Compound-specific Isotope Analysis Research Articles

Multi-element Compound-Specific Stable Isotope Analysis (2H, 13C, 15N, 33/34S) to characterize the mechanism of sulfate and hydroxyl radical reaction and photolysis of benzothiazole

Multi-element Compound-Specific Stable Isotope Analysis (2H, 13C, 15N, 33/34S) to characterize the mechanism of sulfate and hydroxyl radical reaction and photolysis of benzothiazole

Does mercury biomagnification in a boreal lake food web vary year-round? - A comparison using bulk δ15N and compound-specific δ15N of amino acids.

Seasonality characterises northern latitude lakes, however, limited knowledge exists regarding seasonal fluctuations in mercury (Hg) biomagnification. This study tested for these fluctuations year-round in the food web of a boreal humic lake (Lake Pääjärvi, in southern Finland) and for differences between two methods of trophic level (TL) determination. A food web sample was collected in three open-water seasons and one ice-covered season. TL was calculated using bulk nitrogen stable isotopes (δ15N) and compound-specific stable isotope analysis of δ15N in amino acids (CSIA-AA). Biomagnification of total Hg (THg), measured through the linear regression of THg (log10[THg]) and TLs, was detected in all seasons using both isotope methods. No significant differences in seasonal trophic magnification slope (TMS), the slope of the linear regression, in- and between methods were found. However, [THg] baseline estimates, the intercept of the linear regression, were significantly different between methods when comparing the same seasons. [THg] baseline values were generally higher in all seasons in bulk δ15N than CSIA-AA. Results highlight relatively stable biomagnification among seasons in both methods, however, direct comparisons of bulk δ15N and CSIA-AA TLs require further methodological development.

Development of a δ13C and δ34S Isotope Analysis Method for Sulfadimidine and Its Potential to Trace Contaminant Transformation in Groundwater Systems.

The widespread occurrence of micropollutants like the antibiotic sulfadimidine in the environment has become a growing concern. Compound-specific stable isotope analysis (CSIA) offers a powerful tool for tracking the fate of such pollutants, but its application is often limited by low sensitivity. To address this limitation, a large-scale solid-phase extraction method was developed to extract, enrich, and isolate sulfadimidine for δ13C- and δ34S-CSIA. Each step of the method was carefully evaluated, ensuring no detectable isotope artifacts. The limit of quantification was determined as 1.1 nmol of carbon and 1.2 nmol of sulfur directly injected on the column. Applied to groundwater samples from a contaminated site in Denmark, the method allowed for the analysis of concentrations as low as 0.17 mg/L, with a concentration factor of up to 10,000 used to enrich sulfadimidine. This is the first study to analyze δ13C and δ34S for sulfadimidine in aquifer water samples and highlights the potential of CSIA for tracking sulfadimidine transformations in contaminated water environments.

Highly effective energy transfer in the autotroph-heterotroph symbiosis: insights from compound-specific isotope analysis of amino acids

Many species establish symbiotic partnerships with different organisms to benefit energetically from living together to fit into environments, and such symbiosis is frequently found in the modern ocean as well as throughout Earth’s history. For example, coral reef ecosystems represent one of the most productive and biologically diverse ecosystems in the modern ocean, which is simply explained by an assumption that many autotroph-heterotroph symbiotic species found in there increase the efficiency of trophic transfer from primary producers (i.e., algal symbionts) to primary consumers (i.e., animal hosts), and that such high efficiency may be propagated to entire food webs. However, this high efficiency has not been proved and illustrated with quantitative data in the trophic transfer of photosynthates from algal symbionts to animal hosts. In the present study, we measured the energetic balance between degradation and biomass growth, which is a major factor of the efficiency of trophic transfer, based on the analysis of stable nitrogen isotope ratios of amino acids for several species including sea anemones, stony corals, zoanthids, and soft corals, that were bred under an autotrophic condition in a laboratory aquarium. The results confirm that the symbiosis indeed provides highly effective energy transfer of algal photosynthates to animal hosts, and allow us to quantify that the energy transfer in the symbiosis increases by approximately twice of that when non-symbiotic herbivorous species feed on primary producers. These results induce a new perspective that the effective energy transfer driven by symbiosis is a critical factor controlling the development of highly productive and biologically diverse ecosystems in the modern ocean as well as throughout Earth’s history.

A Novel Method to Determine the Carbon Isotopic Composition of Inositol Hexaphosphate (Phytate) in Soil by Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry.

Understanding the decomposition of inositol hexaphosphate (phytate), the dominant form of organic phosphorus (OP) in soil, is vital for studying phosphorus (P) cycling in terrestrial ecosystems. However, the lack of multiple stable P isotopes complicates the study of phytate dynamics under natural conditions and over long periods. A novel method is presented to determine the carbon isotopic composition of inositol in phytate using compound-specific isotope analysis. For this purpose, phytate was extracted from soil and purified via ion exchange chromatography, followed by dephosphorylation, derivatization, and analysis using GC-MS and GC-C-IRMS. Pure compounds were also analyzed to assess protocol efficiency, identify isotopic fractionations, and apply isotopic corrections due to derivatization. Phytate extracted from soil samples was identified using GC-MS chromatograms. Replicate analyses of the pure compounds indicated that the protocol is highly reproducible. The carbon isotopic composition (δ13C) showed a high reproducibility, with values varying by less than 0.5‰ and with no detectable isotopic fractionation during sample preparation. The δ13C values of phytate in soil samples reflected the dominant vegetation type (C3 or C4) growing at the study site. This study offers a novel approach of determining δ13C values of inositol of phytate in environmental samples, offering new opportunities to investigate and quantify OP dynamics based on stable carbon isotopes.

Insights into anaerobic biotransformation of polychlorinated biphenyls in Dehalococcoides mccartyi CG1 through kinetic and stable isotopic analysis.

Insights into anaerobic biotransformation of polychlorinated biphenyls in Dehalococcoides mccartyi CG1 through kinetic and stable isotopic analysis.

Insight into natural attenuation of tributyl phosphate by indigenous anaerobic microbes in soils: Implication by stable carbon isotope fractionation and microbial community structures.

Insight into natural attenuation of tributyl phosphate by indigenous anaerobic microbes in soils: Implication by stable carbon isotope fractionation and microbial community structures.

High litter quality enhances plant energy channeling by soil macro-detritivores and lowers their trophic position.

Detritus-based resources, that is, plant litter, are a major energy source for many living organisms and are considered to be a key determinant of primary production and nutrient cycling. Earthworms are among the most important macro-detritivores in terrestrial food webs and play a crucial role in facilitating these processes in terrestrial ecosystems. Yet, the influence of litter quality on earthworm nutrition, and consequently on soil food web dynamics, has remained largely underexplored, mainly for methodological reasons. Here, we combined bulk and compound-specific stable isotope analysis of amino acids to investigate the dietary contribution of different quality litter resources to earthworm species of different ecological groups. Our findings show that earthworms acquired most essential amino acids from bacterial (~60%) and plant (~30%) resources, with the latter increasing in importance with higher litter quality, resulting in lower trophic positions across earthworm species. The high bacterial contribution to earthworms corresponds to the dominance of bacteria in the experimental soil, suggesting that bacteria served as an important intermediate link in transferring detritus-based resources to earthworms. Bacterial contributions were notably higher in the soil-feeding earthworm species than in the litter-feeding earthworm species, likely due to more pronounced ingestion of soil by soil-feeding earthworms. Overall, our study indicates that a major group of soil macro-detritivores, earthworms, receive detrital resources via the bacterial energy channel. Further, it underscores the important role of litter quality in shaping the trophic niches of detritivores, thereby influencing the overall structure of soil food webs.

Insights from multiple stable isotopes (C, N, Cl) into the photodegradation of herbicides atrazine and metolachlor.

Insights from multiple stable isotopes (C, N, Cl) into the photodegradation of herbicides atrazine and metolachlor.

Role of membrane porosity in passive sampling of aquatic contaminants for stable isotope analysis: enhancement of analyte accumulation rates and selectivity

Compound-specific isotope analysis (CSIA) is a potent method for illustrating the in situ degradation of aquatic contaminants. However, its application to surface and groundwater is hindered by low contaminant concentrations, typically in the nanogram-per-litre range, requiring the processing of large water volumes. Polar organic chemical integrative samplers (POCIS) have shown promising results when combined with CSIA, yet their extended deployment time to accumulate sufficient analyte mass remains a major limitation. In our study, we addressed this issue by increasing the pore size of the polyethersulfone membrane (PES) from 0.1 to 8 μm. This resulted in significant increases in the mass accumulation rates of atrazine (3.5-fold), S-metolachlor (3.4-fold), and boscalid (3.0-fold). Importantly, the larger pore sizes did not compromise isotopic integrity, with Δδ13C≤+0.4±0.1‰ and Δδ15N≤-0.6±0.4‰, both within accepted uncertainties. Additionally, we observed an enhanced selectivity of the larger pores towards the target analytes over humic acids, whereas no significant increase in (bio)fouling potential was detected for the 8 μm membrane, as demonstrated by gravimetric analysis, SEM measurements, mass accumulation rates, and isotope ratios of fouled and unfouled POCIS. Our findings show that increasing the membrane pore size from 0.1 to 8 μm reduces deployment time and expedites the accumulation of analyte mass required for gas chromatography isotope ratio mass spectrometry, offering a promising method to expand CSIA for low-concentration pesticide analysis in the field.Graphical abstract

Amino acid stable carbon isotopes in nail keratin illuminate breastfeeding and weaning practices of mother – infant dyads

Compound-specific stable carbon isotope analysis of amino acids (CSIA-AA) is widely used in ecological studies to analyze food-webs and is gaining use in archaeology for investigating past diets. However, its use in reconstructing breastfeeding and weaning practices is not fully understood. This study evaluates the efficacy of stable carbon isotope analysis of amino acids in early life diet reconstruction by analyzing keratin from fingernail samples of three mother-infant pairs during late gestation and early postpartum periods. Our results show that stable carbon isotope ratios (δ13C) of glycine, and to a lesser extent glutamate, effectively trace the onset of exclusive breastfeeding and the end of weaning in infants. We propose that glycine’s ‘conditionally essential’ metabolic pathway during infancy allows it to reflect maternal glycine δ13C, indicating breastmilk consumption. Subtle changes in glutamate δ13C likely result from its ‘non-essential’ status. Additionally, δ13C values of glycine and glutamate indicate maternal physiological and pathological stress due to catabolic effects such as gluconeogenesis. These findings have significant implications for ecological and archaeological research using CSIA-AA for dietary reconstructions. They highlight the need to understand how metabolic pathways affecting δ13C of amino acids may change over an individual’s lifespan or be altered due to various forms of stress.

Two-Dimensional Liquid Chromatography-Isotope Ratio Mass Spectrometry Opens New Possibilities in the Field of Compound-Specific Stable Isotope Analysis.

Compound-specific stable isotope analysis (CSIA) using liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) is a powerful tool for determining the isotopic composition of carbon in analytes from complex mixtures. However, LC-IRMS methods are constrained to fully aqueous eluents. Previous efforts to overcome this limitation were unsuccessful, as the use of organic eluents in LC-IRMS was deemed impossible. In our study, we developed a two-dimensional (2D) LC-IRMS method that, for the first time, enables the use of organic-containing eluents in an LC-IRMS setting. Initial experiments with caffeine were performed using a sample loop modulator with 20% methanol in the mobile phase of the first dimension, while separating the organic fraction from the analyte in the second dimension. Comparing results with one-dimensional (1D) LC-IRMS methods showed high precision with δ13C values in 2D measurements (-34.98 ± 0.04 ‰) closely matching 1D results (-34.95 ± 0.12 ‰). In the next step, incorporation of an at-column dilution (ACD) modulator allowed for the successful use of methanol concentrations up to 40% in the first dimension, with the ACD modulator effectively mitigating both peak fronting and carbon background interference, without losing any precision or accuracy of the measurements (δ13CCaffeine = -34.92 ± 0.03 ‰). All developed methods showed a method detection limit lower than 5 mg of carbon L-1 (mgC L-1), which is a major improvement compared with previous studies on caffeine analysis with LC-IRMS. This proof-of-concept study on 2D-LC-IRMS opens vast new possibilities for future CSIA research across diverse fields, including environmental science, pharmaceuticals, and food chemistry.

Beef, butter, and broth: cooking in 16th-century Sweden

We present the organic residue analysis of sherds of 50 cooking vessels from the 16th-century town of Nya Lödöse, Sweden. We confirm previous analyses showing that lipids are absorbed by glazed ceramic. By analyses of biomarkers and compound-specific stable carbon isotope analyses of fatty acids, we show that pipkins and pans were used for cooking ruminant carcass products, dairy, and plant foods. The dominance of ruminant fat and dairy reflects the importance of oxen and butter in the local food culture. The vessels included in the present study show some degree of specialized function. Pipkins had more traces of ruminant carcass fats compared to pans. Medium and large-sized pipkins contained a combination of animal fats and plant traces, possibly representing the preparation of stews. In contrast, the smallest pipkins showed no traces of plant foods and might have been used to melt animal fat. Pans had more traces of butter and had been exposed to higher temperatures, indicating frying. Flat pans were, to a higher degree, used for the frying of fish than the deep ones, but fish seem nonetheless to be underrepresented in the lipid residue data. According to zooarchaeological and historical data, fish, pork, and poultry were important parts of the diet, but as traces of these foodstuffs are scarce in the organic residue analysis, it may be inferred that they were prepared differently—boiled in metal cauldrons, roasted on metal spits over the open fire, or consumed in their dried, salted, or smoked state without further preparation.

Potential of Compound-Specific Isotope Analysis (CSIA) to Trace Galaxolide Reactivity and Origin

Potential of Compound-Specific Isotope Analysis (CSIA) to Trace Galaxolide Reactivity and Origin

Highly Efficient Compositional and Compound Specific Isotopic Analysis of Volatile Primary Amines and Ammonia in the Murchison Meteorite Using SPME On-Fiber Derivatization: Optimization for Bennu Sample Analyses.

Extraterrestrial amines and ammonia are critical ingredients for the formation of astrobiologically important compounds such as amino acids and nucleobases. However, conventional methods for analyzing the composition and isotopic ratios of volatile amines suffer from lengthy derivatization and purification procedures, high sample mass consumption, and chromatographic interferences from derivatization reagents and non-target compounds. Here we demonstrate a highly efficient method to analyze the composition and compound specific isotopic ratios of C1 to C6 amines as well as ammonia based on solid phase micro-extraction (SPME) on-fiber derivatization. 2,3,4,5,6-pentafluorobenzyl chloroformate (PFBCF) adsorbed on a solid phase SPME fiber is subsequently exposed to the headspace of the water extract of the Murchison meteorite to selectively extract, derivatize and concentrate volatile amines and ammonia. PFBCF does not directly contact the aqueous solution containing other soluble organics. An aliquot of volatile amines and ammonia in the headspace are selectively derivatized on the SPME fiber and subsequently thermally desorbed onto the GC injector for analysis. Only the amounts of amines required for either compositional or isotopic analysis are derivatized and consumed in the process, preserving the bulk fraction of amines and ammonia for other analyses, and the process does not affect other volatile compound classes. Carbon and hydrogen isotopic ratios of amines are obtained by isotopic mass balance. The exceptional selectivity and sensitivity of SPME on-fiber derivatization of volatile amines in carbonaceous chondrite extracts allow minimization of sample consumption. Carbon and hydrogen isotopic values of individual amines in the Murchison meteorite are consistent with their extraterrestrial origin, with a substantial fraction inherited from interstellar molecular clouds. SPME on-fiber derivatization is well suited for analyzing extraterrestrial materials, especially precious asteroid return samples.

Spatiotemporal variations in integrated trophic positions of stream macroinvertebrate communities

To understand energy and material cycles on surface Earth, it is important yet challenging to estimate trophic transfer through ecosystems. To address this issue, the integrated trophic position (iTP), defined as a biomass-weighted average TP of a given food web, is useful because the iTP can be a proxy for the configuration of ecological pyramid. Here we conducted the compound-specific nitrogen isotope analysis of amino acids for macroinvertebrate communities collected from the Ado and Yasu Rivers in the Lake Biwa watershed, Japan, to estimate their iTP values. Unlike previous studies, no clear relationships between iTP and biodiversity (Shannon index H’) were found. However, by comparing the irrigated period and the non-irrigated period within the Yasu River, the decrease in iTP values was fairly characterized by the increase in H’. A significant difference in the observed iTP values compared to those reported in the previous study suggests that the configuration of ecological pyramid in stream ecosystems is dynamic rather than static. We also found that the iTP values of stream macroinvertebrate communities (2.37 ± 0.24) (n = 43), marine mesozooplankton communities (2.33 ± 0.34) (n = 14), and animal communities with various taxonomic groups (2.42 ± 0.21) (n = 158) are all comparable with each other, suggesting that partial communities involving macroinvertebrates well represent the configuration of total ecological pyramid. This finding clearly delineates the promising performance of the iTP index for the trophic transfer of energy, which should be further explored in a variety of ecosystems.

Influence of saline water and heavy rain on the fate of chlorinated ethenes in groundwater characterized by compound-specific isotope and microbial data.

Influence of saline water and heavy rain on the fate of chlorinated ethenes in groundwater characterized by compound-specific isotope and microbial data.

Land-ocean connections in organic carbon cycling amid the Early Triassic (Smithian-Spathian) revealed through compound specific isotope analysis

Land-ocean connections in organic carbon cycling amid the Early Triassic (Smithian-Spathian) revealed through compound specific isotope analysis

Phase transfer and photodegradation of DBP in water–sediment systems explored by compound-specific isotope analysis

Phase transfer and photodegradation of DBP in water–sediment systems explored by compound-specific isotope analysis

High-resolution isotope dietary analysis of Mesolithic and Neolithic humans from Franchthi Cave, Greece.

Franchthi Cave, in the Greek Peloponnese, is a well-known Paleolithic, Mesolithic and Neolithic site, with several human burials. In many parts of Europe there is clear evidence from archaeological and isotopic studies for a diet change between the Mesolithic and Neolithic periods. This is especially the case in coastal contexts where there is often a shift from predominantly marine food diets in the Mesolithic to terrestrial (presumably domesticated) foods in the Neolithic. However, at Franchthi Cave previous isotope research did not show changes in diets between these two periods, and also showed relatively little input from marine foods in diets in either time period, despite the coastal location of the site and the presence of marine shellfish and fish, including tuna. High-resolution compound specific amino acid isotope analysis reported here from humans from the Lower Mesolithic and Middle Neolithic periods confirms the previous bulk isotope results in showing little or no consumption of marine foods in either time period. However, it is important to note that our isotopic sample does not come from episodes when tuna is abundant and therefore do not cover the whole range of known diets from the site. Conversely, in our sample there is some evidence of marine food consumption (likely seaweed) by sheep in the Neolithic period. We also report here five direct AMS radiocarbon dates for the five analyzed humans from the site.