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MAPAN

, Volume 32, Issue 1, pp 33–38 | Cite as

Thermal Heating Induced Fractionation Effect on δ15N Measurements (Using Continuous Flow Isotope Ratio Mass-Spectrometry) for Samples Containing Lower N Contents

  • Rajesh Agnihotri
  • Ravi Sawlani
  • Chhemendra Sharma
  • M. V. S. N. Prasad
Original Paper

Abstract

Simultaneous measurements of stable isotopes of Nitrogen (N), Carbon (C) and Sulfur (S) in a single aliquot of sample using stable isotope mass spectrometry coupled with elemental analyzer (EA) in a continuous flow mode has provided added advantages for stable isotopic data community scientifically as well as economically. For NCS isotopic measurements, certain configurational changes were adapted in the EA setup such as (1) introduction of ‘purge and trap columns’ for adsorbing and desorbing analyte CO2 and SO2, and (2) introduction of in-line ring heater to cover for the entire passage between combustion and reduction reactor to prevent any condensation of analyte gases. These modifications were made to achieve necessary accuracy and precision NCS isotopic measurements. However, the presence of in-line ring heater appears to have an influence on δ15N measurements especially for samples containing lower N amounts (≤2 μmoles). We compared δ15N measurements in both NCS and NC modes by reconfiguring same EA (Vario Pyrocube) connected with Isoprime mass spectrometer with wide range variability in N content. We observed a decreasing pattern in δ15N values with increasing N contents (till the true δ15N value is approached), which is an opposite trend compared to that typically observed with the NC mode of EA setup. We surmise thermal heating of the passage from the combustion and reduction reactors is most likely responsible for the observed pattern. Measured δ15N values for samples containing lower N (≤2 μmoles), however, could be corrected using appropriate correction procedure.

Keywords

N isotopes NCS mode NC mode Elemental analyzer Continuous flow mass spectrometry 

Notes

Acknowledgments

Authors are thankful to Director CSIR-NPL for facilities and logistics. This paper is a part of project sanctioned by the CSIR under its XII Five Year Plan network project ‘AIM_IGPHim (PSC-0112)’. We greatly appreciate Prof. Mark Altabet for providing his laboratory standard (ε amino n- caprioc acid) for standardization of CF-EA-IRMS. Dr. Koushik Dutta helped in editing the manuscript.

References

  1. [1]
    S. G. Karapurkar, A. Methar and R. Agnihotri, Measurement of C and N isotopes of geological samples using Delta V Plus Stable Isotope Ratio Mass Spectrometer via different preparatory systems. Technical report published by National Institute of Oceanography, NIO/TR-02/(2008).Google Scholar
  2. [2]
    M. J. Higginson and M.A. Altabet. Comparison of nitrogen isotopic values from different preparation methods. Paleoceanography, 18 (2003) 1015. doi: 10.1029/2000PA000616.Google Scholar
  3. [3]
    R. Agnihotri, R. Kumar, M.V.S.N. Prasad, C. Sharma, S.K. Bhatia and B.C. Arya. Experimental setup and standardization of a continuous flow stable isotope mass spectrometer for measuring stable isotopes of Carbon, Nitrogen and Sulfur in Environmental samples. MAPAN-J. Metrol. Soc. India, 29 (2014)195.Google Scholar
  4. [4]
    H. Avak and B. Fry., Precise and Accurate Measurement of δ15N on < 10 μg NApplication Flash Report No. G 29 (1999).Google Scholar
  5. [5]
    F. Fourel, C. Lécuyer, F. Martineau and M. Seris, S isotopic analyses using new purge and trap EA-IRMS technology. Rapid Commun. Mass Spectrom., 28 (2014), 2587.CrossRefGoogle Scholar
  6. [6]
    R. Agnihotri, T.K. Mandal, S. Karapurkar, M. Naja, R. Gadi, Y.N. Ahammed, A. Kumar, T. Saud, and M. Saxena, Stable carbon and nitrogen isotopic composition of bulk aerosols over India and Northern Indian Ocean, Atmos. Environ., 45 (2011), 2828–2835.ADSCrossRefGoogle Scholar
  7. [7]
    R. Agnihotri, S. G. Karapurkar,V. V. S. S. Sarma, K. Yadav, M. D. Kumar, C. Sharma and M. V. S. N. Prasad, Stable isotopic and chemical characteristics of bulk aerosols during winter and summer seasons at a station in Western Coast of India (Goa), Aerosol Air Qual. Res., 15 (2015), 888–890.Google Scholar
  8. [8]
    S.G. Aggrawal, K. Kawamura, G.S. Umarji, E. Tachibana, R.S. Patil and P.K. Gupta, Organic and inorganic markers and stable C-, N-isotopic compositions of tropical coastal aerosols from megacity Mumbai: sources of organic aerosols and atmospheric processing, Atmos. Chem. Phys., 13 (2013), 4667–4680.ADSCrossRefGoogle Scholar
  9. [9]
    S. Doney, N. Mahowald, I. Lima R. Feeley and F. Mackenzie, Impact of anthropogenic atmospheric nitrogen and sulfur deposition on ocean acidification and the inorganic carbon system. Proc. National Acad. Sci., 104 (2007), 14580–14585 doi: 10.1073/pnas.0702218104.ADSCrossRefGoogle Scholar
  10. [10]
    P. Choudhary, J. Routh and G.J. Chakrapani, A 100- year record of changes in organic matter characteristics and productivity in Lake Bhimtal in the Kumaon Himalaya, NW India J. Paleolimnol., 49 (2013), 129.Google Scholar
  11. [11]
    R. Agnihotri, S.K. Bhattacharya, M.M. Sarin and B.L.K. Somayajulu. Changes in surface productivity, sub-surface denitrification and SW monsoon during the Holocene: a multi proxy record from the eastern Arabian Sea, The Holocene, 13(5), (2003), 701–713.CrossRefGoogle Scholar
  12. [12]
    R. Agnihotri, S. Kurian, M. Fernandes, K. Reshma, W. D’ Souza and S.W.A. Naqvi. Variability of subsurface denitrification and surface productivity in the coastal eastern Arabian Sea over the past seven centuries, The Holocene, 18(5), (2008), 755–764.CrossRefGoogle Scholar
  13. [13]
    O. Hadas, M.A. Altabet, R. Agnihotri (2009) Seasonally varying N isotope biogeochemistry in Lake Kinneret, Israel, Limnol. Oceanogr., 54 (2009), 75–85.CrossRefGoogle Scholar
  14. [14]
    B. Fry., Coupled N, C and S stable isotope measurements using a dual-column gas chromatography system Rapid Commun. Mass Spectrom., 21 (2007), 750.Google Scholar
  15. [15]
    Y. Pan, S. Tian, D. Liu, Y. Fang, X. Zhu, Q. Zhang, B. Zheng, G. Michalski and Y. Wang, Fossil fuel combustion-related emissions dominate atmospheric ammonia sources during severe haze episodes: evidence from 15 N-stable isotope in size-resolved aerosol ammonium, Environ. Sci. Technol., (2016) doi: 10.1021/acs.est.6b00634.Google Scholar
  16. [16]
    S.G. Aggarwal, Recent developments in aerosol measurements techniques and the metrological issue, MAPAN-J. Metrol. Soc. India, 25(3) (2010), 165–189.Google Scholar

Copyright information

© Metrology Society of India 2016

Authors and Affiliations

  • Rajesh Agnihotri
    • 1
    • 2
  • Ravi Sawlani
    • 1
  • Chhemendra Sharma
    • 1
  • M. V. S. N. Prasad
    • 1
  1. 1.Radio and Atmospheric Science DivisionCSIR-National Physical LaboratoryNew DelhiIndia
  2. 2.Birbal Sahni Institute of PalaeosciencesLucknowIndia

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