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The aim of this work is to characterize the geographical origin of cocoa beans and coffee beans. This study aims to contribute to the traceability of raw materials in order to fight against falsification. For this purpose, we based our work on the measurement of isotope ratios in 13C, 15N and 18O. The multi-element isotope ratios have been evaluated as a means to distinguish fermented cocoa beans of different geographic and varietal origins. The isotopic ratios of 13C, 15N and 18O were measured in theobromine obtained from samples of fermented cocoa beans. Twenty-two (22) samples of different geographical origins covering the four mainland cocoa producing areas were analyzed on the one hand and on the other hand, 16 caffeine samples from various origins were also analyzed. The treatment of the values resulting from these isotopic analyzes by statistical methods, namely the principal component analysis (PCA) makes it possible to visualize the discriminations between the different origins. The most discriminating variables identified as responsible for the geographic and varietal differences were the δ15N, δ13C and δ18O values of cocoa beans and certain extracts and tissues. We have shown that the isotope ratios are correlated with the altitude and precipitation conditions encountered in the different cocoa growing regions.

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One of the principal theories about the origin of life is based on the abiotic reduction of carbon oxides to various organic molecules in hydrothermal systems. This synthesis is most favored in ultramafic environments undergoing hydrothermal alteration where the serpentinization reaction efficiently produces H2. Nevertheless, decades of hydrothermal experiments have hardly succeeded in producing abundant organic volatiles such as CH4 and short-chain hydrocarbons. On another hand, natural observations have shown the occurrence of other abiotic compounds such as organic acids in fluids and carbonaceous matter (CM) within serpentinized rocks. But organic acids as carbon source and CM as product have not been investigated so far in experiments reproducing hydrothermal peridotite alteration. Here, we explored the effect of formic acid (HCOOH) on the serpentinization reaction and possible feedback effects on carbon speciation in both fluid and solid. We performed reactions at 300°C and 250 bar using peridotite powder (2, CO, and CO2. After 4 months, H2, CO, CO2, CH4 and short-chain alkanes (mainly ethane) were measured in the fluid, and the powder was completely indurated. The solidified powder displayed a black and white layering perpendicular to fluid diffusion. Its analysis showed the advancement of the serpentinization reaction, and the incorporation of carbon compounds into the solid phase. XRD analysis indicated 70% of serpentinization. SEM-EDX observations showed peculiar texture with large and localized euhedral magnetite grains alternating with larger magnetite grains mixed with C-enriched areas of long chrysotile fibers. FT-IR measurement attested of the widespread formation of carbonaceous material in the solid. Liquid analyses are under progress. Those first results suggest that serpentine formation not only provides additional H2 to the system, but also mineral surfaces that could play a role in the precipitation of carbonaceous material and carbon speciation in natural systems. The nature and formation mechanisms of this latter remain to be addressed but this opens new paths for abiotic organic synthesis under hydrothermal conditions. In addition to their implications as an abiotic carbon source for deep hydrocarbon degraders ecosystems, it could have important implications for the total carbon cycle.

International audience; Deciphering the role of sulfur in biogeochemical cycles strongly relies on its stable isotope composition, which ultimately depends on the ability to quantitatively recover different sulfur species from geological samples. For decades most studies have been restricted to the 34S/32S composition of bulk samples, using simple methods based on the analysis of SO2 released by sample combustion combined to mass spectrometry. The wet chemistry procedures required to selectively extract specific sulfur species were generally avoided due to their tediousness and inefficiency for some complex matrices, especially when targeting organic sulfur. With the recent advent of multi-isotope studies (investigating the minor sulfur stable isotopes 33S and 36S) which rely either on the analysis of sulfur as SF6, or on the use of secondary ion or multi-collector inductively coupled plasma mass spectrometry, wet chemistry-based preparation procedures were brought back to the stage with a renewed interest in developing procedures better adapted to the investigation of specific sulfur species. Here we propose a new stepwise chemical procedure for the quantitative recovery and multi-isotope analysis of organic sulfur from both solvent soluble (total lipid extract) and insoluble (kerogen) fractions, based on a wet oxidation by sodium hypochlorite. This procedure also allows the multi-isotope analysis of inorganic sulfur species (elemental sulfur, sulfates and sulfides) in the same sample. Its application to different well-known petroleum source rocks and to an oil demonstrates its relevance for disentangling the interactions between the different sulfur pools and for shedding new light on the sulfur biogeochemical cycle.

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International audience; Breast cancer is the most common cancer in women worldwide. Despite the information provided by anatomopathological assessment and molecular markers (such as receptor expression ER, PR, HER2), breast cancer therapies and prognostics depend on the metabolic properties of tumor cells. However, metabolomics have not provided a robust and congruent biomarker yet, likely because individual metabolite contents are insufficient to encapsulate all of the alterations in metabolic fluxes. Here, we took advantage of natural 13 C and 15 N isotope abundance to show there are isotopic differences between healthy and cancer biopsy tissues or between healthy and malignant cultured cell lines. Isotope mass balance further suggests that these differences are mostly related to lipid metabolism, anaplerosis and urea cycle, three pathways known to be impacted in malignant cells. Our results demonstrate that the isotope signature is a good descriptor of metabolism since it integrates modifications in C partitioning and N excretion altogether. Our present study is thus a starting point to possible clinical applications such as patient screening and biopsy characterization in every cancer that is associated with metabolic changes. Medical applications of stable isotopes are now widespread, like the well-known 13 C-urea breath assay for ulcer detection 1. This takes advantage of 13 C-labelling and thus usually neglects differences in reaction rates between isotopic forms, because the isotopic signal used for diagnosing is far above small natural variations in 13 C. By contrast, the use of isotopes at natural abundance exploits such subtle differences (referred to as isotope effects) to identify bottlenecks in metabolic pathways (rate-limiting steps) or the contribution of multiple elemental sources (mass balance), without the need to introduce expensive isotope tracers into the patient. Isotope effects in metabolism are mostly caused by enzymatic reactions that preferentially consume substrates containing either the light or the heavy isotope (isotopologues) and therefore, the natural isotope abundance in metabolites depends on metabolic fluxes and source substrates 2. For example, the natural 13 C abundance in respired CO 2 has been used to trace diet composition and substrate changes during exercise 3,4. In cancer biology, the use of natural variations in Cu and S stable isotopes in hepatocellular carcinoma has been attempted recently 5. But to our knowledge, no study has looked at alterations of natural isotope abundance in breast cancer. Due to changes in primary C and N metabolism such as increased glycolysis, glutaminolysis and nucleotide synthesis 6 , important changes in 13 C and 15 N natural abundance can be anticipated. To address this question, we examined the isotopic signature of intact breast cancer biopsies (mostly from invasive ductal carcinoma, IDC) and cultured breast cancer cell lines (Supplementary Tables S1 and S2) using elemental analysis coupled to isotope ratio mass spectrometry (EA-IRMS). This technique has been recently shown to be applicable to the biochemical analysis of cancerous cell lines 7 .

The measurement of the nitrogen isotope ratio of taurine (2-aminoethanesulphonic acid) in biological samples has a large number of potential applications. Taurine is a small water-soluble molecule which is notoriously difficult to analyze due to its polarity and functionality. A method is described which allows the determination of the natural abundance delta N-15 values of taurine and structural analogues, such as 3-amino-1-propanesulphonic acid (APSA), by isotope ratio mass spectrometry interfaced to gas chromatography (GC-irm-MS). The one-step protocol exploits the simultaneous derivatization of both functionalities of these aminosulphonic acids by reaction with triethylortho-acetate (TEOA). Conditions have been established which ensure quantitative reaction thus avoiding any nitrogen isotope fractionation during derivatization and workup. The differences in the delta N-15 values of derivatized and non-derivatized taurine and APSA all fall within the working range of 0.4 parts per thousand (-0.02 to 0.39 parts per thousand). When applied to four sources of taurine with various delta N-15 values, the method achieved excellent reproducibility and accuracy. The optimized method enables the determination of the natural abundance delta N-15 values of taurine over the concentration range 1.5-7.84 mu mol.mL(-1) in samples of biological origin. Copyright (C) 2010 John Wiley & Sons, Ltd.

Two-dimensional nuclear magnetic resonance (2D NMR) forms a powerful tool for the quantitative analysis of complex mixtures such as samples of metabolic relevance. However, its use for quantitative purposes is far from being trivial, not only because of the associated experiment time, but also due to its subsequent high sensitivity to hardware instabilities affecting its precision. In this paper, an alternative approach is considered to measure absolute metabolite concentrations in complex mixtures with a high precision in a reasonable time. It is based on a ``multi-scan single shot'' (M3S) strategy, which is derived from the ultrafast 2D NMR methodology. First, the analytical performance of this methodology is compared to the one of conventional 2D NMR. 2D correlation spectroscopy (COSY) spectra are obtained in 10 min on model metabolic mixtures, with a precision in the 1-4% range (versus 5-18% for the conventional approach). The M3S approach also shows a better linearity than its conventional counterpart. It ensures that accurate quantitative results can be obtained provided that a calibration procedure is carried out. The M3S COSY approach is then applied to measure the absolute metabolite concentration in three breast cancer cell line extracts, relying on a standard addition protocol. M3S COSY spectra of such extracts are recorded in 20 min and give access to the absolute concentration of 14 major metabolites, showing significant differences between cell lines.

Cyanide is one of the common poisons in murders. When cyanide has been used, to identify the origin of cyanide may be necessary in the forensic investigation. We have examined the possibility of distinguishing different commercial cyanide samples through the δ 13 C and δ 15 N values and developed a protocol for the isotope analysis of cyanide extracted from several matrices as food and medicine. Several cyanide precipitates were tested for the isotope analysis. The results show that cupric ferrocyanide Cu 2 [Fe(CN) 6 ] is the most appropriate precipitate for the analysis. Thirteen batches of KCN and nine batches of NaCN chemicals were randomly chosen from different suppliers. The cyanides were converted to cupric ferrocyanide and then analysed by isotope ratio mass spectrometry coupled to elemental analysis (EA-IRMS). The isotopic signature of the commercial samples varied from −51.96 to −25.77‰ for δ 13 C and from −4.51 to +3.81‰ for δ 15 N, highlighting the potential of applying EA-IRMS technique to identify cyanide from different batches and sources. The influence of the cyanide extraction and isolation from spiked matrix on the isotopic analysis was also studied. Three matrices: orange juice, yogurt drink and a medicine were tested. In many cases, the isotopic analysis results obtained from the original cyanides precipitates and those isolated from the matrices showed a good accordance, especially for δ 15 N. In some matrices, the 13 C analysis was interfered by co-precipitates. With carefully elaborated working protocol, determining the isotope ratio of N and C in cyanide by EA-IRMS is a promising method for forensic investigations.