Language：English   Publisher：JOHN WILEY & SONS LTD  

The isotope ratios of ethanol, an important constituent or ingredient of some foods and various beverages and fuels, provide information about biological and geographical origin and quality. We have developed an improved method for measuring the isotope ratio of ethanol in various samples by gas chromatography-high temperature conversion or combustion-isotope ratio mass spectrometry (GC-TC/C-IRMS) with headspace solid-phase microextraction (HS-SPME). A HS-SPME method was developed by optimizing several different parameters, including salt addition, incubation temperature and time, and extraction time. The HS-SPME method enabled us to determine the isotope ratio at low ethanol concentrations (0.08 mM) in 50 min with good precision (+/- 0.3 parts per thousand for delta C-13 and +/- 5 parts per thousand for delta D). An advantage of this technique is that it can be adapted for use with samples which have high viscosity and contain many matrix compounds, such as alcoholic and non-alcoholic beverages. Copyright (C) 2008 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.3753

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DOI： 10.1002/rcm2977

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DOI： 10.1002/rcm2977

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Language：English   Publisher：ELSEVIER SCIENCE SA  

We measure the (CH4)-C-13/(CH4)-C-12 ratio of methane diluted with air or nitrogen to investigate the applicability of our laser spectrometer to real environmental samples. We developed a 1.66 mu m diode laser absorption spectrometer and demonstrated high precision on pure methane, but for practical observations it is appropriate to measure the samples directly without purification. We examine effects of different pressure, concentration and the kind of gases for diluting between samples and a working-standard on the measurement. The effects are found to be small and the high repetitive precision (reproducibility) of similar to 0.1 parts per thousand (1 sigma) is obtained at 10 and 1% methane concentrations without any correction or automatic control of the gas conditions. At 0.1% concentration, however, the precision stays at similar to 1 parts per thousand. It is expected that the high precision of similar to 0.1 parts per thousand at the 0.1% concentration cannot be achieved, due to saturation of the signal intensity at high pressure of the sample in a multi-pass cell, caused by pressure broadening of methane absorption lines. The relationship between the isotopic ratio measured by the laser and that by the isotopic ratio mass spectrometer (IRMS) is linear with small fluctuations, but the slope is slightly different from unity. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.snb.2005.05.019

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Language：English   Publisher：TAYLOR & FRANCIS LTD  

The isotope ratios of carbon, hydrogen, and oxygen of rectified alcohols were determined to distinguish their botanical and geographical origins by continuous flow-isotope ratio mass spectrometry (CF-IRMS). The C-13/ C-12 and O-18/O-16 ratios of 27 fermented alcohols with known origins showed clusters derived from each botanical origin, viz. corn, sugarcane, wheat, and tapioca. C3 and C4 plants were easily distinguishable by the C-13/C-12 ratio. Sugarcane and corn are both C4 plants, and they showed small differences in isotope ratios. The combination plots of the D/H and O-18/O-16 ratios enabled us to designate the geographical origins of alcohol derived from the same kind of crop, such as Chinese or American corn. The chemically synthetic and fermented alcohols were clearly distinguished by D/H and O-18/O-16 ratios. Isotope ratios were useful for origin identification of alcohol. We plan to construct a database of alcohol isotope ratios to determine the origins of raw materials in alcohol.

DOI： 10.1271/bbb.69.2193

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

We measured the stable carbon and hydrogen isotope ratios of atmospheric methane (CH4) from western Siberia to obtain information about local CH4 sources. Isotopic mass balance calculations yielded stable hydrogen and carbon isotope values for CH4 released in the Surgut region, ranging from -50 parts per thousand to -33 parts per thousand and -484 parts per thousand to -420 parts per thousand, respectively. These isotopic source signatures could not be understood in terms of mixing of CH4 from major sources in this region, which include natural wetlands and oil/gas fields. Based on this observation, we suggest the necessity for further investigation of the distribution and isotopic values of CH4 sources in this region. (C) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.orggeochem.2005.01.016

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The stable carbon and hydrogen isotopic compositions (delta(13)C and delta D, respectively) of methane (CH4) in automobile exhaust were determined in order to quantify by mass balance the contribution from this source to atmospheric CH4 in an urban area of Nagoya, Japan. Both delta(13)C and delta D values of CH4 in automobile exhaust increased in accordance with the model year of the engine, probably as a result of isotope fractionation effects associated with oxidation over metal catalysts in the catalytic converter of modern vehicles. Thus, CH4 emissions from recent automobiles exhibit conspicuous C-13 and D enrichment compared to the flux from other major anthropogenic sources, such as natural gas leakage, landfills and rice paddies. Using average delta(13)C and delta D CH4 values estimated for local sources, automobile exhaust in Nagoya, Japan, was determined to contribute significant amounts (up to 30%) of CH4 to the troposphere in the study area. (C) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.orggeochem.2005.01.003

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Measurement of the hydrogen isotope ratio (D/H ratio) in atmospheric methane by isotope ratio mass spectrometry has been less developed so far, compared to that of the carbon isotope ratio (C-13/C-12 ratio). This is because of the requirement for a large sample size (about 1001 of atmosphere, assuming a methane concentration of similar to1.8 ppm) and the complicated and time-consuming method of sample preparation. In this study, we examined an on-line method for measurement of the D/H ratio of atmospheric methane by a gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/TC/IRMS) technique. This method is less laborious, more rapid (about 1 h per sample) and attains high precision (+/-3.1parts per thousand) using a much smaller sample (similar to120-360 ml of atmosphere). Its application to isotopic characterization, and hence identification of source of methane and estimation of methane budgets, was demonstrated by examination of urban atmosphere samples collected in November 2001 at Yokohama, Japan. The D/H ratio of atmospheric methane in the urban area ranged throughout the day from -98parts per thousand to -118parts per thousand, showing a fluctuation with time that correlated with that of the methane concentration. Assuming that the fluctuation was caused by local methane emissions from anthropogenic sources, i.e., vehicles, industries, and landfill sites, the contribution from each source to-the local methane was estimated by a combination of the D/H ratio with the C-13/C-12 ratio of atmospheric methane. The-estimation indicates that the contribution from each source varied considerably throughout the day and that the methane emitted from landfill sites averaged 70%. (C) 2003 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S1352-2310(03)00030-X

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Language：English   Publisher：JOHN WILEY & SONS LTD  

Molecular and intramolecular carbon isotope measurements of acetic acid present in natural environments have been performed by off-line procedures. The off-line method is complicated and time-consuming and requires micromolar to millimolar amounts of sample. This limits geochemical isotopic studies, especially at the intramolecular level, on acetic acid present in natural samples. Here, we examine an on-line measurement of intramolecular carbon isotope distribution of acetic acid using continuous-flow isotope ratio mass spectrometry (CF-IRMS) coupled with an on-line pyrolysis system. This is achieved by measurement of the respective carbon isotope ratios of CH4 and CO2 produced by on-line pyrolysis of acetic acid. Results for authentic standards of pure acetic acid demonstrated the practicality of this on-line method, although the carbon isotope ratio of the methyl group could not be determined directly. The precision of the carbon isotope measurements was 0.4parts per thousand (1sigma). The carbon isotope distribution determined by the on-line method was identical to that determined by the conventional off-line method within analytical error. The advantages of the online method compared with the conventional off-line method are that it is less laborious, requires less analytical time (less than one hour per sample) and, most importantly, uses smaller sample sizes (ca. 10 nanomole). An application of this on-line method to natural geochemical samples will provide an insight into the geochemical cycle of acetic acid. Copyright (C) 2002 John Wiley Sons, Ltd.

DOI： 10.1002/rcm.678

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Carbon isotopic analyses of 24-ethytlcholest-5-en-3 beta -ol in a marine sediment core (KH-79-3, C-3) covering the last 30,000 years. using gas chromatography/isotope ratio mass spectrometry (GC/IRMS), are presented. The source of 24-ethylcholest-5-en-3 beta -ol is unclear from the abundances for marine and terrestrial biomarkers. However, the carbon isotope results for this sterol exhibit a clear indication of the sources. The carbon isotopic composition (delta C-13) Of 24-ethylcholest-5-en-3 beta -ol in the C-3 core ranges from -23.3 to -32.0 parts per thousand over the past 30,000 years. After the last glacial period (10-73 cm section; 2-9 ka), 24-ethylcholest-5-en-3 beta -ol is derived from marine algae (-24.2+/-1.1 parts per thousand on average). However, in the last glacial stage (140-274 cm section; 15-29 ka), it is likely that the value indicates a terrestrial higher plant origin (-30.5+/-0.9 parts per thousand on average). The trend in the isotopic composition of 24-ethylcholest-5-en-3 beta -ol is nearly consistent with paleoclimatic changes around the Japan Sea over the past 30,000 years. (C) 2001 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0146-6380(00)00180-7

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Two hopanoids, 17 beta>(*) over bar * (H),21 beta>(*) over bar * (29)-hop-22(29)-ene (diploptene) and 17 beta>(*) over bar * (H),21 beta>(*) over bar * (H)-bishomohopanoic acid (beta betaC(32)-HA), are the most abundant among the pentacyclic triterpenoids found in Recent sediments of the Pacific Ocean alongside the Japanese Islands. The concentration of diploptene normalized to organic carbon content is higher in sediments where C-37 polyunsaturated alkene (a biomarker of Haptophytes) is in high concentration, suggesting that the diploptene may be associated with the accumulation of marine organic matter. In open marine settings, delta C-13 values of beta betaC(32)-HA range from -23.8 to -19.4 parts per thousand (relative to PDB), being enriched in C-13 relative to diploptene (-31.6 to -26.3 parts per thousand) by 5-9 parts per thousand. Thr isotopic difference indicates the presence of at least partially different sources for the two hopanoids. While diploptene is derived from cyanobacteria and chemotrophic bacteria in the water column or sediment, bishomohopanoic acid may be produced mainly by heterotrophs in the sediment using marine organic matter. In contrast, the delta C-13 values of the two hopanoids From river and bay sediments are similar (similar to -31 to -29 parts per thousand), indicating a common source derived from soil components (terrestrial plants or bacteria in soils). (C) 2000 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0146-6380(00)00112-1

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Language：English   Publisher：AMER GEOPHYSICAL UNION  

The organic and isotopic geochemical study of two sediment cores (KH-79-3, L-3, and KH-79-3, C-3) from the Oki Ridge in the Japan Sea has revealed that total organic carbon (TOC) mass accumulation rates are extremely high in the 12-11 ka(calendar age) interval and TOC in the sections in the 24-17 ka interval is depleted in C-13 by 3.5 parts per thousand relative to Holocene sediments. Alkenone sea surface temperature (SST) shows a decrease from 18 degrees to 14 degrees C from 17.5 to 11.6 ka and a sharp increase from 14 degrees to 19 degrees C from 11.6 to 11.1 ka. The SST changes are associated with the inflow of cold seawater with the vertical water mixing and the inflow of warm Tsushima Current into the Japan Sea. The delta(13)C values for both 24-methylcholesta-5,22-dien-3 beta-ol (diatom marker) and dinosterol (dinoflagellate marker), are at their minimum from 24 to 17 ka, while those for long-chain alkenones are not. The theoretical considerations on delta(13)C for biomarkers suggest low photosynthetic carbon demand of diatoms and dinoflagellates from 24 to 17 ka.

DOI： 10.1029/1998PA900014

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Language：Japanese   Publisher：The Japanese Association of Organic Geochemists  

Measurements of the stable carbon isotopic compositions (δ¹³C) of individual hydrocarbons extracted from the Japan Sea sediments are reviewed. It was demonstrated that the compound-specific δ¹³C, when combined with organic molecular geochemistry, is quite useful not only for identifying detailed sources of sedimentary hydrocarbons but also for assessing the paleo-biogeochemical conditions of the Japan Sea.

DOI： 10.20612/rog.14.0_3

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Carbon isotopic compositions of long-chain n-alkanes in cores KH-79-3 (C-3 and L-3) taken from the Oki Ridge (37 degrees 04'N, 134 degrees 42'E, water depth 935 m) in the Japan Sea were measured by gas chromatography/isotope ratio mass spectrometry. Fluctuations in the carbon isotopic composition of terrestrially derived material, as determined from delta(13)C(n-alkane) (weighted average of delta(13)C values for higher plant-derived n-C-29 and n-C-31 alkanes), range from -29.1 to -32.1 parts per thousand for the past 85 kyr in core KH-79-3, C-3. delta(13)C(n-alkane) values in colder climates (O-18 stages 2 and 4) are depleted in C-13 by approximately 1 parts per thousand relative to those in warmer climates (stages 1, 3 and 5.(1)). This suggests that the temporal variations of the delta(13)C values for higher plant-derived n-alkanes exhibit a close relationship with glacial-interglacial cycles.
The results over the past 30 kyr (C-14 age) reveal that the delta(13)C(n-alkane) values shifted abruptly from -31.1 +/- 0.5 parts per thousand to -29.9 +/- 0.4 parts per thousand at around 10 kyr B.P., with the isotopic values remaining relatively constant thereafter. This positive (1.2 parts per thousand) shift in delta(13)C(n-alkane) values can be attributed to one or both of the following factors: (i) enhancement of primary productivity on land; and (ii) change in vegetational types (e,g. C4/C3 plants ratios and/or changes in the species of C3 plants). (C) 1999 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0146-6380(99)00012-1

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Language：English   Publisher：GEOCHEMICAL SOC JAPAN  

Stable carbon isotopic compositions were determined for diploptene in the sediment core KH-79-3, L-3 (core length: 235 cm) taken from the Oki Ridge in the southern part of the Japan Sea. Two major groups of diploptene with different delta(13)C values were recognized. The first group appears in the 0-130 cm section (present to 10 kyr B.P.) of the core, the delta(13)C values being -25.0 +/- 0.7 parts per thousand on average. Diploptene in this section should have originated from cyanobacteria. The second group which is strongly depleted in C-13 (-53.1 +/- 5.3 parts per thousand on average), is observed in the 145-204 cm section (12-21 kyr B.P.). Diploptene in this section might have originated from methanotrophic bacteria. This indicates that an anoxic bottom water condition was developed during 12-21 kyr B.P. (the last glacial period), which was perhaps caused by the development of seawater stratification in the Japan Sea.

DOI： 10.2343/geochemj.31.315

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Carbon isotope composition of individual long-chain n-alkanes from Tokyo Bay sediments (a 3 m-core sample and surficial sediment samples) was determined by using gas chromatography/isotope ratio mass spectrometry (GC-IRMS). DeltaC-13 values for C27-C33 n-alkanes in shallow (0-40 cm in depth, present-1965 AD) sections range from -31.5 to -28.2 parts per thousand, showing even carbon number n-alkanes being isotopically heavier than the co-occurring odd n-alkanes. C27-C33 n-alkanes in the deep sections (70-220 cm in depth) have the deltaC-13 values ranging from -29.6 to -32.9 parts per thousand (average value: 31.2 +/- 0.7 parts per thousand), with no isotopic differences between odd and even numbered n-alkanes. The results for n-alkanes in shallow sediments are satisfactorily explained by a two end-member mixing model of indigenous higher plant wax n-alkanes with n-alkanes from oil pollution. The onset of significant levels of pollution in Tokyo Bay was between 1960 and 1965.

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Language：English   Publisher：Kluwer Academic Publishers  

Organic geochemical study of bulk organic matter (OM), hopanoid hydrocarbon and normal hydrocarbon (C23∼C35) was conducted for a 936-cm-long sediment core sample from the Oki Ridge of the Japan Sea (Core KH-79-3, C-3
37°03.5′ N, 134°42.6′E, water depth 935 m). Stable carbon isotopic ratios were also measured for both bulk OM and individual hydrocarbons. The following results were obtained: (1) The weight ratios of total organic carbon to total nitrogen range from 6.2 to 9.4 in the core. The δ13C values of bulk OM range from -25.1∼-20.7%.. The δ13C values of OM in the sections of 140∼190 cm are lower (-25∼-24‰) than those in the other sections (-23∼-21‰). This result indicates that OM in the core except for the 140∼190 cm sections is essentially of marine origin. (2) The δ13C value of diploptene (a hopanoid hydrocarbon) in the last glacial maximum (LGM), is -66.3‰ (vs. PDB), which indicates it originating in methanotrophic bacteria. This result provides evidence to support for the previous ideas (Oba et al., 1980, 1984
Masuzawa and Kitano, 1984) that the bottom waters in the Japan Sea were anoxic in LGM. (3) Long chain (C23∼C35) n-alkanes of higher-plant wax origin were found throughout the core. Their concentration is high in 140∼190 cm in depth, suggesting that eolian dust load was high in LGM. (4) The n-alkane/TOC ratio increases with decreasing δ13C values of bulk OM. This result indicates that the load of terrestrial (probably eolian dust-derived) OM to the Japan Sea became higher in colder climates. (5) The CPI values of long-chain n-alkanes are different in different δ13O stages of paleoclimate, probably reflecting variations in species of terrestrial higher plants as a result of climatological adaptations. © 1994 Journal of the Oceanographic Society of Japan.

DOI： 10.1007/BF02253478

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Language：Japanese   Publisher：The Mass Spectrometry Society of Japan  

An isolation procedure of microgram amounts of long-chain n-alkanes from crude oil using molecular sieve was examined for its applicability to stable carbon isotope analysis by gas chromatography/isotope ratio mass spectrometry (GC/IRMS).<br>The procedure examined is as follows: molecular sieve (type 5A, 200 mg) in 1 ml of isooctane solvent are mixed with a saturated hydrocarbon fraction extracted from an appropriate amount (approx. 20 mg) of crude oil and stayed at room temperatures for more than 3 hours. Long-chain n-alkanes are isolated by extraction with n-hexane after dissolution of the resulting molecular sieve with 47% hydrofluoric acid solution. The recoveries were 90±6% for C₁₅~C₃₄ n-alkanes when their total amounts applied do not exceed 1.4 mg. No effect of the isolation procedure on carbon isotope ratios of n-alkanes was observed.

DOI： 10.5702/massspec.42.237

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Other Link： https://jlc.jst.go.jp/DN/JALC/00028360995?from=CiNii

Language：English   Publisher：The Mass Spectrometry Society of Japan  

A gas chromatography/isotope ratio monitoring mass spectrometry (GC/IRMS) method was established for the determination of stable carbon isotopic compositions of individual saturated n-fatty acids ranging from C₁₆ to C₃₀. The fatty acids were derivatized to their methyl esters using BF₃/methanol, and three n-alkanes were used as internal isotopic standard. Isotopic mass balance calculation indicated that the esterification caused no isotopic fractionation between the methyl ester moiety of fatty acid and methanol used. Therefore, isotopic correction was made by one additional carbon atom with the δ¹³C value of methanol. Analytical accuracy (deviation of the corrected δ¹³C values determined by GC/IRMS from those determined by a conventional method) and precision (standard deviation) were satisfactory for 90 to 360 ng of individual standard fatty acids examined. The accuracy was ±0.3‰ for average of several analyses, and the precision within 0.3‰. This method was applied to the δ¹³C determination of n-fatty acids ranging from C₂₀ to C₃₀ in a marine sediment.

DOI： 10.5702/massspec.42.315

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Other Link： https://jlc.jst.go.jp/DN/JALC/00030499836?from=CiNii

Language：English   Publisher：The Mass Spectrometry Society of Japan  

A gas chromatography/isotope ratio monitoring mass spectrometry (GC/IRMS) method was established for the determination of stable carbon isotopic compositions of individual saturated n-fatty acids ranging from C₁₆ to C₃₀. The fatty acids were derivatized to their methyl esters using BF₃/methanol, and three n-alkanes were used as internal isotopic standard. Isotopic mass balance calculation indicated that the esterification caused no isotopic fractionation between the methyl ester moiety of fatty acid and methanol used. Therefore, isotopic correction was made by one additional carbon atom with the δ¹³C value of methanol. Analytical accuracy (deviation of the corrected δ¹³C values determined by GC/IRMS from those determined by a conventional method) and precision (standard deviation) were satisfactory for 90 to 360 ng of individual standard fatty acids examined. The accuracy was ±0.3‰ for average of several analyses, and the precision within 0.3‰. This method was applied to the δ¹³C determination of n-fatty acids ranging from C₂₀ to C₃₀ in a marine sediment.

DOI： 10.5702/massspec.42.315

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Other Link： https://jlc.jst.go.jp/DN/JALC/00030499836?from=CiNii

Language：English   Publisher：GEOCHEMICAL SOC JAPAN  

Carbon isotope compositions of long-chain n-alkanes (C-27 similar to C-33) in selected samples from a Tokyo Bay sediment core (0 similar to 3 m in depth) were determined by gas chromatography/ isotope ratio mass spectrometry (GC-IRMS). delta(13)C values of the n-alkanes in the shallow sections (0 similar to 40 cm in depth, present similar to 1965 AD) range from -31.5 to -28.2 parts per thousand relative to the PDB standard, showing that even carbon-numbered n-alkanes are isotopically heavier than the odd numbered ones. The n-alkanes in the deeper sections (190 similar to 220 cm in depth) show the values ranging from -29.6 to -31.4 parts per thousand (average value: -30.7 +/- 0.6 parts per thousand) without any significant difference among the n-alkanes. The results of n-alkanes in the shallow sections are explained by an addition of oil-derived n-alkanes to higher plant wax n-alkanes observed in the deeper sections.

DOI： 10.2343/geochemj.27.385

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