Simultaneous determination of palladium, platinum and rhodium in crude platinum samples by activation analysis and high-resolution gamma spectrometry

Instrumental neutron-activation analysis using a Ge(Li) detector has been investigated for the simultaneous determination of platinum, palladium and rhodium in crude platinum samples contained in lead cupels. This technique proved feasible and appears promising for extension to the determination of most of the noble metals.     

The determination of all the platinum group elements and gold in rocks and ore by neutron activation analysis after preconcentration by a nickel sulphide fire-assay technique on large samples

The noble metals are inhomogeneously distributed in sulphide ores and their host rocks. It is therefore necessary to analyse large sample sizes to obtain representative analyses. A nickel sulphide fire assay technique has been adapted to extract the noble metals from a large sample size (50 g) into a nickel sulphide button. Subsequently the fire assay button is dissolved in hydrochloric acid and the solution is filtered. The noble metal residue retained on the filter paper is analysed quantitatively by i.n.a.a. techniques. This method is rapid, relatively inexpensive and has better sensitivities for all the noble metals than other analytical techniques.     

Interferences and their elimination in the determination of the noble metals by atomic-absorption spectrophotometry

A number of serious interferences in the determination of the noble metals by atomic-absorption spectrophotometry have been investigated, and ways of eliminating them considered. The use of the nitrous oxide and acetylene flame reduced many of the interferences but also reduced the sensitivity. Additions of lanthanum, copper sulphate, copper + cadmium sulphate, uranium, and vanadium as releasing agents were effective in the removal of interferences for one or more of the noble metals in the air-acetylene flame. Uranium additions were found to be effective in removing mutual interferences associated with the noble metals (osmium and indium were not tested) whereas vanadium removed mutual and base-metal interferences. The precision and accuracy of methods of analysis based on the use of uranium and vanadium were acceptable, and the application of these methods to the analysis of noble metals collected by various procedures is briefly discussed.     

On-line preconcentration and separation of palladium, platinum and iridium using alpha-amino pyridine resin with flame atomic absorption spectrometry

A flow injection on-line microcolumn method has been studied for the separation and preconcentration of noble metals, Pd, Pt and Ir, followed by flame AAS determination. An alpha-amino pyridine resin was used as preconcentration reagent. Non-noble metals studied could be eliminated by 2M HCl solution in the rinsing stage. A group-eluent for all Pd, Pt and Ir was studied. Separation of individual noble metals could also be accomplished using selective eluents. This approach can be used both for the separation and determination of Pd, Pt and Ir in samples. The sensitivities and the sample frequency have been improved. The method has been applied to certified samples.     

Radiochemical determination of trace noble metals in silver artefacts

Radiochemical separations are essential for the determination of trace elements in silver artefacts by neutron activation analysis due to the high levels of both short and long-lived activities produced by the matrix, but the sensitivity of the technique permits the examination of small samples. The noble metals are considered most significant from a diagnostic standpoint, and radiochemical techniques have been developed for their determination in samples of a few milligrams. Methods have been investigated for the determination of Pd, Rh, Ir and Pt in samples removed from museum specimens of known provenance.     

Comparison between the distributions of excitation temperatures and the analytical line intensities of noble metals in two-jet arc plasmatrons used in atomic emission analysis

The results of a study of DGP-50 and new EDP-355 argon two-jet plasmatrons, which are used in the atomic emission analysis of geological samples, are reported. The distributions of temperatures and the analytical line intensities of noble metals with torch height were measured for either of the plasmatrons. It was found that the temperature reached in the EDP-355 plasmatron was higher than that in the DGP-50 plasmatron at equal flow rates of a plasma-forming gas. A decrease in the flow rate of a plasma-forming gas in the EDP-355 plasmatron resulted in an increase in the analytical lines of noble metals by a factor of 1.5–2. It was found experimentally that the EDP-355 plasmatron is a promising source for emission spectral analysis in the determination of noble metals.     

Determination of noble metals by neutron-activation analysis

The scope and limitations of neutron-activation analysis in the field of the platinum metals are discussed. Special attention is given to interferences that occur in determination of noble metals in platinum metals and in natural samples. The problem of standards, carriers and chemical yield determination is emphasised. A recommendation is given of modern techniques for counting radionuclides formed by neutron activation of the platinum metals.     

Surface and subsurface examination of graphite tubes after electrodeposition of noble metals for electrothermal atomic absorption spectrometry

The modification phenomena of noble metals (Pd, Ir, Rh) electrodeposited onto the inner surface of pyrolytic graphite (PG) coated furnaces were investigated mainly by electron microprobe analysis with energy dispersive X-ray emission detection. The conditions of electrodeposition were optimized in order to achieve the best analytical performance of atomic absorption measurements. Investigations concerning the distribution of noble metals on the tube surface and in-depth were performed at different stages of the tube history. It was found that the noble metals used for the modification do not form a compact layer on the surface but penetrate into the pyrolytic graphite structure already at the deposition step. When two metals were deposited together, both penetrated into the graphite structure. The degree of penetration of the pyrolytic graphite at high temperature differs for various metals. It was also demonstrated that electrodeposited noble metals remain in sub-surface domains of the graphite for hundreds of atomization cycles, which means that they can be used as permanent modifiers.     

Fluorine Oxidants in the Analytical Chemistry of Noble Metals

This review is devoted to the physicochemical fundamentals and analytical practice of the use of fluorine oxidants in the decomposition of various naturally occurring and in-process materials containing noble metals. The experience in the application of halogen fluorides, xenon fluorides, and potassium tetrafluorobromate to the analysis and certification of the most difficult to decompose samples with the total precious metal contents from clarke values to 100% was summarized. The advantages of fluoride analytical procedures over traditional methods were demonstrated by examples of the most refractory test samples.     

Enrichment of trace amounts of gold, silver, palladium and platinum by precipitate flotation

Summary An organic precipitant, p-dimethylaminobenzilidenerhodanine (DABR), is used as the gatherer in precipitate flotation to enrich trace amounts of gold, silver, palladium and platinum from acidic media in the presence of surfactants. The DABR dissolved in dimethylformamide (DMF) does not affect the determination of the enriched metals with electrothermal atomic absorption spectrometry. The presence of a 10²- to 10⁴-fold excess of other usual ions does not interfere with the flotation owing to the high selectivity of DABR for the noble metals in acidic media. As little as 1 ng/l of gold in aqueous solution can thus be determined by AAS. The method has been applied to determine the noble metals in various ore samples with satisfactory results.Dedicated to Prof. Kuang Lu Cheng, University of Missouri, Kansas City, USA on the occasion of his 70th birthdayPresented in part at the Third China-Japan Joint Symposium on Analytical Chemistry, Hefei, China, May, 1988     

A new quantitative radiochemical separation procedure to determine Ir at 10−12 g/g level in geological samples by a long chain primary amine extraction

A radiochemical separation procedure has been set up to determine Ir of 10^?12 g/g level and other noble metals in geological samples by using a long chain s-alkyl primary amine, N-1923, as an extractant. A series of factors affecting the chemical recovery of Ir were considered, including extractant, diluent, oxidant, oxidation temperature an time, extraction acidity, reflux acidity and time, etc. Some improvements in the procedure for geological samples were made, i.e. eliminating interference from chromium and raising recoveries of noble metals in geological samples. The extraction percentages of noble metals are more than 95% in one step of extraction and of base metals are generally less than 0.5%.     

Determination of trace and ultra-trace amounts of noble metals in geological and related materials by graphite-furnace atomic-absorption spectrometry after separation by ion-exchange or co-precipitation with tellurium

Two methods for determining mug/g and ng/g levels of the noble metals, except for osmium, in ores, concentrates, mattes, and silicate and iron-formation rocks are described. After sample decomposition with hydrofluoric acid and aqua regia, followed by fusion of any insoluble residue with sodium peroxide, the noble metals are separated from the matrix elements by either cation-exchange or co-precipitation with tellurium. The resulting eluate, or the solution obtained after dissolution of the tellurium precipitate, is evaporated to dryness and the noble metals are ultimately determined in a 1M hydrochloric acid medium by graphite-furnace atomic-absorption spectrometry. The ion-exchange method is recommended for the determination of mug/g levels of gold, silver and platinum-group elements, whilst the tellurium co-precipitation method is recommended for ng/g levels of platinum-group elements. The latter method is not recommended for the determination of ng/g levels of silver and gold in rocks, because of interference from tellurium during atomization in the furnace. Results obtained by these methods for 15 international reference samples, including four Canadian iron-formation rocks, are compared with other published data.     

Application of “Direct” beta particle excitation for the determination of noble metals in catalysts by radioisotope excited X-ray fluorescence

A new technique was applied for exciting X-rays for X-ray fluorescence analysis by “direct” beta excitation for the determination of noble metals in catalytic materials.     

The rapid isolation and determination of iridium after simultaneous liquid-liquid extraction and determination of platinum,palladium, rhodium and gold

The proposed method provides a rapid isolation of iridium form the other noble metals, as well as from Ni, Cu, Fe, Cr, Co and Na. The scheme comprises an initial removal of ruthenium and osmium by volatilization of their tetroxides followed by the simultaneous extraction of platinum, palladium, rhodium and gold as their 2-mercaptobenzothiazole—tin(II) chloride complexes into chloroform. Iridium in the raffinate is complexed by the same reagent system, after boiling, and extracted into chloroform. The extracts after evaporation of the solvent are converted to hydrochloric acid solutions and the noble metals are determined by atomic absorption spectrometry. Satisfactory results are obtained for various noble metal solutions, and for a solid platiniferous sample.     

On the methodology of radiochemical neutron activation analysis of noble matals

Two different radiochemical procedures were developed: chelate ion resin exchange and amine solvent extraction. Two kinds of new Chinese chelate resins (NANKAI-3926 and BEI-5) and a new longchain primary amine N₁₉₂₃ were compared with the Srafion NMRR and the tertiary amine N₂₃₅ in absorption performance of noble metals, respectively. Influences of various experimental conditions, e. g. sample digestion, acidity, equilibrium time, as well as elution of noble metals, on analytical sensitivity and chemical yield were discussed. Combining with neutron activation, the radiochemical separation procedures developed were used to determine the noble metal contents in the geological samples from Permian/Triassic boundary in South China.     

贵金属组试剂聚硫醚吸附性能和应用的研究

我们合成了类似文献报道的聚硫醚(PTE)。通过各种性能实验,确定了试剂结构为HO CH_2—S CH_2OH,对Au、Pd、Pt、Rh、Ir、Ru、Os的吸附率在98％以上,且不吸附常见的非贵金属。分离富集效果优于文献。像PTE能吸附全部8个贵金属且饱和吸附容量非常大的吸着剂,尚属少见。     

Trends in sorption preconcentration combined with noble metal determination.

Nowadays much attention is being paid to the determination of trace amounts of noble metals in geological, industrial, biological and environmental samples. The most promising techniques, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and electrothermal atomic absorption spectrometry (ETAAS) are characterized by high sensitivity. However, the accurate determination of trace noble metals has been limited by numerous interferences generated from the presence of matrix elements. To decrease, or eliminate, these interferences, the sorption preconcentration of noble metals is often used prior to their instrumental detection. A great number of hyphenated methods of noble metal determination using sorption preconcentration have been developed. This review describes the basic types of available sorbents, preconcentration procedures and preparations of the sorbent to the subsequent determination of noble metals. The specific features of instrumental techniques and examples of ETAAS, FAAS, ICP-AES, ICP-MS determinations after the sorption preconcentration of noble metals are considered. The references cited here were selected mostly from the period 1996 - 2006.     

模糊聚类-偏最小二乘回归光度法同时测定地质样品中金铂钯铑的研究

将模糊聚类分析与偏最小二乘法相结合,对地质样品中吸收光谱严重重叠的贵金属多组份体系进行解析,较好地解决了计算光度分析中校准模型的优化问题,使计算结果的精度得到了显著提高,分析结果的相对误差小于 10%,标准偏差小于 0.67,明显优于一般偏最小二乘 (PLS)法。采用小锍试金法消除样品中贱金属元素的干扰,其回收率为 92%～107%,标准偏差为 0.10～0.67;相对标准偏差为 4.7%～11.0%。并对影响聚类效果的参数选择作了讨论。     

由类水滑石前驱体制备的CuZnAl复合氧化物催化剂催化湿氧化处理苯酚

The efficiency of several noble metals for catalytic wet oxidation (CWO) of various pollutants has been demonstrated[1,2]. However, the noble metals are expensive, affecting greatly the economics of the corresponding process.     

Polyurethane foam of the polyether type as a solid polymeric extractant for cobalt and iron from thiocyanate media

By combining instrumental and radiochemical neutron activation analysis, up to 47 elements including major, minor, and trace elements, have been determined in lake sediment samples. Instrumental neutron activation involving both short and long irradiations is used to determine 40 elements including most of the environmentally important ones. A radiochemical separation procedure allows the determination of 7 noble metals. The accuracy and precision of the method are 5–10%.