A nafion/crown ether film electrode and its application in the anodic stripping voltammetric determination of traces of silver

Glassy carbon electrodes are modified by coating with dicyclohexyl-18-crown-6 in Nafion-117. The electrode is used for a very sensitive anodic stripping voltammetric determination of silver. High sensitivity is obtained owing to the release of crown molecules from the silver-crown complex during the deposition. The detection limit is 2×10^?12 M after electrodeposition for 30 min. The recommended supporting electrolyte is 4×10^?3–7×10^?3 M potassium chloride in 0.01 M nitric acid with a deposition potential of ?0.30 V vs. SCE and a linear potential scan. Three typical calibration graphs were linear over the range 2×10^?11–1×10^?8 M for deposition times of 30, 20 and 8 min, respectively. The silver content of reagent-grade ammonium nitrate was found to be 0.48×10^?4% with a relative standard deviation of 3.7% (n=7) for parallel determinations.     

Time‐Dependent Surface Plasmon Resonance Spectroscopy of Silver Nanoprisms in the Presence of Halide Ions

Herein, we find that the surface plasmon resonance (SPR) spectra of silver nanoprisms in the presence of halide ions change gradually with reaction time. The changes in the spectra correspond to the shape transformation of silver nanoprisms. There are threshold concentrations of halide ions that initiate the shape‐transformation reaction. The threshold concentrations for Cl^?, Br^?, and I^? are about 3×10^?4 M , 1×10^?6 M , and 1.5×10^?6 M , respectively. Any concentrations of the added halide ions above these thresholds can eventually etch the silver nanoprisms into nanodisks if the reaction time is long enough. The higher the concentration of the halide ions, the higher the etching rate will be. The kinetics of the shape transformation of the silver nanoprisms can be studied by recording their time‐dependent surface plasmon resonance (SPR) spectra on a commercial UV/Vis–NIR spectrometer. The peak positions of in‐plane dipole SPR bands of silver colloids in the presence of chloride and bromide ions can be fitted very well with the biexponential functions. We propose that the fast components of the biexponential behaviors should correlate to the truncating effect on the corners of silver nanoprisms, and the slow component should correlate to the redeposition of the truncated residues onto the basal plane of the nanoplates.     

Indirect Atomic Absorption Spectrometric Determination of Ammonia,Thiosulfate and Cyanide in an Unsegmented Flow System

Abstract

A flow injection analysis method (FIA), has been developed for the determination of cyanide, thiosulfate and ammonia by atomic absorption spectrometry (AAS). Aqueous solution of the analyte was injected into an on-line column containing glass beads and packed with silver chloride and deionized water was used as the carrier. The analyte dissolves the silver chloride and the dissolved silver complex is introduced to the nebulizer of the AAS. This method has proved to be sensitive, simple and precise. Detection limits of 1.0 × 10^?7 M, 5.0×10^?7 M and 5.0x10^?6M were obtained for thiosulfate, cyanide and ammonia, respectively. The precision of the technique was 2.0%, 2.4% and 1.4% in case of thiosulfate, cyanide and ammonia, respectively. The effects of flow rate and sample volume on the FIA/AAS signals are presented.     

Flow-injection spectrophotometric determination of chloride with an on-line solid mercury(II) thiocyanate minicolumn and bromide with a silver thiocyanate minicolumn

Flow-injection spectrophotometric procedures are described for the determination of chloride and bromide using on-line solid mercury(II) thiocyanate and silver thiocyanate minicolumns, respectively. The linear response ranges for chloride and bromide are 0.28 × 10^?4?8.5 × 10^?4 M and 0.38 × 10^?4?2.4 × 10^?4 M, respectively. The sample throughput for both systems is 100 h^?1. The lifetime of the minicolumns is 50 and 200 injections, respectively.     

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.     

Rapid Method for the Micro-Determination of Hydrazine by Amperometric Titration With Potassium Iodate

Abstract

An amperometric method, with potassium iodate as the titrant, for the rapid and precise determination of micro amounts of hydrazine salts is described. Hydrazine dihydrochloride, hydrazine sulfate and hydrazine hydrate could be quantitatively analyzed at the concentration range of 4 × 10^?7 -4×10^?3 M in the presence of 5 M hydrochloric acid. Hydrazine salts, 2×10^?4 -4×10^?3 M, were titrated in 5 minutes with a relative error and a relative standard deviation of 0.1%. It was also found that hydrazine dihydrochloride can be precisely determined, without any interference, even in the presence of hydroxylamine which is ten times as much as the former.

The suitable applied potential between the rotating platinum indicator microelectrode and the silver plate-silver chloride reference electrode was + 0.7V.     

New method for determining small concentrations of chloride ion

A new method has been devised for the determination of concentrations of chloride ion from approximately 10^-6 to 2·10^-4 M. The test solution is equilibrated with solid silver chloride, the silver ion concentration is determined by potentiometric titration with iodide ion, and the chloride concentration is calculated by the solubility product principle. Chloride concentrations near 10^-6 M can be determined with an accuracy of about ±5%, and at 10^-5 M the error is within ±0.5%. Chloride concentrations above 2-3· 10^-4 M cannot be accurately determined because of the formation of AgCl₂^-.     

Entwicklung einer flieβinjectionsmethode zur bestimmung von chlorid im spurenbereich durch leitfähighkeitsdiffernzenA flow-injection method for the determination of trace amounts of chloride

The indirect determination of chloride in water is based on measurement of the difference in conductivity after the sample has passed through ion-exchange columns in the hydrogen form and silver form. The linear response range is about 0.5–10 μg g^?1 chloride (with 3 μg g^?1 nitrate and 5 μg g^?1 sulfate); the detection limit is about 50 ng g^?1 chloride but depends strongly on the concentrations of other anions.     

Anion-selective properties of alkali metal-free lead phosphate glasses containing silver chloride and their application in an ion-selective electrode

Alkali-free lead phosphate glasses containing silver chloride have been developed for anion responsive sensors. From measurements of the final glass compositions by electron probe microanalysis, it became clear that some of chloride ions in the glass bulk were not volatilized during the glass melting process. Compared with phosphate glasses containing silver oxide, the new glass electrodes containing silver chloride could respond more rapidly, although the response behaviour for anionic species were similar. From the electrode potential vs. time curve for the anionic species, the potential rapidly reached equilibrium when these concentrations varied from 10^?5 to 10^?2 M. The response times, t₉₅, to thiocyanate of the new glass electrode and the phosphate glass electrode containing silver oxide were 30 and 110 s, respectively. Moreover, the response time required for an initial potential change with a concentration jump of thiocyanate with the new glass electrode was found to be independent of the membrane thickness within about 2 mm and of the measuring temperature between 15 and 40°C. It is concluded that the diffusion process of species such as silver ion in the glass bulk does not take part in the initial part of the response behaviour.     

Direct determination of traces of silver in mercury by voltammetry at the hanging mercury drop electrode in acetonitrile medium

A direct method for the determination of silver in mercury is described. The sample of mercury is introduced into the container of the hanging mercury drop electrode and the anodic voltammograms are recorded in a 0.1 M lithium perchlorate solution in acetonitrile. The anodic peak of silver obtained under these conditions is well separated from the mercury dissolution current. The peak height is proportional to silver concentration over the wide range 2 × 10^?6 mol dm^?3 (1.6 × 10^?6%) to at least 2.0 × 10^?2 mol dm^?3. No prior separation is needed; the procedure requires less than 20 min. The diffusion coefficient of silver in mercury was determined at several temperatures. It was found that silver in mercury does not form intermetallic compounds with copper, lead, thallium, cadmium, tin and bismuth.     

Applications of ion-exchange minicolumns in a flow-injection system for the spectrophotometric determination of anions

Displacement of thiocyanate from a strongly basic ion-exchange resin by other anions is used to determine common anions at the 10^?5–10^?4 M level by spectrophotometric detection of the iron(III)/thiocyanate complex. Chloride and sulphate can be removed by incorporating a pre-column containing a cation-exchange resin in the silver form followed by a zinc reductor, thus allowing the determination of nitrate in their presence. Binary mixtures (e.g., chloride and nitrate) can be determined simultaneously by splitting the sample in the flow system so that part goes through the chloride suppressor (giving a nitrate response only) and part by-passes it giving a response to both chloride and nitrate.     

Determination of silver in solution with a piezoelectric detector after electrodeposition

Silver in solution is determined in situ by frequency change of a piezoelectric quartz crystal due to electrodeposition on the electrode of the crystal immersed in the solution. A test solution containing EDTA for masking other metal ions flows through a thermostated cell which contains the crystal with platinum-plated electrodes. The frequency change is proportional to the silver concentration in the range 10^?6?3 × 10^?5 M after electrodeposition for 10 min, and 2 × 10^?7?1 × 10^?6 M for 1 h.     

Indirect atomic absorption spectrometric determination of mixtures of chloride and iodide by precipitation in an unsegmented flow system

Chloride and iodide are injected into a carrier silver nitrate and the precipitates formed are retained on a stainless-steel filter, so that total chloride and iodide can be determined by the decrease in the atomic absorption signal for silver. The silver chloride precipitate is subsequently dissolved with ammonia and chloride only is determined. Iodide is determined by difference. Mixtures of these anions at μg ml^?1 levels can be determined for chloride/iodide ratios from 7.5:1 to 1:60, with a sampling frequency of ca. 10 h^?1. Applications to the determination of chloride in foodstuffs and wines are described. Up to 10 samples per hour can be handled and 50–100 samples can be run before the filter must be cleaned.     

Ruthenium(III) Schiff's Base Complex as Novel Chloride Selective Membrane Sensor

A novel chloride PVC‐based membrane sensor based on a ruthenium(III) Schiff's base complex, as an excellent neutral carrier, has been developed. The ruthenium complex, in combination with a ketonic plasticizer and a cationic additive led to ISEs with fundamental characteristics, such as slope sensitivity, short response times and selectivity coefficients, which were sufficient for practical applications. The sensor with composition of 30% PVC, 62% benzyl acetate, 5% ruthenium(III) Schiff's base complex and 3% hexadecyltrimethyl ammonium bromide displays near‐Nernstian behavior in a wide concentration range (1.0×10^?1–3.0×10^?6 M with slope of ?54.5±0.5) with a detection limit of 2.0×10^?6 M (71.0 ng per mL). The response of the electrode is independent on pH in the range of 4.0–10.0 and can it be used for at least ten weeks. The proposed electrode shows a very short response time (<20 s) in whole concentration range. The sensor displays high selectivity toward chloride ions over several organic and inorganic anions. It was successfully applied for the determination of chloride in serum samples. It was also used as an indicator electrode in the potentiometric titration of chloride ions with silver nitrate solution.     

Kinetics of silver dissolution in sulfide containing thiocarbamide electrolytes

Effective values of reaction order with respect to ligand P, transfer coefficient α, and exchange current i ₀ at constant silver surface coverages θ by sulfide ions are measured. The employed solutions contained from 0.4 to 0.05 M thiocarbamide, 0.5 M HClO₄, 10^?4 M AgNO₃, and from 10^?5 to 10^?4 M Na₂S. It is shown that the exchange current grows approximately linearly from 10^?5 to 1.5 × 10^?4 A/cm² at θ increase in the range from zero to 0.8, while α and P values grow negligibly in the ranges of 0.4–0.45 and 0.9–1.1, accordingly. The obtained results are compared with the data of similar studies of the gold behavior in acidic thiocarbamide solutions. The possible reasons for the different effects of sulfide ion chemisorption on the anodic dissolution of gold and silver in the studied solutions are discussed.     

Determination of trace amounts of silver with a chemically modified carbon paste electrode

A method for the determination of trace amounts of silver with a chemically modified carbon paste electrode is described. The modified electrode is prepared by simply mixing a chelating resin (a polythioether backbone and dioxymonosulphur polyethylene polyimines in the side-chain polymer) with graphite powder and Nujol oil. By immersing the electrode in a silver sample solution (pH = 6.5–7.5), silver can be adsorbed on the electrode surface and then determined by voltammetry in a separate blank solution. The response depends on the concentration of silver and the preconcentration time. For a preconcentration time of 5 min, the detection limit is about 3 × 10^?10 M and the linear range is from 5 × 10^?10 to 1 × 10^?7 M with a relative standard deviation of 4%. Many common metal ions have no or little effect on the determination of silver. The recommended procedure was applied to the determination of trace amounts of silver in waste water.     

Selective determination of silver in solution by adsorption on a piezoelectric quartz crystal

Electrodeposition of metal ions on the crystal is eliminated by using a specially constructed transistorized oscillator. When tartrate, citrate, EDTA or their mixtures are present, silver adsorption occurs. The frequency change is proportional to the silver concentration in the range 2 × 10^?7?1 × 10^?5 M after adsorption for 10 min from a 1 mM EDTA/3 mM tartrate solution. No significant interferences are caused by other metal ions. On the basis of cyclic voltammetric studies, it is suggested that silver is adsorbed as a silver (I) complex.     

Novel Poly(ethylene glycol)s Bearing Tributyltin Carboxylate End Groups as Ionophores in the Development of Chloride Ion‐Selective Electrodes

The potentiometric response characteristics of electrodes based on PVC membranes containing novel polyethylene glycols (PEGs) with tributyltin carboxylate end groups as ionophores for chloride ions were studied in 0.1 M HEPES solution, at the spontaneous pH. The effects of solvent mediator, amount of cationic additive, amount of ionophore and PEG chain length on the behavior of the sensors were investigated. The membranes with the best composition responded to chloride concentration in a linear range from 10^?4 to 10^?1 M Cl^? with a nearly Nernstian slope and a detection limit of 6.5×10^?5 M. The sensor showed a short response time (<25 s) in the whole concentration range and an operational lifetime of about one week for the most performing PVC membranes. In comparison with ISEs based on anion exchangers the interferences from the more lipophilic anions were greatly reduced, as inferable by the selectivity coefficients determined with the matched potential method at chloride concentration of 3.0×10^?3 M.     

Novel Bromide PVC‐Based Membrane Sensor Based on Iron(III)‐Salen

A novel bromide PVC‐based membrane sensor, based on iron(III)‐salen (IS) as an electroactive material, is successfully developed. The sensor possesses the advantages of low detection limit (6.0×10^?6), wide working concentration range (7.0×10^?6–1.0×10^?1 M), Nernstian behavior (slope of 59.0±0.5 mV per decade), low response time (<15 s), wide working pH range (3–9), and specially, high bromide selectivity over a wide variety of organic and inorganic anions, specially iodide, chloride, and hydroxide ions. The electrode was used in the direct potentiometric determination of hyoscine butylbromide, and as an indicator electrode in potentiometric titration of bromide ions with silver ions.     

Determination of picomolar concentrations of bromide with a piezoelectric detector by catalysis of the permanganate/iodide reaction

The piezoelectric quartz crystal has been utilized to detect iodine produced by the bromide- catalyzed oxidation of iodine to iodate by permanganate in acidic solution. After extraction of iodine into toluene, the resulting frequency change caused by iodine adsorption on the crystal electrode is proportional to bromide concentration over the range 0.5–5 × 10^?12 M. Only silver (I), mercury(II) and large concentrations of chloride interfere significantly. The crystal detector is also used to indicate the end-point of a chloride titration with silver.