Simplified method for the determination of Ru, Pd, Re, Os, Ir and Pt in chromitites and other geological materials by isotope dilution ICP-MS and acid digestion

Applicability of the Dose Spiking Electron Paramagnetic Resonance Method for the Quantitative Measurements of Low Doses in Alanine Dosimetry

Ionizing radiation generates unpaired electrons or free radical centers in alanine. The electron paramagnetic resonance (EPR) detects, identifies, and quantifies these free radicals, proportional to the absorbed dose. The accurate measurements of low doses using EPR dosimetry with alanine are highly challenging due to (1) the weak EPR dosimetric signal from low dose alanine and measurement errors, (2) the sample anisotropy in crystalline alanine, and (3) the background signals from sample impurities. This study explores the feasibility of using the dose spiking EPR technique to overcome these challenges and decreases the detection limit up to 20 milligray (mGy) in a low dose measurement using EPR. The measurement errors from the sample anisotropy were reduced by rotating the samples relative to the constant magnetic field direction using a goniometer and averaging the resulting EPR spectra. This technique decreased the measurement errors at high doses; however, it was insufficient to decrease the detection limit and increase the measurement accuracy at low doses (<0.5 Gy). As a result, the high measurement accuracy at the high doses (>4 Gy) was exploited to increase the accuracy at the low doses using the dose spiking EPR technique. To this end, the low-dose alanine sample, undetectable and not reliably measurable in the X-band continuous wave (CW) EPR spectrometer, spikes with a high dose (4 Gy). Then, the total dose was measured and subtracted from a spike dose to get the initial low dose. This technique detected and measured the low doses with reliable accuracy (±10%). As a result, we concluded that this method has great potential to solve the low dose measurement problems in alanine dosimetry.

Analytical Methods for Os Isotope Ratios and Re-PGE Mass Fractions in Geological Samples

The recent advances in analytical methods of Re-Os and PGE in geological materials including sample dissolution, chemical separation, mass spectrometric determinations, as well as the developments of matrix-matched reference materials for data quality control are thoroughly reviewed. Further, the in-situ measurement methods for Re-PGE mass fractions and 187Os/188Os ratios, as well as the measurement methods for stable isotope ratios of Re and PGE are also briefly reviewed. This review stands as a comprehensive reference for researchers to consider in the development of measurement methods for Re-PGE mass fractions and 187Os/188Os ratios in geological materials.

Origin of uranium isotope variations in early solar nebula condensates

High-temperature condensates found in meteorites display uranium isotopic variations ((235)U/(238)U), which complicate dating the solar system's formation and whose origin remains mysterious. It is possible that these variations are due to the decay of the short-lived radionuclide (247)Cm (t 1/2 = 15.6 My) into (235)U, but they could also be due to uranium kinetic isotopic fractionation during condensation. We report uranium isotope measurements of meteoritic refractory inclusions that reveal excesses of (235)U reaching ~+6% relative to average solar system composition, which can only be due to the decay of (247)Cm. This allows us to constrain the (247)Cm/(235)U ratio at solar system formation to (1.1 ± 0.3) × 10(-4). This value provides new clues on the universality of the nucleosynthetic r-process of rapid neutron capture.

The potential impact of municipal solid waste incinerators ashes on the anthropogenic osmium budget

Osmium release from Municipal Solid Waste Incinerators (MSWI), even if acknowledged to occur at least over the last fifteen years, remains overlooked in the majority of recent studies. We present the osmium concentration and (187)Os/(188)Os isotopic measurements of different kinds of bottom and fly ash samples from MSWI plants and reference materials of incinerator fly ash (BCR176 and BCR176R). The analysis of the unknown ash samples shows a relatively wide range of (187)Os/(188)Os ratios (0.24-0.70) and Os concentrations (from 0.026 ng/g to 1.65 ng/g). Osmium concentrations and isotopic signatures differ from those of other known Os sources, either natural or manmade, suggesting a mixture of both contributions in the MSWI feedstock material. Furthermore, the comparison between the BCR176 and the renewed BCR176R indicates a decrease in Os concentration of one order of magnitude over the years (from 1 to 0.1 ng/g) due to improved recycling efficiency of Os-bearing waste. The estimated annual amount of Os from a typical incinerator (using average Os values and MSWI mass balance) is 13.4 g/a. The osmium potentially released from MSWI smokestacks is predicted to be from 16 to 38 ng Os/m(2)/a, considering a medium size country having 50 MSWI facilities; therefore much higher than the naturally transported osmium from continental dust in the atmosphere (about 1 pg Os/m(2)/a). MSWI systems are considered one of the best options for municipal solid waste management in industrialised countries, but their contribution to the Os budget can be significant.

An improved Fe-Ni sulfide fire assay method for determination of Re, platinum group elements, and Os isotopic ratios by inductively coupled plasma- and negative thermal ionization-mass spectrometry

An improved Fe-Ni sulfide fire assay method has been developed for determination of Re, the platinum group elements (PGE), and Os isotopic ratios using inductively coupled plasma-mass spectrometry (ICP-MS) and negative thermal ionization-mass spectrometry (NTI-MS). Recovery of Re using the neoclassical NiS fire assay technique is very low, but recoveries of up to 75% can be achieved by using Fe-Ni sulfide as a collector and Na2B4O7 as a flux. Using isotope dilution for determination of Re, a number of standard reference materials were analyzed for PGE and Re, and the results are consistent with their certified values. Multiple analyses of the reference standard GBW 07290 produced precisions ranging from 2.2% for Os to 5.9% for Ir. The detection limits are 2 pg g(-1) for Ru, 1.5 pg g(-1) for Rh, 25 pg g(-1) for Pd, 23 pg g(-1) for Re, 0.7 pg g(-1) for Os, 1 pg g(-1) for Ir, and 6 pg g(-1) for Pt. The low procedural blank of Os (1.3 pg g(-1)) makes the Fe-Ni sulfide fire assay suitable for analysis of Os isotopic compositions. Using NTI-MS, the 187Os/188Os ratios were measured for WPR-1 and they are consistent with literature values.

Estimation of platinum in environmental water samples with solid phase extraction technique using inductively coupled plasma mass spectrometry

A solid phase extraction technique for the determination of platinum(IV) at trace levels by inductively coupled plasma mass spectromA solid phase extraction technique for the determination of platinum(IV) at trace levels by inductively coupled plasma mass spectrometry (ICP-MS) was developed. The method was based on retention of platinum in a sample on silica gel modified with aminepropyl groups. The retention of platinum(IV) from the sample solution and the recovery of platinum with 1.0 mol L−1 thiourea solution were quantitative. The relative standard deviation (RSD) was calculated as 5% (n = 7) at the 10 ng L−1 level. The enrichment factor was found to be (50-fold) for 250 mL of water sample. Under optimum conditions, the method detection limit (MDL) was found to be 1 ng L−1 for platinum in water matrices. Recoveries of Pt from spike addition to atmospheric water samples were quantitative (80–95%). The present method was used for the determination of platinum in precipitation, throughfall and runoff water samples.

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.

Direct determination of platinum group elements and their distributions in geological and environmental samples at the ng g−1 level using LA–ICP–IDMS

Laser ablation inductively coupled plasma isotope dilution mass spectrometry (LA-ICP-IDMS) was applied to the direct and simultaneous determination of the platinum group elements (PGEs) Pt, Pd, Ru, and Ir in geological and environmental samples. A special laser ablation system with high ablation rates was used, along with sector field ICP-MS. Special attention was paid to deriving the distributions of PGEs in the pulverized samples. IDMS could not be applied to the (mono-isotopic) Rh, but the similar ablation behavior of Ru and Rh allowed Rh to be simultaneously determined via relative sensitivity coefficients. The laser ablation process produces hardly any oxide ions (which usually cause interference in PGE analysis with liquid sample injection), so the ICP-MS can be run in its low mass resolution but high-sensitivity mode. The detection limits obtained for the geological samples were 0.16 ng g(-1), 0.14 ng g(-1), 0.08 ng g(-1), 0.01 ng g(-1) and 0.06 ng g(-1) for Ru, Rh, Pd, Ir and Pt, respectively. LA-ICP-IDMS was applied to different geological reference materials (TDB-1, WGB-1, UMT-1, WMG-1, SARM-7) and the road dust reference material BCR-723, which are only certified for some of the PGEs. Comparisons with certified values as well as with indicative values from the literature demonstrated the validity of the LA-ICP-IDMS method. The PGE concentrations in subsamples of the road dust reference material correspond to a normal distribution, whereas the distributions in the geological reference materials TDB-1, WGB-1, UMT-1, WMG-1, and SARM-7 are more complex. For example, in the case of Ru, a logarithmic normal distribution best fits the analyzed concentrations in TDB-1 subsamples, whereas a pronounced nugget effect was found for Pt in most geological samples.

Determination of platinum(IV) by UV spectrophotometry

A simple, rapid and sensitive spectrophotometric procedure for the determination of platinum has been elaborated. Pt traces were determined in the form of the PtCl(6)(2-) complex in hydrochloric acid solution whose concentration varies from 0.01 to 2 mol L(-1) by measuring the absorbance at 260 nm. The detection limit is 4.7 x 10(-7) mol L(-1), the linearity range from 2 x 10(-6) mol L(-1) to 7 x 10(-6) mol L(-1), and the correlation coefficient is r=0.9990. No significant interferences were observed from a majority of the investigated ions, such as Zn(II), Pb(II), Mn(II), Cd(II), Co(II) and Ni(II) with the exception of Cu(II), Sb(III), Fe(III), Pd(II), Sn(II) and I(-) ions. The method was successfully applied for the determination of Pt traces in different solid samples and the recovery from inorganic materials was studied.

Sample digestion methods for the determination of traces of precious metals by spectrometric techniques

Recent advances in digestion methods used in the analysis of precious metal samples by spectrometric techniques are reviewed. The applicability of a fire assay, a wet acid treatment, chlorination and alkaline oxidizing fusion to a quantitative recovery of metals from various materials is discussed. Data on the precious metal contents obtained by using particular digestion methods as well as UV-VIS spectrophotometry, atomic absorption spectrometry, atomic emission spectrometry and inductively coupled plasma mass spectrometry in the examination of various samples are tabulated.