Insoluble Silver Salts Research Articles

Indicator-Free Argentometric Titration for Distance-Based Detection of Chloride Using Microfluidic Paper-Based Analytical Devices.

We described an indicator-free argentometric titration strategy using a microfluidic paper-based analytical device. This strategy was based on the formation of insoluble silver salts by reactions occurring between analytes and titrant (Ag+) on a paper channel. After the insoluble silver salts were formed and precipitated on the channel, the paper substrate modified with the surplus titrant on the channel turned reddish-brown by exposure of the devices to a simple and cheap UV light source for 5 min, generating a colored band on the channel. Distance-based detection of chloride was achieved by measuring the length of the colored band with a detection limit of 1.7 mg L–1 Cl–. This method was used to detect chlorides in tap water, with an analytical result (10.1 ± 1.2 mg L–1) agreeing well with that obtained by a classical conventional precipitation titration (9.8 mg L–1), which was based on the measurement of the consumed volume of titrant. This paper-based precipitation titration method is free of skilled personnel and has advantages of low reagent/sample consumption, disposability, portability, and simple operation over the conventional precipitation titration. More importantly, being free of any indicator, this method may be used to detect more species than the conventional precipitation titrations, which are limited by the indicator, for example, CO32– and SO42–, which could form insoluble silver salts in aqueous liquids. Additionally, comparing with most of those paper-based titrimetry reported previously, this presented precipitation titration is free of any indicator or ion selective electrode to detect the end point of titration.

Antibacterial Properties of Microfiltration Membranes Modified by Silver Nitrate

The modification of a nylon microfiltration membrane with silver compounds for the disinfection of drinking water under dynamic conditions has been carried out, and the antibacterial properties of the modified membranes have been studied. It has been revealed that the initial microfiltration membrane is not capable of complete removal of microorganisms from water. It has been determined that membrane modification with the silver compounds leads to the complete disinfection of the water. In this case, the modification does not lead to a significant decrease in the specific productivity of the membranes. Insoluble silver salts are distributed on the membrane surface in the form of particles from 0.1 to 5 μm. Depending on the type of the silver compound used for the treatment of membranes, the silver content ranges from 5.11 to 9.06 wt %. The most uniform distribution of silver over the entire membrane surface and the maximum content are achieved by treating the membrane with an AgNO3 solution.

Synthesis and characterization of silver nanoparticles from (bis)alkylamine silver carboxylate precursors

A comparative study of amine and silver carboxylate adducts [R1COOAg-2(R2NH2)] (R1 = 1, 7, 11; R2 = 8, 12) as a key intermediate in NPs synthesis is carried out via differential scanning calorimetry, solid-state FT-infrared spectroscopy, 13C CP MAS NMR, powder X-ray diffraction and X-ray photoelectron spectroscopy, and various solution NMR spectroscopies (1H and 13C NMR, pulsed field gradient spin-echo NMR, and ROESY). It is proposed that carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination as opposed to bridging bidentate coordination of pure silver carboxylates resulting from the formation of dimeric units. All complexes are packed as lamellar bilayer structures. Silver carboxylate/amine complexes show one first-order melting transition. The evidence presented in this study shows that phase behavior of monovalent metal carboxylates are controlled, mainly, by head group bonding. In solution, insoluble silver salt is stabilized by amine molecules which exist in dynamic equilibrium. Using (bis)amine-silver carboxylate complex as precursor, silver nanoparticles were fabricated. During high-temperature thermolysis, the (bis)amine-carboxylate adduct decomposes to produce silver nanoparticles of small size. NPs are stabilized by strongly interacting carboxylate and trace amounts of amine derived from the silver precursor interacting with carboxylic acid. A corresponding aliphatic amide obtained from silver precursor at high-temperature reaction conditions is not taking part in the stabilization. Combining NMR techniques with FTIR, it was possible to follow an original stabilization mechanism.Graphical abstractThe synthesis of a series (bis)alkylamine silver(I) carboxylate complexes in nonpolar solvents were carried out and fully characterized both in the solid and solution. Carboxyl moieties in the presence of amine ligands are bound to silver ions via chelating bidentate type of coordination. The complexes form layered structures which thermally decompose forming nanoparticles stabilized only by aliphatic carboxylates.

Large-scale synthesis of size-controllable silver nanoplates and their application in detecting strong oxidants in aqueous solutions

A scalable approach for preparation of Ag nanoplates in one-step is reported. Well-defined Ag nanoplates were obtained by reducing silver nitrate with hydrazine hydrate in the presence of insoluble silver salt, such as AgSCN, AgCl, AgBr, AgI, Ag2CO3, Ag2SO3, and Ag2C2O4. The size of Ag nanoplates can be well controlled by simply adjusting the ratio of Ag seeds to the amount of AgNO3. The exclusive formation of Ag nanoplates was due to the homogeneous nucleation of Ag nanoparticles is avoided in the presence of a small amount of counterions of insoluble silver salts, and large-scale synthesis with a yield ca.75 times higher than the record was achieved. In addition, a detecting strategy toward oxidizing substances in aqueous solutions was summarized based on the change of the surface plasma absorption via the size variation of the Ag nanoplates. This detecting method combines the advantages of generality, rapidity, simplicity, as well as a low detection limit and a wide linear response range.

Ethanol to hydrocarbons using silver substituted polyoxometalates: Physicochemical and catalytic study

Thermally stable and insoluble silver salts of 12-molybdophosphoric acid with varying amount of Ag cations were prepared. XRD results indicated the presence of single phase of AgxH3−xPMo12O40 (0<x<3). FTIR and Raman results indicated that Ag was incorporated in the secondary structure of Keggin ion. The catalytic conversion of ethanol increased in the order of H3PMo>Ag2PMo>Ag1PMo>Ag3PMo. Pure H3PMo is highly selective to dimethyl ether formation; in contrast AgxH3−xPMo12O40 catalysts offered better ethylene selectivity. The pyridine adsorption studies revealed that increase of Ag incorporating led to increase the Lewis acid sites.

Efficacy of silver-bearing external ventricular drainage catheters: a retrospective analysis

Catheter-related infection of CSF is a potentially life-threatening complication of external ventricular drainage (EVD). When using EVD catheters, contact between the ventricular system and skin surface occurs and CSF infection is possible. The aim of this analysis was to compare the efficacy of silver-bearing EVD catheters for reducing the incidence of infection with standard nonimpregnated EVD catheters in neurosurgical patients with acute hydrocephalus. Two hundred thirty-one consecutive patients were retrospectively reviewed. Of these, 164 were enrolled in the final analysis. Six patient charts were incomplete or missing, 15 patients were excluded because of catheter insertion within the previous 30 days, 6 because of a suspected CSF infection before ventriculostomy, 7 because the catheter was removed < 24 hours after insertion, and 33 patients because of the requirement of bilateral ventriculostomy. The control group with standard nonimpregnated EVD catheters consisted of 90 patients. The study group with silver-bearing EVDs consisted of 74 patients. For assessing the primary outcome, the authors recorded all CSF samples and liquor cell counts routinely obtained in sterile fashion. After removal of the catheters, they also reviewed microbiology reports of the removed catheters to assess colonization of the catheter tips. The occurrence of a positive CSF culture, colonization of the catheter tip, or liquor pleocytosis (white blood cell count > 4/microl) was approximately 2 times less in the study group with silver-bearing EVD catheters than that in the control group (18.9% compared with 33.7%, p = 0.04). Positive CSF cultures alone occurred 2 times less frequently for microorganisms in the study group (2.7% compared with 4.7%, p = 0.55). Silver-bearing catheters were 4 times less likely to become colonized as nonimpregnated EVDs (1.4% compared with 5.8%, p = 0.14). Liquor pleocytosis was half as likely in the study group (17.6% compared with 30.2%, p = 0.06). Although of limited sample size and thus underpowered for subgroup analysis, this analysis indicates that EVD catheters impregnated with silver nanoparticles and an insoluble silver salt may reduce the risk of catheter-related infections in neurosurgical patients.

Gravimetric and volumetric determination of the purity of electrolytically refined silver and the produced silver nitrate

Silver is, along with gold and the platinum-group metals, one of the so called precious metals. Because of its comparative scarcity, brilliant white color, malleability and resistance to atmospheric oxidation, silver has been used in the manufacture of coins and jewelry for a long time. Silver has the highest known electrical and thermal conductivity of all metals and is used in fabricating printed electrical circuits, and also as a coating for electronic conductors. It is also alloyed with other elements such as nickel or palladium for use in electrical contacts. The most useful silver salt is silver nitrate, a caustic chemical reagent, significant as an antiseptic and as a reagent in analytical chemistry. Pure silver nitrate is an intermediate in the industrial preparation of other silver salts, including the colloidal silver compounds used in medicine and the silver halides incorporated into photographic emulsions. Silver halides become increasingly insoluble in the series: AgCl, AgBr, AgI. All silver salts are sensitive to light and are used in photographic coatings on film and paper. The ZORKA-PHARMA company (Sabac, Serbia) specializes in the production of pharmaceutical remedies and lab chemicals. One of its products is chemical silver nitrate (argentum-nitricum) (l). Silver nitrate is generally produced by dissolving pure electrolytically refined silver in hot 48% nitric acid. Since the purity of silver nitrate, produced in 2002, was not in compliance with the p.a. level of purity, there was doubt that the electrolytically refined silver was pure. The aim of this research was the gravimetric and volumetric determination of the purity of electrolytically refined silver and silver nitrate, produced industrially and in a laboratory. The purity determination was carried out gravimetrically, by the sedimentation of silver(I) ions in the form of insoluble silver salts: AgCl, AgBr and Agi, and volumetrically, according to Mohr and Volhardt. The purity of electrolytically refined silver obtained volumetrically, according to Volhard, was 99.49%. The results suggest that the purity of electrolytically refined silver was higher than 99%. After all of these determinations, the purity of electrolytically refined silver was examined by atomic absorption spectrometry and the results confirmed that the purity of electrolytically refined silver was 99.99%. Electrolytically refined silver contained other metals: Mn, Cu, Fe, Zn, Pb, Cd, and the contents of these metals were: 1.15 ppm; 0.75 ppm; 0.65 ppm; 1.82 ppm; &lt; 0.07 ppm and &lt; 0.01 ppm, respectively.

The 3,4‐O‐Carbonate Protecting Group as a β‐Directing Group in Rhamnopyranosylation in Both Homogeneous and Heterogeneous Glycosylations as Compared to the Chameleon‐Like 2,3‐O‐Carbonates.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The 3,4-O-Carbonate Protecting Group as a β-Directing Group in Rhamnopyranosylation in Both Homogeneous and Heterogeneous Glycosylations As Compared to the Chameleon-like 2,3-O-Carbonates

It is demonstrated that the beta-selectivity observed in the insoluble silver salt mediated couplings of 2,3-O-carbonate-protected rhamnosyl bromides is uniquely due to the heterogeneous nature of the reaction. In homogeneous solution these same donors are alpha-selective, a fact that is attributed to the half-chair conformation of these substances which reduces the energy barrier to oxacarbenium ion formation. It is suggested that the 2,3-O-carbonate group be dubbed torsionally arming in the manno- and rhamnopyranose series. When the carbonate group is removed to the 3,4-O-position a beta-selective system is formed, in both homogeneous and heterogeneous conditions, and it is demonstrated that this selectivity arises from the combination of the electron-withdrawing nature of the carbonate and its inability to take part in neighboring participation.

Improved microwave digestion procedure for inductively coupled plasma mass spectrometric determinations of inorganic bromide residues in foodstuffs fumigated with methyl bromide

An improved microwave digestion procedure is described for the inductively coupled plasma mass spectrometric (ICP-MS) determination of inorganic bromide residues in foodstuffs fumigated with methyl bromide. It is based on the addition to the usual acid oxidizing mixture of small amounts of silver ions which cause bromides from the mineralized matrix to precipitate as sparingly soluble AgBr, thus, avoiding losses due to their conversion into volatile products. The silver bromide precipitate separated from the digested sample is dissolved with ammonia and the cationic complex [Ag(NH 3) 2] + thus formed is removed on a cation-exchange column. The resulting solution is finally acidified and added with indium internal standard, to make it suitable for inductively coupled plasma mass spectrometric (ICP-MS) analysis. This modified procedure has been tested for the analysis of synthetic KBr samples by obtaining totally satisfactory results, in that bromide recoveries ranging from 98.6 to 100.2% were found, with an overall standard deviation of 5.17%. Its application to the bromide determination in some mushroom samples is reported and the results found are compared with those obtained on the same samples mineralized by conventional alkali fusion. The proposed procedure can be extended to the determination in biological samples of other anions which may be lost during a conventional acid oxidizing microwave mineralization, but are able to form insoluble silver salts.

The concept of “scaleable reactor” in the precipitation of silver halide photographic microcrystals

The various types of silver halide microcrystals used in the photographic industry are all obtained by precipitation techniques. Highly insoluble silver and halide salts are used and the high kinetics of the nucleation and growth phenomena involved in the precipitation process often limit their capability to be scaled without further costly and time-consuming reformulation. A new concept of “scaleable reactor” for the precipitation of silver halide microcrystals has been developed, which allows to greatly speed-up or even eliminate the translation work between scales. It is based on the simple evidence that, in highly nonlinear systems such as precipitation reactors, scale-up is better ensured when all the critical parts of the process are exactly the same at all scales. Therefore, the concept of scaling by replication instead of the conventional scaling by dimensional changes according to phenomenological laws was studied further. The system presented in this paper uses both batch reactors and auxiliary side-arm loops containing elementary cell(s) in which all the reactants are separately injected. The side-arm loops are connected to the batch reactor which acts as a holding tank and in which only slow kinetics reactions, such as Ostwald ripening, take place, so that the reaction zone remains separated from the bulk. Scaling is ensured by the exact replication of the side-arm loop, the number of replicates being equal to the scale-up factor, while the batch reactor volume varies accordingly to the scale-up factor. The design of the elementary cell, based on the principle of Tee-mixers, was carefully optimized. The batch reactor designs were also studied at several scales, and macromixing compared at different scales. A large range of experimental results are available, demonstrating the validity of the concept for several sizes and morphologies of silver halide crystals.

Voltammetric Behavior of 2-Mercaptopyrimidine at a Silver Electrode

Electrochemical characteristics of 2-mercaptopyrimidine (MPD) have been studied by linear scan voltammetry at a silver disk electrode (AgE). It was found that at appropriate potentials MPD can adsorb on and interact with the electrode to form an insoluble silver salt on the surface. As the potential is made more negative two cathodic peaks appear at −0.66 V and −1.28 V, respectively. The peak at −0.66 V is attributed to the reduction of the sparingly soluble silver compound of MPD, and the other to the reduction of MPD to pyrimidine, which was confirmed by capillary electrophoresis. The deposition/stripping behavior of MPD is discussed and possible mechanisms are proposed. Additionally, the influence of some surfactants and halides on the shape and height of the stripping peaks was determined. It was observed that cationic surfactants such as cetylpyridinium bromide and hexadecyltrimethylammonium bromide can dramatically increase the peak height and decrease the peak width of the peak at −0.66 V.

Unexpected phenomena in glycosylations of acceptors with L‐idose configuration

AbstractFor the synthesis of Galß(1 → 4)IdoA disaccharides 1, several glycosylations of L‐iduronic acid derivatives 5 and 13 and of L‐idopyranose derivative 21 were performed with differently protected D‐galactopyranosyl donors under various conditions. It was found that these coupling reactions mainly led to the formation of the undesired α‐interglycosidic linkage, even when the donor contained a participating group at C‐2. On the other hand, coupling of the corresponding D‐glucopyranosyl donor 19 with 13 led to a much higher β/α ratio (2/1). By changing the conformation of the acceptor into the 1,6‐anhydro‐L‐idopyranose acceptor 23, 90% of the desired β‐coupled disaccharide was obtained in the glycosylation with galactopyranosyl donor 12. Finally it was found that the α/β ratio of the condensation with 25, promoted by an insoluble silver salt, was influenced in an unusual way by the substituents at the galactosyl bromide.

Superadditive catalysis of homogeneous redox reactions with mixed silver–gold colloids

As silver can be more easily oxidized than gold, certain electrocatalytic reactions occur more rapidly with silver as catalyst than with gold. On the other hand, in the presence of halide and some other anions an autoinhibition of the silver-catalysed reaction takes place because of the formation of an insoluble silver salt at the surface of this metal. This inhibition can be avoided, however, if a small amount of gold was deposited on silver. With electrocatalytic oxidation of N,N-dimethyl-p-phenylenediamine as a model reaction, the advantage of a silver–gold colloid compared with pure silver or gold colloids can be demonstrated.

ChemInform Abstract: Studies Directed Towards the Synthesis of Sulfated and Non‐Sulfated Glyco‐Conjugate Fragments Using Insoluble Silver‐Salt Promoters.

AbstractScope and limitations of the known silver‐salt promoted β‐glycosylation (cf.

Studies directed towards the synthesis of sulphated and non‐sulphated glyco‐conjugate fragments using insoluble silver‐salt promoters

AbstractThe synthesis of three fucosylated oligosaccharides (i.e. compounds 8, 10 and 14) and a keratan sulphate fragment (i.e. compound 24) is presented. The formation of β bonds in these glyco‐conjugate fragments was promoted by insoluble silver salts, while non‐participating groups are present at C‐2 of the glycosyl bromide. Thus, glycosyl donors can be used which have also been employed for a glycoside synthesis. It was found that insoluble silver salt promoters can be very worthwile for the formation of β bonds in larger oligosaccharides when relatively reactive glycons with suitable substitution pattern are condensed with reactive aglycons. The application of this coupling methodology is of special advantage for the synthesis of functionalized oligosaccharides (such as 24), which synthesis may require the use of building blocks having non‐participating (e.g. benzyloxy or azido) protecting groups at C‐2.

Potentiometric detection of halides and pseudohalides in anion chromatography

A small piece of silver wire, coated with an insoluble silver salt, can be used as a selective potentiometric detector for halides in ion chromatography. Several coated electrodes were examined by electron microscopy and their response to various anions evaluated in a flow-injection system. A silver/silver chloride was found to be a selective and reproducible detector for chloride, bromide, iodide, thiocyanate and thiosulfate separated by ion chromatography. Calibration curves were non-linear and had slopes ranging from 40 to 60 mV per concentration decade in the range 0.1–2 mM. A working range of 0.05–2 mM was used. This electrode is also satisfactory when gradient elution is used in ion chromatography.

A note on the use of porous silver silicates as promoter in carbohydrate coupling reactions

AbstractDifferent insoluble silver salts were used to promote the β‐glycosidic bond formation between the aglycon methyl (2,3,4‐tri‐O‐benzyl‐α‐D‐glucopyranosyl bromide) uronate (1) and the aglycon 3‐O‐acetyl‐1,6‐anhydro‐2‐azido‐2‐deoxy‐D‐glucopyranose (2). The different promoters have different activity, but do not affect the β/α ratio (β/α = 1.5/1) of this coupling reaction. The most reactive promoter is Ag (I) on silica‐alumina with enhanced cation capacity.

Substituent effects in carbohydrate chemistry, Part III+. Effects of C‐2 substituents on coupling reactions promoted by insoluble silver salts

AbstractCoupling reactions have been performed in the 2‐deoxy‐2‐azido‐α‐D‐glucopyranosyl bromide series (i.e. compounds 2, 3, and 4) and with the corresponding 2‐O‐methyl and 2‐O‐(2,2,2‐trifluoro‐ethyl)‐substituted α‐D‐glucopyranosyl bromides (i.e. compounds 1 and 7, respectively) using aglycon 5 in the presence of insoluble silver salt promoters. It was found that coupling of 2‐deoxy‐2‐azido derivatives gave much higher β/α ratios than did the corresponding reactions of the 2‐O‐alkylglucopyranosyl bromides. We assume that through‐bond interactions are responsible for these effects. Other substituent effects are also presented and it is concluded that β‐coupling reactions can be performed in the absence of a participating group at C‐2 if the glycons are appropriately protected. Thus, high β/α ratios may be obtained if acetoxy groups are present at C‐4 and/or 2‐azido‐2‐deoxy functions at C‐2, whereas benzyloxy or allyloxy groups, should be present at C‐3 and C‐6. Furthermore, coupling of galacto‐ and manno‐pyranosyl glycons also gives rise to higher β/α ratios than does coupling of the corresponding glucopyranosyl derivatives.

Substituent effects in carbohydrate chemistry, Part II+. Coupling reactions involving gluco‐ and galacto‐pyranosyl bromides promoted by insoluble silver salts

AbstractCoupling reactions have been conducted between α‐D‐glyco‐ and galacto‐pyranosyl bromide derivatives and 3‐O‐acetyl‐1,6‐anhydro‐2‐azido‐2‐deoxy‐β‐D‐glucopyranose in the presence of insoluble silver salt promoters. It was found that 4‐O‐acyl functions increase the β/α ratio of the disaccharide formation relative to 4‐O‐alkyl functions, whereas 3‐O‐ and 6‐O‐acyl functions decrease this ratio. It was also found that coupling of α‐D‐galactopyranosyl bromide derivatives gave much higher β/α ratios than did reactions with the corresponding α‐D‐glucopyranosyl bromides.