Hello Fabrizio,

The answer is 'no' (!), especially if your 'standard gas' is elemental hydrogen. Let me cite from our recent paper in Analytical Chemistry (see citation and doi given at the end):

Accurate determinations of relative stable isotope ratios of hydrogen (δ2H), carbon (δ13C), and nitrogen (δ15N) require 2-point normalization5 using at least two isotopic reference materials (RMs, also called standards) with contrasting isotopic compositions to (i) anchor the isotopic scale and (ii) compensate for differences in responses of instruments, which commonly compress isotope–δ scales.6,7,8,9 The development of suitable organic stable isotope RMs has not kept pace with the rapid development of analytical continuous flow IRMS methods, forcing many practitioners to resort to a single RM and accept the increased analytical uncertainties that accompany ignorance of the relevant isotope–δ scale compression factor. In order to minimize matrix effects, a standard should be chemically as similar as possible to the unknown sample, and therefore organic RMs should be used to normalize δ values of organic samples. The fundamental “principle of identical treatment of sample and RM” in the analytical process10 does not permit the use of pulses of “standard gases” of CO2, H2, or N2 as primary anchors of isotope–δ scales because such gas pulses have not passed through the same GC, EA, combustion of high-temperature-conversion (HTC), etc. interfaces before being admitted into the mass-spectrometer. The proper role of “standard gas pulses” is that of a mediator between the introduction of RMs within the same sequence, to correct for drift of the IRMS over time, whether during the course of a long GC analysis or between sequential EA analyses. Instead, the RMs (local or international) are interspersed among unknowns, and only through them can the measurements be normalized to isotope–δ scales.

Schimmelmann, A., H. Qi, T.B. Coplen, W.A. Brand, J. Fong, W. Meier-Augenstein, H.F. Kemp, B. Toman, A. Ackermann, S. Assonov, A.T. Aerts-Bijma, R. Brejcha, Y. Chikaraishi, T. Darwish, M. Elsner, M. Gehre, H. Geilmann, M. Gröning, J.-F. Hélie, S. Herrero-Martín, H.A.J. Meijer, P.E. Sauer, A.L. Sessions, and R.A. Werner (2016) New organic reference materials for hydrogen, carbon, and nitrogen stable isotope-ratio measurements: caffeines, n-alkanes, fatty acid methyl esters, glycines, L-valines, polyethylenes, and oils. Analytical Chemistry 88 (8), 4294-4302. http://dx.doi.org/10.1021/acs.analchem.5b04392 Supporting Information: http://pubs.acs.org/doi/suppl/10.1021/acs.analchem.5b04392

Cheers,
Arndt Schimmelmann

On 5/10/2016 1:36 PM, Fabrizio Colosimo wrote:
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Dear all,

I was just wondering if anyone has some suggestions about reference gas standards for H isotopes.

I’m analysing C and H isotopes in hydrocarbon contaminated soils. I’m using a certified gas tank with a δ2H = -261.8 [‰] vs. VSMOW (Agroisolab GmbH, Germany). Is this a good standard gas? Also, it will be enough for all the calculation required?

Many thanks for your help, it will be much appreciated.

Fabrizio



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Arndt Schimmelmann, Ph.D. | Senior Scientist
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