Studies on iridium and platinum determination in metallic rhodium by NAA and CPAA

The determination of Ir and Pt in rhodium neutron monitors was investigated via¹⁹²Ir and¹⁹⁹Au after neutron activation, via¹⁹¹Pt and¹⁹⁴Au–¹⁹⁶Au after proton activation. Ir was determined by instrumental NAA. A chemical separation of gold, with a yield measurement method by a radioactive tracer, was developed for platinum determination after neutron or proton irradiation.     

Determination of gold in biological materials by radiochemical neutron activation analysis

A radiochemical neutron activation analysis procedure was developed for the determination of trace amounts of gold in biological materials. The procedure was realized with irradiation of reference and test samples in a nuclear reactor, selective and quantitative separation of gold using inorganic MnO₂ Resin and gamma-ray spectrometric measurement of ¹⁹⁸Au. The method is characterized by a low limit of detection of gold at ng g^?1 level. Results shows that the method can be applied to the determination of trace amounts of gold in tissues for medical research.     

Beryllium-7 as a tracer of stratospheric ozone: A case study

A new method is presented for the determination of Au and Pt in biological materials based on neutron activation analysis with radiochemical separation of gold. Separation of gold by electrolytic deposition on a niobium cathode ascertains the highest radiochemical purity without any interference from calcium or other major elements. With¹⁹⁹Au as indicator for platinum the gold content of the sample not only strongly affects the limit of detection, but also causes interference by double neutron capture. Replicate analyses of BCR Certified Reference Materials No. 184, 185 and 186 were carried out.Presented at the MTAA-8 Conference, September 16–20, 1991, Vienna, Austria.     

Analytical characterization of a silica gel sorbent with thioetheric sites

The sorption behavior of a newly synthesized silica gel sorbent with thioetheric sites (STS) towards microgram levels of Au(III), Pt(IV) and Pd(II) was studied. Au(III) is quantitatively (>95%) sorbed in the pH region of 1–9. The sorption of Pt(IV) starts at pH 1 and does not exceed 25% in the entire pH region examined. The sorption of Pd(II) starts at pH 7 and reaches 80% at pH 9. The sorption of Au(III) on STS at pH 1 is not affected by milligram amounts of Ni(II), Zn(II), Fe(III), Cu(II), Pb(II), Cd(II) or Co(II). Au(III) is quantitatively eluted with a 5% aqueous solution of thiourea. The adsorption capacity of STS towards Au(III) is 195 mg g⁻¹. The detection limit (DL) of Au(III) (3σ, n = 9) is 25 ng mL⁻¹. The RSD at a level of 10 × DL is about 2%. Solid-phase extraction of trace amounts of Au(III) on the STS sorbent, followed by its flame AAS determination in the eluate was applied to the determination of gold in geological samples. The results obtained for the gold content in the samples were in good agreement with those of the ICP-AES analysis.     

The search for internal isotopic tracers in metallurgical materials

In a search for internal isotopic tracers in metallurgical materials a group of elements has been chosen which can be determined by the neutron activation method with the higher sensitivity. A method has been developed for the determination of W, As, Au, La, In, Sc, Re and Ir in metallurgical materials. The separation of the elements was carried out using extraction and precipitation. The determination of the elements was carried out in samples of chamotte brick and washed ores. The limits of the determination of the elements are of the order of 10⁻¹¹ g for Au, 10⁻¹⁰ g for In and La and 10⁻⁹ g for As, W, Sc, Re and Ir. The large scatter of the results indicates the inhomogeneity of the materials analyzed.     

Differential pulse anodic stripping voltammetric determination of Cd and Pb at a bismuth glassy carbon electrode modified with Nafion, poly(2,5-dimercapto-1,3,4-thiadiazole) and multiwalled carbon nanotubes

A simple, cheap, and nonpolluting method was developed for the cloud point extraction of gold (Au) and palladium (Pd). It is based on the complexation reaction of Au and Pd with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and micelle mediated extraction of the complex using the non-ionic surfactant poly(ethylene glycol) mono-p-nonylphenyl ether (PONPE 7.5). Under the optimized experimental conditions, the enrichment factors are 16 and 17 for Au and Pd, respectively, for 15?mL of preconcentrated solution. The limits of detection are 3.8???g?L^?1 and 1.8???g?L^?1 for Au and Pd, respectively. The relative standard deviations are 1.4% for Au and 0.6% for Pd (n?=?11). The method was successfully applied to the determination of Au and Pd in certified reference materials and mine samples.

Efficient Electrocatalytic Detection of Epinephrine at Gold Electrodes Modified with Self‐Assembled Metallo‐Octacarboxyphthalocyanine Complexes

Electrocatalysis of epinephrine at gold electrode pre‐modified with the self‐assembled monolayer of cysteamine and subsequently integrated with novel metallo‐octacarboxyphthalocyanine (MOCPc where M=Fe, Co and Mn) complexes (Au‐Cys‐MOCPc) was investigated. The electrodes showed response to the presence of epinephrine. The oxidation peak potential (E_p/V vs. Ag|AgCl, sat'd KCl) and charge transfer resistance (R_ct (kΩ)) in epinephrine solution depend markedly on the central metal of the phthalocyanine cores: Au‐Cys‐FeOCPck_ch=4.1×10⁷ M^?1 s^?1) which is higher than that of the Au‐cys‐CoOCPc or Au‐cys‐MnOCPc electrode. Mechanism, recognizing the mediation of the electrocatalytic process by the central M(II)/M(III) redox processes was proposed. Epinephrine electro‐oxidation at the Au‐cys‐FeOCPc electrode was studied in more details for the response characteristics. The diffusion coefficient of epinephrine was evaluated as (2.62±0.23)×10^?9 cm² s^?1. It was established that Au‐Cys‐FeOCPc is suitable for sensitive determination of epinephrine in physiological pH (7.40) conditions showing linear concentration range of up to 300 nM, with excellent sensitivity (0.53±0.01 nA nM^?1), and very low limits of detection (13.8 nM) and quantification (45.8 nM). The peak separation between ascorbic acid and epinephrine is large enough (190 mV) to permit simultaneous determination of both epinephrine and ascorbic acid in physiological pH 7.4 conditions using the Au‐cys‐FeOCPc electrode. Au‐cys‐FeOCPc electrode was successfully used for the determination of epinephrine in epinephrine hydrochloric acid injection with recovery of ca. 98.4%.     

Separation of gold on a selective chelating ion exchanger and in situ determination by gamma-spectroscopy

For the separation and determination of low gold concentrations in the sub g g^–1 range in ore and sediment samples an analytical technique has been developed, based on the selective adsorption of gold on the chelating resin, Srafion NMRR, and the in situ determination of the retained gold by instrumental neutron activation analysis (INAA), using the 411.8 keV line of the isotope¹⁹⁸Au. In the case of higher gold concentrations Au could be directly determined in the ore by the technique of loss-free counting in spite of the high radioactivity of the investigated samples. By the described procedure it was possible to determine Au amounts in the range of ng g^–1 sediments.     

A nanocomposite made from conducting organic polymers and multi-walled carbon nanotubes for the adsorption and separation of gold(III) ions

We describe a new method for the separation and preconcentration of traces of Au(III) in environmental samples. Sorbents made from modified multiwalled carbon nanotubes and conducting polymers (PANI and PEDOT) were used for solid-phase extraction. The Au(III) ions are adsorbed as a result of the interaction with the electron pairs of =N- and -S- groups. Effects of pH value, flow rate and volume of sample, type, volume and concentration of eluent, and the adsorption capacity were investigated. The maximum adsorption capacity of MWCNTs/PANI and MWCNTs/PEDOT are 159 and 176?mg?g^?1, and the detection limits of this method are below 0.3 and 0.5?ng?mL^?1, respectively. The procedure was successfully applied to the determination of traces of Au(III) in a reference material and in environmental samples.

The express simultaneous neutron activation determination of gold,palladium and platinum

The method of express neutron-activation (NA) determination of Au, Pd and Pt has been developed. The method is based on the quantitative isolation of¹⁹⁸Au+¹⁹⁹Au and¹⁰⁹Pd activities by extraction with organic sulfides. The radiation of¹⁰⁹Pd is measured on a thin NaI(Tl) crystal and that of¹⁹⁸Au and¹⁹⁹Au on a Ge(Li) detector. The calculations of interferences from gold have been performed for various neutron fluxes and various cadmium ratios. Some interferences introduced by other competitive nuclear reactions into the determination of Pt by its daughter isotope¹⁹⁹Au are discussed.     

Determination of platinum in urine and serum after the administration of cisplatin by neutron activation analysis

A simple neutron activation method is described for platinum determination in urine and serum of dogs when studying the pharmacokinetics of cisplatin, an antitumour drug. The procedure is based on the nuclear reaction¹⁹⁸Pt(n, ψ, β_?)¹⁹⁹Au, a radiochemical separation of gold, and gamma-spectrometry of the radionuclide¹⁹⁹Au. Gold is separated as metal by coprecipitation with selenium after the addition of ascorbic acid in a highly acidic medium. The interference contribution of¹⁹⁹Au originating from stable gold is evaluated, too.     

Activation analysis of platinum in gold via199Au

Platinum is determined in gold by activation analysis by means of¹⁹⁹Au after separation of the matrix at the end of irradiation before the daughter nuclide forms. The method involves the radiochemical separation of gold by chloro-complex extraction with MIBK from 1N HCl, and energy-selective pulse counting of¹⁹⁹Au at 158 keV. The irradiation problems are presented. The dependence of the extractability of the gold chloro-complexes on the acidity and the type of solvent are investigated. The procedure of analysis is described. The results obtained in determining 5–700 ppm Pt in Au, Pd and Rh are discussed.     

Fast Simultaneous Adsorptive Stripping Voltammetric Determination of Ni(II) and Co(II) at Lead Film Electrode Plated on Gold Substrate

A fast adsorptive stripping voltammetric procedure for simultaneous determination of Ni(II) and Co(II) in the presence of nioxime as a complexing agent at an in situ plated lead film electrode was described. The time of determination of these ions was shortened due to the application of gold as a substrate for lead film. At gold substrate lead film formation and accumulation of Ni(II) and Co(II) complexes with nioxime proceeds simultaneously. To obtain a stable signals for both ions a simple procedure of activation of the electrode was proposed. Calibration graphs for an accumulation time of 20 s were linear from 5×10^?9 to 1×10^?7 mol L^?1 and from 5×10^?10 to 1×10^?8 mol L^?1 for Ni(II) and Co(II), respectively. The procedure with the application of a lead film electrode on a gold substrate was validated in the course of Ni(II) and Co(II) determination in certified reference materials.     

Acid extraction and cloud point preconcentration as sample preparation strategies for cobalt determination in biological materials by thermospray flame furnace atomic absorption spectrometry

A thermospray flame furnace atomic absorption spectrometer (TS-FF-AAS) was employed for Co determination in biological materials. Cobalt presents a high atomization temperature and consequently poor sensitivity is obtained without changing its thermochemical behavior. The effect of different complexing agents on sensitivity was evaluated based on the formation of Co volatile compounds. A cloud point procedure was optimized for Co preconcentration for further improvement of sensitivity. Samples were treated with 1 mol l^− 1 hydrochloric acid solution for quantitative extraction of Co without simultaneous extraction of Fe, since it is a strong interferent. After the extraction and preconcentration steps, a sample volume of 150 μl was introduced into the hot Ni tube using air as carrier at a flow-rate of 0.4 ml min^− 1. The best sensitivity was attained using ammonium pyrrolidinedithiocarbamate (APDC) and Triton X-114 was employed for implementation of the cloud point procedure. The detection limit obtained for Co was 2.1 μg l^− 1 and the standard deviation was 5.8% for a solution containing 100 μg l^− 1 (n = 10). Accuracy was checked using two certified reference materials (tomato leaves and bovine liver) and results were in agreement with certified values at a 95% confidence level. Employing the developed procedure, Co were quantified in different biological materials (plant and animal tissues). The proposed method presents suitable sensitivity for cobalt determination in the quality control of foods.     

Selective solid-phase extraction and separation of trace gold, palladium and platinum using activated carbon modified with ethyl-3-(2-aminoethylamino)-2-chlorobut-2-enoate

Activated carbon was chemically modified with ethyl-3-(2-aminoethylamino)-2-chlorobut-2-enoate to obtain a material for selective solid-phase extraction of trace Au(III), Pd(II) and Pt(IV) prior to their determination by inductively coupled plasma atomic emission spectrometry. Experimental conditions such as effects of pH, shaking time, sample flow rate and volume, elution and interfering ions were studied. The ions Au(III), Pd(II) and Pt(IV) can be quantitatively adsorbed on the new sorbent from solution of pH 1. The adsorbed ions were then eluted with 0.1 mol L^?1 hydrochloric acid and containing 4% thiourea. Many common ions do not interfere. The adsorption capacity of the material is 305, 92, and 126 mg g^?1 for Au(III), Pd(II) and Pt(IV), respectively, and the detection limits are 5, 11 and 9 ng mL^?1. The relative standard deviation is less than 3.0% (n?=?8) under optimum conditions. The method was validated by analyzing two certified reference materials and successfully applied to the preconcentration and determination of these ions in actual samples with satisfactory results.

Gold and silver determination in Waters by SPHERON® Thiol 1000 preconcentration and ETAAS

A reliable procedure for the electrothermal atomic absorption spectrometry (ETAAS) determination of gold and silver in waters at trace level is described. The method is based on prior separation and preconcentration of the metals using a chelating sorbent SPHERON® Thiol 1000 after acidification of water samples (pH < 3) with nitric acid. Optimization of analytical variables during enrichment and ETAAS determination of the metals are discussed. The accuracy of the method is verified by analysis of certified reference materials. The limits of determinations based on 10 σ definition were 0.005 ng cm^?3 for Au and 0.02 ng cm^?3 for Ag. Precision of studied elements determination expressed by relative standard deviation varied in the range from 2.9 % to 16.4 %.     

Very accurate,simultaneous determination of trace amounts of Co and Ni in biological materials by radiochemical neutron activation analysis

A very accurate and sensitive method for the simultaneous determination of trace amounts of Co and Ni in biological materials has been elaborated. The method is based on radiochemical neutron activation. Irradiation of samples in Cd-shielded channel of a nuclear reactor assures balanced activity ratio of⁵⁸Co and⁶⁰Co isotopes and favourable detection limits for both nickel and cobalt. Column chromatography (ion exchange and extraction) has been used for the quantitative and selective isolation of the determined radionuclides. High accuracy of the method has been demonstrated by the analysis of several certified reference materials.     

Multiwalled carbon nanotubes microcolumn preconcentration and determination of gold in geological and water samples by flame atomic absorption spectrometry

The potential of multiwalled carbon nanotubes (MWNTs) as solid-phase extraction adsorbent for the separation and preconcentration of gold has been investigated. Gold could be adsorbed quantitatively on MWNTs in the pH range of 1–6, and then eluted completely with 2 mL of 3% thiourea in 1 mol L^− 1 HCl solution at a flow rate of 0.5 mL min^− 1. A new method using a microcolumn packed with MWNTs as sorbent has been developed for the preconcentration of trace amount of Au prior to its determination by flame atomic absorption spectrometry. Parameters influencing the preconcentration of Au, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been examined and optimized. Under the optimum experimental conditions, the detection limit of this method for Au was 0.15 µg L^− 1 with an enrichment factor of 75, and the relative standard deviation (R.S.D) was 3.1% at the 100 µg L^− 1 Au level. The method has been applied for the determination of trace amount of Au in geological and water samples with satisfactory results.     

Rapid determination of gold in Romanian auriferous alluvial sands, concentrates and rocks by 14 MeV NAA

The nuclear and spectral interferences in the 14 MeV neutron activation analysis (NAA) of gold from Romanian auriferous alluvial sands, concentrates and rocks have been studied and the optimum of activation, cooling and measuring times was determined for a maximum peak-to-background ratio for gold. The contribution of the nuclear interfering elements in the samples, Hg and Pt, to the concentration of gold has been calculated and, concluded that the nuclear reactions ¹⁹⁷Au(n,2n)¹⁹⁶Au, ¹⁹⁷Au(n,2n)^196mAu and ¹⁹⁷Au(n,n')^197mAu can be used for gold determination, with minimal errors. Using the nuclear reactions ¹⁹⁷Au(n,n')^197mAu and ¹⁹⁷Au(n,2n)¹⁹⁶Au the spectral interferences are minimal and are due to Rb, Ti and V for a short irradiation and to Se for a long one. Two methods of fast gold determination were proposed for auriferous alluvial sands and rocks in the range of 20-2500 ppm, under the optimum conditions established so that the systematic errors of analysis due to the gold accompanying elements can be considerably diminished. For measuring the induced gamma-radioactivity in the samples either a short irradiation (25 seconds) with a NaI(Tl) detector or a long irradiation (3000 seconds) with a Ge(Li) detector were used. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nickel determination in biological materials at ultratrace level by fast neutron radiochemical activation analysis

Using radiochemical separation of cobalt following the fast neutron reaction⁵⁸Ni(n, p.)⁵⁸Co and long high fluence irradiation, we attempted to improve the determination limit for Ni to the nanogram and sub-nanogram level. A Compton suppression spectrometer was shown to be the best choice compared to co-axial or well-type HPGe detectors. Results for low level biological reference materials such as serum and milk powder are discussed. Use of both dried and pre-ashed samples showed that losses of Ni and Co on ashing are non-significant. The influence of the silica ampoule blank was also investigated.