Isotope Ratio Mass Spectrometry

Compound-specific isotope analysis (CSIA) by gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) is a powerful technique for the sourcing of substances, such as determination of the geographic or chemical origin of drugs and food adulteration, and it is especially invaluable as a confirmatory tool for detection of the use of synthetic steroids in competitive sport. We review here principles and practices for data processing and calibration of GCC-IRMS data with consideration to anti-doping analyses, with a focus on carbon isotopic analysis ( 13 C/ 12 C). After a brief review of peak definition, the isotopologue signal reduction methods of summation, curve-fitting, and linear regression are described and reviewed. Principles for isotopic calibration are considered in the context of the Δ 13 C = δ 13 C M -δ 13 C E difference measurements required for establishing adverse analytical findings for metabolites relative to endogenous reference compounds. Considerations for the anti-doping analyst are reviewed.

We report the first demonstration of Comprehensive Two-dimensional Gas Chromatography Combustion Isotope Ratio Mass Spectrometry (GC×GCC-IRMS) for the analysis of urinary steroids to detect illicit synthetic testosterone use, of interest in sport doping. GC coupled to IRMS (GCC-IRMS) is currently used to measure the carbon isotope ratios (CIR, δ 13 C) of urinary steroids in anti-doping efforts; however, extensive cleanup of urine extracts is required prior to analysis to enable baseline separation of target steroids. With its greater separation capabilities, GC×GC has the potential to reduce sample preparation requirements and enable CIR analysis of minimally processed urine extracts. Challenges addressed include on-line reactors with minimized dimensions to retain narrow peaks shapes, baseline separation of peaks in some cases, and reconstruction of isotopic information from sliced steroid chromatographic peaks. Difficulties remaining include long-term robustness of on-line reactors and urine matrix effects that preclude baseline separation and isotopic analysis of low concentration and trace components. In this work, steroids were extracted, acetylated, and analyzed using a refined, home-built GC×GCC-IRMS system. 11-hydroxy-androsterone (11OHA) and 11-ketoetiocolanolone (11KE) were chosen as endogenous reference compounds (ERC) because of their satisfactory signal intensity, and their CIR was compared to target compounds (TC) androsterone (A) and etiocholanolone (E). Separately, a GC×GC-qMS system was used to measure testosterone (T)/EpiT concentration ratios. Urinary extracts of urine pooled from professional athletes, and urine from one individual that received testosterone gel (T-gel) and one individual that received testosterone injections (Tshot) were analyzed. The average precisions of δ 13 C and Δδ 13 C measurements were SD(δ 13 C) approximately ± 1‰ (n=11). The T-shot sample resulted in a positive for T use with a T/EpiT ratio of > 9 and CIR measurements of Δδ 13 C > 5‰, both fulfilling World Anti-Doping Agency criteria. These data show for the first time that synthetic steroid use is detectable by GC×GCC-IRMS without need for extensive urine cleanup.

Rationale: Potential post-mortem alteration to the oxygen isotope composition of biogenic silica is critical to the validity of palaeoclimate reconstructions based on oxygen isotope ratios (δ 18 O values) from sedimentary silica. We calculate the degree of oxygen isotope alteration within freshly cultured diatom biogenic silica in response to heating and storing in the laboratory. The experiments used freshly cultured diatom silica. Silica samples were either stored in water or dried at temperatures between 20 °C and 80 °C. The mass of affected oxygen and the associated silica-water isotope fractionation during alteration were calculated by conducting parallel experiments using endmember waters with δ 18 O values of -6.3 to -5.9 ‰ and -36.3 to -35.0 ‰. Dehydroxylation and subsequent oxygen liberation were achieved by stepwise fluorination with BrF 5 . The 18 O/ 16 O ratios were measured using a ThermoFinnigan MAT 253 isotope ratio mass spectrometer. Results: Significant alterations in silica δ 18 O values were observed, most notably an increase in the δ 18 O values following drying at 40-80 °C. Storage in water for 7 days between 20 and 80 °C also led to significant alteration in δ 18 O values. Mass balance calculations suggest that the amount of affected oxygen is positively correlated with temperature. The estimated oxygen isotope fractionation during alteration is an inverse function of temperature, consistent with the extrapolation of models for high-temperature silica-water oxygen isotope fractionation. Conclusions: Routinely used preparatory methods may impart significant alterations to the δ 18 O values of biogenic silica, particularly when dealing with modern cultured or field-collected material. The significance of such processes within natural aquatic environments is uncertain; however, there is potential that similar processes also affect sedimentary diatoms, with implications for the interpretation of biogenic silica-hosted δ 18 O palaeoclimate records. The oxygen isotope composition of biogenic silica has become a widely used tool for reconstructing past climate and environmental change, particularly using diatom frustules extracted from lacustrine and marine sediments 1,2 and phytoliths extracted from plants and soils. In principle, the oxygen isotope composition of biogenic silica (δ 18 O silica , relative to Vienna Standard Mean Ocean Water (VSMOW)) reflects the temperature and oxygen isotope composition of water (δ 18 O water ) in which the silica was precipitated, e.g. during diatom growth. 6 However, since the pioneering analyses in the 1960s, the application of δ 18 O silica values in palaeoclimatology has been beset by problems related to the secondary alteration of oxygen isotopes due to the presence of hydroxyl groups within the silica matrix.

In order to generate a reliable and long‐lasting stable isotope ratio standard for CO2 in samples of clean air, CO2 is liberated from well‐characterized carbonate material and mixed with CO2‐free air. For this purpose a dedicated acid reaction and air mixing system (ARAMIS) was designed. In the system, CO2 is generated by a conventional acid digestion of powdered carbonate. Evolved CO2 gas is mixed and equilibrated with a prefabricated gas comprised of N2, O2, Ar, and N2O at close to ambient air concentrations. Distribution into glass flasks is made stepwise in a highly controlled fashion. The isotopic composition, established on automated extraction/measurement systems, varied within very small margins of error appropriate for high‐precision air‐CO2 work (about ±0.015‰ for δ13C and ±0.025‰ for δ18O). To establish a valid δ18O relation to the VPDB scale, the temperature dependence of the reaction between 25 and 47°C has been determined with a high level of precision. Using identical...

Rationale: The last decade has seen a dramatic increase in the application of serial sampling of human dentine in archaeology. Rapid development in the field has provided many improvements in the methodology, in terms of both time resolution as well as the ability to integrate more isotope systems in the analysis. This study provides a comparison of two common sampling approaches, allowing researchers to select the most suitable approach for addressing specific research questions. Methods: Two common approaches for sequential sampling of human dentine (micro-punches and micro-slices) are compared in terms of viability and efficacy. Using archaeological deciduous second molars and permanent first molars, this study
demonstrates how the two approaches capture aspects of the weaning process in different ways. In addition, different aspects related to the extraction protocols, such as the thickness of the central slide and the solubilisation step, are also evaluated.
Results: While both approaches show similar intra-tooth isotopic patterns, the micropunches approach is preferable for research that requires a very fine temporal resolution, while the micro-slices approach is best for research where δ34S values are needed, or when the samples are poorly preserved. In addition, the solubilisation step has a large effect on collagen yield, and, to a lesser extent, on isotopic compositions. Therefore, it is important to ensure that only samples that have undergone the same pre-treatment protocol are directly compared.
Conclusions: We present the pros and cons of the two micro-sampling approaches and offer possible mitigation strategies to address some of the most important issues related to each approach.

A simple urine pretreatment procedure, leading to extracts free of interferences and permitting a precise and accurate IRMS analysis of formestane was developed, validated and employed in doping control. A combinatorial approach of GC-MS/MS and GC-C-IRMS provides specific detection of endogenous steroid misuse for improved doping analysis. The main aim of this study was to propose a threshold of 25 ng/mL beneath which the detected formestane is considered as being endogenous and no further investigation on GC-C-IRMS is required. Samples with urinary formestane concentrations above 25 ng/mL and beneath the WADA 150 ng/mL MRPL are forwarded to IRMS. Data collected from the testosterone and androstenedione excretion studies together with the results from the endogenous population suggests that this 25 ng/mL threshold provides a good balance between a sufficiently large detection window and not having to perform unnecessary IRMS analyses on negative urine samples.

Recent publications have shown that the concentrations of minor metabolites such as formestane and 6α-hydroxyandrostenedione (6αOH-ADION) are import parameters, capable of increasing the specificity and efficiency of steroid abuse screening. The importance of such minor metabolites has been recognised for some time, but setting up concentration thresholds is not that straightforward with a single quadrupole gas chromatograph mass spectrometer (GCMS) because of the low concentrations and this is especially the case for 6αOH-ADION. The main aim of this study was to propose a concentration threshold above which the detected 6αOH-ADION is considered as being suspicious and isotope ratio mass spectrometry (IRMS) is recommended. 2128 routine doping control samples from athletes that entered our lab and were not found suspicious for the intake of any doping substance were used to determine the baseline concentrations of 6αOH-ADION. For this purpose, the more sensitive GCMS/MS was used, capable of quantifying these low concentrations with high reliability. A urinary concentration threshold of 5 ng/mL was set. Concentrations above this threshold are considered as suspicious and are forwarded to IRMS for confirmation in routine practice. In addition, an IRMS method was developed, capable of determining the 13 C value of 6αOH-ADION. If a urine sample has an elevated 6α-OH-ADION concentration and normal 13 C values for the traditional IRMS target compounds, we are still able to check the 13 C value of 6αOH-ADION. Six excretion studies were executed to stress the applicability of the threshold by visualising the concentration and δ 13 C value time profiles of 6αOH-ADION.

Strontium isotopes (87 Sr/ 86 Sr) are increasingly used as a provenance tool in multiple disciplines. Application to biological materials requires knowledge of the variation in bioavailable 87 Sr/ 86 Sr across the landscape, potentially in the form of an isoscape (a quantitative model of spatial isotopic variability). This paper summarizes and provides advice on our current understanding of the main concerns in creating and interpreting isoscapes of bioavailable 87 Sr/ 86 Sr. Isoscape creation approaches include domain mapping, geostatistical contour mapping and machine learning, the last becoming more readily achievable with the availability of software packages. It is critically important to develop isoscapes at a resolution appropriate for addressing the research questions. Choice of sample materials depends on the research questions and availability: plants or fauna with small ranges are favoured, with some analytes (snails, soil leachates) posing challenges. Interpreting 87 Sr/ 86 Sr in biological tissues requires considering Sr metabolism and the timing of tissue formation, thus far underappreciated. The numerous sources of error involved in developing and applying isoscapes must be recognized to avoid over-interpreting data and spurious provenance precision. We hope this paper will help researchers investigating provenance, mobility, landscape use and migration to develop the most appropriate isoscapes for their purposes, and possible future use by others.

The natural 13C/12C isotope composition (δ13C) of plants and organic compounds within plant organs is a powerful tool to understand carbon allocation patterns and the regulation of photosynthetic or respiratory metabolism. However, many enzymatic fractionations are currently unknown, thus impeding our understanding of carbon trafficking pathways within plant cells. One of them is the 12C/13C isotope effect associated with invertases (EC 3.2.1.26) that are cornerstone enzymes for Suc metabolism and translocation in plants. Another conundrum of isotopic plant biology is the need to measure accurately the specific δ13C of individual carbohydrates. Here, we examined two complementary methods for measuring the δ13C value of sucrose, glucose and fructose, that is, off‐line high‐performance liquid chromatography (HPLC) purification followed by elemental analysis and isotope ratio mass spectrometry (EA‐IRMS) analysis, and gas chromatography‐combustion (GC‐C)‐IRMS. We also used these methods...

Rates of benthic denitrification were measured using two techniques, membrane inlet mass spectrometry (MIMS) and isotope ratio mass spectrometry (IRMS), applied to sediment cores from two NO 3 À -rich streams draining agricultural land in the upper Mississippi River Basin. Denitrification was estimated simultaneously from measurements of N 2 :Ar (MIMS) and 15 N[N 2 ] (IRMS) after the addition of low-level 15 NO 3 À tracer ( 15 N:N ¼ 0.03-0.08) in stream water overlying intact sediment cores. Denitrification rates ranged from about 0 to 4400 lmol NÁm À2 Áh À1 in Sugar Creek and from 0 to 1300 lmol NÁm À2 Áh À1 in Iroquois River, the latter of which possesses greater streamflow discharge and a more homogeneous streambed and water column. Within the uncertainties of the two techniques, there is good agreement between the MIMS and IRMS results, which indicates that the production of N 2 by the coupled process of nitrification/denitrification was relatively unimportant and surfacewater NO 3 À was the dominant source of NO 3 À for benthic denitrification in these streams. Variation in stream NO 3 À concentration (from about 20 lmol/L during low discharge to 1000 lmol/L during high discharge) was a significant control of benthic denitrification rates, judging from the more abundant MIMS data. The interpretation that NO 3 À concentration directly affects denitrification rate was corroborated by increased rates of denitrification in cores amended with NO 3 À . Denitrification in Sugar Creek removed 11% per day of the instream NO 3 À in late spring and removed roughly 15-20% in late summer. The fraction of NO 3 À removed in Iroquois River was less than that of Sugar Creek. Although benthic denitrification rates were relatively high during periods of high stream flow, when NO 3 concentrations were also high, the increase in benthic denitrification could not compensate for the much larger increase in stream NO 3 À fluxes during high flow. Consequently, fractional NO 3 À losses were relatively low during high flow.

We demonstrate that one can measure low levels of 2 H labeling (e.g., <0.025% excess 2 H) by exchanging hydrogen (deuterium) in water with acetone and subjecting samples to gas chromatography-pyrolysisisotope ratio mass spectrometry. This analytical method circumvents the need to use typical off-line reduction methods that convert water to hydrogen gas prior to isotope ratio mass spectrometry or the need to purchase extra peripheral devices that would permit the direct analysis of water labeling. This method enables routine measurements of fatty acid oxidation in rodents; that is, one administers a 2 H-labeled fatty acid(s) and then quantifies the production of 2 H-labeled water.

Tracing methods of non-European EVOOs commercialized worldwide are becoming crucial for effective authenticity controls. Limited analytical studies of these oils are available on a global scale, similar to those of European EVOOs. We report for the first time the fatty acid concentrations, bulk-oil 2 H/ 1 H, 13 C/ 12 C, and 18 O/ 16 O ratios and fatty acid 13 C/ 12 C ratios of 43 authentic monovarietal EVOOs from different geographical regions in Argentina and Uruguay. The samples were obtained from a wide range of latitudes and altitudes along an E-W profile, from lowlands near the Atlantic Ocean to the pre-Andean highlands near the Pacific Ocean. Principal component scores were used to cluster EVOOs into three groups-central-western Argentina, central Argentina, and Uruguay-based on nine stable isotope ratios and the oleic-linoleic acid concentration ratio. The bulk 2 H/ 1 H and 18 O/ 16 O values and 13 C/ 12 C of palmitoleic and linoleic acids provide good tools for differentiating these oils via linear discriminant analysis.

The present study proposed the cheese differentiation, according to geographical production area and with respect to species (cow, sheep) of two traditional cheese specialties, (salty and ripened), produced in Transylvania, Romania. For this purpose, the elemental profile and carbon isotopic ratios ( 13 C/ 12 C) of cheese and extracted casein were corroborated through statistic supervised techniques to get the best discrimination markers. The manganese content, along with Rare Earth Elements (REE) concentrations, proved to be very powerful predictors, for the traditional salted cheese mainly, due to the direct influence of the local salted water. Despite that proposed techniques are not acknowledged methods for species differentiation, this approach allowed a successful discrimination of the animal species that produced the raw materials for cheese manufacturing (milk). The results generated by the developed chemometric model, for species differentiation, were compared with those obtained using Isoelectric focusing (IEF) and DNA tests. The proposed association of isotopic and elemental markers allowed a differentiation better than 92 % for geographical provenance, of each investigated cheese specialties while, for species discrimination (cow vs. sheep) a percentage of 100 % was obtained.

We determined both carbon and nitrogen isotope ratios of ten organic reference materials (CERKU-01 to CERKU-10) in the Center for Ecological Research (CER), Kyoto University, and three organic reference materials (BG-A, BG-P and BG-T) in the Institute of Biogeosciences (BioGeos), JAMSTEC, using an internationally recommended calibration method of two-point anchoring. The reference materials cover ! 13 CVPDB range of -34.92 to -9.45‰ and ! 15 NAir range of -5.22 to 22.71‰, and can be used to measure isotope ratios of naturally occurring substances.

We have developed a new inlet system for a gas sample isotope ratio mass spectrometer (IRMS). It is based on the well-known open split design from the gas chromatography/mass spectrometry (GC/MS) system due to its simplicity. The advantages over the conventional double inlet system with the metal bellows design include an improved reproducibility mainly due to a highly controllable pressure and temperature adjustment, a markedly lowered memory effect due to an uninterrupted gas flow through the ion source which limits adsorption/desorption processes on surfaces, and a single inlet capillary circumventing problems of asymmetrical behavior of sample and reference inlet paths. Furthermore, sample consumption is of the same order as for conventional measurements (i.e. about 0.4 mmol per hour), of which however only 2 mmol/h is used for the actual isotope ratio determination since the major gas amount acts as a gas flow seal against the atmosphere, corresponding to a 100-200 fold overkill. This may be improved in future systems.

Strontium isotopes (87 Sr/ 86 Sr) are increasingly used as a provenance tool in multiple disciplines. Application to biological materials requires knowledge of the variation in bioavailable 87 Sr/ 86 Sr across the landscape, potentially in the form of an isoscape (a quantitative model of spatial isotopic variability). This paper summarizes and provides advice on our current understanding of the main concerns in creating and interpreting isoscapes of bioavailable 87 Sr/ 86 Sr. Isoscape creation approaches include domain mapping, geostatistical contour mapping and machine learning, the last becoming more readily achievable with the availability of software packages. It is critically important to develop isoscapes at a resolution appropriate for addressing the research questions. Choice of sample materials depends on the research questions and availability: plants or fauna with small ranges are favoured, with some analytes (snails, soil leachates) posing challenges. Interpreting 87 Sr/ 86 Sr in biological tissues requires considering Sr metabolism and the timing of tissue formation, thus far underappreciated. The numerous sources of error involved in developing and applying isoscapes must be recognized to avoid over-interpreting data and spurious provenance precision. We hope this paper will help researchers investigating provenance, mobility, landscape use and migration to develop the most appropriate isoscapes for their purposes, and possible future use by others.

The use of stable isotope-labeled polymers in in situ biodegradation tests provides detailed information on the degradation process. As isotope-labeled raw chemicals are generally expensive, it is desirable to prepare polymer samples with high production yields and high isotope-labeling ratios. The biodegradable plastic poly[(R)-3-hydroxybutyrate)] (P(3HB)) is produced by microorganisms. In this study, to produce carbon 13 (13C)-labeled P(3HB) from [U-13C6]D-glucose (13C-glucose), the culture conditions needed for high production yields and high 13C-labeling ratios were investigated using Ralstonia eutropha NCIMB 11599 and recombinant Escherichia coli JM109. We found that over 10 g/L of P(3HB) could be obtained when these microorganisms were cultured in Luria-Bertani (LB3) medium containing 3 g/L NaCl and 40 g/L 13C-glucose, while 1.4–4.7 g/L of P(3HB) was obtained when a mineral salt (MS) medium containing 20 g/L 13C-glucose was used. The 13C-labeling ratio of P(3HB) was determined...

An analytical concept using stable isotope fractionation for analyzing persistent organic pollutants (POPs) in food webs was developed and tested. We have evaluated methods for the extraction and clean-up of hexachlorocyclohexane isomers (HCHs) as the model compounds of POPs from water, soil, plant, milk, fish oil and pork liver in order to study the reactive transport processes of HCHs in food webs using multi-element compoundspecific isotope analysis (CSIA). The extraction and clean-up methods were evaluated for recovery efficiency and isotope effects. The precision and accuracy for carbon, hydrogen and chlorine isotope analysis was within the analytical precision of ±0.5‰, ±5‰ and ±0.3‰, respectively. The method was applied for stable isotope analysis of HCHs in possible food webs from soil to plants, and to animals. Isotope compositions of HCHs in cow/buffalo milk and dung, wild animal livers and seal blubber were obtained and compared to the sources of HCHs. The magnitude of isotope enrichment demonstrated the potential of CSIA for analyzing reactive transport processes of HCHs in the food web. The concept using multi-element stable isotope analysis can be applied for source identification, characterization of degradation mechanisms, and particularly contaminant accumulation in the food web, which demonstrate the potential in new scientific areas for CSIA.

Increasing applications of compound-specific chlorine isotope analysis (CSIA) emphasize the need for chlorine isotope standards that bracket a wider range of isotope values in order to ensure accurate results. With one exception (USGS38), however, all international chlorine isotope reference materials (chloride and perchlorate salts) fall within the narrow range of one per mille. Furthermore, compoundspecific working standards are required for chlorine CSIA, but are not available for most organic substances. We took advantage of isotope effects in chemical dehalogenation reactions to generate (i) silver chloride (CT16) depleted in 37 Cl/ Cl and (ii) compound-specific standards of the herbicides Acetochlor and S-Metolachlor (Aceto2, Metola2) enriched in 37 Cl/ 35 Cl. Calibration against the international reference standards USGS38 (-87.90 ‰) / ISL-354 (+0.05 ‰) by complementary methods (gas chromatography -isotope ratio mass spectrometry, GC-IRMS, versus gas chromatography -multi-collector inductively coupled plasma mass spectrometry, GC-MC-ICPMS) gave a consensus value of δ 37 ClCT16 = -26.82 ± 0.18 ‰. Preliminary GC-MC-ICPMS characterization of commercial Aceto1 and Metola1 versus Aceto2 and Metola2 resulted in tentative values of δ 37 ClAceto1 = 0.29 ± 0.29 ‰, δ 37 ClAceto2 = 18.54 ± 0.20 ‰, δ 37 ClMetola1 = -4.28 ± 0.17 ‰ and δ 37 ClMetola2 = 5.12 ± 0.27 ‰. The possibility to generate chlorine isotope in-house standards with pronounced shifts in isotope values offers a much-needed basis for accurate chlorine CSIA.

Groundwater contamination by hazardous substances including chlorinated solvents has become a serious widespread problem, representing a substantial liability. Evaluation of contaminant sources in groundwater plumes, which has significant relevance for assignment of responsabilities for groundwater remediation, is one of the key aspects that consultants and environmental agencies have to deal with in contaminated groundwater. In recent years, compound-specific stable isotope analysis have become a valuable methodology that is employed as an indicator of chemical and biological degradations of chlorinated solvents in groundwater and as a tool to distinguish different plumes (fingerprinting) and trace them back to the release source point. In this study, chlorine and carbon stable isotopes were used to identify the origin of trichloroethene (TCE) in a co-mingled plume that can be associated to a primary in-site source and an off-site TCE source link to biodegradation of perchloroethene (PCE). The stable isotope data showed a very distinct and significantly different isotopic fingerprint for the primary source of TCE compared to the off-site source. This difference can be observed in the co-mingled TCE plume downgradient from the two TCE sources clearly showing that the off-site TCE source is contributing to the in-site TCE plume. These results showed the great potential of the combined use of 37 Cl and 13 C for fingerprinting organic contaminant sources in groundwater.

AbstractÐTotal lipid extracts and solvent insoluble organic matter in soils from the Park Grass Experiment at Rothamsted Experimental Station, Harpenden, U.K. were studied to determine the eect of pH on the preservation/degradation of plant derived biomolecules. Analyses involved high temperaturegas chromatography (HT-GC), HT-GC±mass spectrometry (HT-GC±MS), GC combustion±isotope ratio MS (GCC±IRMS) and ¯ash pyrolysis±GC (Py±GC) and Py±GC±MS. The plots selected for study have pH values ranging from 3.7 to 7.3, with acidic soils exhibiting two distinct horizons (i.e. humic rich top layer and mineral soil). The total lipid extracts of the soil samples with low pH exhibited higher relative abundances of long-chain (>C 20 ) organic acids believed to be derived largely from oxidation of plant lipids. The vegetation signature in the low molecular weight fraction is only retained in the humic rich top layer. The signal in the mineral layer is believed to derive primarily from previous vegetation. Compound speci®c stable carbon isotope (d 13 g) measurements of long-chain n-alkanols are considered to re¯ect dierences in the rate of incorporation of plant lipids into the humic top layer related to the grass species dominating the standing vegetation. In the soil samples of low pH, lignin contributes to the high molecular weight fraction of the humic layer. In contrast, the mineral layer of the same soil shows little evidence of intact lignin, but is instead dominated by amino acid pyrolysis products, probably deriving from (degraded) polypeptides. The pyrolysates of the mineral soils of high pH yield a distribution of products similar to that found in the deeper layer of the low pH samples but with evidence of lignin derived moieties. Overall, soil pH was found to have a signi®cant eect on the preservation of higher plant derived biomolecules including ligno-cellulose.

Studies performed during the last two decades have shown that lipids are preserved in association with a wide range of artefacts and ecofacts recovered from archaeological sites, e.g. pottery vessels and skeletal remains. The majority of work in this area has focused on the use of molecular structures (`biomarkers') and distributions (`¢ngerprints') to assess the nature and origin of commodities associated with past cultural, economic and agricultural practices. However, since lipids, like all other classes of biomolecule, are a¡ected by degradation (both pre-and post-burial), emphasis is now being placed on the complementary use of diagenetically robust, compound-speci¢c stable isotope measurements to enhance the scope and reliability of archaeological interpretations. A feature of the 13 C values of individual lipids, rather than bulk measurements of biochemically more heterogeneous materials, lies in their capacity to re£ect di¡erences in both the isotopic composition of the carbon sources used in their biosynthesis and the routing of dietary lipids and their metabolites in consumer organisms. This isotopic information, accessible by gas chromatography ^combustion-isotope ratio mass spectrometry, has opened up new avenues of investigation concerning human activity in prehistory.

Strontium isotopes (87 Sr/ 86 Sr) are increasingly used as a provenance tool in multiple disciplines. Application to biological materials requires knowledge of the variation in bioavailable 87 Sr/ 86 Sr across the landscape, potentially in the form of an isoscape (a quantitative model of spatial isotopic variability). This paper summarizes and provides advice on our current understanding of the main concerns in creating and interpreting isoscapes of bioavailable 87 Sr/ 86 Sr. Isoscape creation approaches include domain mapping, geostatistical contour mapping and machine learning, the last becoming more readily achievable with the availability of software packages. It is critically important to develop isoscapes at a resolution appropriate for addressing the research questions. Choice of sample materials depends on the research questions and availability: plants or fauna with small ranges are favoured, with some analytes (snails, soil leachates) posing challenges. Interpreting 87 Sr/ 86 Sr in biological tissues requires considering Sr metabolism and the timing of tissue formation, thus far underappreciated. The numerous sources of error involved in developing and applying isoscapes must be recognized to avoid over-interpreting data and spurious provenance precision. We hope this paper will help researchers investigating provenance, mobility, landscape use and migration to develop the most appropriate isoscapes for their purposes, and possible future use by others.

Differences in the stable carbon isotope ratios of plants utilizing the C3 vs. C4 photosynthetic pathway have been used to broadly identify the natal host origins of herbivorous insects. This study explored whether adequate variation exists between the carbon isotope ratios of different C3 plants in the host range of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) to enable accurate identification of natal host‐plant species. Isotope ratio mass spectrometry (IRMS) analysis of 13C/12C ratios of moths reared on four crop plant species [Gossypium hirsutum (L.), Nicotiana tabacum L., Glycine max (L.) Merrill, and Arachis hypogaea L.] and two common weed species [Geranium carolinianum L. and Linaria canadensis (L.) Chaz.] revealed a range of δ13C values within that expected for plants utilizing the C3 photosynthetic pathway. Analysis of vegetative and reproductive tissues from the plants utilized in the study resulted in statistically different δ13C values for some plant species...

Polyethylene is probably the most used plastic material in daily life and its accurate analysis is of importance. In this communication the chemical structure of polyethylenes is studied in detail using conventional analytical pyrolysis (Py-GC/MS), bulk stable isotopic analysis (IRMS) and pyrolysis compound specific stable isotopic analysis (Py-CSIA) to measure stable isotope proportions (δ 13 C, δ 15 N and δD) of polyethylene pyrolysis compounds. Polyethylene pyrolysis yields triplet peaks of n-alkanes, α-alkenes and α,ω-alkanedienes. No differences were found for bulk δ 13 C among different polyethylene types. However, conspicuous differences in δD were evident. It was possible to assign structure δ 13 C and δD values to specific polyethylene pyrolysis products in the range 12-18 carbon chain length. Conspicuous differences were found for the pyrolysis products with unsaturated moieties showing significant higher δD values than saturated chains (alkanes) that were deuterium depleted. In addition, a full isotopic fingerprinting (δ 13 C, δ 15 N and δD) for a dye (o-chloroaniline) contained in a polyethylene is reported. To the best of our knowledge this is the first application Py-CSIA to the study of a synthetic polymer. This hyphenated analytical technique is a promising tool to study synthetic materials, providing not only a fingerprinting, but also allowing the traceability of the polymerization process and the origin of the materials.

Etruria contained one of the great early urban civilisations in the Italian peninsula during the first millennium BC, much studied from a cultural, humanities-based, perspective, but relatively little with scientific data, and rarely in combination. We have addressed the unusual location of twenty inhumations found in the sacred heart of the Etruscan city of Tarquinia, focusing on six of these as illustrative, contrasting with the typical contemporary cremations found in cemeteries on the edge of the city. The cultural evidence suggests that the six skeletons were also distinctive in their ritualization and memorialisation. Focusing on the six, as a representative sample, the scientific evidence of osteoarchaeology, isotopic compositions, and ancient DNA has established that these appear to show mobility, diversity and violence through an integrated bioarchaeological approach. The combination of multiple lines of evidence makes major strides towards a deeper understanding of the role of these extraordinary individuals in the life of the early city of Etruria.

Etruria contained one of the great early urban civilisations in the Italian peninsula during the first millennium BC, much studied from a cultural, humanities-based, perspective, but relatively little with scientific data, and rarely in combination. We have addressed the unusual location of twenty inhumations found in the sacred heart of the Etruscan city of Tarquinia, focusing on six of these as illustrative, contrasting with the typical contemporary cremations found in cemeteries on the edge of the city. The cultural evidence suggests that the six skeletons were also distinctive in their ritualization and memorialisation. Focusing on the six, as a representative sample, the scientific evidence of osteoarchaeology, isotopic compositions, and ancient DNA has established that these appear to show mobility, diversity and violence through an integrated bioarchaeological approach. The combination of multiple lines of evidence makes major strides towards a deeper understanding of the role of these extraordinary individuals in the life of the early city of Etruria.

The pottery assemblage from the Maharski prekop site was analysed to obtain insights into vessel use and husbandry practices. Total lipid extracts of pottery samples were subjected to gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), gas chromatography–combustion–isotope ratio mass spectrometry (GC–C–IRMS) and soft ionisation electrospray mass spectrometric techniques ESI Q–TOF MS and ESI Q–TOF MS/MS. The charred organic deposits on vessels were AMS 14C dated. The results show that some vessels were used for cooking ruminant meat, while in other traces of mixed non–ruminant and ruminant meat or plants and animal meat cooking were identified. Some vessels were used for milk processing.

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This study monitors variations in isotopes and elements in relation to grape variety, environmental factors and provenance in order to address the wine authenticity issue. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) assessed the wines' elemental content. Sitespecific nuclear isotope fractionation-nuclear magnetic resonance and isotope ratio mass spectrometry methodologies determined in authentic and commercial wines the distribution of the naturally occurring stable isotopes of the deuterium/ hydrogen (D/H) ratios and carbon ( 13 C/ 12 C) in ethanol of wine and oxygen ratio ( 18 O/ 16 O) in wine water. Chemometrics delineated the elements and isotopes responsible for wine classification. Specifically, unsupervised principal component analysis (PCA) framed the importance of grape variety and provenance, while supervised analysis pinpointed the vineyard effect and highlighted the contribution of the vintage year. Validation steps ensured that the extracted models do not predict randomly and their results are reliable. In fact, the acquired results can be incorporated to the EU Wine Isotopic Databank database providing both a guide and a tool for eventual candidatures for denomination of origin and support both Cypriot wine and winemakers. In this context, this research contributes to authenticity assurance of wines and adds value to final products, while it helps controlling hazards arising from environmental changes.

CiteSeerX - Document Details (Isaac Councill, Lee Giles): The microbial community compositions of surface and subsurface marine sediments and sediments lining burrows of marine polychaetes and hemichordates from the North Inlet estuary (near Georgetown, SC) were analyzed ...

Cavity ring‐down spectroscopy (CRDS) is a highly sensitive laser technique that allows the analysis of isotopic signals and absolute concentration of individual molecular species in small‐volume samples. Here, we describe a protocol to quantify photosynthetic 13C‐uptake rates of marine phytoplankton by using the CRDS technique (13C‐CRDS‐PP). We validated our method by comparing the 13C‐PP rates measured between CRDS and isotope ratio mass spectrometry (IRMS) in samples with different carbon content (30–160 μgC). The comparison revealed that 13C‐CRDS‐PP rates were highly correlated with those obtained by IRMS (Spearman correlation coefficient, ρ = 0.95, p &lt; 0.0001, n = 15), with a mean difference between the two estimates of ± 0.08 mgC m−3 h−1. Moreover, the slope of the relationship between CRDS and IRMS results was not significantly different from 1 (F = 0.03, p = 0.86), and the intercept did not differ from 0 (F = 1.4, p = 0.24), indicating that there was no bias in the CRDS re...

Abundant tricyclic diterpanes (i.e., pimarane, dehydroabietane and simonellite) and tetracyclic diterpanes (e.g., phyllocladane) were detected in coal samples from the third member of the Shahejie Formation, Lower-Eogene, Liaohe Basin, China. Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) analyses show that the carbon isotopic composition of terrigenous tricyclic and tetracyclic diterpenoid hydrocarbons are about 4-6% enriched in 13 C compared to n-alkanes in the same samples. In addition, the pimaranes and phyllocladane have comparatively narrow stable carbon isotopic compositions among the different samples, with a slightly wider range in 13 C compositions for the abietanes (i.e., abietane, dehydroabietane and simonellite). The n-alkanes and triterpenoids reflect the 13 C compositions of higher plant wax.

Abundant tricyclic diterpanes (i.e., pimarane, dehydroabietane and simonellite) and tetracyclic diterpanes (e.g., phyllocladane) were detected in coal samples from the third member of the Shahejie Formation, Lower-Eogene, Liaohe Basin, China. Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) analyses show that the carbon isotopic composition of terrigenous tricyclic and tetracyclic diterpenoid hydrocarbons are about 4-6% enriched in 13 C compared to n-alkanes in the same samples. In addition, the pimaranes and phyllocladane have comparatively narrow stable carbon isotopic compositions among the different samples, with a slightly wider range in 13 C compositions for the abietanes (i.e., abietane, dehydroabietane and simonellite). The n-alkanes and triterpenoids reflect the 13 C compositions of higher plant wax.

New tools for the determination of characteristic parameters for food authentication are requested to prevent food adulteration from which health concerns, unfair competition could follow. A new coupling in the area of compound-specific carbon 13 isotope ratio (␦ 13 C) analysis was developed to simultaneously quantify ␦ 13 C values of sugars and organic acids. The coupling of ion chromatography (IC) together with isotope ratio mass spectrometry (IRMS) can be achieved using a liquid interface allowing a chemical oxidation (co) of organic matter. Synthetic solutions containing 1 polyol (glycerol), 3 carbohydrates (sucrose, glucose and fructose) and 12 organic acids (gluconic, lactic, malic, tartaric, oxalic, fumaric, citric and isocitric) were used to optimize chromatographic conditions (concentration gradient and 3 types of column) and the studied isotopic range (-32.28 to -10.65‰) corresponds to the values found in food products. Optimum chromatographic conditions are found using an IonPac AS15, an elution flow rate of 0.3 mL min -1 and a linear concentration gradient from 2 to 76 mM (rate 21 mM min -1 ). Comparison between ␦ 13 C value individually obtained for each compound with the coupling IRMS and elemental analyzer, EA-IRMS, and the ones measured on the mixture of compounds by IC-co-IRMS does not reveal any isotope fractionation. Thus, under these experimental conditions, IC-co-IRMS results are accurate and reproducible. This new coupling was tested on two food matrices, an orange juice and a sweet wine. Some optimization is necessary as the concentration range between sugars and organic acids is too large: an increase in the filament intensity of the IRMS is necessary to simultaneously detect the two compound families. These first attempts confirm the good results obtained on synthetic solutions and the strong potential of the coupling IC-co-IRMS in food authentication area.

The fine tuning of porosity in sol gel based devices makes possible the design of novel applications in which the transport of molecules through the oxide gel plays a crucial role. In this work we develop a new method for the simultaneous analysis of diffusion and adsorption of small diffusing probes, as anionic and cationic dyes, through silica mesoporous hydrogels synthesized by sol-gel. The novelty of the work resides in the simplicity of acquisition of the experimental data (by means of a desk scanner) and further mathematical modeling, which is in line with high throughput screening procedures, enabling rapid and simultaneous determination of relevant diffusion and adsorption parameters. Net mass transport and adsorption properties of the silica based hydrogels were contrasted to dye adsorption isotherms and textural characterization of the wet gels by SAXS, as well as that of the corresponding aerogels determined by Field Emission Scanning Electron Microscopy (FESEM) and N 2 adsorption. Thus, the validation of the results with well-established characterization methods demonstrates that our approach is robust enough to give reliable physicochemical information on these systems.

Levoglucosan is a thermal decomposition product of cellulose in particulate matter. δ13C value of levoglucosan could be used in studying the combustion mechanisms and chemical pathways. In order to introduce a minimum number of carbon atoms, based on the stereostructure of levoglucosan, a two-step derivatization method with methylboronic acid and MSTFA was developed and carefully optimized. The recommended reaction temperature is 70°C; the reaction time is 60 min for MBA and 120 min for MSTFA derivatization; and the molar ratio of levoglucosan : MBA : MSTFA is 1 : 1: 100 and 1 : 1: 120 and the reagent volume ratio of MSTFA : pyridine is between 1 : 3 and 1 : 4. The developed method achieved excellent reproducibility and high accuracy. The differences in the carbon isotopic compositions of the target boronate trimethysilylated derivative between the measured and calculated ranged from 0.09 to 0.36‰. The standard deviation of measured δ13C value of levoglucosan was between 0.22 and 0....

The accuracy and precision of gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) measurements are highly dependent on analyte purity. Reliable analysis of urinary steroids for doping control therefore requires extensive and time-consuming sample preparation (i.e. liquid chromatography fraction collection) prior to GC-C-IRMS analysis. The use of two-dimensional GC (GC-GC) with heart-cutting (Deans Switch) as a possible approach to reduce the sample purification required for IRMS analysis is described herein. The system uses a low thermal mass oven (LTM) incorporated into an existing GC-C-IRMS system. GC-GC allowed the use of a cyanopropyl/phenyl column in the first dimension to optimize the separation of underivatized steroids, while a phenyl-methylpolysiloxane column in the second dimension focuses the selectively cut analytes into narrower peaks for more sensitive and reliable MS analysis. In addition, to confirm analyte identity, eluent from the second GC was split, with 20 % entering a scanning MS, and 80 % flowing to the IRMS. As a proof concept, the developed method was then used to analyze a single spot urine (5 ml) from an individual receiving T therapy (2 Â 50 mg sachets of Testogel W ). The T delta value (À27.8 %, [T] = 38 ng/ml) was clearly distinct from 11-ketoetiocholanolone (À22.5 %) (used as an endogenous reference compound (ERC)), indicating T as being of exogenous origin. The simultaneous analysis by the scanning MS yielded a full scan mass spectrum of the same chromatographic peak, thus confirming the peak to be T.

The accuracy and precision of gas chromatography combustion isotope ratio mass spectrometry (GC‐C‐IRMS) measurements are highly dependent on analyte purity. Reliable analysis of urinary steroids for doping control therefore requires extensive and time‐consuming sample preparation (i.e. liquid chromatography fraction collection) prior to GC‐C‐IRMS analysis. The use of two‐dimensional GC (GC‐GC) with heart‐cutting (Deans Switch) as a possible approach to reduce the sample purification required for IRMS analysis is described herein. The system uses a low thermal mass oven (LTM) incorporated into an existing GC‐C‐IRMS system. GC‐GC allowed the use of a cyanopropyl/phenyl column in the first dimension to optimize the separation of underivatized steroids, while a phenyl‐methylpolysiloxane column in the second dimension focuses the selectively cut analytes into narrower peaks for more sensitive and reliable MS analysis. In addition, to confirm analyte identity, eluent from the second GC wa...

A new fast high‐precision on‐line technique is described for the determination of hydrogen isotope ratios of water by continuous‐flow mass spectrometry. For the first time H2/H2O‐equilibration using a platinum catalyst has been used in a fully continuous process. A significant reduction in the H2/H2O‐equilibration time is achieved by a complete vaporization of the water and by increasing the exchange temperature to 100°C. The analysis time is only ∼5 min/sample which includes equilibration and processing. Measurement precision and accuracy are better than 1‰ and sample consumption is only ∼5 μL. This new technique allows the measurement of a wide range of aqueous samples either in a semi‐continuous way (discrete samples are injected one after another) or in a fully continuous way. This allows us, for the first time, to make continuous measurements of ice cores. Copyright © 2003 John Wiley & Sons, Ltd.

Oxygen isotope ratio determination on any of the water phases (water vapor, water, ice) is of great relevance in different research fields such as climate and paleoclimate studies, geological surveys, and hydrological studies. The conventional technique for oxygen isotope measurement involves equilibration with carbon dioxide gas for a given time with a subsequent isotope determination. The equilibration technique is available in different layouts, but all of them are rather time-consuming. Here we report a new on-line technique that processes water samples as well as ice samples. The same principal, CO 2 hydration, is used but speeded up by (i) a direct injection and full dissolution of CO 2 in the water, (ii) an increased isotope exchange temperature at 50 °C, and (iii) a rapid gas extraction by means of an air-permeable membrane into a continuous helium flux supplying the isotope ratio mass spectrometer with the sample gas. The precision is better than 0.1‰ which is only slightly larger than with the conventional equilibration technique. This on-line technique allows analysis of 1 m of ice with a resolution of 1-3 cm, depending on the meltwater flux, within 1 h. Similarly, continuous and fast analysis can be performed for aqueous samples for hydrological, geological, and perhaps medical applications.

We have used ahigh-precision, high efficiency method for themeasurementof the 2 H/ 1 H ratios of hydrous silicates (amphiboles) and nominally anhydrous minerals (NAM) such as clinopyroxene, garnet and diamond, which are usually extremely resistant to pyrolysis. This opens up new fields of investigation to better understand the conditionsof formation fordeep-Earth minerals. The technique described hereinvolvesIsotopic Ratio Mass Spectrometry (IRMS) online in continuous flow mode with an Elemental Analyzer (EA) using-purge and trap‖ technology rather than conventional packed column-GC gas separation. The system is equipped with a special high temperature furnace reaching 1500°C, with a longer hot zone and improved temperature stability. Emphasis is put on the efficiency of the system to reliably pyrolyserefractory minerals difficult to analyse with other conventional systems. RESULTS:While conventional systems usually fail to generate hydrogen suitable for isotopic analyses, with the technique presented here we were able to measure 2 H/ 1 H ratios from 4diamond samples ( 2 H= -60, -77, -84 and -79‰ V-SMOW; average SD =4.5‰; n=2),3 garnet samples ( 2 Hfrom -70 to -63‰), and 9 clinopyroxenes ( 2 H from -92 to -58‰) associated with7 amphiboles ( 2 Hfrom -76 to -27‰) from single mantle rock. The possibility of using such a system to reliably measure 2 H/ 1 H ratios from refractory minerals, which are usually extremely difficult to analyse, offers a new tool of investigation for giving us unrivaled clues to study the Earth's deep interiors.

The IsoFoodTrack database is a comprehensive, scalable, and flexible platform designed to manage isotopic and elemental composition data for a wide range of food commodities. It supports research in food authenticity and fraud detection by integrating isotopic data with rich metadata, including geographical, production, and methodological details. The database is built for scalability, allowing the addition of new commodities, analytical methods, and metadata fields, while ensuring interoperability with external databases through standardized formats and API integration. Based on the data collected in IsoFoodTrack using statistical, chemometric and machine learning approaches it has a capability to identify and classify the origin of food commodities. IsoFoodTrack also supports isotope mapping (isoscapes), providing spatially continuous predictions that enhance the detection of food fraud. Rigorous quality control measures ensure high data reliability, and the user-friendly web interface facilitates easy access and visualization. Openly accessible through platforms like National Center for Biomedical Ontology (NCBO) BioPortal, IsoFoodTrack is positioned for future expansion and integration of open-access data, making it a vital tool for researchers and regulatory agencies in ensuring food authenticity and traceability.

Complete removal of carbonates from calcareous soil samples is critical for accurate measurement of the quantity and isotopic signature (d 13 C) of soil organic carbon (SOC). Carbonates confound SOC and d 13 C measurements because they have d 13 C values ranging from (10 to '2, whereas those of soil organic carbon range from (27 to (13, depending on the source of plant residues. Commonly used methods for removing carbonates involve treatment with acid followed by repeated water washings; however, these methods are time consuming, labour-intensive and lead to losses of acid-and water-soluble organic carbon. Fumigation of soil samples with HCl was evaluated as an alternative method, and the time required for complete carbonate removal was determined in this study. Moistened soil samples, taken from 0-to 10-cm and 30-to 50-cm depths, were exposed to HCl vapours for periods of 0, 6, 12, 24, 48, 72, and 96 h, followed by measurements of total C and d 13 C using coupled elemental analyzer-isotope ratio mass spectrometry. The minimum time required to remove all carbonates was ca. 30 h and 56 h for surface and subsurface soils containing 0.80 and 1.94% inorganic C, respectively. Therefore, the fumigation period required is dependent on the total carbonate content of the sample and the nature of the carbonate (pedogenic vs lithogenic). In our study, the rate of removal of inorganic carbon was 0.08Á0.10 mg h (1 for soil samples sizes with 2.4 to 5.8 mg of carbonate-C, a rate similar to previous studies on acid fumigation. A ''correction factor'' was used to account for a change in sample mass due to fumigation and is necessary for accurate determination of SOC concentration using our proposed methodology.