Ratio Mass Spectrometry Research Articles

Simultaneous detection of testosterone, nandrolone, and boldenone esters in dried blood spots for doping control in sports by liquid chromatography-tandem mass spectrometry.

Testosterone, nandrolone, and boldenone, which are listed as doping substances on the World Anti-Doping Agency Prohibited List, are mostly available commercially in esterified forms. Isotope ratio mass spectrometry (IRMS) represents a key tool for identifying these substances, as they are hydrolyzed and discharged in the urine as pseudo-endogenous substances. However, IRMS, which comprises a complicated process, cannot achieve the direct detection of steroid esters in blood samples. These substances can be detected using dried blood spots (DBSs), reducing the impact of esterase hydrolysis. Here, a simultaneous liquid chromatography-tandem mass spectrometry method for detecting 28 steroid (13 testosterone, nine nandrolone, and six boldenone) esters was developed using three DBS types of samples, including a cellulose paper and polymer. The substances were first derivatized with methyloxime to increase their sensitivities (the limits of detection were <0.1-0.4, <0.1-0.9, and <0.1-0.9ng/mL for the testosterone, nandrolone, and boldenone esters, respectively). Further, the DBS absorbents were verified since the effect of interferences depended on it. Next, a study involving seven participants was conducted to detect intramuscularly administered testosterone enanthate (100 mg). Polymer and cellulose papers were used to collect blood from their upper arms and fingertips, respectively, and testosterone enanthate was identified and detectable at both blood-collection sites for up to 144 and 216 h, respectively. Furthermore, testosterone enanthate was detectable in the DBS samples stored under refrigeration after 6 months, indicating the stable nature of DBS.

Geographical origin identification of Pujiang Kyoho grapes in China using stable isotope and elemental profiles

Grapes are an important seasonal fresh fruit in China, and their quality and nutrition is closely linked to their geographical origin. Stable isotopes and elemental profiles of grapes and corresponding soils from different regions and harvest years were determined using isotope ratio mass spectrometry (IRMS) and inductively coupled plasma mass spectrometry (ICP-MS). Results showed that stable isotope ratios and most elemental contents of grapes were significantly correlated to distinct regions and different harvest years. Na, Li, V, Co, Ni and Pb contents of grapes and corresponding soils were positively correlated, while Mg, Cu, Rb and Sr were negatively correlated (p < 0.05). A supervised chemometric model (random forest) was used to discriminate PGI Pujiang grapes from four other grape producing regions with 100% accuracy. These findings confirm that stable isotopes and multi-elements combined with chemometric analysis can effectively improve the accuracy of grape origin identification and minimize fraudulent mislabeling.

Purity Assessment of Honey Based on Compound Specific Stable Carbon Isotope Ratios Obtained by LC-IRMS.

The use of stable carbon isotope ratios (δ13C) of sugar fractions of honey is a powerful tool to detect adulteration with sugar syrups. This is accomplished by calculating differences of the δ13C values between individual honey saccharides and comparing them to published purity criteria. A liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) method for the determination of δ13C values of sugars in honey was previously validated by an interlaboratory comparison, but no further guidance was given how to include the obtained precision figures of the compound-specific δ13C values in the purity assessment of honey. To use existing data to estimate the standard deviation of the repeatability (sr) and reproducibility (sR) of differences (Δ δ13C) between the δ13C values of individual honey saccharides. Previously published δ13C values were used to calculate differences (Δ δ13C values) between δ13C fructose-δ13C glucose, δ13C glucose-δ13C disaccharides, etc. in a honey sample; sr and sR of Δ δ13C values were calculated according to ISO 5725-2:2019. The Δ δ13C sr and sR values were essentially of the same magnitude as the sr and sR values of δ13C values of the sugar fractions. The precision of the Δ δ13C values was used to estimate the critical difference for comparing a test result with a reference value according to ISO 5725-6:1994. This varied between 0.26 and 1.10‰. The estimated critical differences can be used to determine whether a honey test result complies with published Δ δ13C purity criteria. The proposed procedure will increase confidence in decisions based on compound-specific δ13C values regarding the conformity of honey with published purity criteria.

Research on the Application of Isotope Ratio Mass Spectrometry Technology in Traceability Detection of Stimulants

Research on the Application of Isotope Ratio Mass Spectrometry Technology in Traceability Detection of Stimulants

A rapid method for the determination of stable hydrogen isotope ratios of acetic acid in vinegar.

Vinegar is an everyday condiment made from fermented grains or fruits. It contains acetic acid which is the main organic material produced by fermentation. Vinegar suffers from the authenticity problem of exogenous adulteration due to the indistinguishability of low-cost chemical sources of synthetic acetic acid from acetic acid produced by fermentation. It is necessary to establish a simple and rapid measurement technique. Determination was according to the total acid content of vinegar diluted with acetone to a certain concentration. Online separation and determination of acetic acid δD in vinegar were carried out using gas chromatography-pyrolysis-isotope ratio mass spectrometry. An HP-Plot/U column was selected for online separation of acetic acid and water with molecular sieve characteristics. At the same time, combined with the instrument blowback function to remove water. Dilute solvent acetone was treated with a molecular sieve to remove trace water. The reproducibility of this method is less than 3‰. The long-term stability is within a reasonable error range. The accuracy correlation coefficient is greater than 0.99. The δD values of acetic acid in vinegar (-264.5 ± 20.3‰) and from chemical sources (-30.5 ± 90.8‰) were obtained. A rapid method was developed for identification of different sources of acetic acid. These different sources of acetic acid exhibited significant hydrogen isotope distribution characteristics. Additionally, it was observed that the carboxyl hydrogen of acetic acid exhibited facile exchange with water. In future investigations, we aim to mitigate this interference.

Isotope Ratio Mass Spectrometry for Geographical Origin Authentication and Adulteration Determination in Food Products

Isotope Ratio Mass Spectrometry for Geographical Origin Authentication and Adulteration Determination in Food Products

Oxygen Isotope and Fluorine Impurity Signatures during the Conversion of Uranium Ore Concentrates to Nuclear Fuel.

Within the front end of the nuclear fuel cycle, many processes impart forensic signatures. Oxygen-stable isotopes (δ18O values) of uranium-bearing materials have been theorized to provide the processing and geolocational signatures of interdicted materials. However, this signature has been minimally utilized due to a limited understanding of how oxygen isotopes are influenced during uranium processing. This study explores oxygen isotope exchange and fractionation between magnesium diuranate (MDU), ammonium diuranate (ADU), and uranyl fluoride (UO2F2) with steam (water vapor) during their reduction to UOx. The MDU was precipitated from two water sources, one enriched and one depleted in 18O. The UO2F2 was precipitated from a single water source and either directly reduced or converted to ADU prior to reduction. All MDU, ADU, and UO2F2 were reduced to UOx in a 10% hydrogen/90% nitrogen atmosphere that was dry or included steam. Powder X-ray diffraction (p-XRD) was used to verify the composition of materials after reduction as mixtures of primarily U3O8, U4O9, and UO2 with trace magnesium and fluorine phases in UOx from MDU and UO2F2, respectively. The bulk oxygen isotope composition of UOx from MDU was analyzed using fluorination to remove the lattice-bound oxygen, and then O2 was subsequently analyzed with isotope ratio mass spectrometry (IRMS). The oxygen isotope compositions of the ADU, UO2F2, and the resulting UOx were analyzed by large geometry secondary ion mass spectrometry (LG-SIMS). When reduced with steam, the MDU, ADU, and UO2F2 experienced significant oxygen isotope exchange, and the resulting δ18O values of UOx approached the values of the steam. When reduced without steam, the δ18O values of converted ADU, U3O8, and UOx products remained similar to those of the UO2F2 starting material. LG-SIMS isotope mapping of F impurity abundances and distributions showed that direct steam-assisted reduction from UO2F2 significantly removed F impurities while dry reduction from UO2F2 led to the formation of UOx that was enhanced in F impurities. In addition, when UO2F2 was processed via precipitation to ADU and calcination to U3O8, F impurities were largely removed, and reductions to UOx with and without steam each had low F impurities. Overall, these findings show promise for combining multiple signatures to predict the process history during the conversion of uranium ore concentrates to nuclear fuel.

Employing 11-Ketotestosterone as a Target Analyte for Adrenosterone (11OXO) Administration in Doping Controls.

Adrenosterone (Androst-4-ene-3,11,17-trione, 11OXO) is forbidden in sports according to the Prohibited List of the World Anti-Doping Agency. The administration of 11OXO may be detected by monitoring the urinary concentrations of its main human metabolites 11β-hydroxy-androsterone and 11β-hydroxy-etiocholanolone. Preliminary urinary concentration and concentration ratio thresholds have been established for sports drug testing purposes, but adaptations are desirable as the suggested limits would result in numerous suspicious findings due to naturally elevated concentrations and ratios. Recently, the metabolism of 11-oxo-testosterone (KT) was investigated in the context of anti-doping research, resulting in a preliminary urinary concentration threshold and a confirmation procedure based on the determination of carbon isotope ratios (CIRs). Gas chromatography coupled to isotope ratio mass spectrometry was employed to investigate the CIRs of selected steroids. As KT is also a metabolite of 11OXO, the developed protocols for KT have been tested to elucidate their potential to detect the administration of 11OXO after a single oral dose of 100 mg. In order to further improve the analytical approach, the threshold for urinary concentrations of KT was re-investigated by employing a reference population of n = 5232 routine doping control samples. Quantification of urinary steroids was conducted by employing gas chromatography coupled to triple quadrupole mass spectrometry. Derived from these, a subset of n = 106 samples showing elevated concentrations of KT was investigated regarding their CIRs. By means of this, potentially positive samples due to the illicit administration of 11OXO or KT could be excluded, and the calculation of reference population-derived thresholds for the concentrations and CIR of KT was possible. Based on the results, the urinary concentration threshold for KT is suggested to be established at 130 ng/mL.

Comparative Analysis of Water Isotopic Compositions: Evaluating Isotope Analyzer for Soil and Extraction Method for Stem Water

Stable isotopes of water (δ2H and δ18O) are reliable tracers for the investigation of plant–soil–water interactions in forest ecosystems. However, variations in isotopic compositions may arise due to differences in analytical instruments and water extraction methods. In this study, we conducted three different experiments to identify isotopic differences caused by analytical and methodological variations. First, we analyzed soil water by using the two most commonly applied methods: isotope ratio mass spectrometry (IRMS) and cavity ring-down spectroscopy (CRDS). Second, we compared the isotopes in xylem water extracted from the stems of nine tree species using cryogenic vacuum distillation (CVD) with different heating times. Third, we compared the compositions in xylem water extracted with three different methods: mechanical squeezing using a pressure chamber (PC), an induction module (IM), and CVD. The differences in isotopic composition between IRMS and CRDS were significant but minimal. Soil properties were not significant factors contributing to differences between the two instruments. For the xylem water extraction with CVD, each of the nine tree species required heating for more than three hours. Significant differences were observed in δ2H among the three extraction methods for xylem water. Xylem water extracted by CVD showed more depleted values compared to those obtained by PC and IM. Our results highlight the importance of considering analytical and methodological variations in stable isotope analysis.

Forensic investigation of falsified antimalarials using isotope ratio mass spectrometry: a pilot investigation

We explored whether isotope ratio mass spectrometry (IRMS) is useful to investigate the origin of falsified antimalarials. Forty-four falsified and genuine antimalarial samples (artesunate, artemether-lumefantrine, dihydroartemisinin-piperaquine and sulphamethopyrazine-pyrimethamine) were analyzed in bulk for carbon (C), nitrogen (N), and oxygen (O) element concentrations and stable isotope ratios. The insoluble fraction (“starch”) was extracted from 26 samples and analyzed. Samples of known geographical origin maize, a common source of excipient starch, were used to produce a comparison dataset to predict starch source. In both an initial (n = 18) and a follow-on set of samples that contained/claimed to contain artesunate/artemether (n = 26), falsified antimalarials had a range of C concentrations less than genuine comparator antimalarials and δ13C values higher than genuine comparators. The δ13C values of falsified antimalarials suggested that C4 plant-based organic material (e.g., starch derived from maize) had been included. Using the known-origin maize samples, predictions for growth water δ18O values for the extracted “starch” ranged from − 6.10 to − 1.62‰. These findings suggest that IRMS may be a useful tool for profiling falsified antimalarials. We found that C4 ingredients were exclusively used in falsified antimalarials versus genuine antimalarials, and that it may be possible to predict potential growth water δ18O values for the starch present in falsified antimalarials.

Development of a Matrix‐Matched Barite Reference Material (NWU‐Brt) for Calibration of In Situ S Isotope Measurements by Laser Ablation Multi‐Collector Inductively Coupled Plasma‐Mass Spectrometry

A new matrix‐matched reference material (NWU‐Brt) with sulfur isotope ratios resembling those of natural barites has been developed for in situ S isotope measurements by laser ablation multi‐collector inductively coupled plasma‐mass spectrometry (LA‐MC‐ICP‐MS). A 100 g quantity of natural barite crystal was milled to ultra‐fine particles and sintered to a solid block using a fast hot‐pressing sintering technique (FHPS). We report δ34S ratios determined by isotope ratio mass spectrometry (IRMS), solution nebuliser multi‐collector inductively coupled plasma‐mass spectrometry (SN‐MC‐ICP‐MS) and LA‐MC‐ICP‐MS, involving up to six participating laboratories. The homogeneity of δ34S ratios of the synthesised barite was tested by LA‐MC‐ICP‐MS with an analytical spot size of 53 μm. The LA‐MC‐ICP‐MS results show that NWU‐Brt demonstrates a satisfactory homogeneous composition and is an appropriate material for calibrating δ34S ratios in barite. IRMS and SN‐MC‐ICP‐MS produced mean δ34S values of +14.17 ± 0.42‰ (2s) and +14.27 ± 0.23‰ (2s), respectively. The results of LA‐MC‐ICP‐MS analyses are consistent with the IRMS and SN‐MC‐ICP‐MS ratios within uncertainty. Overall, our results confirm the suitability of NWU‐Brt for the calibration of δ34S ratios in barite using LA‐MC‐ICP‐MS.

Affordable event and monthly rain samplers: Improving isotopic datasets to understand meteorological processes.

Water-stable isotopes in rainfall are powerful tracers of atmospheric processes at different spatial and temporal scales. However, commercially available rain samplers for isotopic analysis are prohibitively expensive, especially for high spatial resolution networks and studies conducted in developing countries. A low-cost, simple, and robust sampler was designed for event and monthly rainfall samplings. Rainfall collectors were built based on existing designs provided in the literature and using easily accessible materials. Event samplers were filled with different volumes of reference water and left for 72 h in laboratory conditions to determine the minimum amount of rainfall to be collected to minimize isotopic fractionation, from both postsampling evaporation and equilibration. Samples were analyzed using dual-inlet isotope ratio mass spectrometry and cavity ring-down spectroscopy. For samples larger than 4% of the bottle's capacity, the evaporative enrichment due to Rayleigh distillation is negligible compared to the overall analytical uncertainty. Using a tube connecting the funnel to the water sample has proved to reduce postsampling evaporation by at least five times. To limit water self-diffusion, we recommend collecting the largest rainfall amount possible. Under these conditions, these collectors are suitable for rainfall sampling for isotopic analysis. This low-cost methodology will enable isotopic sampling of precipitation at high spatial resolutions and democratize the use of isotopes for hydrological studies in developing countries. All instructions for building and using these samplers are made openly accessible to the scientific community so they can be repeated and adapted to the needs of each project.

A modified laser ablation-isotope ratio mass spectrometry method for in situ analysis of sulfur isotope composition of sulfides.

A novel laser ablation-isotope ratio mass spectrometry (LA-IRMS) method for in situ analysis of sulfur isotopes in sulfides has been developed. Instead of the in situ reaction applied by the traditional laser microprobe, the analyte gas preparation in this method is separated temporally and spatially from the LA, resulting in improved precision and accuracy. Our LA-IRMS system combines an ultraviolet LA system, an elemental analyzer (EA), a custom-built cryogenic concentration system, a continuous-flow interface, and an IRMS. The sulfide aerosol particles generated from LA were transferred by a helium carrier gas from the ablation cell into the reaction tube and were then converted into SO2 . Subsequently, SO2 was enriched in two cold traps and was finally introduced into the ion source of the IRMS through the continuous-flow interface. We measured three synthetic and four natural sulfide reference materials to test the performance of this method. Precisions of ±0.25‰-±0.48‰ and ±0.32‰-±0.64‰ (1SD, n = 5) for δ34 S values of synthetic and natural sulfide standards can be obtained for spot sizes ranging from 64 to 80 μm. Measured values and their recommended values showed a good linear relationship (R2 within 0.998 and 0.9995) with the slope of approaching unity (within 1.0509 and 1.1313). Data from the measurement of reference materials showed that the precision and accuracy of our method were satisfactory. This method is a powerful tool for in situ sulfur isotope measurement of sulfides and can be further applied to in situ carbon and oxygen isotope analyses.

Identification of provenance of Basmati rice grown in different regions of Punjab through multivariate analysis

High-priced Basmati rice is vulnerable to deliberate mislabeling to increase profits. This type of fraud may lower consumers’ confidence as inferior products can affect brand reputation. To address this problem, there is a need to devise a method that can efficiently distinguish Basmati rice grown in regions that are famous versus the regions that are not suitable for their production. Therefore, in this investigation, thirty-six samples of Basmati rice were collected from two zones of Punjab province (one known for Basmati rice) of Pakistan which is the major producer of Basmati rice. The elemental composition of rice samples was assessed using inductively coupled plasma-optical emission spectrometry and an organic elemental analyzer, whereas data on δ13C was acquired using isotopic ratio-mass spectrometry. Regional clustering of samples based on their respective cultivation zones was observed using multivariate data analysis techniques. Partial least squares-discriminant analysis was found to be effective in grouping rice samples from the different locations and identifying unknown samples belonging to these two regions. Further recommendations are presented to develop a better model for tracing the origin of unidentified rice samples.

Naturally occurring radioactive materials in offshore infrastructure: Understanding formation and characteristics of baryte scale during decommissioning planning

Contaminants, including naturally occurring radioactive material (NORM) of the 238-uranium and 232-thorium decay series, have been recognized as a global research priority to inform offshore petroleum infrastructure decommissioning decisions. This study aimed to characterize pipeline scale retrieved from a decommissioned subsea well tubular pipe through high-resolution elemental mapping and isotopic analysis. This was achieved by utilizing transmission electron microscopy, Synchrotron x-ray fluorescence, photostimulated luminescence autoradiography and Isotope Ratio Mass Spectrometry. The scale was identified as baryte (BaSO4) forming a dense crystalline matrix, with heterogenous texture and elongated crystals. The changing chemical and physical microenvironment within the pipe influenced the gradual growth rate of baryte over the production life of this infrastructure. A distinct compositional banding of baryte and celestine (SrSO4) bands was observed. Radioactivity attributed by the presence of radionuclides (226Ra, 228Ra) throughout the scale was strongly correlated with baryte. From the detailed scale characterization, we can infer the baryte scale gradually formed within the internals of the tubular well pipe along the duration of production (i.e., 17 years). This new knowledge and insight into the characteristics and formation of petroleum waste products will assist with decommissioning planning to mitigate potential radiological risks to marine ecosystems.

Authentication of Fennel, Star Anise, and Anise Essential Oils by Gas Chromatography (GC/MS) and Stable Isotope Ratio (GC/IRMS) Analyses.

The aromatic compound (E)-anethol is widely used in the flavor, fragrance, and medicinal industries. This compound is commonly produced through steam distillation of fennel, star anise, and anise seed. Given the cost of production, these natural and authentic essential oils are commonly adulterated with lower-cost natural materials or synthetic alternatives. The current study investigates essential oil profiles (gas chromatography/mass spectrometry) and stable isotope ratios (gas chromatography/isotope ratio mass spectrometry) of the abundant compound (E)-anethol in both authentic reference standards (n = 15) and commercially available samples (n = 30). This multifaceted analytical approach establishes techniques for ensuring the authenticity of essential oil sources of (E)-anethol and was then used to evaluate the current essential oil market sources of (E)-anethol. These findings report that adulteration of (E)-anethol-containing natural products takes various forms, and a multifaceted analytical approach is recommended for authentication. Of the commercial samples analyzed for this report, 27% were adulterated.

Exploring δ13 C data compatibility in a broad δ13 C range: Reassembling δ13 C values obtained for NIST CO2 RMs 8562-8564 at different laboratories.

Stable isotope datasets obtained in different laboratories over years must be compared and combined. The strict compatibility in δ13 C at ±0.01‰ and ±0.02‰, k= 1, respectively, is required for observations of greenhouse gases CO2 and methane. That implies the long-term compatibility of calibrations realized at different laboratories. Thus far, this level of compatibility has not been demonstrated for pure CO2 in a broad δ13 C range and over years. We reassemble the δ13 C obtained in different laboratories for NIST CO2 RMs 8562-8564, which are pure CO2 gases. If the measurements are based on independent calibrations and reported on the same 17 O correction framework, δ13 C of all three RMs can be used to estimate the long-term δ13 C data compatibility. δ13 C values obtained in different laboratories for NIST CO2 RMs 8562-8564 (a range of δ13 C from ~ -3.7‰ to ~ -41.6‰) from 1998 to 2020 agree within their uncertainties. Two NIST studies (1999 and 2004) have combined data from several laboratories using different Isotope ratio mass spectrometry (IRMS) methods and somewhat different approaches. Three single-laboratory studies (2003, 2008, and 2020) have used the same type of IRMS and similar approaches. The δ13 C values from these laboratories agree within ±0.01‰, k= 1, over the entire δ13 C range and have uncertainties about two times lower than those obtained at NIST by combining data from several laboratories. The δ13 C values for NIST CO2 RMs 8562-8564 obtained in three laboratories using the same IRMS (2003, 2008, and 2020) agree within ±0.01‰, k= 1. First, this confirms the long-term stability in δ13 C of RMs 8562-8564. Second, this example of compatibility in δ13 C calibrations on pure CO2 , from -3.7‰ to -41.6‰, is relevant to stable isotope measurements of greenhouse gases CO2 and methane. Third, this confirms the high accuracy of the δ13 C(air-CO2 ) calibrations performed in 2003 and 2008 for the project Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrumented Container (CARIBIC).

Comparison of analytical approaches for the detection of oral testosterone undecanoate administration in men.

For antidoping laboratories, the determination of an illicit testosterone (T) administration in urine samples remains a difficult process as it requires the determination of the exogenous origin by carbon isotope ratios (CIRs) of testosterone and its metabolites. As a complement to the urinary analysis, targeting testosterone esters (e.g. testosterone undecanoate [TU]) in serum samples by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) could represent a simpler approach compared with isotope ratio mass spectrometry (IRMS). These two approaches both lead to the direct detection of the administration of exogenous T but with a difference in effort and complexity of the analysis. To compare the detection window obtained with the two strategies, serum and the corresponding urine samples collected from an administration study with oral TU were analysed. Results showed that, at all timepoints where the intact TU was detected in serum, the CIRs of urinary steroids were also not in agreement with an endogenous origin. IRMS analysis required more effort but resulted in slightly longer detection windows than the ester analysis. Finally, this comparison study showed that, in the presence of a suspicious urinary steroid profile, the LC-MS/MS steroid esters analysis in the corresponding serum samples can be very helpful. If steroid esters are not detected, the IRMS analysis can then be conducted on the urine sample afterwards. Overall, the combination of matrices might facilitate the detection of prohibited T administration in sports, especially for athletes with naturally low T/E ratios.

High-Temporal-Resolution In Situ Sensor for Oceanic CO2 Isotope Measurement Enabling Multidimensional Isotope Tracing Analysis (R13C, R18O, and R17O) via Laser Absorption Spectroscopy.

Combined in situ analysis of oceanic CO2 concentrations and diverse C and O isotope characteristics can offer a unique perspective with multiple isotopic tracing dimensions for identifying marine biogeochemical processes. Applying this strategy in marine environments is urgently required, yet it faces inherent challenges in terms of existing analytical methods and instruments, e.g., a lack of in situ sensors, limited detectable isotope variety, and low-temporal-resolution data. Here, we report an underwater in situ dissolved CO2 isotope sensor based on mid-infrared tunable diode laser absorption spectroscopy (MIR-TDLAS) and membrane extraction technology. Through the proposed targeted strategies, the sensor is capable of providing high-temporal-resolution in situ measurement of all monosubstituted isotopes of dissolved CO2 (16O13C16O, 18O12C16O, and 17O12C16O) at marine background concentrations. The sensor is demonstrated to provide comparable precision to that of isotope ratio mass spectrometry. At 400 ppmv, the precision for R13C, R18O, and R17O could achieve 0.084, 0.042, and 0.013‰, respectively, for a 1 s integration time. By enabling a high-frequency in situ analysis in fixed-point time-series field deployment, a 17O anomaly with strong regularity is observed, which is not obvious in 18O and 13C, and therefore, the superiority of the proposed multidimensional in situ isotope tracing strategy is demonstrated. The developed sensor has great potential to open up new prospects for advancing marine carbon research.

Elemental (CNS) and isotopic (δ13C and δ15N) characterization of local sources to atmospheric dust at Trombay, Mumbai, using elemental analyzer–isotope ratio mass spectrometry

Particulate matter (PM) in the air has significant implications for human health and the environment, particularly in urban areas with high concentrations. This study focuses on the isotopic (δ13C and δ15N), elemental (CNS) as well as the total carbon to total nitrogen ratio (TC/TN) characterization of PM in Trombay, Mumbai. Monthly atmospheric dust samples were collected from 2016 to 2020 during the premonsoon and postmonsoon seasons. The average elemental concentrations for premonsoon samples were N (1.73% ± 0.25%), C (7.38% ± 0.72%), S (0.84% ± 0.13%), and TC/TN ratio (4.38 ± 0.86). For postmonsoon samples, the average elemental concentrations were N (1.47% ± 0.185%), C (6.95% ± 1.04%), S (0.84% ± 0.13%), and TC/TN ratio (4.80 ± 0.94). The average δ13C values for premonsoon and postmonsoon seasons were −24.31 ± 1.15‰ and −24.56 ± 1.20‰, respectively. The average δ15N values for premonsoon and postmonsoon seasons were 5.22 ± 1.92‰ and 4.57 ± 1.32‰, respectively. The results showed variations in elemental concentrations between the seasons, with higher values observed in premonsoon samples which can be attributed to increased dust generation from land and sea. Overall, this study provides insights into the local sources and characteristics of PM in the Trombay area and highlights the importance of long-term monitoring to understand the seasonal variations in PM composition.