Trace Amounts Of Silver Research Articles

Plant-mediated synthesis of zinc oxide (ZnO) nanoparticles using Alnus nepalensis D. Don for biological applications

An aqueous bark extract of A. nepalensis D. Don was utilized to prepare zinc oxide (ZnO) nanoparticles through a green method, which is more economical, eco-friendly, and effective for exploring several biological applications and toxicity assessments against brine shrimp nauplii. The prepared ZnO nanoparticles were characterized using several characterizing techniques. The surface morphology and the elemental composition of the prepared ZnO NPs was analyzed by field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray (EDX) analysis. The colour of the solution was changed from reddish-brown to white indicating the formation of ZnO NPs which shows UV–vis absorption at 361 nm. The various functional groups of the organic compounds present in plant extract act as reducing and stabilizing agents in the formation of nanoparticles. The involvement of these functionalities in the formation of nanoparticles is indicated by the shifts and changes in the IR spectra of both the plant extract and the ZnO nanoparticles. The size of the nanoparticles was determined to be 15.31 nm with XRD analysis while the FE-SEM revealed the average grain size of 67.29 nm with irregular shape. The elemental composition of ZnO NPs shows a greater atomic percentage of zinc compared to other elements (C, N, Ni, O, and Ag), with an intense peak of zinc observed at approximately 1 keV. The trace amount of silver is due to the impurities present in the reagent used in the experiment. The antioxidant property of ZnO nanoparticles was evaluated with an IC₅₀ of 53.02 ± 3.43 μg/mL. The ZnO nanoparticles exhibited significant antibacterial activity against Klebsiella pneumoniae and Escherichia coli, with zones of inhibition (ZOI) of 18 mm and 23 mm, respectively as compared to the positive control neomycin of ZOI 28 mm against K. pneumoniae. The potential antibacterial activity of the ZnO NPS was revealed as the MIC and MBC against K. pneumoniae of 0.39 mg/mL and 0.78 mg/mL, respectively. In addition, the prepared ZnO nanoparticles showed toxicity against brine shrimp nauplii of LC₅₀ 16.59 μg/mL. The results of this study impart that plant-assisted synthesized ZnO nanoparticles possess significant antibacterial properties that reduce oxidative stress in human cells, ultimately contributing to cancer prevention.

Treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching

This research investigates the extraction of copper from copper-containing leaching residue, which includes 33.45% of copper, 14.14% of iron, 23.87% of sulfur and trace amounts of silver and other elements. Roasting the copper-containing residue under air and oxygen flow convert sulfides into sulfate, followed by water and acid leaching to extract copper. The process parameters, including leaching temperature, sulfuric acid concentration, leaching time, solid-to liquid ratio, and agitation speed, were optimized for both water and acid leaching methods. Results showed that the maximum copper dissolution efficiency was 93.12% with water leaching, and 97.16% with acid leaching. Chemical analysis revealed that the water and acid leaching residue contained 48.13% and 31.64% of iron, respectively. This study provides valuable insights into the process optimization for copper extraction from copper-containing leaching residue, which can inform the development of more efficient and sustainable methods for metal recovery.

SEM-EDX and FTIR analysis of archaeological ceramic potteries from southern Italy.

Sherds of ancient ceramics potteries, dating back to the seventh century BC and excavated from southern Italy, were analyzed in terms of microstructure and porosity (SEM), elemental composition (EDX), chemical bonding and mineralogical components (FTIR) in order to establish correlation with firing temperature, firing condition and provenance. Si/Al ratio from EDX analysis showed three major categories of raw materials (illite/montmorillonite, kaolinite and mullite), suggesting difference in provenance. Uniformly sized silica nanoparticle (0.7μm diameter) and trace amount of silver are being reported for the first time in one sample. Anorthite mineral and quartz inclusion was detected by FTIR in certain samples. All samples showed a prominent band for Si-O stretching, which shifted from 1062cm-1, broadened and appeared as doublet, relative to processing temperature. FTIR results proved incomplete dihydroxylation and undissociated carbonate in three samples, indicating a firing temperature of 700-800°C, whereas other samples were fired above 900°C. Only one sample among these three showed bloating pores in between interconnecting glassy matrix in SEM image, indicating a firing temperature of 1100-1200°C. The absence of magnetite along with significant Fe and Mn content indicated the formation of jacobsite, an iron manganese spinel complex, MnFe2O4, which is responsible for the black gloss effect in two particular samples and can be further confirmed by XRD. The presence of numerous small pores in SEM image of one of these two samples (1.2μm diameter) was indicative of extended vitrification at higher temperature than the other one. However, magnetite was responsible for black gloss effect in two other samples, proving difference in provenance. Therefore, SEM-EDX and FTIR results can offer valuable insight into the firing conditions, gloss decoration and provenance of ancient ceramic potteries.

Influence of pH on wet-synthesis of silver decorated hydroxyapatite nanopowder.

Here, effect of solution pH on precipitation of silver decorated hydroxyapatite (Ag-HAp) nano powder during its wet-synthesis was systematically studied. XRD pattern of Ag-HAp nano powder synthesised at pH ranging from 5 to 10 shows that calcium hydrogen phosphate was formed as dominating phase when the solution pH was between 5 and 9 and this phase was gradually transformed into a stable HAp above pH 9. A quantitative analysis of silver amount in Ag-HAp nano powder synthesised at different pH showed that silver can be precipitated to its maximum amount at pH 8 and the further addition of ammonia leads to the formation of a silver-ammonium complex, thereby remaining in the solution. HR-TEM and XPS analysis further confirmed the presence of silver in HAp nanocrystals, synthesised at an optimum pH 9. This trace amount of silver in HAp nano powder showed effective antibacterial activity against Staphylococcus aureus and Escherichia coli. In addition, the cytocompatibility studies carried out on MG63 cells further confirmed the present optimised silver concentration of the Ag-HAp nano powder is well within the toxic limit to be useful in various biomedical applications.

Geology and geochemistry of the sediment-hosted Cheshmeh-Konan redbed-type copper deposit, NW Iran

The several-hundred-m-thick Miocene Upper Red Formation in northwestern Iran hosts stratiform and fault-controlled copper mineralization. Copper enrichment in the percent range occurs in dm-thick carbonaceous sandstone and shale units within the clastic redbed sequence and consists of fine-grained disseminated copper sulfides (chalcopyrite, bornite, chalcocite) and supergene alteration minerals (covellite, malachite and azurite). The copper mineralization formed after calcite cementation of the primary rock permeability. Copper sulfides occur mainly as replacement of diagenetic pyrite, which, in turn, replaced organic matter. Electron microprobe analysis on bornite, chalcocite and covellite identifies elevated silver contents in these minerals (up to 0.12, 0.72 and 1.21wt%, respectively), whereas chalcopyrite and pyrite have only trace amounts of silver (<0.26 and 0.06wt%, respectively). Microthermometric data on fluid inclusions in authigenic quartz and calcite indicate that the Cu mineralization is related to a diagenetic fluid of moderate-to low temperature (Th=96–160°C) but high salinity (25–38wt% CaCl2 equiv.). The range of δ34S in pyrite is −41.9 to −16.4‰ (average −31.4‰), where framboidal pyrite shows the most negative values between −41.9 and −31.8‰, and fine-grained pyrite has relatively heavier δ34S values (−29.2 to −16.4‰), consistent with a bacteriogenic derivation of the sulfur. The Cu-sulfides (chalcopyrite, bornite and chalcocite) show slightly heavier values from −14.6 to −9.0‰, and their sulfur sources may be both the precursor pyrite-S and the bacterial reduction of sulfate-bearing basinal brines. Carbonates related to the ore stage show isotopically light values of δ13CV-PDB from −8.2 to −5.1‰ and δ18OV-PDB from −10.3 to −7.2‰, indicating a mixed source of oxidation of organic carbon (ca. −20‰) and HCO3− from seawater/porewater (ca. 0‰). The copper mineralization is mainly controlled by organic matter content and paleopermeability (intragranular space to large fracture patterns), enhanced by feldspar and calcite dissolution. The Cheshmeh-Konan deposit can be classified as a redbed-type sediment-hosted stratiform copper (SSC) deposit.

Determination of trace amount of silver in water samples by flame atomic absorption after preconcentration by ZnO nano sorbent

ABSTRACTA simple and fast method based on solid phase extraction (SPE) applying zinc oxide (ZnO) nanoparticles and atomic absorption spectrometry (AAS) was developed for the trace amount determination of silver (Ag) in aqueous samples. The method linearity was in the range of 14 to 700 ng mL−1. The extraction efficiency of Ag was greater than 98% and limit of detection (LOD) was 4.2 ng mL−1. The preconcentration factor was 200 and the relative standard deviation (RSD%) of the method was 3.7% (n = 6).

Sulfide mineral chemistry investigation of sediment-hosted stratiform copper deposits, Nahand-Ivand area, NW Iran

Copper mineralization in Nahand-Ivand area, NW Iran, appears as disseminated copper sulfides along a redox boundary between gray sandstone and microconglomerate and hematitic sandstones, siltstones and shaly marl. Geochemical analyses of the Nahand-Ivand deposits show as much 35wt.% Cu and 730ppm Ag in the gray sandstone. Electron probe micro-analysis (EPMA) was used to determine the mineralogical composition and distribution patterns of copper and silver-bearing phases mainly in pyrite and Cu-bearing sulfides. The EPMA data were essential for evaluating the distribution and partitioning of potential economically-valuable components between co-existing minerals. Furthermore, they contribute to a better understanding of the genesis of the Nahand­Ivand copper deposits and will guide further exploration in the region.The EPMA results from different types of pyrite reveal Cu contents as high as 0.32wt.%, 1.10wt.%, and 2.88wt.% for framboidal pyrite (PyI), overgrowths on framboidal pyrite (PyII), and diagenetic pyrite (PyIII), respectively. This successive increase of copper from PyI to PyIII is attributed to a continuous supply of copper that replaces framboidal pyrite in turn by the more copper-rich digenetic pyrite. Because of hydrothermal overprinting, pyrite has been replaced by djurleite, roxbyite, and other nonstoichiometric Cu–S minerals that include covellite. The EPMA study indicates that covellite contains significant concentrations of Ag (locally >1wt.%). In contrast. only trace amounts of silver have been detected in pyrite and other copper sulfides, indicating that covellite is the major Ag-carrier in the ore. According to textural relationships, such open space filling, impregnation, and replacement textures, and the EPMA results, later stage copper-bearing fluids were responsible for the silver enrichment in the Nahand-Ivand deposits.

Determination of trace element silver in animal serum, tissues and organs by microwave digestion-ICP-MS

Nowadays, the silver is widely used in the biological field and its biological safety catches great attention. It is important to know the distribution of silver ions within the biological organism and the toxic threshold concentration in the tissue. Therefore, a highly sensitive method for measurement of trace amount of silver ion in the medical biological samples is needed. With its high sensitivity for detection of metal ions, inductively coupled plasma mass spectrometry (ICP-MS) method is well suited for quantification of trace amount of silver ion in such samples, but method development is still in its infancy. Consequently, a simple and convenient method for determination of trace amount of silver in the animal serum, tissues or organs was developed, in which the samples were subjected to the microwave digestion, followed by the ICP-MS analysis. To begin with, the samples of serum, muscle, bone marrow, bone, heart, liver, spleen, and kidney were sequently processed in 5 mL of HNO3 and 2 mL of H2O2 solution. Then the samples were completely digested by microwave with the power of 2 000 watts. The temperature was raised gradually by 3-step program. Moreover, the data achieved were reproducible and the method was time saving and especially for large amounts of sample processing. Then the digested solutions were diluted to constant volume. Finally, the concentration of 107Ag in the samples was analyzed by the method of ICP-MS under the optimized conditions. Element yttrium (Y) was used as the internal standard to compensate for matrix suppression effect and improve the accuracy of measurement. For one thing, the analytical results showed that the detection limit of the trace element 107Ag was 0.98 μg · kg(-1), and furthermore, the correlation coefficient of standard curve was 0.999 9. For another thing, the recovery rate of the silver element ranged from 98% to 107%, which was calculated according to measured quantity before adding standard, adding standard and measured quantity after adding standard. At the same time, the relative standard deviation (RSD) of the method was in the range of 2.0%-4.3%. The concentrations of element silver in animal serum, tissues and organs were determined by the aboved method. The obtained results showed that silver ions were mainly accumulated in the liver after they were intaken into the body. The results suggested that the microwave digestion-ICP-MS method could accurately determine the trace element Ag in the body. The method developed has good feasibility and is suitable for the determination of trace element Ag in various types of medical and biological samples, especially for large quantities of biological samples. The process has the advantages of easysample processing and it is simple and convenient. In addition, the accurate results could be obtained in a short time with high sensitivity. Last but not least, the method provides the guidance for the determination of trace elements in other biological samples.

Gold Gilding and Pigment Identification on a Post-Byzantine Icon from Kastoria, Northern Greece

The investigation of gilded gold, black and red pigments from the Byzantine icon of Panagia from the church of Agioi Anargyroi Gymnasiou in Kastoria, northern Greece is the aim of this study. Small fragments, having a gold leaf finish, were detached from the icon and were analyzed by Environmental Scanning Electron Microscopy coupled to Energy Dispersive System (ESEM-EDS) and Raman microscopy. The chemical (EDS) composition of the gilding material revealed a high gold content alloy (Au 81.34 wt%) with trace amounts of silver (Ag 1.66 wt%), copper (Cu 0.62 wt%) and iron (Fe 0.58 wt%). The Raman spectrum of the gold leaf showed characteristic bands at 236, 369, and 468 cm−1. The red pigment on the surface comprises of Hg, S, and minor amounts of Pb and is attributed to the minerals cinnabar (HgS) and minium (Pb3O4). The black pigment has high carbon content, attributed to organic material (black carbon). The micro-Raman spectroscopy provided a more detailed determination of the composition of the red and black pigments. In particular, the vivid red color was attributed to cinnabar (bands at 253 and 342 cm−1). Particles of black carbon (bands at 1345 and 1577 cm−1) and oxalates (band at 861 cm−1) were determined on the black pigments. Dark regions on the pigmented surface were assigned to a mixture of cinnabar [bands at 253 and 342 cm−1] and minium [bands at 120, 142, 288, and 545 cm−1]. The latter lead oxides might have been used either as a dryer or a burnish agent for the gold leaf. The micro-structural and chemical analysis of several distinct strata of the icon, as observed under ESEM, revealed a red-colored stratum beneath the gold leaf, with an iron aluminosilicate composition. This is the so-called bole (red clay) commonly used as sub-strata for gilding art objects. Multiple layers of white ground material, composed of gesso (gypsum) underlie the bole strata. Moreover, one thin organic binder (animal glue) was is observed within the gesso ground of the icon.

Chemical modification of alumina surface by immobilization of 1-((5-nitrofuran-2-yl)methylene)thiosemicarbazide for extractive concentration of silver ions

A column, solid phase extraction (SPE), preconcentration method was developed for determination of silver by using alumina coated with 1-((5-nitrofuran-2-yl)methylene)thiosemicarbazide and determination by flame atomic absorption spectrometry. The separation/preconcentration conditions for the quantitative recovery were investigated. At pH 2, the maximum sorption capacity of Ag+ was 7.5 mg g−1. The linearity was maintained in the concentration range of 0.02–11.0 µg mL−1 in the final solution or 0.14–1.10 × 104 ng mL−1 in the original solution for silver. The preconcentration factor of 140 and relative standard deviation of ±1.4% was obtained, under optimum conditions. The limit of detection (LOD) was calculated as 0.112 ng mL−1, based on 3σbl/m (n = 8) in the original solutions. The proposed method was successfully applied to the determination trace amounts of silver in the environmental samples such as tea, rice and wheat flour, mint, and real water samples.

Mineral chemical investigation on sulfide mineralization of the Istala deposit, Gümüşhane, NE-Turkey

The mineralogy of the Istala deposit, Gümüşhane, northeastern Turkey, was studied in detail, and a geochemical investigation was carried out using electron probe micro-analysis (EPMA). Sphalerite, galena, chalcopyrite and pyrite are the major sulfide minerals found in the Istala deposit, with minor amounts of bornite, idaite, tetrahedrite–tennantite, anilite, yarrowite, mckinstryite, covellite and chalcocite. In addition to these, barite and a small quantity of quartz occur as gangue minerals. Based on the textural relations and mineral assemblages, five different stages of crystallization have been recognized. Mineral paragenesis of the first four stages has been found to be similar, whereas clear enrichment has been observed in the modal abundance of the copper sulfide mineral assemblage at the fifth-stage ore formation. Whole-rock geochemical analyses of the Istala ore show an enrichment of Ag content up to 3328ppm. Optical observations and EPMA study indicated that abundant silver mineralization was found in the Istala ore, especially during the later-stage ore deposition. Repetition to the presence of native silver in the samples, a significant amount of silver was incorporated in bornite, idaite, tetrahedrite–tennantite, anilite, yarrowite, mckinstryite, covellite and chalcocite, whereas a trace amount of silver has been detected in sphalerite, galena, chalcopyrite and pyrite. The homogenization temperatures (Th) of the primary fluid inclusions were measured between 98 and 284°C, with frequency peaks around 140°C, 190°C and 240°C. All data obtained support the theory that later stage copper-rich sulfides, formed under the low temperature conditions, are responsible for the large amounts of silver content in the Istala mine.

Solid phase extraction of trace amounts of silver (I) using dithizone-immobilized alumina-coated magnetite nanoparticles prior to determination by flame atomic absorption spectrometry

A new, simple, fast and reliable solid-phase extraction (SPE) method has been developed to separation/preconcentration of trace amounts of silver ion from environmental water samples using dithizone/sodium dodecyl sulfate immobilized on alumina-coated magnetite nanoparticles (DTZ/SDS-ACMNPs) and its determination by flame atomic absorption spectrometry. The coating of alumina on Fe3O4 NPs not only avoids the dissolving of Fe3O4 NPs in acidic solution, but also extends their application without sacrificing their unique magnetization characteristics. This method avoided the time-consuming column-passing process of loading large volume samples in traditional SPE through the rapid isolation of DTZ/SDS-ACMNPs with an adscititious magnet. Optimal experimental conditions including amount of DTZ/SDS, pH value, standing time, sample volume, type, volume and concentration of eluent and co-existing ions have been studied and established. Under the optimal experimental conditions, the detection limit for Ag(I) with enrichment factors of 100 was found to be 0.52 ng mL−1 and its relative standard deviations (RSD) was 3.4% (n = 10, C = 5.0 µg mL−1). The linear range of calibration curve for Ag(I) was 2–5000 ng mL−1 with a correlation coefficient of 0.9991. The proposed method was successfully applied to the determination of target analyte in different water and wastewater samples. The validity of the method has been checked by applying it to study the recovery of silver ion in spiked water and wastewater samples.

Radiochemical separation of 109Cd from a silver target

A radiochemical separation method was developed for the separation of 109Cd from a nat.Ag target (6.6 g, pressed into a 19 mm disc). The method comprised of two stages. In the first stage, after dissolution of the target in nitric acid, silver was separated from Cd by precipitation into the metallic form using 20 g of Cu turnings for the reduction of Ag+ ions. In the second stage, 109Cd in the filtrate, that contained trace amount of silver and substantial quantity of Cu(I), was purified by use of a Bio-Rad AG1-X10 anion-exchange resin. The ion-exchange chromatography employed a column with (1.6 cm i.d. and 4 cm length) with a flow rate of 2 ml/min throughout the separation. 109Cd was quantitatively recovered from the first stage and the recovery yield from the ion-exchange chromatography was greater than 96%. 2M HCl containing H2O2 was used for the adsorption of 109Cd and elution of Cu. 109Cd was eluted by 50 ml 1M HNO3. The concentrations of stable isotopes of Ag and Cu in the final solution (5 ml 0.05M HCl) were measured by an ICP-OES method and found to be <1 ppm.

Optical gratings embedded in photosensitive glass by photochemical reaction using a femtosecond laser

We describe a new approach to the internal refractive index modification of glass by a femtosecond (fs) laser. The glass we used is a photosensitive glass Foturan which contains trace amounts of silver. Silver nanoparticles, which is responsible for the refractive index change, can be formed in the glass after exposed to the fs laser and then postbaked at an appropriate temperature between 500 degrees C and 550 degrees C. In this work, latent images of grating structures are first inscribed into the photosensitive glass by photochemical reaction of a tightly focused fs laser beam with an intensity much lower than the threshold of optical breakdown. After this step, no measurable diffraction can be observed by irradiating the gratings with a He-Ne laser beam. The samples are then baked at 520 degrees C for various durations from 3h to 18h. Diffraction of the optical grating embedded in the glass can now be observed, and the diffraction efficiency increases with postbaking duration, indicating that a refractive index change occurs in the modified regions. The relationship between the refractive index change and the postbaking duration is systematically investigated.

Catalytic Kinetic Spectrophotometric Determination of Trace Amounts of Silver in Triton X-100 Micellar Medium

A catalytic method has been developed for the determination of trace amounts of Ag+ in Triton X-100 micellar medium. The method is based on the catalytic effect of silver(I) on the rate of a ligand substitution reaction between potassium ferrocyanide and 4,7-biphenyl-1,10-phenanthroline (BPT). The reaction was followed spectrophotometrically at 536 nm by measuring the induction period. Beer's law was obeyed in the range of 0–0.040 µg/mL Ag+ and the apparent molar absorptivity was 2.43 × 106 L mol−1 cm−1. Both the influence of reaction variables and the interference of coexistent ions were studied. The proposed method has been applied to the wastewater samples with satisfactory results. The recoveries were between 93.2 and 107% and the RSD was below 4.0%.

The Leaching of Gold in Cyanide Solutions in the Presence of Impurities II. The Effect of Silver

In the present study, a rotating electrochemical quartz crystal microbalance was used to investigate the effect of silver on the leaching of gold in aerated alkaline cyanide solutions. It was found that trace amounts of silver in the solid phase significantly enhances the leaching rate, and it is believed that the role of silver is to disrupt the film of AuCN which exists on the gold surface. In the presence of silver, the rate‐determining step is the mass transfer of reactants, with the rate being limited by cyanide diffusion at low cyanide concentrations, and oxygen diffusion (jointly) at high cyanide concentrations. Such a result is similar to the pioneering results of Kudryk and Kellogg [J. Met., 6, 541 (1954)], suggesting that their work was carried out using silver contaminated gold. Complementary electrochemical studies showed that the oxidation of gold containing 1% silver was cyanide diffusion controlled at relatively low overpotentials, suggesting that surface films do not hinder the oxidation of gold/silver alloys in the same way in which they block the oxidation of pure gold. © 2000 The Electrochemical Society. All rights reserved.

PRE‐COLUMBIAN METALLURGY: TECHNOLOGY, MANUFACTURE, AND MICROPROBE ANALYSES OF COPPER BELLS FROM THE GREATER SOUTHWEST*

Twenty‐four cast copper crotals (commonly called bells), one 'spilled bell’, one tinkler bell and a number of minerals from locations throughout the Greater Southwest were analysed for their elemental composition by a PIXE nuclear microprobe at Los Alamos National Laboratory, New Mexico, USA. Sixteen bells contained minor and trace amounts of silver, antimony, arsenic, lead, and in some cases tin, strontium, and selenium. Nine bells contained little or no detectable amounts of these elements. This suggests that several workshops throughout the Greater Southwest and Mexico might have manufactured these bells.

Chemical modifier methods for the determination of bismuth and silver in nickel-based alloys and steels by Zeeman electrothermal atomization

A reliable ETAAS method for determining trace amounts of silver and bismuth in a wide range of nickel superalloys and steels has been developed. This uses a single matrix calibration based on nickel and suitable chemical modifiers, such as hafnium and tartaric acid for bismuth and ammonium dihydrogen phosphate for silver. Detection limits are 0.06 µg dm–3 for silver and 1 µg dm–3 for bismuth. The method allows a wide range of alloy types to be analysed from a common set of calibration standards, which considerably simplifies and shortens the analysis.

Flame atomic absorption spectrometric determination of silver in geological materials using a flow-injection system with on-line preconcentration by coprecipitation with diethyldithiocarbamate

Trace amounts of silver in geological samples were determined by flame atomic absorption spectrometry. The analyte was preconcentrated and separated from the bulk of the matrix by on-line coprecipitation with the iron(II)-diethyldithiocarbamate complex in the presence of 1,10-phenanthroline in a flow-injection system. The precipitate was collected in a knotted reactor without using a filter. The precipitate was dissolved in isobutyl methyl ketone and introduced directly into the nebulizer-burner system of an atomic absorption spectrometer. 1,10-Phenanthroline was added to the sample solution to mask large concentrations of iron(II). The tolerance of the method for iron was thus increased to 4 g 1 −1. An enhancement factor of 26 and a concentration efficiency of 28 min −1 were obtained for a coprecipitation time of 45 s, resulting in a sampling frequency of 62 h −1. The detection limit (3σ) in the sample solution of 0.5 μg 1 −1. The relative standard deviation at the 30 μg 1 −1 level was 2.1%. The analytical results obtained for geological reference materials were in good agreement with the certified values.

Preconcentration of trace amounts of silver and cadmium by ion exchange and micro-extraction from water for flame atomic absorption spectrometry

A method based on a combination of ion exchange and micro-extraction is suggested for preconcentrating silver and cadmium from lake water. These metals were sorbed on a mini-column loaded with a strongly basic anion-exchange resin in the form of halide complex anions, and then silver was eluted with 6 mol l–1 hydrochloric acid and cadmium with 2 mol l–1 nitric acid. The metals were further concentrated into 0.2 ml of butyl acetate with potassium iodide and Zephiramine as extraction agents. For flame atomic absorption spectrometric determination, 20 µl of the organic phase were nebulized. Optimum conditions for ion exchange and liquid–liquid extraction were established, and data on interferences, precision and detection limits were determined. Using calibration graphs, the contamination level of cadmium in preconcentration processes was also estimated. Sub-µg l–1 levels of silver and cadmium in water could be determined with a concentration factor of 10 000 by the proposed method.