Strategies for the analysis of coal by laser ablation inductively coupled plasma mass spectroscopy

A comparison between a laser-induced breakdown spectrometry-partial least squares (LIBS-PLS) method and methods based on some well-known techniques, such as induced-coupled plasma-atomic emission spectrometry (ICP-AES), flame atomic absorption spectrometry (FAAS), and atomic scanning microscopy (ASM) is presented in order to both validate the content of gold and silver in alloys to be used as solid standards and develop an alternative to the established methods for the hallmark of gold and silver in jewelry pieces. 17 alloys with gold concentrations ranging from 100 to 50% and 8 alloys with silver concentrations between 100 and 80% and variable concentrations of other metals usually present in jewels were used as solid standards in LIBS in order to develop a method as general as possible. The results obtained in the analysis of some alloys (9 for gold and 7 for silver) show that the proposed method is comparable with the official one.     

Analytical Analysis of Different Karats of Gold Using Laser Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Time of Flight Mass Spectrometer (LA-TOF-MS)

Laser induced breakdown spectroscopy (LIBS) coupled with a laser ablation time of flight mass spectrometer (LA-TOF-MS) has been developed for discrimination/analysis of the precious gold alloys cartage. Five gold alloys of Karats 18K, 19K, 20K, 22K and 24K having certified composition of gold as 75, 79, 85, 93 and 99.99% were tested and their precise elemental compositions were determined using the laser produced plasma technique. The plasma was generated by focusing beam of a Nd:YAG laser on the target in air and its time integrated emission spectra were registered in the range 250–870 nm. The calibration free LIBS technique (CF-LIBS) was used for the quantitative determination of the constituent elements present in different Karats of gold. Elemental compositions of these gold alloys were also determined using a Laser Ablation time of flight mass spectrometer (LA-TOF-MS). The LIBS limit of detection was calculated from the calibration curves for copper, silver and gold. Results of CF-LIBS and LA-TOF-MS are in excellent agreement with the certified values. It is demonstrated that LIBS coupled with LA-TOF-MS is an efficient technique that can be used to analyze any precious alloys in a fraction of a second.     

Gold recovery onto poly(acrylamide-allylthiourea) hydrogels synthesized by treating with gamma radiation

Poly(acrylamide-1-allyl-2-thiourea) hydrogels, Poly(AAm-ATU), were synthesized by gamma irradiation using a ⁶⁰Co γ source at different irradiation dose rates and in a monomer mixture with different 1-allyl-2-thiourea contents. These hydrogels were used for the specific gold recovery from single and competitive media. It was observed that the gold adsorption capacity onto the hydrogels was high at low pHs and reached a maximum value at pH 0.5. It was found that the adsorption capacity of the hydrogels for gold ions in acidic media around pH 0.5 was high and about 940 mg g⁻¹ dry hydrogel. Adsorption of these hydrogels for gold ions was found to be very fast and also these hydrogels were showed extremely high selectivity to the gold ions in acidic media even when the concentrations of the other metal ions were extremely higher than that of the gold. Because of the high specificity of these hydrogels to gold ions compared with the other metal ions at low pHs, all matrix effects could be easily eliminated by adsorbing gold ions onto the hydrogels at around pH 0.5 and desorbing into 0.8 M thiourea in 3.0 M HCl. The swellability of the synthesized hydrogels varied with irradiation dose rates and increased at high irradiation dose rates. The minimum swellability of the hydrogels was found to be at least 1000% which made it attractive for gold to penetrate into the hydrogels and react with all the functional groups in the interior surface of the hydrogels.     

Study of order—disorder transformation of copper—gold alloys by means of differential thermal analysis

Several copper-gold alloys, with compositions of between 10 and 80 atomic percent of gold, were examined by quantitative DTA from 25 to 500°C. The results are in good agreement with those obtained by other less rapid, but more accurate, methods. All the reactions observed were first-order transformations. A latent heat (180 ± 40 cal g-at^?1) was measured at 405°C for the α″_I → α″_II transformation of the alloy containing 50% of gold. An endothermic effect, corresponding to an order—disorder reaction, was detected for all alloys, up to a composition of over 90 atomic percent of gold.     

The effect of the ordered phase CuAu on the accuracy of emission analysis of gold alloys

The accuracy of emission determinations of gold, silver and copper in ordered Au/Ag/Cu alloys is compared with similar determinations when these alloys are disordered. The relative slope factors, K_Cu and K_Ag, depend on the concentration of copper present. The accuracy obtained in the analysis of the disordered alloys cannot be achieved for the ordered ones unless the standards used closely match the samples in composition. The ordered phase responsible for the effect is CuAu.     

银-金合金催化乙烯氧化反应的动力学研究 Ⅰ. 氧在银-金合金表面上吸附的LEPS势能面

本文用LEPS势能函数描述了氧与银-金合金(110)面的相互作用。计算了不同金配比时氧在合金(110)面上吸附的势能面, 讨论了不同金配比对势能面的影响, 以及对氧吸附的影响。     

Comments on the paper: “Accurate quantitative analysis of gold alloys using multi-pulse laser-induced breakdown spectroscopy and a correlation-based calibration method”

The problem of finding new methods for the analysis of precious alloys has stimulated, in recent years, a number of different proposals for improving the analytical procedures introducing more robust calibration (or calibration-free) methods. In the paper “Accurate quantitative analysis of gold alloys using multi-pulse laser-induced breakdown spectroscopy and a correlation-based calibration method” by G. Galbács, N.Jedinski, G.Cseh, Z. Galbács and L. Túri [Spectrochimica Acta Part B, Volume 63, Issue 5, 591–597 (May 2008)] the authors proposed the use of multiple-pulse LIBS and a correlation-based method for building calibration curves for quantitative analysis of gold alloys. The method is proposed for gold alloys prepared using a fixed proportion of the alloying element. The general case where the relative concentration of the elements of the matrix is not a priori known is not discussed in the paper. In this communication, we will demonstrate that the method proposed is extremely fragile against matrix effects, and therefore cannot be usefully applied for the purpose of actual analytical measurements on gold alloys without a previous knowledge of the matrix composition.     

Determination of arsenic in gold by flow injection inductively coupled plasma mass spectrometry with matrix removal by reductive precipitation

Arsenic was determined in gold by flow injection hydride generation inductively coupled plasma-mass spectrometry following a batch mode reductive precipitation removal of the interfering gold matrix. A solution of potassium iodide, L-ascorbic acid, and hydrochloric acid was used as the reluctant. The recovery of gold by precipitation and filtration was 99 ± 3%. The detection limit for arsenic in gold was 55 ng g⁻¹ in the solid. The concentration of arsenic that was determined in the Royal Canadian Mint gold sample FAU-10 was 29.7 μg g⁻¹ in the solid; this value was indistinguishable, with 95% confidence, from values determined at the Royal Canadian Mint by graphite furnace atomic absorption spectrometry and by inductively coupled plasma-mass spectrometry. The standard deviation for four replicate determinations of the arsenic in FAU-10 was 0.972 μg g⁻¹ in the solid.     

Thermodynamische Untersuchung des systems gold—nickel

The enthalpies of solution of solid nickel in liquid gold at 1110°C in the concentration range between 0 and 42.2 at. % nickel were determined with the aid of a high temperature calorimeter. The enthalpies of solution of gold—nickel solid solutions of the entire concentration range in liquid copper were determined in like manner. From the experimental results the enthalpies of mixing of the liquid and solid gold—nickel solutions could be obtained. An evaluation of the melting equilibria provided the excess entropies and the free enthalpies of mixing of the liquid alloys. Besides the change of the interatomic attraction on alloy formation, the marked difference in atomic radii of the components in the gold—nickel system is of considerable influence on the thermodynamic properties of both the solid and the liquid alloys. This is shown in a discussion.     

Chemical characterization and evaluation of antimicrobial and cutaneous wound healing potentials of gold nanoparticles using Allium saralicum R.M. Fritsch

The use of herbal medicines dates back a long way in history. Herbal medicines have been widely used all over the world since ancient times and have been recognized by physicians and patients for their good therapeutic value as they have fewer adverse effects than modern medicines. Recently, researchers have used gold nanoparticles synthesized by plants in the prevention, control, and treatment of infectious disorders and cutaneous wounds. The aims of this study were to synthesize gold nanoparticles from aqueous extract of Allium saralicum R.M. Fritsch (AuNPs) and assess their therapeutic capacities. The nanoparticles were characterized by UV–visible spectroscopy (UV–Vis), Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). FT-IR results offered polysaccharides and protein in A. saralicum were the sources of reducing power, reducing gold ions to AuNPs. According to XRD analysis, the crystal size of the nanoparticles was 41.6 nm. TEM and FE-SEM images exhibited average diameters of 45 nm for the biosynthesized nanoparticles. The synthesized AuNPs had great cell viability on HUVECs line and showed this method was nontoxic. The 2,2-diphenyl-1-picrylhydrazyl free radical scavenging test indicated similar antioxidant potentials for A. saralicum, AuNPs, and butylated hydroxytoluene. To determine the antifungal and antibacterial properties of HAuCl₄, A. saralicum, and AuNPs, agar diffusion tests were used. The aim of the application both HAuCl₄ and A. saralicum in microbial tests was to investigate the synergism effects between them. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC) were specified by macro-broth dilution assay. AuNPs exhibited higher antifungal and antibacterial effects than all standard antibiotics (p ≤ 0.01). The MIC and MBC of AuNPs against all bacteria were in the ranges 1–4 mg/ml and 2–8 mg/ml, respectively. The MIC and MFC of AuNPs against all fungi were in the ranges 1–4 mg/ml and 2–4 mg/ml, respectively. In vivo part, AuNPs ointment group raised significantly (p ≤ 0.01) the wound contracture, vessel, hydroxyl proline, hexuronic acid, fibrocyte, fibroblast, and fibrocytes/fibroblast rate and decreased significantly (p ≤ 0.01) the wound area, total cells, and lymphocyte compared to other groups in rats. The results of FT-IR, UV–Vis, XRD, TEM, and FE-SEM analyses confirm that the aqueous extract of A. saralicum leaves can be used to yield gold nanoparticles with a notable amount of remedial effects without any cytotoxicity against HUVECs.     

A gold nanoparticle-based immunochromatographic assay: the influence of nanoparticulate size

Four different sized gold nanoparticles (14 nm, 16 nm, 35 nm and 38 nm) were prepared to conjugate an antibody for a gold nanoparticle-based immunochromatographic assay which has many applications in both basic research and clinical diagnosis. This study focuses on the conjugation efficiency of the antibody with different sized gold nanoparticles. The effect of factors such as pH value and concentration of antibody has been quantificationally discussed using spectra methods after adding 1 wt% NaCl which induced gold nanoparticle aggregation. It was found that different sized gold nanoparticles had different conjugation efficiencies under different pH values and concentrations of antibody. Among the four sized gold nanoparticles, the 16 nm gold nanoparticles have the minimum requirement for antibody concentrations to avoid aggregation comparing to other sized gold nanoparticles but are less sensitive for detecting the real sample compared to the 38 nm gold nanoparticles. Consequently, different sized gold nanoparticles should be labeled with antibody under optimal pH value and optimal concentrations of antibody. It will be helpful for the application of antibody-labeled gold nanoparticles in the fields of clinic diagnosis, environmental analysis and so on in future.     

Spontaneous alloying of gold clusters into nanometer-sized antimony clusters

Alloying behavior of gold into nm-sized amorphous antimony (a-Sb) clusters has been studied by transmission electron microscopy (TEM), employing gold clusters in contact with a-Sb clusters. In order to produce gold clusters on individual a-Sb clusters, a-Sb clusters on an amorphous carbon film were cooled down to 96 K, and gold was then condenced on the film. When gold clusters in contact with a-Sb clusters are gradually heated from 96 to 290 K, dissolution of gold into a-Sb clusters sets in around 200K and clusters of a-(Sb-Au) alloys are produced. With increasing annealing temperture, more gold is absorbed into individual a-Sb clusters, and when the gold concentration in a-(Sb-Au) clusters reaches to the stoichiometric composition of AuSb₂, these amorphous clusters crystallize into AuSb2 clusters. The crystallization temperature decreases with decreasing size of initial a-Sb clusters.     

The anodic oxidation of gold + palladium alloys

The anodic oxidation of Au+Pd alloys has been studied in solutions of 1 M H₂SO₄ and 0.1 M K₂SO₄ by voltammetric methods. A linear relationship between oxide reduction maximum and bulk alloy composition, often used to determine the surface composition of homogeneous alloys, could be shown to hold only for alloys up to 60 at% gold. At higher gold content the Au oxide peak must be additionally evaluated. With continuous cycling in acid solution the anodic dissolution of Pd, especially from gold-rich places, leads to a rather heterogeneous surface. The O--chemisorption is not governed by a transfer mechanism from Pd to Au surface atoms. The alloys are able to absorb the oxygen species generated in the positive potential region; however, this ability decreases with increase of the gold content.     

Oberfl?chensegregation an Au-Pd-Legierungen

Summary Measurements of the surface composition of Au-Pd binary alloys performed by Ion Scattering Spectroscopy (ISS) and X-ray Photoelectron-Spectroscopy (XPS) are presented. A set of 11 alloys with different bulk composition was used for these studies. Argon bombardment induced alternation of the surface composition due to preferential sputtering effects and surface segregation due to temperature excursions up to 500 °C have been studied. For quantitative evaluation of the ISS spectra pure metal standards and also calculated scattering cross sections were used. In general, little gold enrichment due to preferential sputtering and strong surface segregation of gold at elevated temperature was found by ISS measurements. The thickness of the altered layer is about 1 or 2 monolayers.     

Effects of iridium content on the physical,microstructure, and assay of gold alloys during the cupellation process

The aim of the present study is developing a simple, commercially available, and inexpensive method for detecting the presence of Ir in gold alloys during the cupellation process to avoid errors in gold assays. In the presence of Ir, the reported gold karat is higher than its actual amount. It is, therefore, economically important to detect Ir in gold alloys because of its lower price than gold. The present study was implemented to investigate the effects of Ir in a gold alloy both on its assay during the cupellation process and on its appearance and microstructural transformations. Visual inspection revealed that the upper surface of Ir-containing beads is typically matte and coarse with black rough cavities of an irregular oval-like shape. Also, the observation of dark spots and lines on just one side of rolled beads, as well as blister-like appendages on parted and annealed cornets, were found to signify the presence of Ir in gold alloys. X-ray analysis along the vertical section of the bead indicated that the amount of Ir on the surface was negligible as it was mainly concentrated at a distance of about 75% from the top of the bead. After the parting and annealing steps, Ir forms cubic-like structures surrounded by fcc Au sponge-like structures. As a consequence, both visual and microstructural examinations of gold alloys during the cupellation process might be used as simple and useful strategies to identify the presence of Ir in gold alloys to prevent incorrect karat reports.     

Non-monotonic behaviour with concentration of the surface tension of certain binary liquid alloys

The surface tension σ(c) of most liquid binary alloys usually varies with concentration c in a monotonic way between the values σ₁ and σ₂ of the two pure metals, and this behaviour is well explained by current models. Some alloys show deviations from this ideal behaviour. One of those is Fe–B. The surface tension of this liquid alloy shows a minimum at 17 atomic % B, which corresponds well with the composition of the eutectic point in the phase diagram, followed by a maximum at a concentration of 24 atomic % B or higher. The usual models for the surface tension of liquid binary alloys do not explain those exceptional features, and we propose that a model involving the concentration fluctuations in the liquid alloy has the proper ingredients to account for the features in Fe–B and similar alloys.     

Rules for stating when a limiting value is exceeded

The paper describes rules for stating whether a measurement result indicates that the value of the measurand, e.g. the concentration of a substance in the blood, is in conformity or not in conformity with given specifications. Examples of the intended applications are control of doping in sports, alcohol level in drivers’ blood, trace metals levels in workers’ blood, the proportion of gold in alloys, certain ingredients in food products and pesticides in drinking water. When limiting value(s) have been established a permissible measurand value is said to be in conformity and a non-permissible value it is said to be in non-conformity. One of the following three statements is asserted: Statement A: The value of the measurand is beyond any reasonable doubt in conformity, Statement B: The value of the measurand is beyond any reasonable doubt in non-conformity, Statement C: Neither conformity nor non-conformity could be demonstrated. The test can be performed as either a one-stage or a two-stage procedure. A two-stage procedure is recommended as especially appropriate when a cheap and fast screening method can be used in the first stage. For normally distributed measurements, a freeware computer program, conform1e.exe, is available for the calculations of the probabilities for Statements A, B and C.     

Water-Diesel Microemulsions Stabilized by an Anionic Extended Surfactant and a Cationic Hydrotrope

Alcohol-free microemulsions were formulated using mixtures of extended surfactant (C_12-14-PO₁₄-EO₂SO₄Na), sodium dodecyl benzene sulfonic acid and cationic hydrotropes with equal amounts of water and diesel. The cationic hydrotropes had short hydrocarbon or propylene oxide chain. The formulation included sodium carbonate to convert naphthenic acids in diesel to soaps. The phase behavior at ambient temperature of oil-free mixtures as a function of NaCl concentration was investigated. Visual inspection as well as cross polarizers were used to detect anisotropy. The microemulsion fish phase diagram and solubilization ratios for diesel and brine in the middle phases were determined. The minimum surfactant concentration needed to initiate middle phase formation was 0.10 wt%.

Salinity scans revealed that optimal salinity can be adjusted according to the hydrophilic/lipophilic nature of the hydrotrope used. Interfacial tension measurements using a spinning drop tensiometer showed a minimum value of 0.0015 mN/m between middle phase microemulsion and excess brine and a value of 0.032 mN/m between diesel and brine.     

Biosynthesis of Gold Nanoparticles by Streptomyces sp. ERI-3 Supernatant and Process Optimization for Enhanced Production

In this study, we present a simple and eco-friendly method for extracellular biosynthesis of gold nanoparticles by Streptomyces sp. ERI-3 cell-free supernatant. The research was also aimed to evaluate the effects of different reaction parameters including incubation temperature, reaction time, HAuCl₄ concentration and pH on gold nanoparticles production. The UV?CVis spectroscopy was used to monitor the formation of gold nanoparticles. The synthesized gold nanoparticles were characterized with XRD, TEM, and SEM. The average particle size ranged from 10 to 30?nm with spherical shape at optimum conditions.     

金纳米粒子在TiO2气凝胶基质上的行为: 光催化活性评价和结构研究

TiO2 -Au aerogels containing different amounts of gold nanoparticles of different sizes (5 and 16 nm) were successfully synthesized using a sol-gel procedure, and were tested for salicylic acid photodegradation under UV irradiation. The structure and morphology of the obtained materials were investigated using X-ray diffraction, transmission electron microscopy, and N2 adsorption-desorption measurements. UV-Vis spectroscopy was used to study the optical properties. The effects of the gold nanoparticles on the TiO2 crystallization process were twofold, as follows: (i) the number of crystallized zones was strongly related to the concentration of the gold nanoparticles, and (ii) the smaller gold particles increased the time taken for the crystallization of the samples. It was found that the noble metal-doped samples exhibited higher degradation rates compared with bare titania. It was found that the most active photocatalyst in each studied system was the sample with the highest concentration of gold nanoparticles. Additionally, the highest degradation rate value was obtained with the smallest Au nanoparticles (46.4 10-3 μmol/(L·s).