Determination Of Isotope Ratios Research Articles

<sup>87</sup>sr/<sup>86</sup>sr ratio in vineyard soils from Portuguese denominations of origin and its potential for origin authentication

<p style="text-align: justify;"><strong>Aim</strong>: The control of geographical origin is one of the most challenging topics regarding wine authenticity. The aim of the present study was to assess the <sup>87</sup>Sr/<sup>86</sup>Sr ratio of vineyard soils from Portuguese Denominations of Origin (DO) and evaluate its suitability as a tool for origin authentication.</p><p style="text-align: justify;"><strong>Methods and results</strong>: An analytical protocol was optimized (chromatographic separation of Sr and Rb, followed by inductively coupled plasma-mass spectrometry (ICP-MS) analysis) for <sup>87</sup>Sr/<sup>86</sup>Sr isotopic ratio determination in soil-wine system. The <sup>87</sup>Sr/<sup>86</sup>Sr ratios of soils from four vineyards located in three Portuguese DO (Dão, Óbidos and Palmela), established on distinct soil types, were determined. Significant differences were found between soils of different DO regions. The soil in the Dão DO, developed on granites, showed a statistically higher <sup>87</sup>Sr/<sup>86</sup>Sr ratio than the other soils, which were developed on sedimentary formations.</p><p style="text-align: justify;"><strong>Conclusion</strong>: The results show clearly that <sup>87</sup>Sr/<sup>86</sup>Sr ratio may represent a suitable fingerprint for these Portuguese DO.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: This study highlights the relevance of setting up an international databank of <sup>87</sup>Sr/<sup>86</sup>Sr values for use for geographical identification and authentication.</p>

C & N Isotope Analysis of Diclofenac to Distinguish Oxidative and Reductive Transformation and to Track Commercial Products

Although diclofenac is frequently found in aquatic systems, its degradability in the environment remains imperfectly understood. On the one hand, evidence from concentration analysis alone is inconclusive if an unknown hydrology impedes a distinction between degradation and dilution. On the other hand, not all transformation products may be detectable. As a new approach, we therefore developed GC-IRMS (gas chromatography-isotope-ratio mass-spectrometry) analysis for carbon and nitrogen isotope measurements of diclofenac. The method uses a derivatization step that can be conducted either online or offline, for optimized throughput or sensitivity, respectively. In combination with on-column injection, the latter method enables determination of diclofenac isotope ratios down to the sub-μgL(-1) range in environmental samples. Degradation in an aerobic sediment-water system showed strong nitrogen isotope fractionation (εN = -7.1‰), whereas reductive diclofenac dechlorination was associated with significant carbon isotope fractionation (εC = -2.0‰). Hence dual element isotope analysis bears potential not only to detect diclofenac degradation, but even to distinguish both transformation pathways in the environment. In an explorative survey, analysis of commercial diclofenac products showed significant differences in carbon and nitrogen isotope ratios, demonstrating a further potential to track, and potentially even to authenticate, commercial production batches.

Charge-mode electrometer measurements of S-isotopic compositions on SHRIMP-SI

Measurement of ion currents is fundamental to isotope ratio measurements. For small signals, discrete ion arrivals can be detected in pulse counting systems. This procedure works well until a few hundred thousand counts per second when dead time and gain drift become significant. Where sufficiently high signal is available, ion currents can be measured directly in Faraday cups coupled to electrometers with high ohmic (1011, 1012Ω) resistors. However, electrometers measuring current are limited by Nyquist–Johnson noise inherent in the high ohmic resistors to effective count rates above 500,000c/s. Electrometers can also be operated in charge mode where the feedback resistor is replaced by a capacitor. In this method, charge can be accumulated on the capacitor and the ion current determined by the change in voltage with time. We have implemented this system on the secondary ion mass spectrometer SHRIMP-SI and demonstrate its performance in comparison to the electron-multiplier pulse-counting system and the current mode of the electrometers for S isotope measurements. Of particular interest to us is the measurement of the low abundance 36S isotope (0.015%). From pyrite samples, we have performed 4-isotope analyses with the initial 36S− count rate of 100,000c/s for a total acquisition time of 720s. For analyses of mass-fractionation-corrected 36S/32S ratios on S isotope standards Ruttan and Balmat, we obtain standard deviations of the measurements of 0.21 and 0.27‰, and standard errors of the means of 0.07 and 0.13‰, respectively. These measurements demonstrate that charge mode can extend the range of electrometer measurements to allow isotope ratio determinations at the 0.1‰ level from signals of 100,000c/s. Charge mode offers a fast, responsive system, with little gain drift, and is ideally suited to in situ analysis on an ion microprobe.

Determination of isotopic ratios of uranium samples using passive gamma spectroscopy with multiple detectors

Uranium samples of various enrichments have been passively counted on the University of Texas detector gamma–gamma coincidence system. By observing gamma rays emitted from 235U and its daughters compared to gamma rays emitted by 238U daughters and comparing the data to standards of known enrichments, a technique has been developed to take a uranium sample of unknown enrichment and passively count it to determine its uranium isotopic concentration. Because the gamma rays from 235U are generally in the low-energy regime, there is a strong susceptibility to background interferences, especially from the Compton background produced from higher energy gamma rays. Other interferences, such as those from the decay series of uranium also exist for 235U gamma rays. In this light, we have collected data using list-mode to produce two-dimensional gamma–gamma coincidence spectra, which allows us to gate the low-energy gamma rays from 235U with gamma rays that are in coincidence. In doing this, much of the low energy interferences are reduced, and one can analyze the 235U gamma rays with high precision. Because of the high density of uranium, self-shielding has significant effects especially in the low-energy regime. To correct for this attenuation the detector system has been modeled by MCNP and self-shielding factors have been calculated across the energy spectrum. A big advantage to this method is the capability of performing this analysis with small (<1 g) samples in a non-destructive and relatively inexpensive manner. If necessary, this analysis can be performed within 24 h if an urgent nuclear forensics scenario arises.

Isotope spectroscopy

AbstractThe measurement of isotopic ratios provides a privileged insight both into nucleosynthesis and into the mechanisms operating in stellar envelopes, such as gravitational settling. In this article, we give a few examples of how isotopic ratios can be determined from high‐resolution, high‐quality stellar spectra. We consider examples of the lightest elements, H and He, for which the isotopic shifts are very large and easily measurable, and examples of heavier elements for which the determination of isotopic ratios is more difficult. The presence of 6Li in the stellar atmospheres causes a subtle extra depression in the red wing of the 7Li 670.7 nm doublet which can only be detected in spectra of the highest quality. But even with the best spectra, the derived 6Li abundance can only be as good as the synthetic spectra used for their interpretation. It is now known that 3D non‐LTE modelling of the lithium spectral line profiles is necessary to account properly for the intrinsic line asymmetry, which is produced by convective flows in the atmospheres of cool stars, and can mimic the presence of 6Li. We also discuss briefly the case of the carbon isotopic ratio in metal‐poor stars, and provide a new determination of the nickel isotopic ratios in the solar atmosphere. (© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Precise determination of Os isotope ratios in the 15–4000 pg range using a sparging method using enhanced-sensitivity multiple Faraday collector-inductively coupled plasma-mass spectrometry

Precise determination of Os isotope ratios in 15–4000 pg Os by sparging-Multiple Faraday Cup-ICP-MS.

Final report of the key comparison CCQM-K98: Pb isotope amount ratios in bronze

Isotope amount ratios are proving useful in an ever increasing array of applications that range from studies unravelling transport processes, to pinpointing the provenance of specific samples as well as trace element quantification by using isotope dilution mass spectrometry (IDMS). These expanding applications encompass fields as diverse as archaeology, food chemistry, forensic science, geochemistry, medicine and metrology. However, to be effective tools, the isotope ratio data must be reliable and traceable to enable the comparability of measurement results.The importance of traceability and comparability in isotope ratio analysis has already been recognized by the Inorganic Analysis Working Group (IAWG) within the CCQM. While the requirements for isotope ratio accuracy and precision in the case of IDMS are generally quite modest, 'absolute' Pb isotope ratio measurements for geochemical applications as well as forensic provenance studies require Pb isotope ratio measurements of the highest quality. To support present and future CMCs on isotope ratio determinations, a key comparison was urgently needed and therefore initiated at the IAWG meeting in Paris in April 2011. The analytical task within such a comparison was decided to be the measurement of Pb isotope amount ratios in water and bronze.Measuring Pb isotope amount ratios in an aqueous Pb solution tested the ability of analysts to correct for any instrumental effects on the measured ratios, while the measurement of Pb isotope amount ratios in a metal matrix sample provided a real world test of the whole chemical and instrumental procedure. A suitable bronze material with a Pb mass fraction between 10 and 100 mg•kg-1 and a high purity solution of Pb with a mass fraction of approximately 100 mg•kg-1 was available at the pilot laboratory (BAM), both offering a natural-like Pb isotopic composition.The mandatory measurands, the isotope amount ratios n(206Pb)/n(204Pb), n(207Pb)/n(204Pb) and n(208Pb)/n(204Pb) were selected such that they correspond with those commonly reported in Pb isotopic studies and fully describe the isotopic composition of Pb in the sample. Additionally, the isotope amount ratio n(208Pb)/n(206Pb) was added, as this isotope ratio is typically measured when performing Pb quantitation by IDMS involving a 206Pb spike.Each participant was free to use any method they deemed suitable for measuring the individual isotope ratios. However, the majority of the results were obtained by using muIti-collector ICPMS or TIMS. The key requirements for all analytical procedures were a traceability statement for all results and the establishment of an uncertainty budget meeting a target uncertainty for all ratios of 0.2 %, relative (k=1). Additionally, the use of a Pb-matrix separation procedure was encouraged.The obtained overall result was excellent, demonstrating that the individual results reported by the NMIs/DIs were comparable and compatible for the determination of Pb isotope ratios. MC-ICPMS and MC-TIMS data were consistent with each other and agree to within 0.05 %. The corresponding uncertainties can be considered as realistic uncertainties and mainly range from 0.02 % to 0.08 % (k=1).As stated above isotope ratios are being increasingly used in different fields. Despite the availability and ease of use of new mass spectrometers, the metrology of unbiased isotope ratio measurements remains very challenging. Therefore, further comparisons are urgently needed, and should be designed to also engage scientists outside the NMI/DI community. Possible follow-up studies should focus on isotope ratio and delta measurements important for environmental and technical applications (e.g. B), food traceability and forensics (e.g. H, C, N, O, S and 87Sr/86Sr) or climate change issues (e.g. Li, B, Mg, Ca, Si).Main text.To reach the main text of this paper, click on Final Report.The final report has been peer-reviewed and approved for publication by the CCQM.

Determination of lead isotope ratios in environmental matrices by quadrupole ICP-MS working at low sample consumption rates

Measurement of lead isotope ratios in environmental matrices using inductively coupled plasma-dynamic reaction cell-mass spectrometry at low sample consumption rates was investigated. Two micro-sample introduction systems were evaluated, namely the PFA micronebuliser associated with a low-volume spray chamber, working at 150 μL min−1 and the total-consumption sample introduction system TISIS, operating at 20 μL min−1. In both cases, the dynamic reaction cell pressurised with ammonia was applied to improve the precision by collisional damping. Under optimal operating conditions, 208Pb/207Pb and 206Pb/207Pb ratios were accurately determined with an internal precision of 0.12–0.13% and 0.17–0.18% (%RSD, n = 10, c = 10 μg L−1; t = 10 s). The sample consumption for the assessed sample introduction systems was less than 1.5 mL and 200 μL, allowing the precise analysis of limited-size samples and pre-concentrates. The developed method was characterised in terms of the analytical working range, in-cell interference, and uncertainty estimation. The applicability of the analytical method was demonstrated by the analysis of the lichen reference material CRM 482, as well as those of several environmental samples collected from polar regions, including atmospheric particulate, snow, marine suspended particulate matter and sediment. In particular, by combining a simple pre-concentration procedure with the application of TISIS, it was possible to perform the lead isotope analysis of Antarctic snow samples at the pg g−1 concentration level.

Determination of radioactive cesium isotope ratios by triple quadrupole ICP-MS and its application to rainwater following the Fukushima Daiichi Nuclear Power Plant accident

A method was developed for the determination of 134Cs/137Cs and 135Cs/137Cs in rainwater samples using a triple quadrupole ICP-MS, with the objective of investigating radioactive cesium isotope ratios released by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. The high background caused by Ba ions and Xe impurities in argon plasma gas has made it difficult to carry out determination of the 134Cs/137Cs and 135Cs/137Cs ratios on conventional ICP-MS instruments without prior chemical separation. In this study, nitrous oxide was used as the reaction gas for reducing the isobaric interference by 134Ba, 135Ba, 137Ba and 134Xe, and an additional quadrupole in front of the reaction cell was shown to effectively remove Sn and Sb that could have produced possible interference such as SbO and SnO by the N2O reaction. The detection limit for 134Cs, 135Cs and 137Cs in solution containing Ba was successfully improved. In order to confirm the applicability of this method to the measurement of 134Cs/137Cs and 135Cs/137Cs ratios of rainwater, four samples were collected for analysis from 40–200 km away from the FDNPP. The measured 134Cs/137Cs ratios in the samples are consistent with the values determined by Ge semiconductor analysis to within the analytical error, suggesting that the developed method can provide reliable isotopic data without any correction of the mass-discrimination effect. No variation was found in the 135Cs/137Cs ratios of the four samples, suggesting either the same contamination source or a uniformly consistent mixing ratio between contamination sources. The measured 135Cs/137Cs ratios in the samples are different from global fall-out values and from that of Chernobyl. This result indicates that the value of the rainwater samples can be used as a radiocesium tracer in the environment.

Rapid, simultaneous separation of Sr, Pb, and Nd by extraction chromatography prior to isotope ratios determination by TIMS and MC-ICP-MS

A straightforward separation scheme is described for the separation of Sr, Pb, and Nd from silicate rocks.

The emerging role of carbon isotope ratio determination in health research and medical diagnostics

Variations in the isotopic signature of carbon in biological samples (e.g. breath, blood and tissues) can be used to monitor shifts in whole body metabolism. As a conservative recorder of our diet, changes in the isotopic signature of carbon in biological samples provide an objective means to distinguish dietary patterns and the relationship with diseases. In addition, metabolic discrimination of carbon within the body can be informative regarding changes in the body's metabolic fuel usage during situations where shifts in the macronutrient oxidation ratio are expected. Therefore, changes in the isotopic signature over time have proven to be a tremendously powerful and sensitive means of detecting and measuring changes in steady-state systems. As such, this review focuses on how a naturally occurring ratio of stable isotopes of carbon (13C/12C) can be used as a biomarker for nutritional and metabolic status, altered macronutrient metabolism, and health and disease.

Accurate Measurement of Isotope Amount Ratios of Lead in Bronze with Multicollector Inductively Coupled Plasma Mass Spectrometry

Isotope amount ratios of lead in a bronze sample have been successfully determined using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). Matrix separation conditions were tested and optimized using ion exchange chromatography with anion-exchange resin, AG1-X8, and sequential elution of the 0.5 M HBr and 7 M HNO3 to separate lead from very high contents of copper and tin in bronze matrix. Mercury was also removed efficiently in the optimized separation condition. The instrumental isotope fractionation of lead in the MC-ICP-MS measurement was corrected by the external stan- dard sample bracketing method using an external standard, NIST SRM 981 lead common isotope ratio standard followed by cor- rection of procedure blank to obtain reliable isotope ratios of lead. The isotope ratios, 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, 208 Pb/ 204 Pb, and 208 Pb/ 206 Pb, of lead were determined as 18.0802 ± 0.0114, 15.5799 ± 0.0099, 38.0853 ± 0.0241, and 2.1065 ± 0.0004, respec- tively, and the determined isotope ratios showed good agreement with the reference values of an international comparison for the same sample within the stated uncertainties

TOWARD A UNIQUE NITROGEN ISOTOPIC RATIO IN COMETARY ICES

Determination of the nitrogen isotopic ratios in different bodies of the solar system provides important information regarding the solar system's origin. We unambiguously identified emission lines in comets due to the 15NH2 radical produced by the photodissociation of 15NH3. Analysis of our data has permitted us to measure the 14N/15N isotopic ratio in comets for a molecule carrying the amine (-NH) functional group. This ratio, within the error, appears similar to that measured in comets in the HCN molecule and the CN radical, and lower than the protosolar value, suggesting that N2 and NH3 result from the separation of nitrogen into two distinct reservoirs in the solar nebula. This ratio also appears similar to that measured in Titan's atmospheric N2, supporting the hypothesis that, if the latter is representative of its primordial value in NH3, these bodies were assembled from building blocks sharing a common formation location.

Large-volume injection combined with gas chromatography/isotope ratio mass spectrometry for the analysis of polycyclic aromatic hydrocarbons

Compound-specific stable isotope analyses of carbon require relatively large amounts of sample for reliable analyses. Commonly applied injections of 1 μL may thus be insufficient for samples with low concentrations of pollutants (e.g. air particulate matter) or when the amount of a sample is limited. A Large-Volume Injection (LVI) method for carbon stable isotope ratio analysis of Polycyclic Aromatic Hydrocarbons (PAHs) was optimized in this study. Gas chromatography/combustion/isotope ratio mass spectrometry (GCCIRMS) and ion trap mass spectrometry (ITMS) were used for the determination of stable carbon isotope ratios and quantification of compounds, respectively. The optimized method resulted in very good reproducibility, even for the most volatile PAH, naphthalene, when a small amount of higher boiling co-solvent was used. No significant fractionation of isotope ratios could be seen and the recoveries of analytes were similar to or better than that of a splitless cold injection. Injection of 100 μL, instead of the commonly used 1 μL, increases the detection limit for PAHs significantly and/or simplifies the sample preparation step. Using our optimized method, stable carbon isotope ratios can be reliably measured in samples with concentrations of PAHs down to 0.05-0.1 ng μL(-1).

In-situ Fe isotope ratio determination in Fe–Ti oxides and sulfides from drilled gabbros and basalt from the IODP Hole 1256D in the eastern equatorial Pacific

In-situ Fe isotope measurements have been carried out to estimate the impact of the hydrothermal metamorphic overprint on the Fe isotopic composition of Fe–Ti-oxides and Fe-sulfides of the different lithologies of the drilled rocks from IODP Hole 1256D (eastern equatorial Pacific; 15Ma crust formed at the East Pacific Rise). Most igneous rocks normally have a very restricted range in their 56Fe/54Fe ratio. In contrast, Fe isotope compositions of hot fluids (>300°C) from mid-ocean-ridge spreading centers define a narrow range that is shifted to lower δ56Fe values by 0.2‰–0.5‰ as compared to igneous rocks. Therefore, it is expected that mineral phases that contain large amounts of Fe are especially affected by the interaction with a fluid that fractionates Fe isotopes during exsolution/precipitation of those minerals.We have used a femtosecond UV-Laser ablation system to determine mineral 56Fe/54Fe ratios of selected samples with a precision of <0.1‰ (2σ level) at micrometer-scale. We have found significant variations of the δ56FeIRMM-014 values in the minerals between different samples as well as within samples and mineral grains. The overall observed scale of δ56Femagnetite in 1256D rocks ranges from −0.12 to +0.64‰, and of δ56Feilmenite from −0.77 to +0.01‰. Pyrite in the lowermost sheeted dike section is clearly distinguishable from the other investigated lithological units, having positive δ56Fe values between +0.29 and +0.56‰, whereas pyrite in the other samples has generally negative δ56Fe values from −1.10 to −0.59‰.One key observation is that the temperature dependent inter-mineral fractionations of Fe isotopes between magnetite and ilmenite are systematically shifted towards higher values when compared to theoretically expected values, while synthesized, well equilibrated magnetite–ilmenite pairs are compatible with the theoretical predictions. Theoretical considerations including β-factors of different aqueous Fe-chlorides and Rayleigh-type fractionations in the presence of a hydrous, chlorine-bearing fluid can explain this observation. The disagreement between observed and theoretical equilibrium fractionation, the fact that magnetite, in contrast to ilmenite shows a slight downhole trend in the δ56Fe values, and the observation of small scale heterogeneities within single mineral grains imply that a general re-equilibration of the magnetite–ilmenite pairs is overprinted by kinetic fractionation effects, caused by the interaction of magnetite/ilmenite with hydrothermal fluids penetrating the upper oceanic crust during cooling, or incomplete re-equilibration at low temperatures.Furthermore, the observation of significant small-scale variations in the 56Fe/54Fe ratios of single minerals in this study highlights the importance of high spatial-resolution-analyses of stable isotope ratios for further investigations.

Method for the determination of concentration and stable carbon isotope ratios of atmospheric phenols

Abstract. A method for the determination of the stable carbon isotopic composition of atmospheric nitrophenols in the gas and particulate phases is presented. It has been proposed to use the combination of concentration and isotope ratio measurements of precursor and product to test the applicability of results of laboratory studies to the atmosphere. Nitrophenols are suspected to be secondary products formed specifically from the photooxidation of volatile organic compounds. XAD-4TM resin was used as an adsorbent on quartz filters to sample ambient phenols using conventional high volume air samplers at York University in Toronto, Canada. Filters were extracted in acetonitrile, with a HPLC (high-performance liquid chromatography) clean-up step and a solid phase extraction step prior to derivatization with BSTFA (bis(trimethylsilyl) trifluoroacetamide). Concentration measurements were done with gas chromatography–mass spectrometry and gas chromatography–isotope ratio mass spectrometry was used for isotope ratio analysis. The technique presented allows for atmospheric compound-specific isotopic composition measurements for five semi-volatile phenols with an estimated accuracy of 0.3–0.5‰ at atmospheric concentrations exceeding 0.1 ng m−3 while the detection limits for concentration measurements are in the pg m−3 range. Isotopic fractionation throughout the entire extraction procedure and analysis was proven to be below the precision of the isotope ratio measurements. The method was tested by conducting ambient measurements from September to December 2011.

An Assessment of Sample Preservation Methods for the Determination of Stable Carbon and Nitrogen Isotope Ratios in Mollusks

The aim of this study was to quantify the effects of preservation methods and preservation times on the stable carbon and nitrogen isotope values in the tissues of six mollusk species (Mytilus edulis, Crassostrea gigas, Ruditapes philippinarum, Acanthochiton seulschnochilon, Littorina brevicula, and Rapana venosa). To identify potential preservation effects on δ13C and δ15N values and to examine temporal changes in the effects of preservation, repeated analyses were carried out after 1 day, 5 days, 15 days, 1 month, 3 months, 6 months, and 12 months of preservation. The results showed that drying preservation was the most suitable method for preserving samples, while freezing and chemical preservation significantly affected the stable isotope values compared with those of the controls. The effects of preservatives on the tissues of different mollusk species were statistically significant for both δ13C and δ15N values. Shifts in the δ13C and δ15N values, due to freezing and chemical preservation, were higher in Acanthochiton seulschnochilon, Littorina brevicula, and Rapana venosa than in the other three species. The effects of preservatives on carbon isotope values were variable. In most cases, the shift of the δ13C values from the control samples were less than 1% for those of the treated samples. The δ13C and δ15N data from the preserved samples could thus be used in food web reconstruction studies. Further studies will be necessary, however, in order to elucidate the effects of preservation type and time on other species.

Determination of lead and isotope ratios in whole blood by inductively coupled plasma mass spectrometry

To establish a method to determine lead and Isotope Ratios in whole blood by inductively coupled plasma mass spectrometry (ICP-MS). The whole blood samples was removed protein by 5% nitric acid , Online join thallium (Tl) as internal standard substance, used lyophilized bovine blood lead and cadmium standard material (GBW09139h and GBW09140h) for quality control of blood lead concentrations. Lead isotope standard substances (GBW04426) is used to determine the correction factor, lead isotope ratios will lead isotope standard reference material NIST SRM981 by icp-ms with samples for testing. Optimize the detection method, detection of blood lead and lead isotope, and the method of linear range r >0.9999, GBW09139h and GBW09140h test results are within the scope of quality control. NIST SRM981 isotope determination precision RSD<1%, NIST SRM981 test results and the certificate of value close to. The method is simple and convenient data is reliable, can meet the total lead (pb) in blood and former isotope simultaneous determination.

Mantle melting in within-plate continental settings: Sr–Nd–Pb and U-series isotope constraints in alkali basalts from the Sicily Channel (Pantelleria and Linosa Islands, Southern Italy)

The origin of the mantle sources of the Na-alkaline magmas erupted within the continental rift of the Sicily Channel and their melting behaviour are here investigated through the determination of Sr, Nd and Pb isotope ratios and U-series disequilibria on basaltic volcanic rocks from Linosa and Pantelleria. The isotope data, along with trace element ratios are used to assess the possible role of the interaction with the continental crust and/or the Sub-Continental Lithospheric Mantle (SCLM). The data show little variation in Sr and Nd isotopes and a continuous trend toward more radiogenic Pb isotope composition from Linosa to the oldest mafic activity of Pantelleria (i.e. Paleo-Pantelleria), with intermediate values measured in the youngest Pantelleria lavas (Neo-Pantelleria). Pantelleria basalts have ubiquitous 230Th-excess ranging from 7% to 20%. These data suggest the magmas are originated within the asthenospheric mantle, with little or no interaction with either the continental crust or the SCLM. The increasing FOZO-like character of the studied magmas and the variation of some key trace element ratios (e.g. Rb/La) argue for an increasing role of recycled oceanic material in the form of eclogite/pyroxenite dispersed within the mantle sources of these magmas. A completely distinct isotope composition is recorded in Neo-Pantelleria hawaiites from Khartibucale, which show significantly higher 87Sr/86Sr and lower 143Nd/144Nd, 206Pb/204Pb, (238U/232Th) and (230Th/232Th), but comparable (230Th/238U) with respect to all the other rocks studied. These rocks cannot be considered co-genetic with other Pantelleria basalts and are interpreted either as related to interaction with partial melts of the SCLM or to be originated from a mantle source enriched by recycled crustal material (EM-like). 235U–231Pa disequilibria were also measured in one Neo-Pantelleria hawaiite and one Neo-Pantelleria basalt. The coupled (230Th/238U)=1.20 and (231Pa/235U)=1.39 of the latter were used to perform quantitative dynamic melting models in order to constrain physical parameters of mantle melting in the Sicily Channel. The combined modelling yielded positive solutions only for high DU/DTh (≥2.5) and low melting rates (Γ<1×10−4kg/m3/a). These data argue against any important role for amphibole in the genesis of these magmas and are consistent with a peridotite source possibly well mixed with recycled components. The modelled values of Γ can also be converted into estimates of the upwelling rate of the mantle that are compatible with slow passive upwelling along the Sicily Channel rift.

Application of laser ablation inductively coupled plasma multicollector mass spectometry in determination of lead isotope ratios in common glass for forensic purposes

Samples of glass used as trace evidence in criminal cases are commonly small, with particle sizes below a millimeter. To perform chemical analysis suitable for forensic purposes, methods capable of analyzing such small samples are required.In this paper, analyses of lead isotope ratios by means of laser ablation inductively coupled multicollector mass spectrometry (LA-MC-ICP-MS) are presented. Sampling by use of laser ablation allows fragments down to 0.1mg to be analyzed with sufficient precision to discriminate between glasses of different origin. In fact, the use of lead isotopes determined by LA-MC-ICP-MS approaches the discrimination attainable by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) analysis of dissolved samples of 5mg or more.Further, we have obtained a probability distribution by two dimensional kernel density estimates for the collected data set as an alternative presentation method to the well-established bivariate plot. The underlying information available from kernel density estimates is of importance for forensic scientists involved in probabilistic interpretation of physical evidence.