Development and characterisation of new glycine certified reference materials for SI-traceable<sup>13</sup>C/<sup>12</sup>C isotope amount ratio measurements

Malinovsky, Dmitry; Dunn, Philip J. H.; Holcombe, Gill; Cowen, Simon; Goenaga‐Infante, Heidi

doi:10.1039/c8ja00281a

Cited by 24 publications

(65 citation statements)

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“…The R sp ( 12 C/ 13 C) value was determined as the reciprocal of the R sp ( 13 C/ 12 C) value which could be measured by offline FIA-CO-IRMS analysis using previously characterised 13 C-labelled glycine with R glycine ( 13 C/ 12 C) = (211 ± 4) (expanded uncertainty, k = 2) for one point calibration [24]. Each analytical run consisted of alternate injections of the two 13 C-labelled compounds (five injections of the glycine and four of the spike).…”

Section: Resultsmentioning

confidence: 99%

“…The sample valine was analysed by FIA-CO-IRMS against synthetic isotope mixtures of glycine previously prepared for absolute carbon isotope ratio measurements. The R glycine ( 13 C/ 12 C) values of the synthetic isotope mixtures were (0.010543 ± 0.000024), (0.011070 ± 0.000025) and (0.011546 ± 0.000026) (expanded uncertainties, k = 2 [24]). Raw instrumental data were the mean and standard deviation of the integrated ion current ratios for the working gas ( n = 6 per analysis) and sample gas ( n = 5 per analysis).…”

Section: Methodsmentioning

confidence: 99%

“…those measuring at m/z 44 and 45). Determination of the spike isotopic composition was achieved by single point calibration using previously characterised 13 C-labelled glycine with R ( 13 C/ 12 C) = (211 ± 4) (expanded uncertainty, k = 2 [24]). The data analysis was again performed in a Kragten-type spreadsheet and included raw R ( 13 C/ 12 C) estimation from the recorded R ( 45 (CO 2 )/ 44 (CO 2 )) values using the SSH 17 O algorithm approach [27], but using updated values for the absolute isotope ratios of VPDB and λ (we have described this data analysis approach in more detail elsewhere [28]).…”

Section: Methodsmentioning

confidence: 99%

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Systematic comparison of post-column isotope dilution using LC-CO-IRMS with qNMR for amino acid purity determination

et al. 2019

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Determination of the purity of a substance traceable to the International System of Units (SI) is important for the production of reference materials affording traceability in quantitative measurements. Post-column isotope dilution using liquid chromatography-chemical oxidation-isotope ratio mass spectrometry (ID-LC-CO-IRMS) has previously been suggested as a means to determine the purity of organic compounds; however, the lack of an uncertainty budget has prevented assessment of the utility this approach until now. In this work, the previously published ID-LC-CO-IRMS methods have not only been improved by direct gravimetric determination of the mass flow of 13C-labelled spike but also a comprehensive uncertainty budget has been established. This enabled direct comparison of the well-characterised ID-LC-CO-IRMS method to quantitative nuclear magnetic resonance spectroscopy (qNMR) for purity determination using valine as the model compound. The ID-LC-CO-IRMS and qNMR methods provided results that were in agreement within the associated measurement uncertainty for the purity of a sample of valine of (97.1 ± 4.7)% and (99.64 ± 0.20)%, respectively (expanded uncertainties, k = 2). The magnitude of the measurement uncertainty for ID-LC-CO-IRMS determination of valine purity precludes the use of this method for determination of purity by direct analysis of the main component in the majority of situations; however, a mass balance approach is expected to result in significantly improved measurement uncertainty.Electronic supplementary materialThe online version of this article (10.1007/s00216-019-02116-2) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Systematic comparison of post-column isotope dilution using LC-CO-IRMS with qNMR for amino acid purity determination

et al. 2019

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“…Analogous to the works of Santamaria-Fernandez, 64,65 Dunn 20,21 and Malinovsky, 19,22 it could be benecial to test our approach using atomic spectrometry methods, like inductively coupled plasma mass spectrometry (ICP-MS). In these studies the ion intensity ratio 13 C + / 12 C + were measured directly.…”

Section: Discussionmentioning

confidence: 99%

“…13 Several laboratories have tried to redetermine the absolute carbon isotope ratio R 13/12 of VPDB. [14][15][16][17][18][19][20][21][22] Malinovsky et al 22 gave an overview of reported values. Currently, the recommended value of R 13/12,VPDB (ref.…”

Section: Introductionmentioning

confidence: 99%

Absolute isotope ratios of carbon dioxide – a feasibility study

Flierl

Rienitz

Brewer

et al. 2020

J. Anal. At. Spectrom.

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Recalculation of stable isotope expressions for HCNOS: EasyIsoCalculator

Skrzypek

Dunn

2020

Rapid Comm Mass Spectrometry

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The stable HCNOS isotope compositions can be reported as (a) the isotope ratio of two stable isotopes (R); (b) the isotope delta value (δ); and (c) the atom fraction of the isotopes (x). Recalculations between these different expressions are needed frequently and require the use of the absolute isotope ratio for the zero points of the stable isotope delta scales (R std). The inconsistent use of R std values may lead to a discrepancy in recalculated results. Methods: We summarised the recalculation procedures between different expressions of the stable isotope compositions and introduced a user-friendly EasyIsoCalculator that allows the recalculation between the main expressions of isotope compositions. We mathematically and empirically evaluated the possible inconsistencies in reporting of the stable isotope data due to the use of different R std and different normalisation methods. Results: The recalculation between δ-values and other expressions of the stable isotope compositions always involves the use of R std. The choice of R std will have a significant influence on the recalculated values. The use of different R std values has a significant influence also on the normalisation of raw values but only when the normalisation is conducted versus the working standard gas value, causing discrepancy, e.g. for δ(13 C/ 12 C) up to 0.3 ‰. Conclusions: Differences in the selection of R std value may lead to significant differences among different laboratories. The uncertainty in the calculations originates primarily from the uncertainty in the R std determination; however, it is lower than the discrepancy arising from the inconsistent use of R std. Consistent use of the same R std values is required to eliminate the unnecessary discrepancy if different data sets are recalculated from delta value to other expressions. 1 | INTRODUCTION Stable HCNOS isotope compositions are reported in different ways, based on common consensus and the requirements of a scientific discipline. The most frequently reported forms are (a) the ratio of two isotopes expressed as a fraction (hereafter referred to as the absolute isotope ratio); (b) the isotope delta value (δ) expressed in native form, in permille (‰), or sometimes permeg; and (c) the atom fraction of the isotopes expressed as a fraction, a percentage (%) or in parts per million (ppm). 1 Reporting of the absolute isotope ratio is consistent with the International System of Units (SI) but is not very widely used for light stable isotopes because it is impractical for reporting very small differences at natural abundance levels. Moreover, the absolute ratio is very rarely directly determined for those elements [e.g. using inductively coupled plasma mass spectrometry (ICP-MS); sometimes, it is indirectly calculated using isotope ratio mass spectrometry (IRMS) analyses]. Typically, the stable isotope composition is determined relative to a working reference material using IRMS and then is reported as a relative ratiothe isotope delta value. The isotope delta notation requires a common...

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Development and characterisation of new glycine certified reference materials for SI-traceable¹³C/¹²C isotope amount ratio measurements

Abstract: Variations in the stable isotopic composition of carbon are used in diverse fields, including biology, environmental sciences, food and drug authentication and forensic applications.

Cited by 24 publications

References 32 publications

Systematic comparison of post-column isotope dilution using LC-CO-IRMS with qNMR for amino acid purity determination

Systematic comparison of post-column isotope dilution using LC-CO-IRMS with qNMR for amino acid purity determination

Absolute isotope ratios of carbon dioxide – a feasibility study

Recalculation of stable isotope expressions for HCNOS: EasyIsoCalculator

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Development and characterisation of new glycine certified reference materials for SI-traceable13C/12C isotope amount ratio measurements

Abstract: Variations in the stable isotopic composition of carbon are used in diverse fields, including biology, environmental sciences, food and drug authentication and forensic applications.

Cited by 24 publications

References 32 publications

Systematic comparison of post-column isotope dilution using LC-CO-IRMS with qNMR for amino acid purity determination

Systematic comparison of post-column isotope dilution using LC-CO-IRMS with qNMR for amino acid purity determination

Absolute isotope ratios of carbon dioxide – a feasibility study

Recalculation of stable isotope expressions for HCNOS: EasyIsoCalculator

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Product

Resources

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Development and characterisation of new glycine certified reference materials for SI-traceable¹³C/¹²C isotope amount ratio measurements