Ultratrace determination of platinum in biological materials via neutron activation and radiochemical separation

A neutron activation analysis scheme based upon a radiochemical separation of the activation products has been developed. The method utilizes the inherent sensitivity of the activation reaction¹⁹⁸Pt(n, γ)¹⁹⁹Pt and counting of the daughter nuclide¹⁹⁹Au. This nuclide is radiochemically separated from interfering activities by homogeneous precipitation as elemental gold. The remaining interference of the secondary reaction¹⁹⁷Au(n,γ)¹⁹⁸ Au(n,γ)¹⁹⁹Au from gold in the samples is quantitatively assessed and corrected. During this process accurate gold concentrations in the samples are obtained at ultratrace levels. The analysis scheme is applied to gold and platinum determinations in biological Standard Reference Materials and human liver specimens. Gold and platinum are determined at concentrations of 5·10^?11 g/g, and at higher levels.     

Interference by neutron induced second order nuclear reaction in activation analysis of platinum group elements after a nickel sulphide fire assay preconcentration

In determining the trace platinum group elements and gold in rocks and ores by the neutron activation analysis after a nickel sulphide fire assay preconcentration, there are interferences due to nuclides produced from second order nuclear reactions. This paper presents the degree of interference calculated over the ranges of long irradiation times and of reactor neutron flux from 1·10¹³ to 1·10¹⁵ n·cm^–2·s^–1. According to the results of these calculations, every one of the second order interfering reactions on the PGE+Au, except the¹⁹⁷Au(n, )¹⁹⁸Au(n, )¹⁹⁹Au reaction, can be neglected under the long irradiation time or high reactor neutron flux. Special attention is given to the interference from gold in the determining platinum.     

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.     

Limit of detection for the determination of Pt in biological material by RNAA using electrolytic separation of gold

Neutron activation analysis based on the¹⁹⁹Au indicator for platinum requires the separation of gold at high radiochemical purity. The limit of detection is strongly affected by the presence of gold; with a gold content of 50 pg/g, irradiating for 5 days at 5·10¹³ n/cm²s is needed to achieve a limit of detection of approximately 30 pg/g. In this case the nuclear interference from gold will exceed the level of platinum by several orders of magnitude and has to be determined with exceedingly high precision. Preliminary results for SRM 1577 Bovine Liver with 95% yield gave consistent results for Au, but Pt could not be detected.     

Determination of precious metals in ores and rocks by thermal neutron activation/γ-spectrometry after preconcentration by nickel sulphide fire assay and coprecipitation with tellurium

The six platinum group elements (Ru, Rh, Pd, Os, Ir and Pt) can be determined in geological samples down to the μg kg^?1 level, by using nickel sulphide fire assay and neutron activation of the residue ramaining after dissolution of the nickel sulphide button in concentrated hydrochloric acid. Losses for the platinum group elements during this dissolution step are usually insignificant, except when the elements are present at ultra-trace levels. The can be recovered from the filtrate by coprecipitation with tellerium. The latter approach also permits determination of silver, which is significantly lost in the hydrochloric acid treatment (recovery <98% instead of typically ≈ 10%). The coprecipitation with tellurium considerably improves the results for gold (recovery ≈ 95% instead of typically 75%).     

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.     

The simultaneous determination of osmium,ruthenium, iridium and gold in platinum by neutron activation analysis

Osmium, ruthenium, iridiuim and gold can be determined simultaneously in 100-mg platinum samples after irradiation for 11 days at a thermal neutron flux of 4'1011 n.cm^-2.sec^-1. An addition method of analysis is used; samples are dissolved in small sealed silica tubes before activation. After irradiation, Os and Ru are distilled from sulfuric acid-sodium bromate, Ru being determined by counting the 498-keV peak of ¹⁰³Ru; Os is determined after a second distillation. Gold is extracted with ethyl acetate from the residue of the first distillation; the ratio ¹⁹⁸Au/¹⁹⁹Au is a direct measure for the gold content, with appropriate correction for the second-order reaction ¹⁹⁶Pt(n,γ)¹⁹⁷Pt→¹⁹⁷Au(n,γ)¹⁹⁸Au. Ir is determined in the residual aqueous phase using the 317-keV peak of ¹⁹²Ir; a correction for the platinum activity (¹⁹¹Pt) is made. The lower limit of determination is ca. 0.5 p.p.m. for ruthenium, ca. 0.2 p.p.m. for osmium, ca. O.1 p.p.m. for gold and ca. O.1 p.p.m. for iridium. After a separation of Pt from Ir, the sensitivity for Ir can easily be improved to < 10 p.p.b.     

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.     

Multielement neutron activation analysis of biological materials using chemical group separation and Ge(Li) gamma spectrometry

Neutron activation analysis (NAA) for the determination of some trace elements in biological materials is described. The method presented permits the simple and rapid determination of Se, Ag, Au, Sb, Pt (via¹⁹⁹Au), Hg, Co, Ni (via⁵⁸Co), Fe, Zn, Mo, Sn, Cr, Cd, Cu and As after radiochemical separation from Na, K, Cs, Rb and partially Br. For this purpose, postirradiation separation by extraction with mercury or zinc amalgam was used. Separation of gold by extraction with ethyl acetate or by precipitation with dimethylglyoxime was applied for the determination of gold and platinum in biological materials.     

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.     

Determination and distribution of gold in Greek bauxites of the Parnassos-Ghiona area by gamma-spectroscopy after ion exchange separation

For the determination of gold in Greek bauxites from the Parnassos-Ghiona area, an analytical technique was used based on the selective adsorption of gold on SRAFION NMRR chelating anion exchanger resin, after leaching the bauxites with aqua regia in a teflon-autoclave at 120 °C, and the determination of the retained gold directly on the resin by instrumental neutron activation analysis (INAA), using the 411.8 keV line of the ¹⁹⁸Au isotope. The procedure allowed to determine Au in concentrations down to ng/g. The obtained data were used to examine the distribution of Au in the profiles of a group of different bauxites from the upper or the called third bauxitic horizon of the Parnassos-Ghiona area in Greece. Especially in the basement of some bauxite deposits unexpected high concentrations of Au up to 2 mg/g have been found. Furthermore, the correlation of Au with other trace elements, found in the bauxitic samples, was investigated.     

Application of radioisotope XRF for the determination of noble metals in aqueous solutions

Radiometric methods of determination of platium and palladium (0.1 to 5% of Pt and 0.1 to 2% of Pd), gold and indium (0.01 to 1% of Au and 1 to 4 g In/l) and of platinum and rhodium (0.1 to 9% of Pt and 0.05 to 1% of Rh) in aqueous solution has been worked out. A suitable measuring device has been designed and constructed. The methods are based on the measurement of characteristic radiation of the L_α line for gold and platinum and of the K-series for indium, palladium and rhodium, as well as on the measurement of scattered radiation from a²³⁸Pu source. The r.m.s. error of the determination varies from 0.01 to 0.10% of Pt, 0.002 to 0.01% of Au and 0.01 to 0.15% of Pd depending on the concentration. In the case of Rh and In the errors are 0.008% and 0.04 g In/l, respectively.     

Reaction mechanism for target-like products from197Au target bombarded with12C ions of energies above 100 MeV/u

Target-like products, that is,^191–200Au,^185–200Pt, and^183–195Ir, from¹⁹⁷Au target bombarded with¹²C ions at the energies of 180, 230, and 400 MeV/u were measured by using off-line gamma-ray spectrometry combined with chemical separation procedures. Spallation systematics by Rudstam reproduces well the measured cross sections for formation of platinum and iridium isotopes. It was found that the cross sections of gold nuclides increase with increase of the incident energy in the range studied and they are enhanced if compared with the reported proton-induced reaction of gold at a similar incident energy. It is suggested that the electromagnetic dissociation process plays a role for production of such gold nuclides.     

Simple spectrophotocolorimetric method for quantitative determination of gold in nanoparticles

A simple spectrophotocolorimetric method devoted to the measurement of gold content in nanoparticles (NPs) was developed. It includes two steps: (i) metal gold NPs (Au NPs) are oxidized into the AuCl₄⁻ anion using a 5 × 10⁻² M HCl-1.5 × 10⁻² M NaCl-7 × 10⁻⁴ M Br₂ solution, next (ii) AuCl₄⁻ concentration is measured using a spectrophotometric assay based on the reaction of AuCl₄⁻ with the cationic form of Rhodamine B to give a violet ion pair complex. This latter is extracted with diisopropyl ether and the absorbance of the organic complex is measured at 565 nm. The method is linear in the range 6-29 μM of AuCl₄⁻ with a limit of detection of 4.5 μM.The analytical method was optimized with respect of bromine excess to obtain complete Au NPs oxidation. The method was applied to two types of Au NPs currently under investigation: citrate-stabilized Au NPs and Au NPs capped with dihydrolipoic acid (Au@DHLA). Both the gold content of Au NPs and the concentration of NPs (using NP diameter measured by transmission electron microscopy) have been calculated.     

Sol particle immunoassays using colloidal gold and neutron activation

The feasibility of performing immunoassays with colloidal gold labels and detection of¹⁹⁸Au by neutron activation has been demonstrated with measurements of human immunoglobulin and of serum antibodies to human immunodeficiency virus type 1. The detection sensitivity achieved after activation in a high flux reactor or with a water moderated²⁵²Cf source, by gamma-counting or by autoradiography, is similar to the sensitivity obtained with absorbance measurements in the more common enzyme immunoassays. The reactor based neutron activation assay allows detection of 10^–16 mol of analyte in routine operation with possible extension to 10^–20 mol. The sensitivity with the 1.3 Ci²⁵²Cf source is limited to about 10^–15 mol. The practical limitations of the assay's sensitivity at this point are due to background signals from reagents and/or nonspecific binding of the gold labeled reagent.     

Cupel assay of gold by an activation method

The difficulties of determining gold in rocks and ores are due to two causes: low gold concentrations in rocks (Clark 1 to 4·10⁻⁷%), and non-uniform distribution of gold in ores. A method is proposed which is based on neutron activation of the lead alloy obtained by cupel melting in the procedure of determining gold by cupel assay. Samples of 50 to 100 g are used for cupel melting. Such large samples guarantee their representativeness. Discs of 2 to 3 g are cut from the lead alloy block and activated in a neutron flux of 10¹¹ to 10¹³ n·cm⁻² sec⁻¹. The gold content is determined from the photopeak of¹⁹⁸Au using a standard for comparison. The sensitivity of the method is 0.02 g/metric ton, its accuracy at a gold content in the order of 1.0 g/metric ton is 10% relative. The method is distinguished by the fact that it is fast and requires little labour.     

MALDI-Q-TOF mass spectrometric determination of gold and platinum in tissues using their diethyldithiocarbamate chelate complexes

A rapid determination method is presented for gold (Au³⁺) and platinum (Pt⁴⁺) in tissues using matrix-assisted laser desorption ionization quadrupole time-of-flight mass spectrometry (MALDI-Q-TOF-MS). Au and Pt ions in wet-ashed tissue solution were reacted with diethyldithiocarbamate (DDC), and the resulting chelate complex ions Au(DDC)₂ ⁺ and Pt(DDC)₃ ⁺ were detected by MALDI-Q-TOF-MS using α-cyano-4-hydroxycinnamic acid as a matrix. The limit of detection (LOD) was 0.8 ng/g tissue and the quantification range was 2–400 ng/g for Au, and the LOD was 6 ng/g tissue and the quantification range was 20–4,000 ng/g for Pt. The Pt levels detected by MALDI-Q-TOF-MS in several tissues of a patient overdosed with cisplatin were nearly the same as those detected by flow-injection electrospray ionization mass spectrometry. The LODs of Au and Pt were 0.04 pg per well (sample spot) and 0.3 pg per well, respectively. To our knowledge, this is the first attempt to quantify Au³⁺ and Pt⁴⁺ ions in tissues by MALDI-Q-TOF-MS.

Metal–Metal Interactions in Heterobimetallic Complexes with Dinucleating Redox‐Active Ligands

The tuning of metal–metal interactions in multinuclear assemblies is a challenge. Selective P coordination of a redox‐active PNO ligand to Au^I followed by homoleptic metalation of the NO pocket with Ni^II affords a unique trinuclear Au–Ni–Au complex. This species features two antiferromagnetically coupled ligand‐centered radicals and a double intramolecular d⁸–d¹⁰ interaction, as supported by spectroscopic, single‐crystal X‐ray diffraction, and computational data. A corresponding cationic dinuclear Au–Ni analogue with a stronger d⁸–d¹⁰ interaction is also reported. Although both heterobimetallic structures display rich electrochemistry, only the trinuclear Au–Ni–Au complex facilitates electrocatalytic C?X bond activation of alkyl halides in its doubly reduced state. Hence, the presence of a redox‐active ligand framework, an available coordination site at gold, and the nature of the nickel–gold interaction appear to be essential for this reactivity.     

Production of cationic 198Au3+ and nonionic 198Au0 for radionuclide therapy applications via the natAu(n,γ)198Au reaction

¹⁹⁸Au (??_max?=?0.96?MeV (98.6?%), ??_max?=?0.412?MeV (95.5?%) and T _1/2 ?=?2.7?days) is a radionuclide with very appealing characteristics. ¹⁹⁸Au has been widely used to treat the uterus, bladder, cervix, prostate, melanoma, breast, skin and other cancers. In the present study, cationic ¹⁹⁸Au⁺³ and nonionic ¹⁹⁸Au⁰ are prepared following thermal neutron irradiation of commercially available natural gold compounds in Tehran Research Reactor via the ^natAu(n,??)¹⁹⁸Au reaction. The prospects in the production of pure ¹⁹⁸Au⁰ and ¹⁹⁸Au⁺³ for radionuclide therapy are discussed and effect of reduction on the activity of radioactive gold is evaluated. Au⁰ particles were synthesized via NaBH₄ reduction of aqueous solutions of hydrogen tetrachloroaurate trihydrate. Then two quartz tubes were charged with cationic ¹⁹⁸Au³⁺ and nonionic ¹⁹⁸Au⁰. After irradiation by thermal neutrons, the samples were analyzed for a period of 1?month by liquid scintillation counter and high purity germanium detector. As a result, ^natAu³⁺ reduction process had no significant effect on the activity of the ¹⁹⁸Au sample. In conclusions, natural gold thermal neutron activation cross section is reasonably high for medical application.     

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.