G. Stingeder

DETERMINATION OF TRACE ELEMENTS BOUND TO SOILS AND SEDIMENT FRACTIONS (IUPAC Technical Report)

This paper presents an overview of methods for chemical speciation analysis of elements in samples of sediments and soils. The sequential leaching procedure is thoroughly discussed, and examples of different applications are shown. Despite some drawbacks, the sequential extraction method can provide a valuable tool to distinguish among trace element fractions of different solubility related to mineralogical phases. The understanding of the speciation of trace elements in solid samples is still rather unsatisfactory because the appropriate techniques are only operationally defined. The essential importance of proper sampling protocols is highlighted, since the sampling error cannot be estimated and corrected by standards. The Community Bureau of Reference (BCR) protocols for sediment and soil give a good basis for most of the solid samples, and the results can be compared among different laboratories.

Determination of Pt, Pd and Rh by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) in size-classified urban aerosol samples

Pt, Pd and Rh concentration levels related to particle size distribution were measured in Viennese aerosol. The urban aerosol was studied over a period of 1 month during summer 2002 in a heavy traffic area. A 6-stage cascade impactor collected classified particles with aerodynamic equivalent diameter (aed) <10 µm. Total suspended particulate matter (aed <30 µm) was assessed by filtering air (open face sampling head). The analysis of Pt, Pd and Rh in aerosol samples required a different strategy for each element to obtain accurate results and maximum sensitivity. Sample preparation was carried out by microwave-assisted acid digestion. For the determination of Pd an anion-exchange procedure was implemented. The digested samples were measured by ICP-SFMS in combination with ultrasonic nebulization and membrane desolvation, utilizing the high-resolution capabilities of this instrument for the determination of Rh. Pt and Pd were quantified by isotope dilution (IDMS), Rh by external calibration. Excellent detection limits of 0.07, 0.06 and 0.05 pg m−3 (impactor substrates) and 0.18, 0.22, 0.14 pg m−3 (open face sampling head substrates) for Pd, Pt and Rh, respectively, could be achieved. Since platinum group elements (PGE) are emitted from car catalysts as a result of mechanical processes, Pt, Pd and Rh were mainly found in the coarse fraction of urban aerosol. Summing up the concentrations assessed for the impactor stages (aed <10 µm) revealed a weekly average of 4.3 ± 1.7, 2.6 ± 0.6 and 0.4 ± 0.1 pg m−3 for Pt, Pd and Rh respectively. Concentration levels of samples collected with the open face sampling head (aed <30 µm) over the period of one week were significantly higher with average values of 38.1 ± 6.3, 14.4 ± 3.1 and 6.6 ± 2.4 pg m−3. Moreover, the presence of a collective of small particles containing the three investigated PGE was shown. Investigation of the impactor samples revealed an analogue size distribution for Pt, Rh and Pd with a maximum at 1–2.15 µm aed. These particles are toxicological relevant, as they penetrate deeply in human lungs (particles of 0.1–2.5 µm aed are deposited in the lung alveoli).

Two dimensional separation schemes for investigation of the interaction of an anticancer ruthenium(III) compound with plasma proteins

On-line 2-dimensional size exclusion/anion exchange chromatography was coupled to inductively coupled mass spectrometry with dynamic reaction cell technology (SEC-IC-ICP-MS) in order to characterize the interaction of the ruthenium-based anticancer drug KP1019 with human plasma proteins in vitro and, for the first time, in vivo. In SEC-ICP-MS studies the drug was found to bind exclusively to the protein fraction of 60–80 kDa in human plasma samples (clinical study/phase 1). The respective size fraction was collected and subsequently analyzed by reversed phase chromatography coupled to electrospray mass spectrometry (LC-ESI-MS) confirming the presence of the two well known transporter proteins, i.e. human serum albumin (HSA) and transferrin (Tf). Hence, for in vivo investigation of KP1019 interaction with HSA and Tf a fully automated SEC-IC-ICP-MS approach was applied. The stoichiometry of the KP1019 protein binding was determined through the molar Ru/S ratio. Human apo-Tf standards incubated with different stoichiometric equivalents of KP1019 were used for species-specific and species-unspecific calibration of the molar Ru/S ratio. Competitive in vitro incubation of KP1019 to both HSA and Tf for ca. 10 h showed that <20% of the overall KP1019 was found to bind to Tf in an equimolar mixture of Tf and HSA. This fraction dropped to 2% in the incubated mixture containing a 10-fold excess of HSA compared to Tf. This implied that less than 2% of KP1019 were expected to bind to Tf in human plasma samples, as they usually contain an even higher excess of HSA. Indeed, the concentration of the KP1019/Tf-adduct was below the limit of quantification in the plasma sample taken from a cancer patient treated with KP1019. Its fraction of the overall KP1019-content was estimated to be <1%. The KP1019/HSA stoichiometry in the plasma samples could be correlated with the individual infusions administered to the cancer patient within 26 days, the largest value being 1.4 (in the related sample, the KP1019/Tf stoichiometry was estimated to be in the range of 0.3–0.5). The KP1019/Tf ratio is in the expected range for a sufficient uptake via the transferrin pathway.

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.

Generalized Model for the Clustering of As Dopants in Si

A model for As clustering in single crystal silicon is presented that allows for the participation of arbitrary numbers of As ions, electrons, and arbitrarily charged vacancies. From this model the saturation behavior of the concentration of unclustered, electrically active As impurities is derived. It is shown that saturation (or electrical solubility) demands the participation of at least one negative charge in the formation of positively charged clusters, be it electron or negative vacancy. By analysis of our own experimental results and those by other authors, this general cluster model indicates that the participation of exactly one negative charge is the most likely case. In the course of this discussion the equilibrium saturation concentration of electrically active As is deduced from experiment as a function of temperature.

Arsenic in field‐collected soil solutions and extracts of contaminated soils and its implication to soil standards

Large concentrations of arsenic in soils, sediments, and freshwaters require risk assessment across the Central Alps and other regions. We measured arsenic concentrations in soil samples collected from 38 sites located in the Austrian Central Alps that had been contaminated due to mining and smelter activities and geogenic mineralization. Medians and ranges of arsenic concentrations (in mg kg—1) in the soil solid phase were: 77.1 (1—3000) for the total (Ast), 19.2 (0—726) for (NH4)2C2O4-extractable (Aso), 2.35 (0—169) for (NH4)2HPO4-extractable (Asp), and 0.143 (0—11.1) for (NH4)2SO4-extractable (Ass) arsenic. Arsenic concentrations in soil solutions (Assol) collected from organic surface layers and mineral horizons at five selected sites using suction cups fitted with nylon membranes ranged from 0 to 171 μg l—1. Typically, the prevailing species of As in the soil solution was As(V). Assol was correlated with Ass (Assol = 0.279 + 15.6 Ass; r2 = 0.938; n = 17) and Ast (Assol = 1.272 + 0.043 Ast; r2 = 0.833; n = 17). Using these empirical models, Assol can be predicted quite accurately based on extraction with 0.05 M (NH4)2SO4 or total arsenic concentrations in the soil. Linking these models to drinking water standards (DWS) we propose soil standards for freshwater protection that vary for Ass (mg kg—1) between 0.62 (for DWS = 10 μg l—1 WHO) and 3.19 (for DWS = 50 μg l—1). Corresponding standards for Ast (mg kg—1) are 203 (DWS = 10 μg l—1) and 1133 (DWS = 50 μg l—1). These considerations demonstrate that changes in legislation on DWS may have dramatic impact on As concentrations in soil that are acceptable for groundwater protection. Arsen in Bodenlosungen und Extrakten kontaminierter Boden und seine Bedeutung fur Bodenstandards Arsenkontaminationen in Boden, Sedimenten und Gewassern erfordern Risk Assessment in den Zentralalpen und anderen Regionen. Arsenmessungen in Bodenproben von 38 geogen oder durch Bergbau und Verhuttung kontaminierten Standorten in den osterreichischen Zentralalpen ergaben folgende Mediane und Spannweiten (in mg kg—1): 77.1 (1—3000) fur Arsen total (Ast), 19.2 (0—726) fur (NH4)2C2O4-extrahierbares (Aso), 2.35 (0—169) fur (NH4)2HPO4-extrahierbares (Asp), und 0.143 (0—11.1) fur (NH4)2SO4-extrahierbares (Ass) Arsen. Die Arsenkonzentrationen in mit Nylonsaugsonden aus organischen und Mineralbodenhorizonten an 5 ausgewahlten Standorten gewonnenen Bodenlosungen (Assol) variierten zwischen 0 und 171 μg As l—1. Die dominierende Arsenspezies in diesen Bodenlosungen war typischerweise As(V). Assol war mit Ass (Assol = 0.279 + 15.6 Ass; r2 = 0.938; n = 17) und Ast (Assol = 1.272 + 0.043 Ast; r2 = 0.833; n = 17) korreliert. Mit diesen empirischen Modellen kann Assol relativ genau aus der in 0,05 M (NH4)2SO4 gemessenen Arsenfraktion oder der Arsengesamtkonzentration geschatzt werden. Uber die Koppelung dieser Modelle mit Trinkwassergrenzwerten (DWS) konnen Bodengrenzwerte fur den Grundwasserschutz abgeleitet werden, welche fur Ass (mg kg—1) zwischen 0.62 (fur DWS = 10 μg l—1 laut WHO) und 3.19 (fur DWS = 50 μg l—1) liegen. Die entsprechenden Grenzwerte fur Ast (mg kg—1) liegen zwischen 203 (DWS = 10 μg l—1) und 1133 mg kg—1 (DWS = 50 μg l—1). Diese Uberlegungen zeigen den enormen Einfluss von Anderungen der Gesetzgebung fur DWS auf die im Hinblick auf den Grundwasserschutz akzeptablen Arsenkonzentrationen im Boden.

Concentrations of selected trace elements in human milk and in infant formulas determined by magnetic sector field inductively coupled plasma-mass spectrometry

Magnetic sector field inductively coupled plasma-mass spectrometry (ICP-MS) was applied to the reliable determination of the 8 essential trace elements cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), selenium (Se), and vanadium (V) as well as the 7 nonessential and toxic elements silver (Ag), aluminum (Al), arsenic (As), gold (Au), platinum (Pt), scandium (Sc), and titanum (Ti) in 27 transitory and mature human milk samples and in 4 selected infant formulas. This advanced instrumentation can separate spectral overlaps from the analyte signal hampering significantly the determination of many trace elements by conventional ICP-MS. Moreover, superior detection limits in the picogram per liter range can be obtained with such magnetic sector field instruments. Therefore, this is the first study to report the concentrations of the elements Ag, Au, Pt, Sc, Ti, and V in human milk and in infant formulas. Concentrations of Ag (median: 0.41 µg/L; range: <0.13–42 µg/L) and Au (median: 0.29 µg/L; range 0.10–2.06 µg/L) showed large variations in human milk that might be associated with dental fillings and jewelry. Pt concentrations were very low with most of the samples below the method detection limit of 0.01 µg/L. Human milk concentrations of Co (median: 0.19 µg/L), Fe (380 µg/L), Mn (6.3 µg/L), Ni (0.79 µg/L), and Se (17 µg/L) were at the low end of the corresponding reference ranges. Concentrations of Cr (24.3 µg/L) in human milk were five times higher than the high end of the reference range. For Al (67 µg/L), As (6.7 µg/L), and V (0.18 µg/L), most of the samples had concentrations well within the reference ranges. All elemental concentrations in infant formulas (except for Cr) were approximately one order of magnitude higher than in human milk.

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.

Investigation of element variability in tree rings of young Norway spruce by laser-ablation-ICPMS

Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) has been used to investigate the elemental variation for tree rings of 20-year-old clonal Norway spruce trees that grew nearby an aluminum smelter. Four years prior to analysis this source of fluoride pollution was shut down and the subsequent variation of the concentration of elements in the tree ring according to their mobility in the tree stem was investigated by means of a LA-ICPMS. The elements Al, Fe, Ca, Ba and Sr showed a significant increase in values after the pollution shutdown. Elements with similar chemical behavior and mobility show similar patterns of distribution. Circular investigations of tree rings show a variation of up to 60% of the elemental concentration depending on the geographical direction following the changing properties (e.g density) of wood. The circular pattern correlate again for elements with similar properties and function. Furthermore, wood which develops in response to unbalanced mechanical pressure, such as wind for example (so called compression wood) shows significant differences in element concentration compared with unstressed wood.

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.