Gold bearing ore assays using 197Au(γ,n)196Au photonuclear reaction

We performed computational and experimental studies of the feasibility of the gold bearing ore assay utilizing the ¹⁹⁷Au(γ,n)¹⁹⁶Au photonuclear reaction. Gold bearing silicate samples were irradiated using bremsstrahlung produced by an electron accelerator with endpoint energies ranging from 25 to 40 MeV. ¹⁹⁶Au yield simulations were benchmarked and experimental results were in good agreement with the predictions. Optimum electron beam energy for photon activation analysis was found to be around 32 MeV which corresponded to a detection limit of 80 ppb. Two-hour gamma-spectroscopy measurements were repeated every 24 h and the optimum sample cooling time was found to be about 100–160 h.     

Displacement solid-phase extraction on mercapto-functionalized magnetite microspheres for inductively coupled plasma mass spectrometric determination of trace noble metals

A flow injection online displacement solid-phase extraction (DSPE) via magnetic immobilization of mercapto-functionalized magnetite microspheres onto the inner walls of a knotted reactor (KR) coupled with inductively coupled plasma mass spectrometry was developed for selective preconcentration and determination of trace noble metals (Ru, Rh, Pd, Pt, Ir and Au) in complex matrices. Online DSPE of 2.7 mL aqueous solution gave the enhancement factors of 32-46 for the six noble metals in comparison with direct nebulization of aqueous sample solution, and the detection limits (3 s) of 2.1 ng L(-1) for Ru, 1.9 ng L(-1) for Rh, 2.5 ng L(-1) for Pd, 1.8 ng L(-1) for Ir, 1.9 ng L(-1) for Pt and 1.7 ng L(-1) for Au. The sample throughput of the developed method was about 20 samples h(-1), and the relative standard deviation for eleven replicate determinations of the noble metals at the 30 ng L(-1) level ranged from 1.2% to 2.1%. The recoveries of Ru, Rh, Pd, Pt, Ir and Au still maintained 90% even after successive 140 cycles of DSPE. The developed method was successfully applied to selective determination of trace Ru, Rh, Pd, Pt, Ir and Au in complex matrices.     

Quantitative analysis of precious metals in automotive shredder residue/combustion residue via EDX fluorescence spectrometry

The recovery of precious metals from automotive shredder residue (ASR) dust/combustion residue is an option that is not usually considered due to the lack of available information. Therefore, before any disposal or recovery application can be considered, it is necessary to determine the significance of the levels and distribution of precious metal in ASR dust/ASR combustion residue. In the present study, quantitative analysis of precious metals (Pt, Pd, Au, Ag and Cu) in the ASR residue samples was performed using energy dispersive X-ray (EDX) fluorescence spectrometer. With the fundamental parameter (FP) method, the X-ray intensity is obtained and the quantitative analysis is performed using theoretical calculation. This method is very effective for quantitative analysis of unknown samples without standard samples. Further, in order to analyse the precious metal distribution within the ASR combustion residues, the microstructural characterisation and elemental mapping were also carried out with the aid of field emission scanning election microscopy combined with electron dispersive spectroscopy (FE-SEM EDS). Significant amount of Pt, Pd, Au, Ag and Cu element concentrations in the ASR residue were identified. Total precious (Pt, Pd, Au, Ag and Cu) metals obtainable values are representing about 12.23 wt% from its initial ASR dust/combustion residues. Considering their relevant concentrations, these metals should be properly recovered for recycling purposes before to dispose or landfill.     

Missing row reconstructed (110), (211) and (311) surfaces for FCC transition metals

Modified embedded atom method (MEAM) has been used to ascertain the change in the surface energy density of (1 × 2) missing row (MR) reconstruction from initial (1 × 1) ideal (110), (211) and (311) surfaces for seven FCC transition metals Au, Pt, Ag, Pd, Rh, Cu and Ni. The results show that the MR reconstruction can be formed naturally on the Au (110), Pt (110) and Pt (311) surfaces and are better than calculated results of the embedded atom method (EAM) while comparing with experimental results. In addition to the surface energy explanation, the results are also explained in terms of the valence electron structure and surface topography. Copyright © 2007 John Wiley & Sons, Ltd.     

Electrothermal atomization-laser induced fluorescence determination of iridium,rhodium, palladium,platinum and gold at the ng/l level in pure water

Trace determination of Au, Rh, Ir, Pd and Pt in pure water solution has been performed by electrothermal atomization-laser induced fluorescence (ETA-LIF). Limits of detection obtained are in the ng/l⁻¹ range, improving previously published absolute limits of detection by one or two orders of magnitude. The day to day reproducibility for iridium is around 8%. Thus, the ETA-LIF technique can be used routinely for the determination of precious metals at ultratrace concentrations.     

Determination of Background Concentrations of Ag,Pd, Pt and Au in Highly Mineralized Ground Waters at Sub-ng L–1 Concentrations by Online Matrix Separation/Pre-Concentration Coupled to ICP-SFMS

Though not regulated in directives such as the Water Framework Directive of the European Union, the investigation of geogenic background concentrations of certain elements such as precious metals is of increasing interest, in particular for the early detection of a potential environmental pollution due to the increased use in various industrial and technological applications and in medicine. However, the precise and accurate quantification of precious metals in natural waters is challenging due to the complex matrices and the ultra-low concentrations in the (sub-) ng L⁻¹ range. A methodological approach, based on matrix separation and pre-concentration on the strong anion exchange resin TEVA^® Resin in an online mode directly coupled to ICP-SFMS, has been developed for the determination of Ag, Pt, Pd and Au in ground water. Membrane desolvation sample introduction was used to reduce oxide-based spectral interferences, which complicate the quantification of these metals with high accuracy. To overcome errors arising from matrix effects—in particular, the highly varying major ion composition of the investigated ground water samples—an isotope dilution analysis and quantification based on standard additions, respectively, were performed. The method allowed to process four samples per hour in a fully automated mode. With a sample volume of only 8 mL, enrichment factors of 6–9 could be achieved, yielding detection limits <1 ng L⁻¹. Validation of the trueness was performed based on the reference samples. This method has been used for the analysis of the total concentrations of Ag, Pt, Pd and Au in highly mineralized ground waters collected from springs located in important geological fault zones of Austria’s territory. Concentrations ranges of 0.21–64.2 ng L⁻¹ for Ag, 0.65–6.26 ng L⁻¹ for Pd, 0.07–1.55 ng L⁻¹ for Pt and 0.26–1.95 ng L⁻¹ for Au were found.     

Determination of trace elements including platinum in tree bark by ICP mass spectrometry

The increasing emission of Pt-group metals from automobile catalytic converters requires the development of highly sensitive procedures for ultratrace analysis of environmental and biological systems. Tree bark, located close to motorway or industrial areas, was utilised as a substrate for collection of airborne particulate matter and samples after digestion (microwave assisted dissolution with HNO₃ and HCl) were analysed by ICP mass spectrometry. The study targeted Pt and other metallic contaminants and involved analysis of some 57 tree bark samples using both quadrupole and double-focusing sector field ICP mass spectrometers. Detection limits for platinum determination in tree bark were 0.03 ng/g (DF-ICP-MS) and 0.2 ng/g (ICP-QMS). The platinum content of the bark samples ranged from 0.07–5.4 ng/g.     

Assessment of exposure to platinum-group metals in urban children

Catalytic converters for automotive traction raise some concern for human health and the environment, due to the release of Pd, Pt and Rh (Pt-Group Metals, PGMs). In fact, the thermal and mechanical conditions under which such devices work (including abrasion effects and hot-temperature chemical reactions with oil fumes) can cause significant release of the PGMs to the environment and eventually affect human health. A pilot investigation was performed to assess the exposure to these metals of 310 schoolchildren aged between 6 and 10 years from the urban and suburban area of Rome. All determinations were performed by high-resolution magnetic-sector inductively-coupled plasma-mass spectrometry after UV irradiation of the samples. The mean concentration values of these metals in urine were found to be (in ng/g creatinine) 7.5±5.4 for Pd, 0.9±1.1 for Pt and 8.5±8.0 for Rh. Urine concentrations of Pd and Rh (but not Pt) were found to be strongly associated with traffic density in the area of residence.     

Determination of trace elements including platinum in tree bark by ICP mass spectrometry

The increasing emission of Pt-group metals from automobile catalytic converters requires the development of highly sensitive procedures for ultratrace analysis of environmental and biological systems. Tree bark, located close to motorway or industrial areas, was utilised as a substrate for collection of airborne particulate matter and samples after digestion (microwave assisted dissolution with HNO3 and HCl) were analysed by ICP mass spectrometry. The study targeted Pt and other metallic contaminants and involved analysis of some 57 tree bark samples using both quadrupole and double-focusing sector field ICP mass spectrometers. Detection limits for platinum determination in tree bark were 0.03 ng/g (DF-ICP-MS) and 0.2 ng/g (ICP-QMS). The platinum content of the bark samples ranged from 0.07-5.4 ng/g.     

Fast determination of gold in large mass samples of gold ores by photoexcitation reactions using 10 MeV bremsstrahlung

The determination of gold is based on the photoexcitation reaction ¹⁹⁷Au(γ,γ’)^197mAu with the half-life of 7.73 seconds and energy of emitted gamma-rays of 279 keV. Three 100 ml aliquots of coarsely ground Au-ore (grains <2 mm) corresponding to ca. 150–180 g were irradiated for 20 seconds with bremsstrahlung of maximum energy 10 MeV produced by a microtron at the electron beam current of 30–40 μA, 1–10 times reactivation was applied. After 3 seconds of decay, samples were measured for 20 seconds using scintillation or semiconductor gamma-spectrometry with the detection limits for an ideal sample down to 0.5 μg·g⁻¹ and 0.1–0.2 μg·g⁻¹ of Au, respectively. Content of U and Th undergoing photo-fission increases the detection limits several times.     

Separation of some platinum group metal chelates with 8-hydroxyquinoline by various high-performance liquid chromatographic methods

Different HPLC methodologies are employed to evaluate the separation and determination of some platinum metals (Pt, Pd, Ir and Rh) after the formation of 8-hydroxyquinolate chelates. With the aim of reducing the number of steps in treating the samples, the method developed did not include the elimination of excess chelating reagent before the analysis of metal chelates. Reversed-phase (RP), non-aqueous reversed-phase (NARP) and normal-phase (NP) HPLC are compared. The RP-HPLC method only permits the quantitative separation of Rh and Pd from the excess reagent. A silica column can be used to separate Ir and Rh by NP-HPLC. The NARP-HPLC method allows for the effective separation of the four elements tested, but the high detection limit (90 ng) for platinum and the peak width do not favour its application for quantitative measurement. Platinum group metals can be quantitatively separated and determined by NP-HPLC using a cyano column in less than 15 min. The broad linear range of all the elements (between 1 and 500 ng) is superior to that which has been previously reported and the detection limits (1.0 ng for Pt, 0.3 ng for Pd, 1.0 ng for Ir and 0.3 ng for Rh) are slightly lower.     

Determination of the noble metals in chromites and other geological materials by radiochemical neutron activation analysis

A procedure is described for determining the noble metals in geological samples of varied composition (Si enriched or Cr enriched). This rapid separation procedure allows very low detection limits for all PGE (except Rh) and Ag. It uses the coprecipitation of Pd, Pt, Au, Ag and Ru with Se and Te, and the fixation of Os on an ion-exchange resin. Ir is systematically determined by epithermal NAA using multiparameter coincidence spectrometry.     

Ion chromatography of chloro complexes of the platinum group metals and gold using bonded phase silica substrates

The ion chromatography of chloro complexes of Au(III), Ir(IV), Ir(III), Os(IV), Pd(II), Pt(IV), Rh(III) and Ru(III) was investigated using anion-exchange and ion-interaction techniques involving silica-based phases. Chloride was either absent or at a very low level and the pH was high enough to enable steel-fabricated liquid chromatography equipment to be used. With anion exchange, Ir(IV), Ir(III), Os(IV) and Pt(IV) gave good stable chromatography and all produced linear calibration plots, except Ir(IV) owing to instability of the sample solution. The detection limits were Ir(III) 5, Os(IV) 10 and Pt(IV) 2 ng ml^?1. The ion-interaction technique was not so successful, only Au(III) and Pd(II) giving stable chromatography. The calibration plots were slightly curved, although acceptable, and the detection limits were 10 and 30 ng ml^?1 for Au (III) and Pd(II), respectively.     

Determination of noble metals in biological samples by electrothermal vaporization inductively coupled plasma mass spectrometry,following cloud point extraction

A simple separation procedure for noble metals based on cloud point extraction is proposed. The analyte ions in aqueous acidic solution, obtained by the acid digestion of the samples, were complexed with O,O-diethyl-dithiophosphate and Triton X-114 was added as a non-ionic surfactant. By increasing the temperature up to the cloud point, a phase separation occurs, resulting in an aqueous phase and a surfactant-rich phase containing most of the analytes that were complexed. The metals in the surfactant-rich phase were determined by electrothermal vaporization inductively coupled plasma mass spectrometry. The extraction conditions as well as the instrumental parameters were optimized. Enrichment factors ranging from 7 (Rh) to 60 (Pt) and limits of detection from 0.6 (Pt) to 3.0 ng l⁻¹ (Rh) were obtained in the digested samples. The extraction was not efficient for Ir. Among the reference materials analyzed in this work, only one (SRM 2670, urine) presented recommended values for Au and Pt. Due to the non-availability of adequate CRMs, accuracy was assessed by spiking known analyte amounts to the acid digests. Recoveries close to 100% were observed for all the studied elements but Ru. Poor agreement between found and recommended values was observed for non-digested urine sample, probably due to the carrier effect of co-extracted residual matrix components. However, good agreement was reached after urine acid mineralization.     

Determination of physiological noble metals in human urine using liquid-liquid extraction and Zeeman electrothermal atomic absorption spectrometry

An extremely sensitive, reliable and simple procedure is described for the determination of physiological palladium, platinum and gold in human urine. The urine samples were adjusted to pH 4 (Pd, Au) or pH 5 (Pt), followed by conversion of the analytes to their pyrrolidinedithiocarbamate complexes. These complexes were separated from the matrix by liquid-liquid extraction into 4-methyl-2-pentanone resulting in a 25-fold enrichment. Determination was by electrothermal atomic absorption spectrometry (ET-AAS) using longitudinal inverse alternating current Zeeman-effect background correction. The limits of detection calculated from three standard deviations of the blank values were 20 ng l⁻¹ for Pd and Au and 70 ng l⁻¹ Pt. Within-day precision (n = 10, 5 μg l⁻¹) ranged 5.2%–7.7%. The procedure is successfully applied to determine urinary palladium, platinum and gold in nine unexposed persons. Palladium levels in urine ranged < 20–80 ng l⁻¹ (arithmetical MEAN=38.7 ng l⁻¹), while gold levels ranged < 20–130 ng l⁻¹ (36.0 ng l⁻¹). Physiological platinum levels in urine were all < 70 ng l⁻¹. The accuracy of the procedure was checked by analyzing a series of urine samples by a second independent method (magnetic sector field inductively-coupled plasma-mass spectrometry) in combination with UV photolysis.     

The determination of gold,platinum, palladium and rhodium by atomic absorption spectrophotometry with an ultrasonic nebulizer and a multi-element high-intensity hollow-cathode lamp with selective modulation

The use of a multi-element high-intensity hollow-cathode lamp with selective modulation and a 2-MHz ultrasonic nebulizer for the determination of Au, Pt, Pd and Rh by atomic absorption spectroscopy is described. The sensitivities for the various elements in aqueous and organic media were studied. Only some organic solutions could be nebulized satisfactorily; a solution containing 95% acetone proved to be the best. For aqueous solutions, the detection limits (concn. giving 0.004 O.D.) were as follows: Au, 0.03 p.p.m.; Pd, 0.02 p.p.m.; Pt. 0.3 p.p.m.; and Rh, 0.09 p.p.m. For a 95% acetone solution the detection limits were: Au, 0.009 p.p.m.; Pd, 0.012 p.p.m.; Pt, 0.20 p.p.m. and Rh, 0.06 p.p.m. The coefficients of variation for aqueous and organic media were satisfactory.     

Luminescence Determination of Copper(I), Silver(I), Gold(I), and Platinum(II) Using 2-Mercapto-5-Benzimidazolesulfonic Acid,also Immobilized on a Silica Surface

2-Mercapto-5-benzimidazolesulfonic acid (MBI), also noncovalently bound to a silica surface, is proposed as a reagent for the low-temperature luminescence determination of Cu(I), Ag(I), Au(I), and Pt(II). Luminescence excitation and luminescence spectra of metal complexes with MBI in solutions and on the adsorbent surface represent broad unstructured bands in the regions 250–400 and 450–700 nm, respectively. The developed procedures for the luminescence and sorption–luminescence determination of Cu, Ag, Au, and Pt with limits of detection at a level of 0.001–0.01 μg on 0.1 g of adsorbent are tested in the determination of metals in natural and industrial samples.     

Determination of precious metals in geological samples by continuous powder introduction microwave induced plasma atomic emission spectrometry after preconcentration on activated carbon

A novel method was developed for analysing geological materials for Au, Ag, Pd and Pt by continuous powder introduction microwave induced plasma atomic emission spectrometry (CPI-MIP-AES). The preconcentration of the trace metals on activated carbon (AC) was performed before conducting MIP-AES measurements in order to obtain accurate and precise analytical results. The method proposed is based on the selective sorption of precious metals that are subsequently introduced to the plasma as a dry particulate aerosol consisted of analytes collected on the sorbent. The technical design and operating conditions of the novel sample introduction system based on the fluidized-bed concept has been optimized. The microwave excitation source with integrated rectangular cavity TE₁₀₁ and vertically positioned plasma torch has been used. The signal stability proved to be adequate for sequential mode of measurements due to the vertical plasma configuration as well as the MIP-AES system compatibility with the CPI technique. Calibration was done using home-made standards obtained by sorption of metals of interest from standard solutions on activated carbon. Precision is typically 1-4% relative standard deviation at the 1 μg g⁻¹ level. Under measurement conditions the detection limits for Ag, Au, Pd and Pt were 24, 43, 57 and 550 ng per 1 g of AC, respectively. The proposed procedure was used for Au, Ag, Pd and Pt determination in the platinum ore SARM-7 as well as Au and Ag in the Chinese soil GBW-07405 certified reference materials. The standard addition technique was used and recoveries revealed that the proposed method shows good accuracy and precision.     

低功率微波等离子体炬原子发射光谱法的研究——超声雾化进样测定金、银、铂、铑、钯

本文提出一种测定贵金属元素的微波等离子体炬原子发射光谱法(MPTAES)。采用自制的超声雾化微量进样装置进样,以氩气为工作气体,探讨了观察高度,微波功率、体系介质、氩气流量和共存元素对被测元素发射信号的影响。选用合适的分析线和MPT光源的工作参数,其方法的检出限分别为5.8(Au)、0.5(Ag)、12(Pt)、1.6(Rh)和t 1.0ng/ml(Pd)。实际样品中金和银的测定结果是令人满意的。     

Measurement of isomeric-yield ratios for the 197Au(γ,n)196m,gAu reactions induced by bremsstrahlung

We measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured with the high-resolution γ-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel analyzer. The measured isomeric-yield ratios for the ¹⁹⁷Au(γ,n)^196m,gAu reactions were (4.95 ± 0.51) × 10^?4, (5.72 ± 0.72) × 10^?4, (6.03 ± 0.50) × 10^?4, and (9.27 ± 0.83) × 10^?4 for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung energy higher than 60-MeV are the first measurement.