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PubMed2003

Serum estradiol-17beta and testosterone levels during silvering in wild Japanese eel Anguilla japonica.

To understand the changes of serum levels of sex steroids in the wild Japanese eel Anguilla japonica during silvering process, eels collected from the Kaoping River of Taiwan from August 2000 through June 2001 were examined. The maturational stages of female eels before and during silvering were divided into four stages: juvenile, sub-adult, pre-silver and silver stages based on skin coloration and oocyte diameter. Male eels were investigated only in the silver stage. Radioimmunoassays were employed to measure serum levels of estradiol-17beta (E(2)) and testosterone (T). The mean liver mass of the female eels increased significantly during silvering, but the mean hepatosomatic index remained constant. In contrast, mean ovarian mass and gonadosomatic index increased significantly during silvering. Serum concentrations of E(2) in females increased significantly during silvering (P<0.05), while E(2) was undetectable in silver males. The mean serum T concentrations increased significantly in females (P<0.05) during silvering, with lowest mean values in the juvenile stage and highest mean value in the silver stage. The mean serum T level in the silver males was significantly lower than in silver females (P<0.05). In conclusion, both serum E(2) and T concentrations increased with ovarian development of wild Japanese eels during silvering, while serum E(2) was undetectable in the silver male eels. The findings support the idea that androgen, but not estrogen, plays a major role in silvering process of the eels in both sexes.

Anguilla↗
PubMed1998

Wound management in an era of increasing bacterial antibiotic resistance: a role for topical silver treatment.

BACKGROUND: Antibiotic-resistant bacteria represent an increasing concern in wound infections. Wound colonization with these organisms normally results in aggressive management of the wound complicated by a greatly limited choice of therapeutic antibiotics. Silver and other noble metals are recognized as potential allies in combating these organisms in wounds. METHODS: Three types of topical silver applications were tested to determine their bactericidal efficacies against clinical isolates of antibiotic-resistant organisms. The silver-based applications represent 3 methods of applying silver to wounds: as a liquid (silver nitrate), incorporated in a cream (silver sulfadiazine) and as a dressing coating (silver-coated dressings). The reduction in the viable bacterial population recovered from test articles after exposure to silver provided a comparative measure of the bactericidal efficacies of these silver applications. RESULTS: All of the products demonstrated an ability to reduce the number of viable bacteria. However, the methods varied in their efficacy against antibiotic-resistant bacteria, with the silver-coated dressing being the most efficacious and silver nitrate the least efficacious. CONCLUSIONS: Silver was demonstrated to be effective at killing the antibiotic-resistant strains tested. The silver-coated dressing was particularly rapid at killing the tested bacteria and was effective against a broader range of bacteria. Silver may be a useful prophylactic or therapeutic agent for the prevention of wound colonization by organisms that impede healing, including antibiotic-resistant bacteria.

Administration, Cutaneous↗
PubMed2001

The physiological effects of a biologically incorporated silver diet on rainbow trout (Oncorhynchus mykiss).

Silver was biologically incorporated into a diet by exposing rainbow trout for 7 days to 100 mg/l of waterborne silver as silver thiosulphate. These fish were processed into a fine powder (trout meal) and pelleted to form a nutritionally balanced feed which was then fed to juvenile rainbow trout (Oncorhynchus mykiss). Fish were fed either a diet containing 3.1 microg/g biologically incorporated silver (an environmentally relevant concentration), or one of three control diets containing approximately 0.05 microg/g Ag for 128 days. All dietary treatments were fed to satiation once daily. Dietary silver did not significantly affect mortality, growth, food consumption, or food conversion efficiency. Furthermore, ion regulation (plasma Na(+) levels and Na(+) influx rates), hematological parameters (hematocrit, plasma protein, hemoglobin levels), plasma glucose, metabolism (oxygen consumption, ammonia and urea excretion rates) and intestinal Na/K-ATPase and amylase activities were all unaffected. Based on the physiological parameters investigated here, this dietary silver exposure appeared to be physiologically benign to rainbow trout. However, silver concentrations in the livers of the silver-fed fish were significantly elevated at day 16, and reached a steady-state level of approximately 20 microg/g Ag by day 36. The concentration specific accumulation rate in the livers of fish fed biologically incorporated silver was about 4.6 orders of magnitude greater than when fed dietary silver sulfide, indicating much greater bioavailability. Despite this increase, hepatic metallothionein concentrations remained unchanged, in contrast to waterborne exposures, indicating that bioaccumulated silver behaves differently depending on whether it is taken up from the diet or from the water. Apart from a significant reduction in hepatic Cu at day 16, liver concentrations of Cu and Zn were not affected by dietary silver. Silver concentrations were also significantly elevated (relative to control fish) in the kidneys of the silver-treated fish on days 88 and 126, and in the gills and plasma at day 126.

Animal Feed↗
PubMed2002

Binding and movement of silver in the intestinal epithelium of a marine teleost fish, the European flounder (Platichthys flesus).

The intestine has been indicated as a site of waterborne silver toxicity in marine fish and chronic effects at the intestine have been observed at concentrations far below acutely toxic level. Thus, models of silver toxicity to marine fish need to consider the intestine as a biotic ligand. The present study characterises binding of silver to the intestine of the European flounder (Platichthys flesus). Everted intestinal sacks were prepared and submersed in a solution mimicking the intestinal fluid of the fish at the acclimation salinity (21 per thousand). Silver was added as (110m)AgNO(3) or (110m)AgNO(3)/AgNO(3) mixtures at concentrations ranging from 1.6 to 950 nM total silver. Appearance of (110m)Ag was analysed in mucosal scrapings, muscle layers, and in the plasma saline on the serosal side of the intestine. The latter represented uptake into blood and other extra-intestinal compartments. Mucosal scrapings consisted of both epithelial cells and mucus and, thus contained adsorbed as well as absorbed silver. Most of the silver in mucosal scrapings was bound to mucus. There was no difference in silver binding between the anterior, mid, and posterior regions of the intestine. Concentration-dependency of silver binding was sigmoidal and saturated above 100 nM total silver. The saturable appearance of (110m)Ag in the plasma saline suggest that silver passage across the intestine is transcellular and carrier mediated. Mucus likely influences uptake of silver by altering its speciation from that in the lumen and by serving as physical barrier for silver binding to the brushborder membrane. A biotic ligand model for marine fish to silver may have to consider these interactions.

Animals↗
PubMed1999

Argyremia in septal cauterization with silver nitrate.

OBJECTIVE: The purpose of this study was to demonstrate silver absorption in blood and hair specimens after septal cauterization with silver nitrate and to discuss the potential toxicity of silver. METHOD: A prospective study of 11 volunteers without any known occupational exposure to silver products or past history of septal cauterization with silver nitrate was undertaken. Subjects were recruited in an academic tertiary care centre from October 1996 to September 1997. The study population consisted of five patients with anterior epistaxis and six healthy volunteers without any bleeding problem. Cauterization was done with one or two silver nitrate applicators directly on the bleeding vessel or Kiesselbach's area. Blood was sampled before cauterization and at specified times after application, while hair strands were sampled only 3 months later. Measurements of silver concentration in whole blood and in hair segments were obtained by inductively coupled plasma mass spectrometry. RESULTS: Silver concentrations in whole blood increased significantly after cauterization (p = .02). The measured peak level seemed to correlate with the number of applicators used. No significant increase in silver concentration was observed in hair samples. CONCLUSIONS: Effective silver absorption occurs with only one or two silver nitrate applicators. Hair has not been as reliable as whole blood to document an acute and fragmentary exposure. The indiscriminate use of silver nitrate is a potential source of silver intoxication.

Absorption↗
PubMed1994

Silver resistance in Pseudomonas stutzeri.

Silver resistance was studied in a silver-resistant Pseudomonas stutzeri AG259 strain and compared to a silver-sensitive P. stutzeri JM303 strain. Silver resistance was not due to silver complexation to intracellular polyphosphate or the presence of low molecular weight metal-binding protein(s). Both the silver-resistant and silver-sensitive P. stutzeri strains produced H2S, with the silver-resistant AG259 strain producing lower amounts of H2S than the silver-sensitive JM303 strain. However, intracellular acid-labile sulfide levels were generally higher in the silver-resistant P. stutzeri AG259 strain. Silver resistance may be due to formation of silver-sulfide complexes in the silver-resistant P. stutzeri AG259 strain.

Bacteria↗
PubMed1979

Simultaneous determination of the amounts of metallic and "reducible" silver in histologic specimens.

Acids and weak complexing agents (pK less than 8) are not able to remove, without leaving a residue, silver bound to biological tissues by ionic or complex bonds ("reducible" silver), whereas, strong complexing agents (pK greater than 8) can also partially or completely dissolve metallic silver formed under the influence of reducing groups in the tissue. For this reason, the chemical nature of the silver contained in tissue sections, be it metallic or reducible, must not be determined on the basis of solubility tests; moreover, the amount of neither of the two above fractions can be determined by removing the other with any kind of washing. Using radioactive impregnating baths, radioactive silver bound to the tissue as reducible silver can be replaced in a quantitative manner with inactive silver ions by means of a one-hour incubation in 1% inactive silver nitrate dissolved in 10% acetic acid, but the radioactive silver existing in reduced (atomic) state will be left unaffected. Consequently, radioactivity remaining in the tissue after the above treatment represents metallic silver. The amount of reducible silver can be calculated by subtracting that of the metallic silver from the total silver content of the sections.

Histocytochemistry↗
PubMed1981

Light and electron microscopic localization of silver in biological tissue.

A method is described that visualizes trace amounts of silver in frozen, paraffin and epon sections from biological tissue. After exposure to light, which ensures reduction of silver ions that are not bound to sulphide, histological sections from animals treated with silver compounds are exposed to a photographic developer containing silver ions. Tissue silver acts as a catalyst for the hydroquinone reduction of silver ions to metallic silver which then accumulates at the site of the trace deposit. Light and electron micrographs showing silver in different organs from albino rats treated with silver lactate are presented. Localization of silver in motor neurons of the spinal gray matter and pons indicates a transport of silver over the blood-brain barrier. Silver precipitates in fetal liver suggest that silver ions can penetrate the placental barrier.

Animals↗
PubMed2005

Accumulation and elimination of silver in Daphnia magna and the effect of natural organic matter.

Body burden is often used as an indicator of the toxic impact of metals such as silver. Natural organic matter (NOM) is reported to reduce silver toxicity to the highly sensitive freshwater crustacean Daphnia magna. However, the effect of NOM on silver burden in these organisms has not been investigated, and literature reports from other aquatic animals suggest that NOM can actually promote silver accumulation. In 24 h accumulation trials NOM exhibited a general trend of reducing whole body silver accumulation. Differences in accumulation profiles between NOM samples were attributed to chloride content stimulating uptake by the formation of diffusible silver chloride complexes. Silver accumulation assayed over 1 h exhibited considerable heterogeneity. Subsequent experiments conducted with varying light conditions during exposure and utilising gut dissection, suggested that these differences were in part due to variable gut silver accumulation. In addition to a general reduction in silver accumulation, NOM also facilitated enhanced elimination of silver from the animals. Rapid elimination of silver from Daphnia, coupled with speciation-, body compartment- and time of day-dependent accumulation suggests that silver body burden may be a poor indicator of silver toxicity in natural environments.

Animals↗
PubMed2002

Removal and sequestration of iodide using silver-impregnated activated carbon.

Two silver-impregnated activated carbons (SIACs) (0.05 and 1.05 wt % silver) and their virgin (i.e., unimpregnated) granular activated carbon (GAC) precursors were investigated for their ability to remove and sequester iodide from aqueous solutions in a series of batch sorption and leaching experiments. Silver content, total iodide concentration, and pH were the factors controlling the removal mechanisms of iodide. Iodide uptake increased with decreasing pH for both SIACs and their virgin GACs. The 0.05% SIAC behaved similarly to its virgin GAC in all experimental conditions because of its low silver content. At pH values of 7 and 8 there was a marked increased in iodide removal for the 1.05% SIAC over that of its virgin GAC, while their performances were similar at a pH of 5. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses prior to reaction with iodide showed the presence of metallic silver agglomerates on the 1.05% SIAC surface. After the reaction, elemental mapping with EDX showed the formation of silver iodide agglomerates. Oxidation of metallic silver was observed in the presence of oxygen, and the carbon surface appears to catalyze this reaction. When the molar ratio of silver to iodide was greater than 1 (i.e., M(Ag,SIAC) > M(I,TOTAL)), precipitation of silver iodide was the dominant removal mechanism. However, unreacted silver leached into solution with decreasing pH while iodide leaching did not occur. When M(Ag,SIAC) < M(I,TOTAL), silver iodide precipitation occurred until all available silver had reacted, and additional iodide was removed from solution by pH-dependent adsorption to the GAC. Under this condition, silver leaching did not occur while iodide leaching increased with increasing pH.

Carbon↗
PubMed2005

Fast and slow deposition of silver nanorods on planar surfaces: application to metal-enhanced fluorescence.

Two methods have been considered for the deposition of silver nanorods onto conventional glass substrates. In the first method, silver nanorods were deposited onto 3-(aminopropyl)triethoxysilane-coated glass substrates simply by immersing the substrates into the silver nanorod solution. In the second method, spherical silver seeds that were chemically attached to the surface were subsequently converted and grown into silver nanorods in the presence of a cationic surfactant and silver ions. The size of the silver nanorods was controlled by sequential immersion of silver seed-coated glass substrates into a growth solution and by the duration of immersion, ranging from tens of nanometers to a few micrometers. Atomic force microscopy and optical density measurements were used to characterize the silver nanorods deposited onto the surface of the glass substrates. The application of these new surfaces is for metal-enhanced fluorescence (MEF), whereby the close proximity of silver nanostructures can alter the radiative decay rate of fluorophores, producing enhanced signal intensities and an increased fluorophore photostability. In this paper, it is indeed shown that irregularly shaped silver nanorod-coated surfaces are much better MEF surfaces as compared to traditional silver island or colloid films. Subsequently, these new silver nanorod preparation procedures are likely to find a common place in MEF, as they are a quicker and much cheaper alternative as compared to surfaces fabricated by traditional nanolithographic techniques.

Chemical Phenomena↗
PubMed1999

Three-body wear of a hand-consolidated silver alternative to amalgam.

Recent studies have investigated a mercury-free silver alternative to amalgam, but the silver powders required a relatively high compaction pressure to consolidate. The aim of the present study was to consolidate a precipitated silver powder into a cohesive solid using an air-driven pneumatic condenser fitted with an amalgam plugger at a clinically realistic load, and to study the mechanisms and rates of three-body wear of the consolidated silver in comparison with that of an amalgam. The silver powder was annealed, rinsed with a dilute acid, and consolidated either in a prepared tooth cavity or in a specimen mold at a load of 15 N. A four-station wear machine was used where each specimen was immersed in a slurry containing polymethyl methacrylate beads, then a steel pin was loaded and rotated against the specimen at a maximum load of 76 N. The flexural strength in MPa (mean +/- SD; n = 10) was 86 +/- 20 for amalgam, 181 +/- 45 for silver with a polished surface, and 202 +/- 21 for silver with a burnished surface. After 4 x 10(5) wear cycles, the wear scar depth in microm was 134 +/- 54 for amalgam, 143 +/- 8 for polished silver, and 131 +/- 9 for burnished silver, which were not significantly different (Tukey's multiple comparison test; family confidence coefficient = 0.95). SEM examination revealed cracks and fracture pits in the worn surface of amalgam, in contrast to a smooth surface in silver. Wear and material removal in amalgam occurred by microfracture and dislodgement of cracked segments, while wear in the silver occurred by ductile deformation and flow of materials. To conclude, the consolidated silver possesses a three-body wear resistance similar to that of amalgam, and a higher resistance to wear-induced damage and cracking than amalgam. The mechanism of wear in amalgam is microfracture and material dislodgement, while that in consolidated silver is ductile deformation and flow of material.

Compressive Strength↗
PubMed1989

[Histopathological study of damage to periodontal tissues by silver alloy metals in rats].

Damage to periodontal tissues caused by dental materials (silver alloy powder) was examined by histopathological observation. Three kinds of silver alloy powder containing copper of various contents, such as that used in the first group: Ag-Cu (25% Cu), second group: Ag-In (5% Cu), and third group: Ag-Sn-Zn (0% Cu), were used to analyze damage to periodontal tissues caused by silver alloy powder. With No. 1/2 round bar, standardized small cavities were prepared in the mesiolingual cervical portion of the upper first molars of rats. Three kinds of silver alloy powder were then inserted into the small cavities. Postoperative changes in the gingival tissues were studied histopathologically. The results were as follows: 1. Under the light microscope, all three groups showed similar tissue reaction. Many dark deposit (metal) were observed in the lamina propria of the gingiva. These dark deposits had been taken into the histiocyte-like cells and multinucleate giant cells. Infiltration of cells was not observed around these dark deposits. Findings among the metals in three groups were of specific structures, which displayed black and dark-brown stained deposits in surrounding silver alloy powder. 2. Under the electron microscope, the first, second and third groups showed similar tissue reactions. Dark deposits (metal) had been taken into the multinucleate giant cells. These cells contained many lysosomes, vacuoles, and endocytosed materials. The deposits consisted of a dence central core of silver alloy powder surrounded by fine needle-like components and filaments of lower electron density. Extremely fine particles were also observed around the basal lamina of capillary vessels and along collagen fibers. 3. By AEM, components of the lower electron density material were identified as silver, copper and sulfur in the first and second group, and silver and sulfur in the third group. The elements in the fine particles were silver and sulfur. 4. Using scanning electron microscope, the micrograph indicated that a barnacle-like structure was formed on the surface of the silver alloy in the gingival tissue. A phenomenon of solubility appeared as stacks of granules firmly attached to the silver alloy surface. 5. The silver element of the silver alloy powder damaged the gingival tissues slightly, resulting in minor tissue reactions. When the range of copper content was from 0% to 25%, the alloys caused no damage to gingival tissue.

Animals↗
PubMed2004

[Change in sliver metabolism after the application of nanometer silver on burn wound].

OBJECTIVE: To investigate the change in silver metabolism after the application of nanometer silver on burn wound. METHODS: Twenty-six burn patients with partial thickness burn covering 6-12% TBSA were enrolled in the study as treatment group (T), and 30 healthy adult volunteers as control group (C). Burn wound covering 5% TBSA was covered with nanometer silver dressing for 5 days. The silver contents in the serum and urine in C group of people and in T group of patients at different time points before and after the application of nanometer silver were measured by atomic absorption spectrum method. The hepatic and renal function was also monitored on the 7th and 14th post treatment days (PTD) after silver application. Tissue samples from the wound and wound edge 14 days after silver application were harvested for the determination of silver content by plumbago stove and atomic absorption spectrum. The silver deposition was also detected by transmission electronic microscope. RESULTS: Compared to those in C group, the silver contents in serum and urine in T group increased on 3rd and 5th PTD, but decreased to the normal level on 14th PTD. Mild hepatic dysfunction occurred in 7 cases on 7 PTD, whereas the renal function remained normal. The tissue mass percentage of silver in burn wound and wound edge was (0.7 +/- 0.1) x 10(-6), but no silver deposition in tissue was observed by transmission electron microscope. CONCLUSION: It was proved to be safe to have the nanometer silver dressing applied on partial thickness burn wound of middle and small areas.

Adolescent↗
PubMed2002

Complexation mechanism of olefin with silver ions dissolved in a polymer matrix and its effect on facilitated olefin transport.

Remarkable separation performance of olefin/paraffin mixtures was previously reported by facilitated olefin transport through silver-based polymer electrolyte membranes. The mechanism of facilitated olefin transport in solid membranes of AgCF3SO3 dissolved in poly(N-vinyl pyrrolidone) (PVP) is investigated. In silver polymer electrolyte membranes, only free anions are present up to the 2:1 mole ratio of [C=O]:[Ag], and ion pairs start to form at a ratio of 1:1, followed by higher-order ionic aggregates above a ratio of 1:2. At silver concentrations above 3:1, the propylene permeance increases almost linearly with the total silver concentration, unexpectedly, regardless of the silver ionic constituents. It was also found that all the silver constituents, including ion pairs and higher order ionic aggregates, were completely redissolved into free anions under the propylene environment; this suggests that propylene can be a good ligand for the silver cation. From these experimental findings, a new mechanism for the complexation reaction between propylenes and silver salts in silver-polymer electrolytes was proposed. The new mechanism is consistent with the linearity between the propylene permeance and the total silver concentration regardless of the kind of the silver constituents. Therefore, the facilitated propylene transport through silver-polymer electrolytes may be associated mainly with the silver cation weakly coordinated with both carbonyl oxygen atoms and propylene.

Journal Article↗
PubMed2000

Bioaccumulation and distribution of silver in four marine teleosts and two marine elasmobranchs: influence of exposure duration, concentration, and salinity.

The bioaccumulation of waterborne silver (added as AgNO(3)) was compared amongst drinking (teleosts: rainbow trout, tidepool sculpin, plainfin midshipmen, and English sole) and non-drinking marine fish (elasmobranchs: Pacific spiny dogfish and long nose skate) exposed to 14.5 µg/l Ag for 21 days in 30-ppt seawater. In addition, 21-day exposures were performed on trout, midshipmen, and sculpin at 0 (control), 1.5, 14.5, and 50 µg/l Ag to evaluate the effect of silver concentration, and on sculpins acclimated to 18 and 30 ppt salinity and sampled periodically up to 21 days to evaluate the effects of salinity and exposure duration. A 48-h acute exposure (250 µg/l Ag) was also carried out on sculpins at 10, 18, 24, and 30 ppt. The 1.5-and 14.5-µg/l Ag levels are of regulatory importance, but are several orders of magnitude higher than normal environmental levels. Silver uptake occurred in all exposures, but internal accumulations were less than proportional to exposure concentration (1.5-50.0 µg/l Ag), and tended to saturate over time, suggesting that physiological regulation occurred. Control (non-exposed) fish exhibited measurable levels of silver in all tissues (10-200 µg Ag/kg wet weight), suggesting that they accumulate silver from the natural environment throughout their lifetimes. After 21-day exposure to 14.5 µg/l Ag, silver levels increased 2-20-fold in most tissues of all species, with the greatest concentrations occurring in the livers of teleosts (order: liver>gills>/=intestines>white muscle) and the gills of elasmobranchs (order: gills>liver>white muscle>intestines). Rainbow trout accumulated more silver than the other teleosts, and were the only species to suffer significant mortality, effects likely associated with added salinity stress. Accumulations were fairly uniform amongst the other teleosts. Similar concentrations in gills and intestines suggested that both branchial and intestinal uptake occurred, with the latter potentially dominant; indeed sole exhibited no silver build-up in the gills. The two elasmobranchs exhibited no silver build-up in intestines but much higher levels in gills, indicating that in the absence of drinking, only branchial uptake occurs. Nevertheless, based on whole liver content, the elasmobranchs accumulated silver 5-15-fold faster than the three teleosts. Over 21-day exposures (1.5-50.0 µg/l Ag) in sculpin, salinity markedly affected silver accumulation, with tissue-specific levels approximately 6-fold higher at 18, than at 30 ppt. However, there was negligible effect of salinity on silver accumulation during 48 h at 250 µg/l Ag. Silver bioaccumulation appears to be markedly affected by speciation. At lower salinities, or higher [Ag], a neutral charged AgCl(aq) complex exists in the water, allowing for increased bioaccumulation to occur. At higher salinity, only less bioavailable, negatively-charged AgCl(n)(1-n) complexes are present (AgCl(2)(-), AgCl(3)(2-), AgCl(4)(3-)).

Journal Article↗
PubMed1997

Coordination Networks of 3,3'-Dicyanodiphenylacetylene and Silver(I) Salts: Structural Diversity through Changes in Ligand Conformation and Counterion.

Coordination networks of 3,3'-dicyanodiphenylacetylene (3,3'-DCPA, 1) with silver(I) salts characterized by single-crystal X-ray analysis are described. Network topology is found to depend on both the counterion and solvent employed during crystallization. The conformation adopted by the ligand varies between planar cisoid and planar transoid. With silver(I) triflate (AgCF(3)SO(3)) in benzene, a sheet structure of composition [Ag(1)CF(3)SO(3)]C(6)H(6) (2) forms in which silver(I) is five-coordinate and bonds to two nitrogen atoms of distinct 3,3'-DCPA molecules, another silver(I) ion, and two oxygen atoms of the triflate ions. Changing the solvent to toluene produces an undulating sheet structure of composition [Ag(2)(1)(CF(3)SO(3))(2)] (3) in which silver(I) is six-coordinate, bonding to a ligand nitrogen atom, to four oxygen atoms of bridging triflate ions, and to a neighboring silver(I) ion. In both triflate structures, 3,3'-DCPA adopts a transoid conformation with respect to the positioning of the nitrile groups. With silver(I) hexafluorophosphate (AgPF(6)), silver(I) hexafluoroarsenate (AgAsF(6)), or silver(I) hexafluoroantimonate (AgSbF(6)), 2-fold interpenetrated sheet structures [Ag(1)(2)]XF(6) (X = P (4), As (5), or Sb (6)) are obtained in which 3,3'-DCPA coordinates to tetrahedral silver(I) ions in a cisoid conformation. In spite of the large difference in counterion size, minimal network deformation is observed among these systems. Interestingly, with silver(I) perchlorate hydrate (AgClO(4).xH(2)O, x approximately 1), 3,3'-DCPA coordinates in a transoid conformation to tetrahedral silver(I) ions to form the 8-fold interpenetrated diamondoid network [Ag(1)(2)]ClO(4).H(2)O (7). An analysis of the packing of these networks is provided, and the results are compared to complementary systems previously reported from our study of coordination networks of dinitriles and silver(I) salts.

Journal Article↗
PubMed2002

Silver speciation during chronic toxicity tests with the mysid, Americamysis bahia.

A 28-day chronic toxicity test and two 7-day chronic estimation toxicity tests were conducted with silver nitrate (AgNO(3)) and the marine invertebrate, Americamysis bahia, in 20 per thousand (parts-per thousand) salinity seawater. One 7-day test was initiated with 7-day-old mysids and the second was initiated with <24-h-old mysids. There was very good agreement between the three toxicity tests. The no-observed-effect concentration (NOEC) values from the 28-day test, the 7-day test initiated with 7-day-old mysids, and the 7-day test initiated with <24-h-old mysids were 34, 65 and 38 microg/l silver, respectively. The 96-h LC50 values from the 28-day toxicity test and the 7-day toxicity test initiated with 7-day old mysids were 260 microg/l, and the 96-h LC50 value from the 7-day toxicity test initiated with <24-h-old mysids was 280 microg/l. Free ionic silver, Ag(+), concentrations measured with a silver electrode were in good agreement with concentrations calculated using total dissolved silver and chloride concentrations. Mean measured concentrations of Ag(+) in the test solutions ranged from 0.99 to 25 ng/l for the dissolved silver concentrations that ranged from 34 to 410 microg/l silver, indicating that free ionic silver varied from 0.003 to 0.006% of the silver dissolved in the 20 per thousand salinity seawater. Understanding the relationship of salinity and silver speciation, and the effect of this relationship on chronic invertebrate toxicity, will be useful for development of a marine biotic ligand model (BLM) and a water quality criterion for silver. This model could provide an important tool for improving the relationship of laboratory toxicity test results and predicted effects in natural environments, where variations in salinity may act to modify the toxicity of silver and other metals.

Animals↗