic coefficient on the surfactant concentration was indicative of the occurrence of aggregation rather than the interactions in the system. Some comments are made on the uncertainty in the value of some parameters in micellar solutions and possible source of error using the VPO technique in these solutions.     

The foam separation of zirconium(IV) from aqueous solutions

Summary The foam separation of zirconium(IV) from chloride solutions has been investigated over the 1.8–12 pH range using sodium lauryl sulphate or cetyl(trimethyl)ammonium bromide as collectors. The effects of gas flow rate, bubbling time, collector and zirconium(IV) concentrations, ageing of the metal ion, and ionic strength have been studied and the results are discussed in relation to the hydrolytic behaviour of zirconium(IV). Under optimum conditions,ca. 99.5% removal can be achieved.     

An inorganic nano-sorbent based on nickel–aluminum–zirconium ternary-layered double hydroxide for solid-phase extraction of chloride ions

A well crystalline nickel?Caluminum?Czirconium ternary-layered double hydroxide was firstly synthesized and applied as a solid-phase extraction sorbent for the separation of trace levels of chloride ions from aqueous solutions. An indirect method was used for monitoring of the extracted chloride ions. For this purpose, the extracted chloride ions were passed through a reaction column containing silver chloranilate powder and the analyte was precipitated as silver chloride. The concentration of chloranilate ions released from the reaction column, which corresponds to the chloride ions concentration, was then determined spectrophotometrically at 530?nm. The effect of several parameters, such as pH, sample loading flow rate, elution conditions, amount of nano-sorbent, sample volume and effect of potential interfering ions on the recovery was investigated. In the optimum experimental conditions, the limit of detection (3?s) and enrichment factor were 0.12 and 40???g?mL^?1, respectively. The calibration graph using the pre-concentration system was linear in the range of 0.25?C3.00???g?mL^?1 with a correlation coefficient of 0.997. The validation of the presented method was checked by the analysis of two certified reference materials. The optimized method was successfully applied to the determination of chloride ions in waters, food and biological samples.     

N,N-二甲基甲酰胺在不同浓度氯化钠水溶液中的稀释过程热力学

应用等温流动微量热法测定了298.15 K时N,N-二甲基甲酰胺(DMF)在纯水及不同浓度氯化钠水溶液中的稀释焓, 根据McMillan-Mayer理论计算得到各级同系焓相互作用系数. 结果表明, DMF在纯水及氯化钠水溶液中的焓对相互作用系数h2均为正值, 并且随着氯化钠浓度的增加, h2的值逐渐增大. 根据溶质-溶质相互作用和溶质-溶剂相互作用对结果进行了解释.     

Composite poly(vinyl alcohol)–poly(sulfone) membranes crosslinked by trimesoyl chloride: Characterization and dehydration of ethylene glycol–water mixtures

Composite membranes prepared from poly(vinyl alcohol) and poly(sulfone) were crosslinked with trimesoyl chloride (TMC) solutions. The degree of crosslinking, crystallinity, surface roughness and hydrophobicity of the crosslinked PVA–PSf membranes were determined from attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM) and contact angle measurements, respectively. Results showed a consistent trend of changes in the physicochemical properties: the degree of crosslinking, crystallinity, surface roughness, hydrophobicity and swelling degree all decrease with increasing crosslinking agent (TMC) concentration and reaction time. The crosslinked membrane performance was assessed with pervaporation dehydration of ethylene glycol solutions at a range of concentrations (30–90 wt% EG) in the feed mixtures. The total flux of permeation was found to decrease, while the selectivity to increase, with increasing TMC concentration and reaction time. The decrease in flux was most prominent at low EG concentrations in the feed mixtures. In addition, the temperature effect on the pervaporation dehydration was investigated in relation to solution–diffusion mechanisms.     

Effect of electrolyte on the chemical polymerization of aniline

Chemical syntheses of polyaniline were performed in HCl (0.4-2.51 M) containing 0.1 M aniline and LiCl or MgCl₂, keeping the total amount of chloride in the reactional medium constant. This was done in order to investigate if the chloride ion, added as salt and not as acid, is incorporated from chloride containing solutions with lower total acid concentration. The synthesis processes were characterized by potentiometric and calorimetric measurements represented in curves containing kinetic parameters of the polymerization process. The analysis of the polymeric materials was performed by infrared spectroscopy, electric conductivity measurements and scanning electron microscopy. It was observed that both the acid and chloride concentration, have an influence on the polymerization rate and the properties of the polyaniline, however, the presence of monovalent (Li⁺) or divalent (Mg⁺²) cations does not seem to have a significant effect. Finally, the conductivity of PAni is lowered by high acid concentrations but high chloride concentrations seem to improve the conductivity.     

Flow-Injection Study and Analytical Applications of the Reactions of Palladium(II) and Platinum(IV) with Tin(II) Chloride in Hydrochloric Acid Solutions

The interaction of palladium(II) and platinum(II) with tin(II) chloride in hydrochloric acid solutions was studied by flow-injection (FI) spectrophotometry. It was found using kinetic measurements in the stopped flow mode that the composition of detected products and the rate of their formation depend on the concentrations of tin(II) and chloride ions in the reaction zone and on the acidity of the solution. Optimal FI conditions were found, and the selectivity of interaction of palladium(II) with tin(II) chloride was estimated for the detection of the signal at 407 nm (yellow form) and 646 nm (green form). It was demonstrated that the reaction of the formation of yellow platinum(IV) complexes is slower than that for palladium(II), especially at rather low concentrations of hydrochloric acid in the reaction flow. Based on the detection of green complexes of palladium(II) with tin(II) chloride, a flow injection method was proposed for the selective spectrophotometric determination of palladium(II) in the presence of other platinum-group metals. The height of the recorded peak is directly proportional to the concentration of palladium(II) in the injected solution in the range of 0.028–0.300 mM. The method was used for the analysis of pharmaceuticals and industrial catalysts.     

Shear-induced phase separation in solutions of wormlike micelles

Polymer solutions in the vicinity of the theta-point are known to undergo shear-induced turbidity or phase separation. The present study shows that a similar phenomenon also occurs for certain wormlike micellar solutions. Wormlike micelles are the self-assembled counterparts of polymers and are characterized by their ability to reversibly break and recombine. In the system of interest, the micelles are formed by the cationic surfactant erucyl bis(hydroxyethyl)methylammonium chloride (EHAC), in conjunction with a salt such as sodium chloride (NaCl) or sodium salicylate (NaSal). Micellar samples that become turbid under shear show evidence of critical concentration fluctuations and may contain predominantly branched micelles. The shear-induced turbidity in these samples correlates with the appearance of flow-dichroism in rheooptic experiments and with an increase in low-q scattering in small-angle light scattering under flow (flow-SALS) experiments. The characteristic "butterfly" pattern, with enhanced scattering in the flow direction and a dark streak perpendicular to the flow direction, is typically observed in flow-SALS. The results suggest that the turbidity is due to a shear-induced growth of concentration fluctuations, which in turn manifests as large anisotropic domains, typically oriented along the vorticity axis.     

Behavior of chalcosine in leaching of carbonyl nickel synthesis residues with copper(II) chloride solutions

The behavior of chalcosine in leaching of carbonyl nickel synthesis residues with copper(II) chloride solutions was studied. The chalcosine leaching was examined in relation to the chloride background concentration, and kinetic features of the process were elucidated.     

Studies on electroosmotic and electrophoretic behavior of cholesterol in aqueous solutions

Electrical properties of cholesterol interfaces have been investigated. For this purpose electroosmotic and hydrodynamic permeation of water, sodium chloride, barium chloride, aluminum chloride, and urea solutions across a cholesterol plug have been investigated. Dependence of electroosmotic permeability on concentration of electrolytes has also been studied. Electrophoretic mobility of cholesterol particles of known size distribution and dispersed in solutions of varying concentrations of electrolytes and urea has also been studied. The data have been used to estimate ζ potentials in order to have a plausible picture of the electrical double layer at the cholesterol/ solution interfaces.     

Studies on the aggregation behaviour of some direct dyes in aqueous solutions

Summary Physicochemical properties of the two direct dyes ChrysophenineG and Chlorazol Sky Blue FF in aqueous solutions, have been studied using solubility and electrical conductivity methods. The results indicate that in aqueous solutions, both dyes in the presence of added sodium chloride start forming aggregates at a critical dye concentration. This critical concentration is a function of the temperature and the concentration of added sodium chloride. An analysis of the conductivity data shows that in all solutions containing dye aggregates the concentration of single dye ions is constant and equal to the critical cocentration. Since the solubility of ChrysophenineG unlike that of Chlorazol Sky Blue FF, is very small in the presence of added sodium chloride, the solubility product principle has been used to experimentally determine mean ionic activity coefficients for the dye ions. These values have been compared with activity coefficients calculated using a suitable form of theDebye-Hückel expression. The results indicate that ChrysophenineG in aqueous solutions behaves as a strong unaggregated 12 valence type electrolyte in dilute solutions below the critical concentration for aggregate formation.Finally, a close correlation has been shown to exist between the critical dye concentrations for aggregate formation and the equilibrium dye bath concentrations at which the aqueous solution adsorption isotherms for these dyes on cotton, viscose and cuprammonium rayon fibres show a marked change in slope leading to the formation of a flat plateau region.     

Chloride distribution coefficient on strongly basic anion-exchange resin: Dependence on co-ion in alkali fluoride solutions

Summary The dependence of the chloride distribution coefficient on the co-ion of solutions of different alkali fluorides, MF, up to 11M is tested on the strongly basic anion-exchange resin AG1-X10. Under the same experimental conditions the distribution coefficient decreases in the following order for M⁺: Na⁺>K⁺>Rb⁺>Cs⁺. This can be explained by the different co-ion-chloride interactions. The consequence of this interaction for a chromatographic separation of chloride is shown with 5M KF and CsF solutions, used as eluants. Depending on the fluoride concentration, the distribution coefficient passes through a minimum value to increase again at higher electrolyte concentration. The non-exchange electrolyte in the resin phase is responsible for this effect. In addition, the bromide and the iodide distribution coefficients up to 10M KF solutions are determined. One results is that the selectivity coefficient between halide ions increases at higher electrolyte concentrations.     

Quantitative analysis of chloride in brackish water: an application to the hyperchromic effect of copper(II) ion with chloride ion.

A new modified method was applied to the determination of chloride anion in brackish water by using a common copper(II) sulfate solution and a spectrophotometer. The result of the quantitative analysis demonstrated that chloride concentrations were 1.61% w/v and 1.74% w/v at ebb tide and flood tide, respectively, of the Muya River. On the other hand, chloride concentrations were 1.17% w/v at ebb tide and 1.65% w/v at flood tide of the Yoshino River. The new method proved that chloride concentration corresponded well with results from Mohr and conductive methods. Therefore, the newly developed method can be exploited as common means to measure chloride concentration in aqueous solutions. Moreover, it is also valuable for application to other types of environmental samples.