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Analytical and Bioanalytical Chemistry (v.405, #9)

Isotope ratio measurements: new developments and applications by Klaus G. Heumann; Torsten C. Schmidt (pp. 2747-2748).

is Emeritus Professor of Analytical Chemistry at Johannes Gutenberg University Mainz. His research interests are in the development and application of analytical methods for determination of trace elements and trace amounts of elemental species, by use of inductively coupled plasma mass spectrometry, thermal ionization mass spectrometry, different types of optical atomic spectrometry, and electroanalysis as detection methods, and high-performance liquid chromatography, capillary electrophoresis, and capillary gas chromatography as separation methods. He has received several awards, including the Clemens Winkler Medal of the German Society for Analytical Chemistry in 2004 for his scientific lifework and for his continuous support of analytical chemistry in Germany. In 2007 he received the European Award for Plasma Spectrochemistry. He is a member of several national and international scientific societies, and was a member of the IUPAC Commission on Atomic Weights and Isotopic Abundances for 12 years, including chairman from 1991 to 1995. obtained his PhD degree in Analytical Chemistry in 1997 from Philipps University Marburg. After a postdoctoral stay at EAWAG/ETH Zurich he became senior scientist at the Center for Applied Geoscience at Eberhard Karls University of Tuebingen where he finished his habilitation 2006. In the same year he was appointed Chair of Instrumental Analytical Chemistry at the University of Duisburg-Essen (W3) and scientific director at the IWW Water Centre in Muelheim an der Ruhr. He has been interested in stable isotope analysis since his postdoctoral work and, in the meantime, been involved in the set-up of four stable isotope laboratories. Research focus in isotope analysis is on compound-specific stable isotope analysis of biogeochemically relevant elements using chromatographic separations with online coupled isotope ratio mass spectrometry. On that topic, with his coworker Maik A. Jochmann, he recently published the first comprehensive textbook. Apart from stable isotope analysis, his current research interests comprise sample preparation in environmental analysis, separation techniques, sorption in natural and engineered systems, and advanced oxidation processes. This year he became chairman of the executive board of the German Water Chemistry Society within GDCh.

Frank Vanhaecke and Patrick Degryse (Eds.): Isotopic analysis. Fundamentals and applications using ICP–MS by Freddy Adams (pp. 2749-2751).

Maik A. Jochmann and Torsten C. Schmidt: Compound-specific stable isotope analysis by Thomas B. Hofstetter (pp. 2753-2754).

Atomic weights: not so constant after all by Willi A. Brand (pp. 2755-2761).

is Head of the Stable Isotope Laboratories at the Max Planck Institute for Biogeochemistry (http://www.bgc-jena.mpg.de/) in Jena, Germany. This service facility specializes in high-precision isotope assessment of relevant air constituents such as CO₂ or CH₄ and has been selected by the World Meteorological Organization as the central calibration laboratory for CO₂ isotopes in air. It also routinely analyze stable isotopes in water, bulk organic matter, and tree rings. A large part of its activities involve standardization, where it cooperates with the IAEA and other research laboratories to provide new certification for reference materials, which are also important for precise atomic weights. Since 2009, W.A. Brand has been Chair of the IUPAC Commission on Isotope Abundances and Atomic Weights (http://www.ciaaw.org).

The need for new isotope reference materials by Jochen Vogl; Martin Rosner; Wolfgang Pritzkow (pp. 2763-2770).

Isotope reference materials are needed to calibrate and validate analytical procedures used for the determination of isotope amount ratios, procedurally defined isotope ratios or so-called δ values. In contrast to the huge analytical progress in isotope ratio analytics, the production of isotope reference materials has not kept pace with the increasing needs of isotope analysts. Three representative isotope systems are used to explain the technical and non-technical difficulties and drawbacks, on one hand, and to demonstrate what can be achieved at its best, on the other hand. A clear statement is given that new isotope reference materials are needed to obtain traceable and thus comparable data, which is essential for all kinds of isotope research. The range of available isotope reference materials and δ reference materials should be increased and matrix reference materials certified for isotope compositions or δ values, which do not exist yet, should be provided.

Keywords: Isotope reference materials; Delta reference materials; Synthetic isotope mixtures; Mass spectrometry; Comparability; Traceability; Measurement uncertainty

Heavy element stable isotope ratios : analytical approaches and applications by Masaharu Tanimizu; Yoshiki Sohrin; Takafumi Hirata (pp. 2771-2783).

Continuous developments in inorganic mass spectrometry techniques, including a combination of an inductively coupled plasma ion source and a magnetic sector-based mass spectrometer equipped with a multiple-collector array, have revolutionized the precision of isotope ratio measurements, and applications of inorganic mass spectrometry for biochemistry, geochemistry, and marine chemistry are beginning to appear on the horizon. Series of pioneering studies have revealed that natural stable isotope fractionations of many elements heavier than S (e.g., Fe, Cu, Zn, Sr, Ce, Nd, Mo, Cd, W, Tl, and U) are common on Earth, and it had been widely recognized that most physicochemical reactions or biochemical processes induce mass-dependent isotope fractionation. The variations in isotope ratios of the heavy elements can provide new insights into past and present biochemical and geochemical processes. To achieve this, the analytical community is actively solving problems such as spectral interference, mass discrimination drift, chemical separation and purification, and reduction of the contamination of analytes. This article describes data calibration and standardization protocols to allow interlaboratory comparisons or to maintain traceability of data, and basic principles of isotope fractionation in nature, together with high-selectivity and high-yield chemical separation and purification techniques for stable isotope studies. Figure Isotope ratios of the elements can vary through almost all the chemical and biochemical reactions in nature

Keywords: Heavy element stable isotopes; Multiple-collector array inductively coupled plasma mass spectrometry; Metallomics; Seawater; Isotope standard; Isotope effect

Isotopic analyses by ICP-MS in clinical samples by Ilia Rodushkin; Emma Engström; Douglas C. Baxter (pp. 2785-2797).

This critical review focuses on inductively coupled plasma mass spectrometry (ICP-MS) based applications for isotope abundance ratio measurements in various clinical samples relevant to monitoring occupational or environmental exposure, human provenancing and reconstruction of migration pathways as well as metabolic research. It starts with a brief overview of recent advances in ICP-MS instrumentation, followed by selected examples that cover the fields of accurate analyte quantification using isotope dilution, tracer studies in nutrition and toxicology, and areas relying upon natural or man-made variations in isotope abundance ratios (Pb, Sr, actinides and stable heavy elements). Finally, some suggestions on future developments in the field are provided.

Keywords: Inductively coupled plasma mass spectrometry; Isotope ratios; Body fluids; Tissues; Clinical samples

Ensuring the reliability of stable isotope ratio data—beyond the principle of identical treatment by J. F. Carter; B. Fry (pp. 2799-2814).

The need for inter-laboratory comparability is crucial to facilitate the globalisation of scientific networks and the development of international databases to support scientific and criminal investigations. This article considers what lessons can be learned from a series of inter-laboratory comparison exercises organised by the Forensic Isotope Ratio Mass Spectrometry (FIRMS) network in terms of reference materials (RMs), the management of data quality, and technical limitations. The results showed that within-laboratory precision (repeatability) was generally good but between-laboratory accuracy (reproducibility) called for improvements. This review considers how stable isotope laboratories can establish a system of quality control (QC) and quality assurance (QA), emphasising issues of repeatability and reproducibility. For results to be comparable between laboratories, measurements must be traceable to the international δ-scales and, because isotope ratio measurements are reported relative to standards, a key aspect is the correct selection, calibration, and use of international and in-house RMs. The authors identify four principles which promote good laboratory practice. The principle of identical treatment by which samples and RMs are processed in an identical manner and which incorporates three further principles; the principle of identical correction (by which necessary corrections are identified and evenly applied), the principle of identical scaling (by which data are shifted and stretched to the international δ-scales), and the principle of error detection by which QC and QA results are monitored and acted upon. To achieve both good repeatability and good reproducibility it is essential to obtain RMs with internationally agreed δ-values. These RMs will act as the basis for QC and can be used to calibrate further in-house QC RMs tailored to the activities of specific laboratories. In-house QA standards must also be developed to ensure that QC-based calibrations and corrections lead to accurate results for samples. The δ-values assigned to RMs must be recorded and reported with all data. Reference materials must be used to determine what corrections are necessary for measured data. Each analytical sequence of samples must include both QC and QA materials which are subject to identical treatment during measurement and data processing. Results for these materials must be plotted, monitored, and acted upon. Periodically international RMs should be analysed as an in-house proficiency test to demonstrate results are accurate.

Keywords: Stable isotope ratio measurements; Isotope-ratio mass spectrometry; Reference materials; Principle of identical treatment; Quality assurance; Quality control

Normalization procedures and reference material selection in stable HCNOS isotope analyses: an overview by Grzegorz Skrzypek (pp. 2815-2823).

The uncertainties of stable isotope results depend not only on the technical aspects of measurements, but also on how raw data are normalized to one of the international isotope scales. The inconsistency in the normalization methods used and in the selection of standards may lead to substantial differences in the results obtained. Therefore, unification of the data processing protocols employed is highly desirable. The best performing methods are two-point or multipoint normalization methods based on linear regression. Linear regression is most robust when based on standards that cover the entire range of δ values typically observed in nature, regardless of the δ values of the samples analysed. The uncertainty can be reduced by 50 % if measurements of two different standards are performed four times, or measurements of four standards are performed twice, with each batch of samples. Chemical matrix matching between standards and samples seems to be critical for δ ¹⁸O of nitrate or δ ²H of hair samples (thermal conversion/elemental analyser), for example; however, it is not necessarily always critical for all types of samples and techniques (e.g. not for most δ ¹⁵N and δ ¹³C elemental analyser analyses). To ensure that all published data can be recalculated, if δ values of standards or the isotope scales are to be updated, the details of the normalization technique and the δ values of the standards used should always be clearly reported.

Keywords: Stable isotope; Normalization; Reference material; Uncertainty; Review

Enantioselective stable isotope analysis (ESIA) of polar herbicides by Michael P. Maier; Shiran Qiu; Martin Elsner (pp. 2825-2831).

Assessing the environmental fate of chiral micropollutants such as herbicides is challenging. The complexity of aquatic systems often makes it difficult to obtain hydraulic mass balances, which is a prerequisite when assessing degradation based on concentration data. Elegant alternatives are concentration-independent approaches like compound-specific isotope analysis or enantiospecific concentration analysis. Both detect degradation-induced changes from ratios of molecular species, either isotopologues or enantiomers. A combination of both—enantioselective stable isotope analysis (ESIA)—provides information on ¹³C/¹²C ratios for each enantiomer separately. Recently, Badea et al. demonstrated for the first time ESIA for the insecticide α-hexachlorocyclohexane. The present study enlarges the applicability of ESIA to polar herbicides such as phenoxy acids: 4-CPP ((RS)-2-(4-chlorophenoxy)-propionic acid), mecoprop (2-(4-chloro-2-methylphenoxy)-propionic acid), and dichlorprop (2-(2,4-dichlorophenoxy)-propionic acid). Enantioselective gas chromatography–isotope ratio mass spectrometry was accomplished with derivatization prior to analysis. Precise carbon isotope analysis (2σ ≤ 0.5‰) was obtained with ≥7 ng C on column. Microbial degradation of dichlorprop, 2-(2,4-dichlorophenoxy)-propionic acid by Delftia acidovorans MC1 showed pronounced enantiomer fractionation, but no isotope fractionation. In contrast, Badea et al. observed isotope fractionation, but no enantiomeric fractionation. Hence, the two lines of evidence appear to complement each other. They may provide enhanced insight when combined as ESIA.

Keywords: Chiral micropollutants; Pesticides; Derivatization; Isotope fractionation; Herbicide; BF₃

Position-specific isotope analysis of the methyl group carbon in methylcobalamin for the investigation of biomethylation processes by Oliver Wuerfel; Markus Greule; Frank Keppler; Maik A. Jochmann; Torsten C. Schmidt (pp. 2833-2841).

In the environment, the methylation of metal(loid)s is a widespread phenomenon, which enhances both biomobility as well as mostly the toxicity of the precursory metal(loid)s. Different reaction mechanisms have been proposed for arsenic, but not really proven yet. Here, carbon isotope analysis can foster our understanding of these processes, as the extent of the isotopic fractionation allows to differentiate between different types of reaction, such as concerted (S_N2) or stepwise nucleophilic substitution (S_N1) as well as to determine the origin of the methyl group. However, for the determination of the kinetic isotope effect the initial isotopic value of the transferred methyl group has to be determined. To that end, we used hydroiodic acid for abstraction of the methyl group from methylcobalamin (CH₃Cob) or S-adenosyl methionine (SAM) and subsequent analysis of the formed methyl iodide by gas chromatography (GC) isotope ratio mass spectrometry (IRMS). In addition, three further independent methods have been investigated to determine the position-specific δ ¹³C value of CH₃Cob involving photolytic cleavage with different additives or thermolytic cleavage of the methyl-cobalt bonding and subsequent measurement of the formed methane by GC-IRMS. The thermolytic cleavage gave comparable results as the abstraction using HI. In contrast, photolysis led to an isotopic fractionation of about 7 to 9 ‰. Furthermore, we extended a recently developed method for the determination of carbon isotope ratios of organometal(loid)s in complex matrices using hydride generation for volatilization and matrix separation before heart-cut GC and IRMS to the analysis of the low boiling partly methylated arsenicals, which are formed in the course of arsenic methylation. Finally, we demonstrated the applicability of this methodology by investigation of carbon fractionation due to the methyl transfer from CH₃Cob to arsenic induced by glutathione. Position-specific isotope analysis of the methyl group in CH₃Cob by abstraction using HI and subsequent analysis of formed CH₃I by GC-IRMS

Keywords: Methylcobalamin; PSIA; Arsenic; Methylation; Hydride generation; Isotope analysis

Compound-specific isotope analysis of benzotriazole and its derivatives by Stephanie Spahr; Sebastian Huntscha; Jakov Bolotin; Michael P. Maier; Martin Elsner; Juliane Hollender; Thomas B. Hofstetter (pp. 2843-2856).

Compound-specific isotope analysis (CSIA) is an important tool for the identification of contaminant sources and transformation pathways, but it is rarely applied to emerging aquatic micropollutants owing to a series of instrumental challenges. Using four different benzotriazole corrosion inhibitors and its derivatives as examples, we obtained evidence that formation of organometallic complexes of benzotriazoles with parts of the instrumentation impedes isotope analysis. Therefore, we propose two strategies for accurate $delta^{13}$ C and $delta^{15}$ N measurements of polar organic micropollutants by gas chromatography isotope ratio mass spectrometry (GC/IRMS). Our first approach avoids metallic components and uses a Ni/Pt reactor for benzotriazole combustion while the second is based on the coupling of online methylation to the established GC/IRMS setup. Method detection limits for on-column injection of benzotriazole, as well as its 1-CH $_{3}$ -, 4-CH $_{3}$ -, and 5-CH $_{3}$ -substituted species were 0.1–0.3 mM and 0.1–1.0 mM for δ¹³C and δ¹⁵N analysis respectively, corresponding to injected masses of 0.7–1.8 nmol C and 0.4–3.0 nmol N, respectively. The Ni/Pt reactor showed good precision and was very long-lived ( $>$ 1000 successful measurements). Coupling isotopic analysis to offline solid-phase extraction enabled benzotriazole-CSIA in tap water, wastewater treatment effluent, activated sludge, and in commercial dishwashing products. A comparison of $delta ^{13}$ C and $delta ^{15}$ N values from different benzotriazoles and benzotriazole derivatives, both from commercial standards and in dishwashing detergents, reveals the potential application of the proposed method for source apportionment.

Keywords: CSIA; Gas chromatography isotope ratio mass spectrometry; Benzotriazole; Corrosion inhibitors; Micropollutants; Source identification

Carbon and nitrogen isotope analysis of atrazine and desethylatrazine at sub-microgram per liter concentrations in groundwater by Kathrin Schreglmann; Martina Hoeche; Sibylle Steinbeiss; Sandra Reinnicke; Martin Elsner (pp. 2857-2867).

Environmental degradation of organic micropollutants is difficult to monitor due to their diffuse and ubiquitous input. Current approaches—concentration measurements over time, or daughter-to-parent compound ratios—may fall short, because they do not consider dilution, compound-specific sorption characteristics or alternative degradation pathways. Compound-specific isotope analysis (CSIA) offers an alternative approach based on evidence from isotope values. Until now, however, the relatively high limits for precise isotope analysis by gas chromatography—isotope ratio mass spectrometry (GC-IRMS) have impeded CSIA of sub-microgram-per-liter scale micropollutant concentrations in field samples. This study presents the first measurements of C and N isotope ratios of the herbicide atrazine and its metabolite desethylatrazine at concentrations of 100 to 1,000 ng/L in natural groundwater samples. Solid-phase extraction and preparative HPLC were tested and validated for preconcentration and cleanup of groundwater samples of up to 10 L without bias by isotope effects. Matrix interferences after solid-phase extraction could be greatly reduced by a preparative HPLC cleanup step prior to GC-IRMS analysis. Sensitivity was increased by a factor of 6 to 8 by changing the injection method from large-volume to cold-on-column injection on the GC-IRMS system. Carbon and nitrogen isotope values of field samples showed no obvious correlation with concentrations or desethylatrazine-to-atrazine ratios. Contrary to expectations, however, δ ¹³ C values of desethylatrazine were consistently less negative than those of atrazine from the same sites. Potentially, this line of evidence may contain information about further desethylatrazine degradation. In such a case, the common practice of using desethylatrazine-to-atrazine ratios would underestimate natural atrazine degradation.

Keywords: Compound-specific isotope analysis; Pesticides; Micropollutants; Field samples; On-column injection

Carbon isotope ratio measurements of glyphosate and AMPA by liquid chromatography coupled to isotope ratio mass spectrometry by Dorothea M. Kujawinski; J. Benjamin Wolbert; Lijun Zhang; Maik A. Jochmann; David Widory; Nicole Baran; Torsten C. Schmidt (pp. 2869-2878).

The interest in compound-specific isotope analysis for product authenticity control and source differentiation in environmental sciences has grown rapidly during the last decade. However, the isotopic analysis of very polar analytes is a challenging task due to the lack of suitable chromatographic separation techniques which can be used coupled to isotope ratio mass spectrometry. In this work, we present the first method to measure carbon isotope compositions of the widely applied herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA) by liquid chromatography coupled to isotope ratio mass spectrometry. We demonstrate that this analysis can be carried out either in cation exchange or in reversed-phase separation modes. The reversed-phase separation yields a better performance in terms of resolution compared with the cation exchange method. The measurement of commercial glyphosate herbicide samples show its principal applicability and reveals a wide range of δ¹³C values between −24 and −34 ‰ for different manufacturers. The absolute minimum amounts required to perform a precise and accurate determination of carbon isotope compositions of glyphosate and AMPA were in the sub-microgram range. The method proposed is sensitive enough to further perform the experiments that are necessary to better understand the carbon isotope fractionation associated to the natural degradation of glyphosate into AMPA. Furthermore, it can be used for contaminant source allocation and product authenticity as well.

Keywords: Herbicides; Carbon isotopes; Glyphosate; AMPA; CSIA; LC-IRMS

Reduction of measurement uncertainty by experimental design in high-order (double, triple, and quadruple) isotope dilution mass spectrometry: application to GC-MS measurement of bromide by Enea Pagliano; Zoltán Mester; Juris Meija (pp. 2879-2887).

Since its introduction a century ago, isotope dilution analysis has played a central role in developments of analytical chemistry. This method has witnessed many elaborations and developments over the years. To date, we have single, double, and even triple isotope dilution methods. In this manuscript, we summarize the conceptual aspects of isotope dilution methods and introduce the quadruple dilution and the concept of exact matching triple and quadruple dilutions. The comparison of isotope dilution methods is performed by determination of bromide ions in groundwater using novel ethyl-derivatization chemistry in conjunction with GC/MS. We show that the benefits of higher-order isotope dilution methods are countered with a greater need for careful experimental design of the isotopic blends. Just as for ID²MS, ID³MS and ID⁴MS perform best when the isotope ratio of one sample/spike blend is matched with that of a standard/spike blend (exact matching).

Keywords: Isotope dilution analysis; Double dilution; Triple dilution; Quadruple dilution; Exact matching; Bromide; Triethyloxonium tetrafluoroborate; GC/MS

Sulphur tracer experiments in laboratory animals using ³⁴S-labelled yeast by J. Giner Martínez-Sierra; F. Moreno Sanz; P. Herrero Espílez; J. M. Marchante Gayón; J. Rodríguez Fernández; J. I. García Alonso (pp. 2889-2899).

We have evaluated the use of ³⁴S-labelled yeast to perform sulphur metabolic tracer experiments in laboratory animals. The proof of principle work included the selection of the culture conditions for the preparation of sulphur labelled yeast, the study of the suitability of this labelled yeast as sulphur source for tracer studies using in vitro gastrointestinal digestion and the administration of the ³⁴S-labelled yeast to laboratory animals to follow the fate and distribution of ³⁴S in the organism. For in vitro gastrointestinal digestion, the combination of sodium dodecyl sulphate-polyacrylamide gel electrophoresis and high-performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC-ICP-MS) showed that labelled methionine, cysteine and other low molecular weight sulphur-containing biomolecules were the major components in the digested extracts of the labelled yeast. Next, in vivo kinetic experiments were performed in healthy Wistar rats after the oral administration of ³⁴S-labelled yeast. The isotopic composition of total sulphur in tissues, urine and faeces was measured by double-focusing inductively coupled plasma mass spectrometry after microwave digestion. It was observed that measurable isotopic enrichments were detected in all samples. Finally, initial investigations on sulphur isotopic composition of serum and urine samples by HPLC-ICP-MS have been carried out. For serum samples, no conclusive data were obtained. Interestingly, chromatographic analysis of urine samples showed differential isotope enrichment for several sulphur-containing biomolecules.

Keywords: Sulphur metabolism; Metabolic tracer; Sulphur-labelled yeast; HPLC-ICP-MS; Urine

Detection of transgenerational barium dual-isotope marks in salmon otoliths by means of LA-ICP-MS by Gonzalo Huelga-Suarez; Beatriz Fernández; Mariella Moldovan; J. Ignacio García Alonso (pp. 2901-2909).

The present study evaluates the use of an individual-specific transgenerational barium dual-isotope procedure and its application to salmon specimens from the Sella River (Asturias, Spain). For such a purpose, the use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in combination with multiple linear regression for the determination of the isotopic mark in the otoliths of the specimens is presented. In this sense, a solution in which two barium-enriched isotopes (¹³⁷Ba and ¹³⁵Ba) were mixed at a molar ratio of ca. 1:3 (N _Ba137/N _Ba135) was administered to eight returning females caught during the spawning period. After injection, these females, as well as their offspring, were reared in a governmental hatchery located in the council of Cangas de Onís (Asturias, Spain). For comparison purposes, as well as for a time-monitoring control, egg and larva data obtained by solution analysis ICP-MS are also given. Otoliths (9-month-old juveniles) of marked offspring were analysed by LA-ICP-MS demonstrating a 100 % marking efficacy of this methodology. The capabilities of the molar fraction approach for 2D imaging of fish otoliths are also addressed.

Keywords: LA-ICP-MS; Otoliths; Transgenerational marking; Barium isotopes

Effect of changes in the deuterium content of drinking water on the hydrogen isotope ratio of urinary steroids in the context of sports drug testing by Thomas Piper; Karoline Degenhardt; Eugen Federherr; Andreas Thomas; Mario Thevis; Martial Saugy (pp. 2911-2921).

The hydrogen isotope ratio (HIR) of body water and, therefore, of all endogenously synthesized compounds in humans, is mainly affected by the HIR of ingested drinking water. As a consequence, the entire organism and all of its synthesized substrates will reflect alterations in the isotope ratio of drinking water, which depends on the duration of exposure. To investigate the effect of this change on endogenous urinary steroids relevant to doping-control analysis the hydrogen isotope composition of potable water was suddenly enriched from -50 to 200 ‰ and maintained at this level for two weeks for two individuals. The steroids under investigation were 5β-pregnane-3α,20α-diol, 5α-androst-16-en-3α-ol, 3α-hydroxy-5α-androstan-17-one (ANDRO), 3α-hydroxy-5β-androstan-17-one (ETIO), 5α-androstane-3α,17β-diol, and 5β-androstane-3α,17β-diol (excreted as glucuronides) and ETIO, ANDRO and 3β-hydroxyandrost-5-en-17-one (excreted as sulfates). The HIR of body water was estimated by determination of the HIR of total native urine, to trace the induced changes. The hydrogen in steroids is partly derived from the total amount of body water and cholesterol-enrichment could be calculated by use of these data. Although the sum of changes in the isotopic composition of body water was 150 ‰, shifts of approximately 30 ‰ were observed for urinary steroids. Parallel enrichment in their HIR was observed for most of the steroids, and none of the differences between the HIR of individual steroids was elevated beyond recently established thresholds. This finding is important to sports drug testing because it supports the intended use of this novel and complementary methodology even in cases where athletes have drunk water of different HIR, a plausible and, presumably, inevitable scenario while traveling.

Keywords: Hydrogen isotope ratio; GC–TC–IRMS; Excretion study; Steroids; Enriched drinking water; Exchangeable hydrogen

Kinetic bromine isotope effect: example from the microbial debromination of brominated phenols by Anat Bernstein; Zeev Ronen; Elena Levin; Ludwik Halicz; Faina Gelman (pp. 2923-2929).

The increasing use of kinetic isotope effects for environmental studies has motivated the development of new compound-specific isotope analysis techniques for emerging pollutants. Recently, high-precision bromine isotope analysis in individual brominated organic compounds was proposed, by the coupling of gas chromatography to a multi-collector inductively coupled plasma mass spectrometer using strontium as an external spike for instrumental bias correction. The present study, for the first time, demonstrates an application of this technique for determining bromine kinetic isotope effects during biological reaction, focusing on the reductive debromination of brominated phenols under anaerobic conditions. Results show bromine isotope enrichment factors (ε) of −0.76 ± 0.08, −0.46 ± 0.19, and −0.20 ± 0.06 ‰ for the debromination of 4-bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol, respectively. These values are rather low, yet still high enough to be obtained with satisfying certainty. This further implies that the analytical method may be also appropriate for future environmental applications.

Keywords: Bromine; Isotope enrichment; GC-MC-ICPMS; CSIA

Influence of precursor solvent extraction on stable isotope signatures of methylamphetamine prepared from over-the-counter medicines using the Moscow and Hypophosphorous routes by Niamh NicDaéid; Saravana Jayamana; William J. Kerr; Wolfram Meier-Augenstein; Helen F. Kemp (pp. 2931-2941).

A number of methods of clandestine manufacture of methylamphetamine involve the extraction and subsequent reaction of pseudoephedrine hydrochloride with other essential chemicals. The precursor can be easily extracted from over-the-counter medication widely available in the UK and elsewhere. Essential chemicals such as iodine and red phosphorous are also readily available and can be extracted from iodine tinctures and matchboxes, respectively. This work reports the repetitive preparation of methylamphetamine using two popular routes (the Moscow and Hypophosphorous synthesis). The focus was on the extraction solvent used for isolation of the precursor chemical and any consequential isotopic variation which may arise in the final product. Six batches of methylamphetamine were prepared under precisely controlled conditions for each synthetic route and for each of three different precursor extraction solvents. Synthesis of the final product from laboratory grade precursor using the synthetic methods described was used as a template for comparison. The resultant IRMS data from all 48 prepared samples suggests some underlying trends in the identification of the synthetic route which may aid in the interpretation of IRMS data derived from clandestine samples.

Keywords: Precursor; Solvent extraction; IRMS; Methylamphetamine

Evaluation strategies for isotope ratio measurements of single particles by LA-MC-ICPMS by S. Kappel; S. F. Boulyga; L. Dorta; D. Günther; B. Hattendorf; D. Koffler; G. Laaha; F. Leisch; T. Prohaska (pp. 2943-2955).

Data evaluation is a crucial step when it comes to the determination of accurate and precise isotope ratios computed from transient signals measured by multi-collector–inductively coupled plasma mass spectrometry (MC-ICPMS) coupled to, for example, laser ablation (LA). In the present study, the applicability of different data evaluation strategies (i.e. ‘point-by-point’, ‘integration’ and ‘linear regression slope’ method) for the computation of ²³⁵U/²³⁸U isotope ratios measured in single particles by LA-MC-ICPMS was investigated. The analyzed uranium oxide particles (i.e. 9073-01-B, CRM U010 and NUSIMEP-7 test samples), having sizes down to the sub-micrometre range, are certified with respect to their ²³⁵U/²³⁸U isotopic signature, which enabled evaluation of the applied strategies with respect to precision and accuracy. The different strategies were also compared with respect to their expanded uncertainties. Even though the ‘point-by-point’ method proved to be superior, the other methods are advantageous, as they take weighted signal intensities into account. For the first time, the use of a ‘finite mixture model’ is presented for the determination of an unknown number of different U isotopic compositions of single particles present on the same planchet. The model uses an algorithm that determines the number of isotopic signatures by attributing individual data points to computed clusters. The ²³⁵U/²³⁸U isotope ratios are then determined by means of the slopes of linear regressions estimated for each cluster. The model was successfully applied for the accurate determination of different ²³⁵U/²³⁸U isotope ratios of particles deposited on the NUSIMEP-7 test samples.

Keywords: U isotope ratios; Laser ablation MC-ICPMS; Single particles; Short transient signals; Data evaluation strategies; Finite mixture model

Concentration measurements and isotopic composition of airborne molybdenum collected in an urban environment by Stephen Lane; Bernadette C. Proemse; Alexander Tennant; Michael E. Wieser (pp. 2957-2963).

Here, we report the first measurements of the molybdenum (Mo) isotopic composition of aerosols collected on Teflon air filters. Mo concentrations and isotopic compositions were measured at selected locations in the city of Calgary, Canada, including a residence, the isotope laboratory at the University of Calgary, the University of Calgary weather station, and the City of Calgary Transit bus garage. Concentrations ranged from 0.07 ng/m³ in the laboratory to 19.0 ng/m³ in the bus garage. The concentrations of Mo in the air samples collected in the bus garage were the highest measured in this study. To date, there are no reported data for the Mo isotopic composition of airborne Mo. In this study, the δ^98/95Mo values measured for the different urban sampling sites and reported relative to SRM 3134, ranged from −0.18 to +0.94 ‰. The results of this investigation suggest that measurements of Mo concentrations and isotopic compositions have the potential to trace anthropogenic emissions in an urban environment.

Keywords: Molybdenum; Isotopes; Isotope dilution mass spectrometry; Metal; Tracer; Air; SRM 3134

Quantification of ⁶⁰Fe atoms by MC-ICP-MS for the redetermination of the half-life by Niko Kivel; Dorothea Schumann; Ines Günther-Leopold (pp. 2965-2972).

In many scientific fields, the half-life of radionuclides plays an important role. The accurate knowledge of this parameter has direct impact on, e.g., age determination of archeological artifacts and of the elemental synthesis in the universe. In order to derive the half-life of a long-lived radionuclide, the activity and the absolute number of atoms have to be analyzed. Whereas conventional radiation measurement methods are typically applied for activity determinations, the latter can be determined with high accuracy by mass spectrometric techniques. Over the past years, the half-lives of several radionuclides have been specified by means of multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) complementary to the earlier reported values mainly derived by accelerator mass spectrometry. The present paper discusses all critical aspects (amount of material, radiochemical sample preparation, interference correction, isotope dilution mass spectrometry, calculation of measurement uncertainty) for a precise analysis of the number of atoms by MC-ICP-MS exemplified for the recently published half-life determination of $^{60}$ Fe (Rugel et al, Phys Rev Lett 103:072502, 2009).

Keywords: Multiple-collector inductively coupled plasma mass spectrometry; Half-life; Isotope dilution

Copper and tin isotopic analysis of ancient bronzes for archaeological investigation: development and validation of a suitable analytical methodology by Eleonora Balliana; Maite Aramendía; Martin Resano; Carlo Barbante; Frank Vanhaecke (pp. 2973-2986).

Although in many cases Pb isotopic analysis can be relied on for provenance determination of ancient bronzes, sometimes the use of “non-traditional” isotopic systems, such as those of Cu and Sn, is required. The work reported on in this paper aimed at revising the methodology for Cu and Sn isotope ratio measurements in archaeological bronzes via optimization of the analytical procedures in terms of sample pre-treatment, measurement protocol, precision, and analytical uncertainty. For Cu isotopic analysis, both Zn and Ni were investigated for their merit as internal standard (IS) relied on for mass bias correction. The use of Ni as IS seems to be the most robust approach as Ni is less prone to contamination, has a lower abundance in bronzes and an ionization potential similar to that of Cu, and provides slightly better reproducibility values when applied to NIST SRM 976 Cu isotopic reference material. The possibility of carrying out direct isotopic analysis without prior Cu isolation (with AG-MP-1 anion exchange resin) was investigated by analysis of CRM IARM 91D bronze reference material, synthetic solutions, and archaeological bronzes. Both procedures (Cu isolation/no Cu isolation) provide similar δ ⁶⁵Cu results with similar uncertainty budgets in all cases (±0.02–0.04 per mil in delta units, k = 2, n = 4). Direct isotopic analysis of Cu therefore seems feasible, without evidence of spectral interference or matrix-induced effect on the extent of mass bias. For Sn, a separation protocol relying on TRU-Spec anion exchange resin was optimized, providing a recovery close to 100 % without on-column fractionation. Cu was recovered quantitatively together with the bronze matrix with this isolation protocol. Isotopic analysis of this Cu fraction provides δ ⁶⁵Cu results similar to those obtained upon isolation using AG-MP-1 resin. This means that Cu and Sn isotopic analysis of bronze alloys can therefore be carried out after a single chromatographic separation using TRU-Spec resin. Tin isotopic analysis was performed relying on Sb as an internal standard used for mass bias correction. The reproducibility over a period of 1 month (n = 42) for the mass bias-corrected Sn isotope ratios is in the range of 0.06–0.16 per mil (2 s), for all the ratios monitored.

Keywords: Copper isotopic analysis; Tin isotopic analysis; Multi-collector ICP–mass spectrometry; Archaeological bronze; Archaeometry

Isotope ratio measurements with a fully simultaneous Mattauch–Herzog ICP-MS by Dirk Ardelt; Aleksandra Polatajko; Oliver Primm; Maurice Reijnen (pp. 2987-2994).

A fully simultaneous ICP-MS, based on a compact Mattauch–Herzog geometry with a permanent magnet and a large, spatially resolving semiconductor ion detector covering the complete inorganic relevant mass range from ⁶Li to ²³⁸U in a single measurement, has been used to determine isotope ratios and assess achievable isotope ratio precisions. Measurements of the ^235/238U isotopic ratio, chosen as example for an isotopic system with a disparate isotope ratio, yielded a precision of 0.05 % relative. To evaluate the expected multi-isotope ratio measurement capabilities of the system used, several isotope ratios spanning a wide range (^6/7Li, ^84/86Sr, ^87/86Sr, ^88/86Sr, ^204/207Pb, ^206/207Pb and ^208/207Pb) were measured simultaneously, using a synthetic multi-element standard as sample. Very satisfying isotope ratio precisions, between 0.5 and 0.04 % relative, depending on the isotope ratio in question were found during the simultaneous multi-isotope ratio measurements. Together with a brief description of the system and measurement procedures employed for this technical note, the results achieved are assessed in view of other existing ICP-MS-based isotope ratio techniques. Figure Fully simultaneous Mattauch-Herzog geometry MS with a spatially resolving semiconductor ion detector (schematic)

Keywords: IR-ICP-MS; Fully simultaneous ICP-MS; Mattauch–Herzog geometry; Spatially resolving semiconductor ion detector; Simultaneous multi-element IR-ICP-MS

A modified lead–matrix separation procedure shown for lead isotope analysis in Trojan silver artefacts as an example by Jochen Vogl; Boaz Paz; Maren Koenig; Wolfgang Pritzkow (pp. 2995-3000).

A modified Pb–matrix separation procedure using NH₄HCO₃ solution as eluent has been developed and validated for determination of Pb isotope amount ratios by thermal ionization mass spectrometry. The procedure is based on chromatographic separation using the Pb·Spec resin and an in-house-prepared NH₄HCO₃ solution serving as eluent. The advantages of this eluent are low Pb blanks (<40 pg mL⁻¹) and the property that NH₄HCO₃ can be easily removed by use of a heating step (>60 °C). Pb recovery is >95 % for water samples. For archaeological silver samples, however, the Pb recovery is reduced to approximately 50 %, but causes no bias in the determination of Pb isotope amount ratios. The validated procedure was used to determine lead isotope amount ratios in Trojan silver artefacts with expanded uncertainties (k = 2) <0.09 %.

Keywords: Analyte–matrix separation; Mass spectrometry; Pb isotope ratio thermal ionization mass spectrometry; Archaeometry

Mercury speciation analysis in human hair by species-specific isotope-dilution using GC–ICP–MS by Laure Laffont; Laurence Maurice; David Amouroux; Patricia Navarro; Mathilde Monperrus; Jeroen E. Sonke; Philippe Behra (pp. 3001-3010).

We optimized a mercury (Hg) speciation extraction method for human hair in combination with species-specific isotope-dilution analysis by gas chromatography–inductively coupled plasma–mass spectrometry (GC–ICP–MS). The method was validated on human hair reference material RM (IAEA-086), which is recommended for analysis of monomethylmercury (MMHg) and inorganic mercury (IHg). Three reagents, hydrochloric acid (HCl), nitric acid (HNO₃), and tetramethylammonium hydroxide (TMAH), and three extraction procedures, at ambient temperature for 12 h, microwave-assisted at 75 °C for 6 min, and oven heated at 80 °C for 2 h were tested. Extraction efficiency, recovery, and potential species transformations were evaluated for each method. The most efficient procedures, with recovery of ~90 % for each species with limited demethylation (<5 %) and methylation (0 %), were HNO₃ digestion, irrespective of temperature, and microwave-assisted TMAH extraction. Acidic extraction with HCl induces significant demethylation, with production of artifacts. To correct for potential demethylation artifacts we recommend spiking with isotopically enriched standards before the extraction step.

Keywords: Metals/heavy metals; Organometals; Speciation; Mass spectrometry/ICP–MS; Biological samples

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Analytical and Bioanalytical Chemistry (v.405, #9)