Christopher Latkoczy

MPI‐DING reference glasses for in situ microanalysis: New reference values for element concentrations and isotope ratios

We present new analytical data of major and trace elements for the geological MPI-DING glasses KL2-G, ML3B-G, StHs6/80-G, GOR128-G, GOR132-G, BM90/21-G, T1-G, and ATHO-G. Different analytical methods were used to obtain a large spectrum of major and trace element data, in particular, EPMA, SIMS, LA-ICPMS, and isotope dilution by TIMS and ICPMS. Altogether, more than 60 qualified geochemical laboratories worldwide contributed to the analyses, allowing us to present new reference and information values and their uncertainties (at 95% confidence level) for up to 74 elements. We complied with the recommendations for the certification of geological reference materials by the International Association of Geoanalysts (IAG). The reference values were derived from the results of 16 independent techniques, including definitive (isotope dilution) and comparative bulk (e.g., INAA, ICPMS, SSMS) and microanalytical (e.g., LA-ICPMS, SIMS, EPMA) methods. Agreement between two or more independent methods and the use of definitive methods provided traceability to the fullest extent possible. We also present new and recently published data for the isotopic compositions of H, B, Li, O, Ca, Sr, Nd, Hf, and Pb. The results were mainly obtained by high-precision bulk techniques, such as TIMS and MC-ICPMS. In addition, LA-ICPMS and SIMS isotope data of B, Li, and Pb are presented.

Investigation of Sr isotope ratios in prehistoric human bones and teeth using laser ablation ICP-MS and ICP-MS after Rb/Sr separation

87Sr/86Sr isotope ratio measurements on bone and teeth tissue were used in order to assess prehistoric human migration. Microstructural changes of skeletal remains caused by post mortem influences (especially dissolving and re-crystallization), may lead to erratic results, if invasive techniques (e.g. digestion and liquid nebulization ICP-MS) are used. Therefore, Rb/Sr separation performed on digested sample solutions prior to ICP-MS measurements was optimized and we developed a procedure to separate Sr from Rb quantitatively to enable a fast and reliable interference free measurement of Sr isotope ratios. As main goal, we have applied LA-ICP-MS on transversal bone cross sections on diagenetically altered and non-altered areas making use of both high lateral resolution and isotope ratio capabilities. Sr isotope ratio measurements on bone material were performed with an instrumental precision between 0.1 and 0.2% RSD by LA-ICP-MS. We could reveal mineralized phases (Brushit) histomorphologically within the cross section of cortical femur samples. Those crystallites showed a significantly increased amount of Rb. The results indicate that these products are exogenous. In addition, human teeth were analyzed for their 87Sr/86Sr isotope ratio primarily to investigate possible differences in enamel and dentine. LA-ICP-MS led to excellent results and shows RSD of isotope ratio measurements of about 0.1–0.2% on both enamel and dentine. One specific individual (from Neolithic Asparn/Schletz) was investigated using the prior methods and showed homogeneous Sr isotope ratios in dentine and bone, while the Sr isotopic composition in enamel was significantly different. This result demonstrates a possible migration of this individual during early childhood.

Strontium isotope ratio measurements in prehistoric human bone samples by means of high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS)

This paper explores the suitability and application range of a commercially available high-resolution ICP-mass spectrometer (Finnigan MAT Element) in determining strontium isotope ratios of human bone samples. Any paleoanthropological interpretation of such samples requires a highly accurate isotopic ratio determination with a precision of at least 0.1% relative standard deviation (RSD). Thus, optimum instrument operating parameters such as sampling time, scan duration, and instrumental bias factors including mass bias and deadtime, were investigated in an initial step. The instrument itself was used without modification but equipped with a commercial microconcentric nebulizer. All experiments were performed under clean room conditions with filtered (class 10.000), temperature controlled, and excess pressured air. Complementary mathematical correction methods like deadtime and mass bias corrections, allowed the achievement of a87Sr/86Sr isotope ratio precision below 0.03% (RSD for n=5). Compared with the certified NIST SRM 987 Strontium Carbonate (Isotopic) value (0.71034±0.00026), our 87Sr/86Sr isotopic ratio revealed a 0.7103±0.0002 match. This optimized procedure was performed on 7000-year-old human skeleton samples from a Neolithic settlement in Asparn/Schletz, Lower Austria, to determine their stable strontium isotope ratio. Specific isotope patterns thereby shed light on the provenance of single individuals.

High-resolution Sr/Ca records in sclerosponges calibrated to temperature in situ

Ratios of strontium to calcium have been analyzed by laser- ablation inductively coupled plasma-mass spectrometry (LA-ICP- MS) in a skeletal section of the sclerosponge Ceratoporella nichol- soni. The growth period, representative of 3 yr, was stained in the skeleton with a fluorochrome (calcein). Temperatures were record- ed at 2 h intervals within the shallow, cryptic reef enclosure that the sclerosponge inhabited on the northern coast of Jamaica, al- lowing the formulation of a direct empirical relationship between Sr/Ca and temperature. To verify this calibration, Sr/Ca ratios of two sclerosponges of the same species from depths of 67 m and 136 m in Exuma Sound, Bahamas, were analyzed by LA-ICP-MS and compared to the temperatures from these depths over a decade prior to collection. The result is an independently verified, high- resolution empirical calibration for the temperature sensitivity of Sr/Ca ratios in the aragonite skeletons of sclerosponges from Ja- maica and the Bahamas. The calibration is a first for C. nicholsoni and indicates that sclerosponges are more sensitive temperature recorders than zooxanthellate corals. It represents an important step in establishing skeletal geochemistry of sclerosponges as a proxy of temperature in the upper 250 m of the ocean.

Precise sulfur isotope ratio measurements in trace concentration of sulfur by inductively coupled plasma double focusing sector field mass spectrometry

Sulfur isotope ratios ( 34 S/ 32 S) were determined by means of inductively coupled plasma double focusing sector field mass spectrometry (ICP-SMS) operated in the medium resolution mode (m/Δm=4000) using a torch with a platinum guard electrode and a microconcentric nebulizer combined with a membrane desolvation unit. The guard electrode together with the nebulizing unit increased the signal intensity of the measured isotopes by two orders of magnitude. The use of the membrane desolvation unit decreased the signal intensity of the corresponding interference (mainly oxygen containing species) significantly. Detection limits in solution of 0.01 ng g –1 , limited only by blank levels, could be achieved. Moreover, sulfur isotope ratios could be determined at concentration levels down to 1 ng g –1 with a precision of better than 0.1% relative standard deviation (RSD) (n=10). A precision of 0.04% RSD could be achieved at higher concentration levels. ICP-SMS has been shown to be an excellent tool for fast and precise isotope ratio measurements in combination with a high sample throughput and minimum sample preparation prior to analysis.

Determination of rare earth elements U and Th in environmental samples by inductively coupled plasma double focusing sectorfield mass spectrometry (ICP-SMS)

The excellent capability of high resolution inductively coupled plasma sectorfield mass spectrometry for measurements of the rare earth elements Th and U is demonstrated by investigating different materials such as geological matrices (sediments, soils), plant tissues and marine animal tissues. Appropriate digestion of the samples resulted in complex matrices, especially in the case of silicate containing samples. The elemental loss in silicate residues of plant material was found to be up to 30% and therefore required HF-containing digestion methods. The high concentration of matrix elements leads to spectral interferences, which are investigated by measuring the elements with different mass resolution. High mass resolution is shown to be a prerequisite for accurate determination of Sc and Y, respectively. Furthermore, effects of non spectral interferences are investigated and could be properly corrected for by using 115 In as internal standard. Moreover, the capability of a microconcentric nebulizer in combination with a membrane desolvation unit compared to a conventional microconcentric nebulizer is discussed with respect to suppression of spectral interferences. Oxide interferences could be reduced to a negligible amount, whereas it could be observed that high salt freight leads to a blockage of the membrane.

Development and evaluation of a standard method for the quantitative determination of elements in float glass samples by LA-ICP-MS.

Forensic analysis of glass samples was performed in different laboratories within the NITE-CRIME (Natural Isotopes and Trace Elements in Criminalistics and Environmental Forensics) European Network, using a variety of Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) systems. The main objective of the interlaboratory tests was to cross-validate the different combinations of laser ablation systems with different ICP-MS instruments. A first study using widely available samples, such as the NIST SRM 610 and NIST SRM 612 reference glasses, led to deviations in the determined concentrations for trace elements amongst the laboratories up to 60%. Extensive discussion among the laboratories and the production of new glass reference standards (FGS 1 and FGS 2) established an improved analytical protocol, which was tested on a well-characterized float glass sample (FG 10-1 from the BKA Wiesbaden collection). Subsequently, interlaboratory tests produced improved results for nearly all elements with a deviation of < 10%, demonstrating that LA-ICP-MS can deliver absolute quantitative measurements on major, minor and trace elements in float glass samples for forensic and other purposes.

Determination of sulfur in fluid inclusions by laser ablation ICP-MS

The quantification capabilities for sulfur microanalysis in quartz-hosted fluid inclusions were investigated with laser ablation (LA) inductively coupled plasma quadrupole mass spectrometry (ICP-Q-MS) and ICP sector field mass spectrometry (ICP-SF-MS) allowing resolution of sulfur from polyatomic interferences. A scapolite mineral sample was used to determine the sulfur concentration in NIST SRM 610 (570 ± 70 µg g−1), which was further validated using EPMA and then used as standard reference material for the fluid inclusion analysis. The sulfur concentration in an assemblage of brine inclusions from a quartz–molybdenum vein was determined to be 5900 ± 2000 µg g−1 measuring 17 inclusions with the ICP-SF-MS and 13 inclusions with the ICP-Q-MS instrument. The agreement between the two ICP-MS instruments for sulfur was ∼5% and well within the overall precision of 35% relative standard deviation. The precision and accuracy was not limited by interferences, but by a so far unknown sulfur contamination source when ablating the host mineral quartz. Due to this contamination, a careful baseline correction is necessary which is described and discussed in detail. Nevertheless, the method developed to determine sulfur maintains the multi-element capabilities for individual fluid inclusions. Limits of detection for sulfur are correlated with the inclusion mass and were found to be ∼ 30–100 µg g−1 for 60 μm inclusions.

Iron-60 Heterogeneity and Incomplete Isotope Mixing in the Early Solar System

Short-lived radionuclides (e.g., 26Al, 53Mn, 60Fe, 182Hf) are widely used to refine the chronology of the early solar system. They provide chronological information, however, only if they were homogeneously distributed in the source region of the objects under scrutiny at the time of their formation. With the high level of precision now achieved on isotopic measurements, very short time intervals can in principle be resolved and a precise evaluation of the initial homogeneity degree becomes increasingly crucial. High-precision nickel isotope data for differentiated meteorites (angrites, ureilites) and chondritic (CB) components allow us to test the initial distribution of radioactive 60Fe and stable Ni isotopes. Although these meteorites appear to have formed nearly contemporaneously, they yield variable initial 60Fe/56Fe ratios. Besides, the CB metal nodules and ureilite silicates show nucleosynthetic anomalies. The new data presented here do not confirm the recently inferred late injection of 60Fe into the protoplanetary disk. Instead, live 60Fe was present, but heterogeneously distributed, from the start of the solar system, revealing an incomplete mixing of material from various nucleosynthetic sources and restricting the use of the 60Fe-60Ni system as a chronometer.

Application of laser ablation (LA-ICP-SF-MS) for the elemental analysis of bone and teeth samples for discrimination purposes

Human bone and teeth fragments can be useful evidence when found in crime scenes and/or mass burials sites. The elemental and isotopic composition of these samples can provide information about environmental exposure events and could also be used to distinguish different individuals. The development and application of robust analytical methods for the quantification of trace elements in these biological matrices may lead to a better understanding of the potential utility of these measurements in forensic analyses. In this paper, we demonstrate the possibility of conducting quantitative analysis of trace metals found in bone remains and suggest a strategy to discriminate between individuals, based on this information. A LA-ICP-SF-MS method using non-matrix matched standard calibration was developed and optimized with bone standard reference materials (SRMs) and subsequently applied to the analysis of real samples. The developed method requires micrograms amount of sample (vs. milligrams required for solution-based analysis) while also reducing the analysis time and resulting in good accuracy (typically <10% bias) and precision (<15% RSD). Additionally, laser ablation allowed using spatial resolution analysis to assess the biogenic elemental composition in buried bone samples. Elemental analysis of bone samples from 12 different individuals provided better discrimination between the individuals when the femur and humerus bones were considered separately (42.7% correct classification with all bones vs. 75.2% and 63.1% for femur bones and humerus bones, respectively). Separation of individuals was achieved by elemental composition of whole teeth samples from 14 individuals, except one case where not all the teeth from the same individual were associated together. Separation of individuals was improved when using elemental composition of the enamel and dentine+cementum layers separately in a set of samples from 7 individuals. These are promising results for the use of elemental analysis by laser ablation ICP-MS for discrimination purposes.